The Test Question Cellular Biology Test 1

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The Test Question Cellular Biology Test 1 - Quiz

A Cell is the basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed. Do you have a good understanding on the cells within our bodies? The test question cellular biology test 1 will aid you in understanding it better. All the best!


Questions and Answers
  • 1. 

    Mitotic chromosomes were first visualized in the 1880s with the use of very simple tools: a basic light microscope and some dyes. Which of the following characteristics of mitotic chromosomes reflects how they were named? 

    • A.

      Motion

    • B.

      Color

    • C.

      Shape

    • D.

      Location

    • E.

      Length

    Correct Answer
    B. Color
    Explanation
    Mitotic chromosomes were named based on their color because in the 1880s, when they were first visualized, they were observed using dyes that stained the chromosomes. The specific dyes used would bind to the chromosomes and make them visible under a basic light microscope. Therefore, the color of the chromosomes played a crucial role in their identification and naming.

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  • 2. 

    Which of the following chemical groups is not used to construct a DNA molecule? (two answers) 

    • A.

      Five-carbon sugar

    • B.

      Phosphate

    • C.

      Nitrogen-containing base

    • D.

      Six-carbon sugar

    • E.

      Cyclic AMP

    Correct Answer(s)
    D. Six-carbon sugar
    E. Cyclic AMP
    Explanation
    The five-carbon sugar, phosphate, and nitrogen-containing base are all components of a DNA molecule. However, a six-carbon sugar and cyclic AMP are not used to construct a DNA molecule.

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  • 3. 

    All functional DNA sequences inside a cell code for protein products. 

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    The statement is false because not all functional DNA sequences inside a cell code for protein products. While some DNA sequences do code for proteins, there are also sequences that code for functional RNA molecules, such as transfer RNA (tRNA) and ribosomal RNA (rRNA). Additionally, there are non-coding DNA sequences that have regulatory functions in gene expression. Therefore, not all functional DNA sequences inside a cell directly code for protein products.

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  • 4. 

    Gene sequences correspond exactly to the respective protein sequences produced from them.

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Gene sequences do not always correspond exactly to the respective protein sequences produced from them. This is because gene sequences undergo a process called post-transcriptional modification, where certain sections of the gene sequence called introns are removed and the remaining sections called exons are spliced together to form the final mRNA sequence. This mRNA sequence is then translated into a protein sequence, which may be further modified through processes like protein folding and post-translational modifications. Therefore, the protein sequence may differ from the original gene sequence due to these modifications.

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  • 5. 

    The human genome has enough DNA to stretch more than 2m. However, this DNA is not contained in a single molecule; it is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes found in each of the somatic cells in your body? 

    • A.

      22

    • B.

      23

    • C.

      44

    • D.

      46

    • E.

      48

    Correct Answer
    D. 46
    Explanation
    The correct answer is 46 because somatic cells in the human body contain 23 pairs of chromosomes. Each pair consists of one chromosome inherited from the mother and one from the father, resulting in a total of 46 chromosomes.

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  • 6. 

    The process of sorting human chromosomes pair by size and morphology is called karyotyping. A modern method employed for kayotyping is called chromosome painting. How were individuals chromosomes shown in a figure in the textbook "painted" as different colors? 

    • A.

      With a laser

    • B.

      Using flurorescent antibodies

    • C.

      Using fluorescent DNA molecules

    • D.

      Using green fluorescent protein

    • E.

      By using Photoshop software

    Correct Answer
    C. Using fluorescent DNA molecules
    Explanation
    Individual chromosomes were shown in a figure in the textbook "painted" as different colors using fluorescent DNA molecules. This method involves labeling specific DNA sequences on each chromosome with different fluorescent dyes. When the chromosomes are viewed under a microscope, the labeled DNA sequences emit different colors of light, allowing for the identification and differentiation of each chromosome. This technique is known as chromosome painting and is a modern method employed for karyotyping.

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  • 7. 

    Chromosomes exist at different levels of condensation, depending on the stage of the cell cycle. 

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Chromosomes undergo changes in their level of condensation throughout the cell cycle. During interphase, chromosomes are less condensed and appear as long, thin threads. However, during mitosis, chromosomes become highly condensed and visible under a microscope. This condensation allows for easier separation and distribution of genetic material during cell division. Therefore, it is true that chromosomes exist at different levels of condensation depending on the stage of the cell cycle.

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  • 8. 

    Eucaryotic chromosomes contain many different sites where DNA replication can be initiated.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Eucaryotic chromosomes contain multiple sites where DNA replication can be initiated. This is because eucaryotic genomes are much larger and more complex compared to prokaryotic genomes. The presence of multiple replication initiation sites allows for efficient and timely replication of the entire genome. Additionally, having multiple initiation sites helps to prevent DNA damage and ensures accurate replication. Therefore, the statement "Eucaryotic chromosomes contain many different sites where DNA replication can be initiated" is true.

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  • 9. 

    Interphase chromosomes are about _________ times less compact than mitotic chromsomes, but still are about _____ times more compact than a DNA molecule in its extended form. 

    • A.

      10; 1000

    • B.

      20:500

    • C.

      5; 2000

    • D.

      50: 200

    • E.

      200: 50

    Correct Answer
    B. 20:500
    Explanation
    During interphase, chromosomes are less compact compared to mitotic chromosomes. The given answer, 20:500, suggests that interphase chromosomes are 20 times less compact than mitotic chromosomes. However, interphase chromosomes are still about 500 times more compact than a DNA molecule in its extended form.

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  • 10. 

    A nucleosome contains two molecules each of histones__________ as well as of histones H3 and H4. 

    • A.

      H1 and H2A

    • B.

      H2A and H2B

    • C.

      H1 and H2B

    • D.

      H1

    • E.

      H2A

    Correct Answer
    B. H2A and H2B
    Explanation
    A nucleosome is a basic unit of DNA packaging in eukaryotic cells. It consists of DNA wrapped around a core of histone proteins. The core histones include H2A, H2B, H3, and H4. Therefore, a nucleosome contains two molecules each of histones H2A and H2B, as well as of histones H3 and H4.

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  • 11. 

    Nucleosomes are formed when DNA wraps_____ times aroudn the histone ocatamer in a  _________ coil 

    • A.

      2.0: right-handed

    • B.

      2.5 left-handed

    • C.

      1.7 left-handed

    • D.

      1.3; right-handed

    • E.

      5.2; left-handed

    Correct Answer
    C. 1.7 left-handed
    Explanation
    Nucleosomes are formed when DNA wraps 1.7 times around the histone octamer in a left-handed coil.

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  • 12. 

    The core histones are small, basic proteins that have a globular domain at the C-terminus and a long extended conformation at the N-terminus. Which of the following is not true of the N terminal "tail" of these histones? 

    • A.

      It is subject to a covalent modifications

    • B.

      It extends out of the nucleosome core

    • C.

      It binds to DNA in a sequence-specific manner

    • D.

      It helps DNA pack tightly

    • E.

      It contains lysine residues

    Correct Answer
    C. It binds to DNA in a sequence-specific manner
    Explanation
    The N-terminal "tail" of core histones is not involved in binding to DNA in a sequence-specific manner. Instead, it is subject to covalent modifications, extends out of the nucleosome core, helps DNA pack tightly, and contains lysine residues. These modifications and interactions with other proteins contribute to the regulation of gene expression and chromatin structure.

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  • 13. 

    The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation? 

    • A.

      Increase in gene expression

    • B.

      Gene silencing

    • C.

      Recruitment of remodeling complexes

    • D.

      Displacement of histone H1

    • E.

      Strengthens the nuclear envelope

    Correct Answer
    B. Gene silencing
    Explanation
    Heterochromatin formation results in gene silencing. This means that the genes within the heterochromatin region are not expressed or transcribed into proteins. The modifications on the N-terminal tail of histone H3 promote the condensation of chromatin into a compact and inactive state, preventing the access of transcriptional machinery to the genes in that region. This leads to the silencing of gene expression within the heterochromatin.

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  • 14. 

    There are five differnt nucleotides that become incorporated into a DNA strand. 

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    The statement is false because there are actually only four different nucleotides (adenine, thymine, cytosine, and guanine) that become incorporated into a DNA strand.

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  • 15. 

    DNA replication is considered semiconservative because_______________

    • A.

      After many rounds of DNA replication, the original DNA double helix is still intact

    • B.

      Each daughter DNA molecule consists of two new strands copied from the parent DNA molecule

    • C.

      Each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand

    • D.

      New DNA strands must be copied from a DNA template

    • E.

      None of the above (are) correct

    Correct Answer
    C. Each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand
    Explanation
    DNA replication is considered semiconservative because each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand. In this process, the original DNA double helix is unwound and each of the separated strands serves as a template for the synthesis of a new complementary strand. This results in two daughter DNA molecules, each with one original strand and one newly synthesized strand. This mechanism ensures that the genetic information is preserved and passed on to the next generation.

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  • 16. 

    How does the total number of replication origins, in bacterial cells compare with thenumber of origins in human cells? 

    • A.

      1 versus 100

    • B.

      5 versus 500

    • C.

      10 versus 1000

    • D.

      1 versus 10,000

    Correct Answer
    D. 1 versus 10,000
    Explanation
    The total number of replication origins in bacterial cells is significantly lower compared to the number of origins in human cells. Bacterial cells typically have only one replication origin, while human cells have approximately 10,000 origins. This difference in the number of origins is due to the complexity and size of the human genome, which requires multiple origins to ensure efficient and timely DNA replication.

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  • 17. 

    Which of the following statements about the newly synthesized strand of human chromosome is true? 

    • A.

      It was synthesized from a single origion solely by continous DNA synthesis.

    • B.

      It was synthesized from a single origin by a mixture of continuous and discontinuous DNA synthesis.

    • C.

      It was synthesized from multiple origins solely by discontinuous DNA synthesis

    • D.

      It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis.

    • E.

      It was synthesized by the use of ATP hydrolysis only.

    Correct Answer
    D. It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis.
    Explanation
    The newly synthesized strand of human chromosome is true because it is synthesized from multiple origins, indicating that DNA replication occurs at multiple sites along the chromosome. Additionally, the synthesis is a mixture of continuous and discontinuous DNA synthesis, suggesting that some portions of the strand are synthesized continuously, while others are synthesized in fragments and later joined together. This process allows for efficient and accurate replication of the chromosome. The use of ATP hydrolysis is not mentioned in the question and therefore not relevant to the answer.

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  • 18. 

    A molecule of bacterial DNA introduced into a yest cell is imported into thenucleus but fails to replicate the yeast DNA. Where do you think the block to replication arises? Choose the protein or protein complex below that is most probably responsible for the failure to replicate bacterial DNA. 

    • A.

      Primase

    • B.

      Helicase

    • C.

      DNA polymerase

    • D.

      Initiator proteins

    • E.

      A, B, and C

    Correct Answer
    D. Initiator proteins
    Explanation
    The block to replication most probably arises from the initiator proteins. Initiator proteins play a crucial role in initiating DNA replication by binding to specific sites on the DNA and recruiting other replication proteins. In this case, the bacterial DNA fails to replicate, suggesting that the yeast cell's initiator proteins may not recognize or interact properly with the bacterial DNA, leading to the failure of replication.

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  • 19. 

    Primase is needed to initiate DNA replication on both the leading strand and the lagging strand. 

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Primase is an enzyme that is responsible for synthesizing short RNA primers, which are necessary for the initiation of DNA replication. These primers provide a starting point for DNA polymerase to begin synthesizing new DNA strands. Since DNA replication occurs in both the leading and lagging strands during DNA synthesis, primase is required to initiate replication on both strands. Therefore, the statement that primase is needed to initiate DNA replication on both the leading and lagging strands is true.

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  • 20. 

    Primase requires a proofreading function that ensures there are no errors in the RNA primers used for DNA replication. 

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Primase is an enzyme responsible for synthesizing RNA primers during DNA replication. It does not possess a proofreading function to check for errors in the RNA primers it generates. The proofreading function is carried out by other enzymes, such as DNA polymerase, which can detect and correct errors in the DNA sequence. Therefore, the statement that Primase requires a proofreading function for the RNA primers is false.

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  • 21. 

    Because all DNA polymerases synthesize DNA in the 5'-to-3' direction, and the parental strands are antiparallel, DNA replication is accomplished with the use of two mechanisms: continuous and discontinuous replication. Indicate whether the following items relate to continuous replication. 

    • A.

      Primase

    • B.

      Single-strand binding protein

    • C.

      Sliding clamp

    • D.

      RNA primers

    • E.

      Leading strand

    Correct Answer
    E. Leading strand
    Explanation
    The leading strand is related to continuous replication because it is synthesized continuously in the 5'-to-3' direction.

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  • 22. 

    Because all DNA polymerases synthesize DNA in the 5'-to-3' direction, and the parental strands are antiparallel, DNA replication is accomplisehd with the use of two mechanisms: continuous and discontinuous replication. Indicate whether the following items relate to continuous replication.  

    • A.

      Primase

    • B.

      Single-strand binding protein

    • C.

      Sliding clamp

    • D.

      RNA primers

    • E.

      Leading strand

    Correct Answer
    E. Leading strand
    Explanation
    The leading strand is related to continuous replication because it is synthesized continuously in the 5'-to-3' direction without any interruptions. The other items listed are not directly related to continuous replication. Primase is responsible for synthesizing RNA primers, which are necessary for DNA replication to begin. Single-strand binding protein helps stabilize the single-stranded DNA during replication. Sliding clamp helps keep the DNA polymerase attached to the template strand. RNA primers are short sequences of RNA that are synthesized by primase and serve as a starting point for DNA synthesis on the lagging strand.

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  • 23. 

    Because all DNA polymerases synthesize DNA in the 5'-to-3' direction, and the parental strands are antiparallel, DNA replication is accomplished with the use of two mechanisms: continuous and discontinuous replication. Indicate whether the following items relate to discontinuous replication. 

    • A.

      Primase

    • B.

      Single-strand binding protein

    • C.

      Sliding clamp

    • D.

      RNA primers

    • E.

      Leading strand

    Correct Answer
    B. Single-strand binding protein
  • 24. 

    Because all DNA polyermases synthesize DNA in the 5'-to-3' direction, and the parental strands are antiparallel, DNA replication is accomplished with the use of two mechanisms: continuous and discontinuous replication. Indicate whether the following items relate to both continuous replication and discontinuous replication. (pick more than 1) 

    • A.

      Primase

    • B.

      Single-stranded protein

    • C.

      Sliding clamp

    • D.

      RNA primers

    • E.

      Leading strand

    Correct Answer(s)
    A. Primase
    C. Sliding clamp
    D. RNA primers
    Explanation
    Primase, sliding clamp, and RNA primers relate to both continuous replication and discontinuous replication.

    Primase is an enzyme that synthesizes RNA primers, which are necessary for the initiation of DNA synthesis on both the leading and lagging strands.

    The sliding clamp is a protein that helps to stabilize DNA polymerase and ensures efficient DNA synthesis on both strands.

    RNA primers are short sequences of RNA that are synthesized by primase and serve as starting points for DNA synthesis on both the leading and lagging strands.

    Therefore, all three items are involved in both continuous and discontinuous replication processes.

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  • 25. 

    The repair of mismatched base pairs or damaged nucleotides in a DNA strand requires a multistep process. Which choice below describes the known sequences of events in this process? 

    • A.

      DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by repair proteins, the gap is filled by DNA polymerase, and the strand is sealed by DNA ligase.

    • B.

      DNA repair polymerase simultaneously removes bases ahead of it and polymerizes the correct sequence behind it as it moves along the template. DNA ligase seals the nicks in the repaired strand.

    • C.

      DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by an exonuclease, and the gap is repaired by DNA ligase.

    • D.

      A nick in the DNA is recognized, DNA repair proteins switch out the wrong base and insert the correct base, and DNA ligase seals the nick.

    • E.

      RNA polymerase simultaneously removes bases ahead of it and polymerizes the correct sequence behind it as it moves along the template. DNA ligase seals the nicks in the repaired strand.

    Correct Answer
    A. DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by repair proteins, the gap is filled by DNA polymerase, and the strand is sealed by DNA ligase.
    Explanation
    The correct answer describes the known sequences of events in the repair of mismatched base pairs or damaged nucleotides in a DNA strand. First, DNA damage is recognized. Then, the newly synthesized strand is identified by an existing nick in the backbone. Next, a segment of the new strand is removed by repair proteins. After that, the gap is filled by DNA polymerase. Finally, the strand is sealed by DNA ligase. This sequence of events ensures that the damaged DNA is repaired and the integrity of the DNA strand is maintained.

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  • 26. 

    Sometimes chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the cytosine in the sequence TCAT is deaminated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication? 

    • A.

      TTAT

    • B.

      TUAT

    • C.

      TGAT

    • D.

      TAAT

    • E.

      ATTA

    Correct Answer
    A. TTAT
    Explanation
    The original sequence is TCAT. If the cytosine in this sequence is deaminated and not repaired, it will be converted to thymine. After two rounds of DNA replication, the mutated sequence will be TTAT.

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  • 27. 

    Ionizing radiation and oxidative damage can cause DNA double-strand breaks. 

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Ionizing radiation and oxidative damage are known to cause DNA double-strand breaks. Ionizing radiation, such as X-rays and gamma rays, have enough energy to remove tightly bound electrons from atoms, leading to the formation of free radicals that can damage DNA. Oxidative damage, on the other hand, occurs when reactive oxygen species, such as hydrogen peroxide and superoxide radicals, react with DNA and cause breaks in the double helix. Therefore, it is true that both ionizing radiation and oxidative damage can cause DNA double-strand breaks.

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  • 28. 

    Several members of the same family were diagnosed with he same kind of cancer when they were unusually young. Which one of the following is the most likely explanation for this phenomenon? It is possible that the individuals with the cancer have ___________. 

    • A.

      Inherited a cancer-causing gene that suffered a mutation in an ancestor's somatic cells

    • B.

      Inherited a mutation in a gene required for DNA synthesis

    • C.

      Inherited a mutation in a gene required for mismatch repair

    • D.

      Inherited a mutation in a gene required for the synthesis of purine nucleotides

    • E.

      Inherited a mutation in a gene required for the synthesis of pyrimidine nucleotides

    Correct Answer
    C. Inherited a mutation in a gene required for mismatch repair
    Explanation
    The most likely explanation for several members of the same family being diagnosed with the same kind of cancer at a young age is that they have inherited a mutation in a gene required for mismatch repair. Mismatch repair is a mechanism that corrects errors in DNA replication, and mutations in genes involved in this process can lead to an increased risk of developing cancer. This explanation suggests that the individuals in the family have a genetic predisposition to cancer due to a faulty mismatch repair gene.

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  • 29. 

    In addition to the repair of DNA double-strand breaks, homologous recombination is a mechanism for generating genetic diversity by swapping segments of parental chromosomes. During which process does swapping occur? 

    • A.

      DNA replication

    • B.

      DNA repair

    • C.

      Meiosis

    • D.

      Transposition

    • E.

      Cytokinesis

    Correct Answer
    C. Meiosis
    Explanation
    During meiosis, the process of swapping segments of parental chromosomes occurs. Meiosis is a specialized form of cell division that occurs in sexually reproducing organisms. It involves the formation of gametes (eggs and sperm) and results in the production of genetically diverse offspring. One of the key events in meiosis is crossing over, where segments of homologous chromosomes are exchanged, leading to genetic recombination and increased genetic diversity. This swapping of segments during meiosis is a fundamental mechanism for generating genetic diversity.

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  • 30. 

    Transcription is similar to DNA replication in that _____________

    • A.

      An RNA transcript is synthesized discontinuously and the pieces are then joined together.

    • B.

      It uses the same enzyme as that used to synthesize RNA primers during DNA replication

    • C.

      The newly synthesized RNA remains paired to the template DNA

    • D.

      Nucleotide polymerization occurs only in the 5'-to-3' direction

    • E.

      Its products are always double stranded

    Correct Answer
    D. Nucleotide polymerization occurs only in the 5'-to-3' direction
    Explanation
    Transcription is similar to DNA replication in that nucleotide polymerization occurs only in the 5'-to-3' direction. This means that during transcription, RNA is synthesized in the 5'-to-3' direction, just like DNA is synthesized during replication. This directionality is important for the proper synthesis and assembly of RNA molecules.

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  • 31. 

    For a cell’s genetic material to be used, the information is first copied from the DNA intothe nucleotide sequence of RNA in a process called 1__________________. Variouskinds of RNA are produced, each with different functions. 2__________________molecules code for proteins,3 __________________ molecules act as adaptors forprotein synthesis,4 __________________ molecules are integral components of theribosome, and5 __________________ molecules are important in the splicing of RNAtranscriptsFill in the blank for # 1 

    • A.

      RRNA

    • B.

      MRNA

    • C.

      SnRNA

    • D.

      TRNA

    • E.

      Transcription

    Correct Answer
    E. Transcription
    Explanation
    The process described in the question where genetic material is copied from DNA into the nucleotide sequence of RNA is called transcription. Transcription is the first step in gene expression, where an RNA molecule is synthesized using a DNA template. This RNA molecule is then used for various functions, such as coding for proteins (mRNA), acting as adaptors for protein synthesis (tRNA), being integral components of the ribosome (rRNA), and being important in the splicing of RNA transcripts (snRNA). Therefore, the correct answer is transcription.

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  • 32. 

    For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called 1__________________. Various kinds of RNA are produced, each with different functions. 2__________________ molecules code for proteins,3 __________________ molecules act as adaptors for protein synthesis,4 __________________ molecules are integral components of theribosome, and5 __________________ molecules are important in the splicing of RNA transcripts.Fill in #2 

    • A.

      RRNA

    • B.

      MRNA

    • C.

      SnRNA

    • D.

      TRNA

    • E.

      Transcription

    Correct Answer
    B. MRNA
    Explanation
    mRNA molecules code for proteins. They carry the genetic information from the DNA to the ribosomes, where protein synthesis occurs. mRNA is transcribed from the DNA during the process of transcription.

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  • 33. 

    For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called 1__________________. Various kinds of RNA are produced, each with different functions. 2__________________ molecules code for proteins,3 __________________ molecules act as adaptors for protein synthesis,4 __________________ molecules are integral components of the ribosome, and 5 __________________ molecules are important in the splicing of RNAtranscripts.Fill in #3 

    • A.

      RRNA

    • B.

      MRNA

    • C.

      SnRNA

    • D.

      TRNA

    • E.

      Transcription

    Correct Answer
    D. TRNA
    Explanation
    The correct answer for #3 is tRNA. tRNA molecules act as adaptors for protein synthesis. They carry amino acids to the ribosome during protein synthesis and match them to the codons on the mRNA molecule. This ensures that the correct amino acids are added to the growing protein chain according to the genetic code.

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  • 34. 

    For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called 1__________________. Various kinds of RNA are produced, each with different functions. 2__________________ molecules code for proteins,3 __________________ molecules act as adaptors for protein synthesis,4 __________________ molecules are integral components of the ribosome, and5 __________________ molecules are important in the splicing of RNAtranscripts.Fill in #4

    • A.

      RRNA

    • B.

      MRNA

    • C.

      SnRNA

    • D.

      TRNA

    • E.

      Transcription

    Correct Answer
    A. RRNA
    Explanation
    rRNA molecules are integral components of the ribosome. The ribosome is the cellular structure responsible for protein synthesis. rRNA molecules help in the formation and functioning of the ribosome, which is essential for the translation of mRNA into proteins. They provide structural support and catalytic activity during protein synthesis. Therefore, rRNA molecules play a crucial role in the overall process of gene expression and protein production in a cell.

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  • 35. 

    For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called 1__________________. Various kinds of RNA are produced, each with different functions. 2__________________ molecules code for proteins,3 __________________ molecules act as adaptors for protein synthesis,4 __________________ molecules are integral components of the ribosome, and5 __________________ molecules are important in the splicing of RNAtranscripts.Fill in #5

    • A.

      RRNA

    • B.

      MRNA

    • C.

      SnRNA

    • D.

      TRNA

    • E.

      Transcription

    Correct Answer
    C. SnRNA
    Explanation
    snRNA molecules are important in the splicing of RNA transcripts.

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  • 36. 

    Select the ways in which the process of eucaryotic transcription differs from the process of bacterial transcription. (check all that apply) 

    • A.

      Bacterial cells contain a single RNA polymerase, eucaryotic have three

    • B.

      Bacteria RNA can initiate transcription with help of additional proteins, whereas eucaryotic RNA polymerase need general transcription factors.

    • C.

      In eucaryotic celsl transcription regulators can influence transcriptional initiation thousands of nucleotide away from the promoter, whereas bacterial regulatory sequence are very close to the promoter

    • D.

      Eucaryotic transcription is affected by chromatin structure and nucleosomes where as bacterial lack nucleosomes.

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    In eukaryotic transcription, there are three RNA polymerases present compared to the single RNA polymerase in bacterial transcription. Bacterial RNA can initiate transcription with the help of additional proteins, while eukaryotic RNA polymerase requires general transcription factors. Transcription regulators in eukaryotic cells can influence transcriptional initiation even thousands of nucleotides away from the promoter, whereas bacterial regulatory sequences are located very close to the promoter. Additionally, eukaryotic transcription is affected by chromatin structure and nucleosomes, whereas bacteria lack nucleosomes. Therefore, all of the above statements are correct in differentiating eukaryotic transcription from bacterial transcription.

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  • 37. 

    You have a segment of DNA that contains the following sequence:5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′3′-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5′If you know that the RNA transcribed from this segment contains the following sequence:5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA–3′Which of the following choices best describes how transcription occurs?

    • A.

      The top strand is the template strand; RNA polymerase moves along this strand from 5' to 3'.

    • B.

      The top strand is the template strand; RNA polymerase moves along this strand from 3' to 5'.

    • C.

      The bottom strand is the template strand; RNA polymerase moves along this strand from 5' to 3'.

    • D.

      The bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5'

    • E.

      Both the top and the bottom strands could be used as the template.

    Correct Answer
    D. The bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5'
    Explanation
    The correct answer is that the bottom strand is the template strand and RNA polymerase moves along this strand from 3' to 5'. This is because during transcription, RNA polymerase synthesizes RNA in the 5' to 3' direction, using the template strand as a guide. In this case, the given RNA sequence is complementary to the bottom strand of the DNA sequence, indicating that this is the template strand and transcription occurs in the opposite direction.

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  • 38. 

    Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads towhich the polynucleotide 5′-TTTTTTTTTTTTTTTTTTTTTTTTT-3′ has been covalently attached. After ashort incubation, the beads are then extracted from the mixture. When you analyze the cellular nucleicacids that have stuck to the beads, which of the following is most abundant?

    • A.

      DNA

    • B.

      TRNA

    • C.

      RRNA

    • D.

      MRNA

    • E.

      TRNA, rRNA and mRNAs are all abundant

    Correct Answer
    D. MRNA
    Explanation
    The polynucleotide sequence 5′-TTTTTTTTTTTTTTTTTTTTTTTTT-3′ is a poly-T sequence, which is complementary to the poly-A tail found at the 3' end of mRNA molecules. Therefore, when mixed with resin beads to which this polynucleotide has been attached, the beads will specifically bind to mRNA molecules through the poly-A tail. This allows for the selective extraction of mRNA from the mixture. Since the question asks for the most abundant nucleic acid that sticks to the beads, the correct answer is mRNA, as it is the only nucleic acid that specifically binds to the beads in this setup.

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  • 39. 

    Name covalent modificiations that can be made to an RNA molecule in eucaryotic cells before the RNA molecules becomes a mature mRNA. 

    • A.

      A poly A tail is added

    • B.

      A 5' cap is added

    • C.

      Introns can be spliced out

    • D.

      All of the above

    • E.

      None of the above

    Correct Answer
    D. All of the above
    Explanation
    In eukaryotic cells, several covalent modifications can be made to an RNA molecule before it becomes a mature mRNA. One modification is the addition of a poly A tail, which is a sequence of adenine nucleotides added to the 3' end of the RNA molecule. Another modification is the addition of a 5' cap, which is a modified guanine nucleotide added to the 5' end of the RNA molecule. Additionally, introns, non-coding regions of the RNA molecule, can be spliced out to remove unnecessary sequences. Therefore, all of the above modifications can occur in eukaryotic cells before an RNA molecule becomes a mature mRNA.

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  • 40. 

    Which of the following statements about the genetic code is correct? 

    • A.

      All codons specify more than one amino acid

    • B.

      The genetic code is redundant

    • C.

      All amino acids are specified by more than one codon

    • D.

      All codons specify an amino acid

    • E.

      Codons encode for 21 different amino acids.

    Correct Answer
    B. The genetic code is redundant
    Explanation
    The genetic code is redundant means that multiple codons can specify the same amino acid. In other words, there is more than one codon that can code for a particular amino acid. This redundancy in the genetic code provides some degree of error tolerance and flexibility in protein synthesis.

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  • 41. 

    The piece of RNA below includes the region that codes the binding site for the initiator tRNA needed intranslation.5′-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3′Which amino acid will be on the tRNA that is the first to bind to the A-site of the ribosome?

    • A.

      Methionine

    • B.

      Arginine

    • C.

      Cystine

    • D.

      Valine

    • E.

      Leucine

    Correct Answer
    A. Methionine
    Explanation
    The sequence "AUG" is known as the start codon and codes for the amino acid methionine. In this case, the RNA sequence includes the start codon "AUG" at the 13th to 15th positions. Therefore, the tRNA that binds to the A-site of the ribosome will carry the amino acid methionine.

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  • 42. 

    Which amino acid would you expect a tRNA with the anticodon 5′-CUU-3′ to carry?

    • A.

      Lysine

    • B.

      Glutamic acid

    • C.

      Leucine

    • D.

      Phenylalanine

    • E.

      Valine

    Correct Answer
    A. Lysine
    Explanation
    A tRNA molecule with the anticodon 5′-CUU-3′ would carry the amino acid lysine. The anticodon on a tRNA molecule pairs with the codon on mRNA during translation, and the codon sequence 5′-CUU-3′ corresponds to the mRNA codon sequence 5′-AAG-3′, which codes for lysine. Therefore, the tRNA with the given anticodon would be specific for lysine.

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  • 43. 

    Below is the sequence from the 3′ end of an mRNA.5′-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3′If you were told that this sequence contains the stop codon for the protein encoded by this mRNA, whatis the anticodon on the tRNA in the P-site of the ribosome when release factor binds to the A-site?

    • A.

      5'-CCA-3'

    • B.

      5'-CCG-3'

    • C.

      5'-UGG-3'

    • D.

      5'-UUA-3'

    • E.

      Not enough information to determine the correct answer

    Correct Answer
    A. 5'-CCA-3'
    Explanation
    The stop codon in mRNA is recognized by a release factor, which binds to the A-site of the ribosome. The anticodon on the tRNA in the P-site of the ribosome must be complementary to the stop codon to ensure proper termination of protein synthesis. In this case, the stop codon is UGA, so the anticodon on the tRNA in the P-site would be 5'-CCA-3', as it is the complementary sequence to UGA.

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  • 44. 

    Which of the following statements about the proteasome is false? 

    • A.

      Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome

    • B.

      Proteases reside in the central cylinder of a proteasome

    • C.

      Misfolded protein are delivered to the proteasome, where theya re sequestered form the cytoplasm and can attempt to refold.

    • D.

      The protein stoppoers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber.

    • E.

      Proteases cleave the polypeptide backbone

    Correct Answer
    C. Misfolded protein are delivered to the proteasome, where theya re sequestered form the cytoplasm and can attempt to refold.
    Explanation
    Misfolded proteins are not delivered to the proteasome to attempt refolding. Instead, they are targeted for degradation by the proteasome. The proteasome recognizes the misfolded proteins and degrades them into smaller peptides. Therefore, the statement that misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold is false.

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