Final Chapter 15 Genes And How They Work

Ribosomes are the polypeptide-making organelles in the cytoplasm that are associated with RNA. They are responsible for protein synthesis and are composed of large protein aggregates. Golgi bodies, lysosomes, the endoplasmic reticulum, and mitochondria are all different organelles with their own specific functions in the cell, but they are not directly involved in polypeptide synthesis like ribosomes are.

The central dogma of biology states that genetic information flows from DNA to RNA to proteins. This means that DNA serves as the template for the synthesis of RNA molecules through a process called transcription, and then RNA molecules serve as the template for the synthesis of proteins through a process called translation. Therefore, the correct answer is DNA→RNA→proteins.

Stop codons are the codons that signal the end of protein synthesis. They do not code for any amino acid, but instead serve as a signal for the ribosomes to release the newly synthesized protein. Anticodons are found on tRNA molecules and are complementary to codons on mRNA, but they do not specifically signal the end of protein synthesis. Nonsense codons, also known as premature stop codons, are mutations that cause the termination of protein synthesis before the full protein is made. Amino acid codons specify the incorporation of specific amino acids into the growing polypeptide chain. Therefore, the correct answer is stop codons.

Both DNA and RNA are composed of nucleotides. Nucleotides are the building blocks of these genetic molecules, consisting of a sugar molecule, a phosphate group, and a nitrogenous base. These nucleotides are linked together in a specific sequence to form the DNA and RNA strands. The complementary base pairs, amino acids, and genes are all important components of genetic material, but they are not the building blocks of DNA and RNA.

Gene expression refers to the process by which the information encoded in a gene is used to synthesize a functional gene product, such as a protein. Transcription is the first step in gene expression, where the DNA sequence of a gene is copied into a messenger RNA (mRNA) molecule. Translation is the second step, where the mRNA molecule is used as a template to synthesize a protein. Therefore, the correct answer is transcription and translation.

The 3-nucleotide sequence of an mRNA is called a codon. A codon is a specific sequence of three nucleotides that corresponds to a specific amino acid or a stop signal during protein synthesis. It acts as a code that determines the order of amino acids in a protein. The anticodon is found on tRNA molecules and is complementary to the codon on mRNA. Amino acids are the building blocks of proteins. Transcript refers to the RNA molecule that is synthesized from DNA during transcription. Template refers to the DNA strand that is used as a guide during transcription.

The number of nucleotides required to specify an amino acid is 3. This is because each amino acid is encoded by a sequence of three nucleotides called a codon. There are a total of 64 possible codons (4 nucleotides raised to the power of 3), which is more than enough to specify the 20 different amino acids found in proteins. Therefore, three nucleotides are needed to uniquely identify each amino acid.

The sequence of bases in mRNA is determined by the complementary base pairing rules between DNA and RNA. In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). In RNA, uracil (U) replaces thymine (T). Therefore, the corresponding sequence of bases in mRNA for the given DNA sequence ATCGCTCC would be UAGCGAGG.

In RNA, adenine pairs with uracil. This is similar to the complementary purine-pyrimidine relationship observed in DNA, where adenine pairs with thymine. Uracil is a pyrimidine base, just like thymine, and it forms a complementary base pair with adenine in RNA. Cytosine and guanine are also present in RNA, but they do not pair with adenine.

The transfer of genetic information from DNA to mRNA is known as transcription. During this process, an enzyme called RNA polymerase binds to the DNA molecule and synthesizes a complementary mRNA strand using the DNA template. This mRNA molecule carries the genetic code from the DNA to the ribosomes, where it is used as a template for protein synthesis in a process called translation. Therefore, transcription accurately describes the transfer of information from DNA to mRNA.

RNA polymerase is the correct answer because it is the enzyme responsible for initiating transcription, the process of synthesizing RNA from a DNA template. RNA polymerase binds to the DNA strand and unwinds it, allowing for the synthesis of an RNA molecule that is complementary to the DNA template. This RNA molecule can then be used to produce proteins or perform other functions within the cell. DNA polymerase, carbonic anhydrase, ATP synthetase, and the transformation principle are not involved in the initiation of transcription.

The nucleotide sequence of an mRNA codon is composed of three bases. This is because each codon consists of three nucleotides, which determine the specific amino acid that will be added to the growing protein chain during translation. Therefore, the correct answer is 3.

In eukaryotes, the empty RNA molecules exit the ribosome from the E site. The E site, also known as the exit site, is one of the three binding sites on the ribosome. It is where the uncharged transfer RNA (tRNA) molecules are released after they have delivered their amino acids to the growing polypeptide chain during translation. The E site is located on the small subunit of the ribosome and is responsible for the efficient recycling of tRNA molecules.

There are four different RNA nucleotides (A, U, G, C) that can be used to construct mRNA codons. Each codon is made up of three nucleotides. Since there are four options for each nucleotide, the total number of unique mRNA codons that can be constructed is 4 * 4 * 4 = 64.

Transcription is the correct answer because it refers to the process in which an RNA polymerase molecule assembles an mRNA molecule that is complementary to the DNA sequence. During transcription, the DNA sequence is used as a template to synthesize a complementary RNA molecule. This process is essential for gene expression as it allows the genetic information encoded in the DNA to be transcribed into RNA, which can then be translated into protein during the process of translation.

Ribosomes are responsible for protein synthesis in cells. They consist of two subunits made up of RNA and large proteins. The RNA component plays a crucial role in decoding the genetic information carried by DNA and facilitating the assembly of amino acids into proteins. The large proteins provide structural support and assist in the catalytic functions of the ribosomes. Therefore, the correct answer is RNA and large proteins.

The correct answer states that the human insulin gene was inserted into a bacterium's genome. This process is known as genetic engineering or gene splicing. By inserting the human insulin gene into the bacterium's genome, the bacterium is able to produce human insulin. This is possible because the genetic code is nearly universal, meaning that the same genetic code is used by all living organisms. Therefore, the bacterium is able to read and interpret the human insulin gene and produce human insulin as a result.

Eukaryotic mRNA molecules contain non-coding sequences called introns that need to be removed before protein synthesis. Introns do not code for proteins and are interspersed within the coding sequences called exons. The process of removing introns and joining exons together is called splicing and is essential for the production of functional proteins. Anticodons, on the other hand, are sequences found in tRNA molecules that complement codons in mRNA during translation. Nucleosomes and chromomeres are structures associated with DNA packaging and chromosome organization, not involved in mRNA processing.

In eukaryotic cells, mRNA is made as a copy of the DNA coding information in the nucleus. This is because the nucleus is where the DNA is located and transcription, the process of making mRNA from DNA, occurs in the nucleus. Once the mRNA is made, it can then be transported to the cytoplasm where it will be used as a template for protein synthesis. The mitochondria, ER, and plasma membrane do not contain DNA and are not involved in the transcription of mRNA.

tRNA molecules transport amino acids to the ribosome for use in building the polypeptide. tRNA, or transfer RNA, is responsible for carrying specific amino acids to the ribosome based on the codons on the mRNA molecule. Each tRNA molecule has an anticodon that is complementary to the codon on the mRNA, ensuring the correct amino acid is added to the growing polypeptide chain. This process is essential for protein synthesis.

The tRNA anticodons are complementary to the DNA triplet code. In this case, the DNA triplet code is ATG CGT. To find the tRNA anticodons, we need to replace each DNA base with its complementary base. A pairs with U, T pairs with A, G pairs with C, and C pairs with G. Therefore, the tRNA anticodons for the given DNA triplet code would be UAC GCA.

Each amino acid has a specific tRNA molecule that can transport it to the site of protein synthesis. Therefore, since there are 20 different types of amino acids used in protein synthesis, the number of different tRNA molecules in humans would be 20.

In eukaryotic cells, protein synthesis occurs in the cytoplasm. This is where ribosomes, the cellular structures responsible for protein synthesis, are located. The nucleus, on the other hand, houses the DNA and is involved in the transcription of DNA into RNA, which is then transported to the cytoplasm for protein synthesis. The Golgi apparatus is involved in the modification, sorting, and packaging of proteins, while the plasma membrane and vacuole have other functions unrelated to protein synthesis.

The "one gene-one enzyme" hypothesis states that each gene is responsible for the production of a single enzyme. This hypothesis was proposed by Beadle and Tatum based on their experiments with the bread mold Neurospora crassa. They observed that mutations in specific genes resulted in the inability of the mold to produce certain enzymes, leading to the conclusion that each gene controls the production of a specific enzyme. This hypothesis laid the foundation for our understanding of the relationship between genes and proteins.

The hereditary information in DNA is conveyed through the production of many proteins and polypeptides. DNA contains genes that encode instructions for the synthesis of proteins. These instructions are transcribed into messenger RNA (mRNA) molecules, which are then translated into proteins. Proteins and polypeptides play crucial roles in various cellular processes and are responsible for the expression of traits and characteristics encoded in the DNA. Therefore, the production of proteins and polypeptides is essential for conveying the hereditary information in DNA.

Genes contain the instructions for building proteins, which are essential for the expression of hereditary traits. Amino acids are the building blocks of proteins, and nucleotides are the building blocks of DNA. Histone molecules are involved in the packaging of DNA, but they are not directly responsible for the connection between genes and hereditary traits. Complementary bases are the pairing nucleotides in DNA, but they are not directly involved in the translation of genes into proteins. Therefore, the correct answer is proteins.

A peptide bond is formed between the carboxyl group of one amino acid and the amino group of another amino acid. This bond is formed through a dehydration synthesis reaction, where a water molecule is removed. The resulting bond is called a peptide bond and it links the amino acids together to form a protein chain. Hydrogen bonds, hydrophobic bonds, and hydrophilic bonds are all different types of interactions between molecules, but they do not specifically refer to the bond between amino acids in a protein chain. Phosphodiester bonds, on the other hand, are found in nucleic acids like DNA and RNA, not in proteins. Therefore, the correct answer is peptide bond.

In eukaryotes, mRNA processing is a crucial step in gene expression, which involves various events such as addition of a 5' cap, addition of a poly A to the 3' end, pre-mRNA splicing, and association with the spliceosome. However, elongation of the transcript is not a part of mRNA processing. Elongation occurs during transcription, where the RNA polymerase adds nucleotides to the growing RNA molecule. Once the pre-mRNA is synthesized, it undergoes processing events to form mature mRNA, but elongation is not one of these events.

The initiation complex for protein synthesis is a complex of molecules that come together to start the process of protein synthesis. It includes a small ribosomal subunit, mRNA, tRNA with methionine, and initiation factors. However, a release factor is not part of the initiation complex. Release factors are proteins that bind to the stop codon on mRNA and help release the newly synthesized protein from the ribosome. They are involved in the termination phase of protein synthesis, not the initiation phase.

During protein synthesis, the ribosome moves along the mRNA molecule, reading the genetic code in groups of three nucleotides called codons. Each codon corresponds to a specific amino acid, and the ribosome attaches the corresponding amino acid to the growing protein chain. This process occurs in a sequential manner, with the ribosome moving three nucleotides at a time on the mRNA, ensuring that the correct amino acids are added in the proper order to form the protein.

The genetic code operates on the principle that each combination of any three nucleotides can act as a codon, meaning that there is flexibility in the sequence of nucleotides that make up a codon. Additionally, a particular codon always specifies the same amino acid, ensuring consistency in the translation of genetic information. Furthermore, all four of the nucleotide bases must be used to form codons, allowing for a diverse range of possible codons. However, the statement that the first nucleotide in every codon is always the same is incorrect. The first nucleotide in a codon can vary, and it is the second and third nucleotides that are more crucial in determining the amino acid specified by the codon.

The tRNA nucleotide sequence that lines up on the mRNA is an anticodon. The anticodon is a specific sequence of three nucleotides on the tRNA molecule that is complementary to a codon on the mRNA. This complementary base pairing allows the tRNA to bring the correct amino acid to the ribosome during protein synthesis. The anticodon ensures that the correct amino acid is added to the growing polypeptide chain, based on the genetic information encoded in the mRNA.

DNA and RNA nucleotides are composed of five carbon sugars, phosphate, and nitrogen bases. Since both DNA and RNA contain nitrogen bases, the total number of nitrogen bases available for use in the two nucleic acids is 5.

Amino acids are attached to tRNA molecules by activating enzymes. These enzymes play a crucial role in the process of protein synthesis by catalyzing the attachment of specific amino acids to their corresponding tRNA molecules. This process, known as aminoacylation or charging of tRNA, ensures that the correct amino acid is attached to the appropriate tRNA molecule, which is then used during translation to assemble the protein according to the codons on the mRNA. Without activating enzymes, the attachment of amino acids to tRNA molecules would not occur accurately, leading to errors in protein synthesis.

The correct answer is that the reading of the code occurs without any punctuation. This means that there are no breaks or pauses between codons when translating the genetic code into amino acids. The information provided by Crick and his coworkers suggests that the codons in the genetic code are read continuously, without any punctuation marks indicating where one codon ends and the next one begins. This allows for a smooth and uninterrupted translation of the genetic code into proteins.

mRNA carries the genetic information from the DNA to the ribosome for protein synthesis. It serves as a template for the assembly of amino acids into a chain during protein synthesis. The sites A, P, and E mentioned in the question are specific locations on the ribosome where the mRNA interacts with tRNA molecules carrying the amino acids. Therefore, the correct answer is mRNA.

The different components of the protein synthesizing machinery include mRNA, tRNA, ribosomes, and RNA polymerase. These components work together to carry out the process of protein synthesis. mRNA carries the genetic information from DNA to the ribosomes, tRNA brings the amino acids to the ribosomes, ribosomes are the site of protein synthesis, and RNA polymerase is responsible for transcribing DNA into mRNA. Amino acids, on the other hand, are not considered a component of the machinery itself, but rather the building blocks used to construct proteins during translation.

Translocation is the correct answer because it refers to the process by which the ribosome moves along the mRNA molecule during protein synthesis. During translocation, the tRNA carrying the growing polypeptide chain is shifted from the A site to the P site of the ribosome, allowing a new tRNA to enter the A site and adding the corresponding amino acid to the growing chain. This movement of the ribosome along the mRNA is essential for translating the nucleic acid sequence into an amino acid sequence, making translocation the appropriate term for this process.