Biology Unit 4 Test 2

Adenine forms a base pair with thymine in DNA. Base pairing is a fundamental principle in DNA structure, where adenine always pairs with thymine, and guanine always pairs with cytosine. This pairing is based on the complementary hydrogen bonding between the nitrogenous bases. Adenine and thymine form two hydrogen bonds between them, creating a stable base pair. Deoxyribose is a sugar molecule found in DNA, but it does not directly form base pairs. Guanine and cytosine are other nitrogenous bases, but they do not pair with thymine.

The Watson and Crick model of DNA is a structure called a double helix, which refers to the two strands of DNA that are twisted around each other in a spiral shape. This model accurately represents the way DNA is organized and provides a clear understanding of its structure and function. The term "double helix" describes the specific shape and arrangement of the DNA molecule, with the two strands forming a twisted ladder-like structure.

Phosphate groups are found in both DNA and RNA as they are essential components of the backbone of both molecules. Guanine and cytosine are also found in both DNA and RNA as they are two of the four nitrogenous bases that make up the genetic code. Ribose and adenine are found only in RNA, while deoxyribose and thymine are found only in DNA.

A prokaryotic cell replicates its DNA before it splits to form new cells, so that each new cell can have genetic material. DNA replication is an essential process in cell division, ensuring that each daughter cell receives a complete set of genetic instructions. Prokaryotic cells lack a nucleus, so their DNA is found in the cytoplasm. Replication involves unwinding and separating the DNA strands, followed by the synthesis of new complementary strands. This ensures that the genetic material is faithfully passed on to the next generation of cells.

RNA includes uracil instead of thymine. DNA contains adenine, guanine, cytosine, and thymine as its four nitrogenous bases. However, in RNA, thymine is replaced by uracil. This difference in the nitrogenous bases allows RNA to perform functions such as transcription and translation, which are essential for protein synthesis. Uracil pairs with adenine during RNA synthesis, forming a complementary base pair. Therefore, the presence of uracil is a characteristic feature of RNA.

During transcription, the process by which genetic information from DNA is copied into RNA, RNA molecules are produced. This occurs when RNA polymerase binds to a specific DNA sequence called a promoter and begins to unwind the DNA helix. It then uses one strand of the DNA as a template to synthesize a complementary RNA molecule. This RNA molecule will carry the genetic information from the DNA to the ribosomes, where it will be used as a template for protein synthesis. Therefore, the correct answer is RNA molecules.

During gene expression, a cell reads the instructions in DNA and uses them to synthesize a protein. This process involves the transcription of DNA into mRNA and the translation of mRNA into a protein. The DNA sequence contains the genetic code that provides instructions for the sequence of amino acids in the protein. The cell's machinery reads this code and assembles the corresponding amino acids to build the protein according to the instructions encoded in the DNA.

The term "spindle fibers" is least closely related to the others because it is not directly associated with protein synthesis or the genetic code. tRNA, polypeptide, and anticodon are all directly involved in the process of protein synthesis, whereas spindle fibers are structures involved in cell division and the separation of chromosomes.

Mutant 1 in Figure 13-7 is the result of an inversion because part of the chromosome reverses direction.

During eukaryotic transcription, an RNA molecule is formed that is complementary to part of one strand of DNA. This means that the RNA molecule is synthesized using one of the DNA strands as a template, and the resulting RNA molecule will have a sequence that is complementary to a specific region of the DNA. The RNA molecule will only be complementary to a portion of the DNA strand, not the entire strand. This process allows for the synthesis of specific RNA molecules that can be used for various cellular functions.

Eukaryotic DNA has more replication forks than prokaryotic DNA because it has more starting places, known as origins of replication. In eukaryotes, the DNA molecules are much larger and more complex than in prokaryotes. Therefore, they require multiple origins of replication to ensure efficient and timely replication of the entire genome. This allows for faster DNA synthesis and ensures that the replication process is completed in a timely manner.

A bacteriophage, also known as a phage, is a type of virus that infects bacteria. It consists of a protein coat, called a capsid, which protects the genetic material inside. The genetic material of a bacteriophage is composed of nucleic acids, either DNA or RNA. These nucleic acids contain the instructions for the virus to replicate and take over the host bacteria's cellular machinery. Therefore, the correct answer is nucleic acid.

Avery concluded that DNA was the transforming factor based on his experiments. He and his colleagues observed that when they destroyed the DNA in a mixture containing the transforming substance, the ability to cause transformation was lost. On the other hand, when they destroyed the proteins and carbohydrates, the transformation still occurred. This led them to conclude that DNA was responsible for the transformation process.

The type of amino acid that is added to the growing polypeptide depends on the codon on the mRNA and the anticodon on the tRNA. This is because the mRNA carries the genetic code for the amino acid sequence, and the tRNA molecules have anticodons that are complementary to the codons on the mRNA. The tRNA molecules bring the corresponding amino acids to the ribosome during translation, where they are added to the growing polypeptide chain based on the codon-anticodon pairing.

The virus in Figure 12-6 consists of two main components: the protein coat on the outside and the genetic material inside. The protein coat, also known as the capsid, surrounds and protects the genetic material, which can be DNA or RNA. This protein coat plays a crucial role in the virus's ability to infect host cells and replicate. It helps in recognizing and attaching to specific receptors on the host cell surface, facilitating the entry of the virus into the cell. Additionally, the protein coat provides stability and structural integrity to the virus particle.

The order of nitrogenous bases in DNA determines the order of amino acids in proteins. This is because DNA carries the genetic information that codes for the synthesis of proteins. The sequence of nitrogenous bases in DNA is transcribed into mRNA, which is then translated into a sequence of amino acids during protein synthesis. The specific order of amino acids determines the structure and function of the protein. Therefore, the correct answer is amino acids.

Hox genes are responsible for controlling the development of body structures in specific regions of an embryo. Mutations in these genes can lead to changes in the organs that form in those specific parts of the embryo. Therefore, the given answer, Hox genes, accurately explains how mutations in these genes can affect organ development.

Chargaff's contribution to the study of DNA was that he showed that adenine and thymine were found in equal percentages in DNA. However, he did not know at the time that this was because of base-pairing.

The accurate transmission of information is most important in sex cells because they carry genetic information from one generation to the next. Any errors or inaccuracies in the transmission of this information can lead to genetic disorders or abnormalities in offspring. Nerve cells, bone cells, and skin cells do not play a direct role in transmitting genetic information, making the accurate transmission less critical in these cell types.

The structural problem preventing adenine from pairing with guanine is that both bases are short. In DNA, adenine pairs with thymine, while guanine pairs with cytosine. Adenine and guanine have different structures, and their respective sizes do not allow them to form a complementary base pair. Therefore, adenine cannot pair with guanine in DNA.

A mutation that involves one or a few nucleotides is called a point mutation. This type of mutation occurs when a single nucleotide is substituted, inserted, or deleted in the DNA sequence. Point mutations can lead to changes in the amino acid sequence during protein synthesis, which can have various effects on the organism's phenotype.