Chap 4 Genes and Cellular Function

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Questions and Answers

Describe the structure of DNA.

DNA is a double helix composed of two strands of nucleotides. Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).

Explain how DNA and histone proteins are organized to form chromosomes.

DNA wraps around histone proteins to form nucleosomes. These nucleosomes are further coiled and condensed to form chromatin fibers, which then coil and fold to form chromosomes.

Discuss the three specific parts of a DNA nucleotide.

A DNA nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).

List the purine nitrogenous bases and the pyrimidine nitrogenous bases and describe which purine base will make hydrogen bonds with which pyrimidine base.

Purines: Adenine (A) and Guanine (G). Pyrimidines: Cytosine (C) and Thymine (T). Adenine (A) pairs with Thymine (T) via two hydrogen bonds, and Guanine (G) pairs with Cytosine (C) via three hydrogen bonds. Signup and view all the answers

Define the terms chromatin, chromosomes, and sister chromatids.

Chromatin: The complex of DNA and proteins (histones) that makes up chromosomes. Chromosomes: Organized structures of DNA and protein found in cells. Sister chromatids: Two identical copies of a single chromosome that are connected by a centromere. Signup and view all the answers

Discuss the four differences between DNA and RNA.

<ol> <li>DNA contains deoxyribose sugar, while RNA contains ribose sugar.</li> <li>DNA uses thymine (T) as a base, while RNA uses uracil (U).</li> <li>DNA is typically double-stranded, while RNA is typically single-stranded.</li> <li>DNA is primarily involved in storing genetic information, while RNA is involved in various roles including protein synthesis.</li> </ol> Signup and view all the answers

State the current definition of a gene.

A gene is a segment of DNA that contains the instructions for making a specific protein or functional RNA molecule. Signup and view all the answers

Describe how DNA codes for protein structure.

DNA codes for protein structure through the sequence of its nitrogenous bases. These bases are read in triplets (codons), with each codon specifying a particular amino acid. The sequence of codons determines the sequence of amino acids in a protein. Signup and view all the answers

Describe the assembly of amino acids into a protein.

Amino acids are assembled into a protein through a process called translation. Messenger RNA (mRNA) carries the genetic code from DNA to ribosomes, where transfer RNA (tRNA) molecules bring the corresponding amino acids to be linked together according to the mRNA sequence. Signup and view all the answers

Discuss the roles of messenger RNA, ribosomal RNA, and transfer RNA.

Messenger RNA (mRNA) carries the genetic code from DNA to the ribosomes. Ribosomal RNA (rRNA) is a component of ribosomes and helps in protein synthesis. Transfer RNA (tRNA) brings specific amino acids to the ribosome to be incorporated into the growing polypeptide chain. Signup and view all the answers

Describe where triplets, codons, and anticodons are found and be able to correctly give the codon and anticodon if given a triplet code.

Triplets are found in DNA, codons are found in mRNA, and anticodons are found in tRNA. For example, if a triplet code in DNA is ATG, the corresponding codon in mRNA would be AUG, and the anticodon in tRNA would be UAC. Signup and view all the answers

Explain the processes of transcription and translation.

Transcription is the process of copying a DNA sequence into an RNA sequence, occurring in the nucleus. Translation is the process of using the RNA sequence to assemble amino acids into a protein, occurring in the ribosomes. Signup and view all the answers

Explain what happens to a protein after its amino acid sequence has been synthesized.

After its amino acid sequence has been synthesized, a protein undergoes folding into a specific three-dimensional structure, often aided by chaperone proteins. It may also undergo post-translational modifications such as glycosylation or phosphorylation, which can affect its function and activity. Signup and view all the answers

Describe the process of DNA replication.

DNA replication is the process of duplicating a DNA molecule. It involves unwinding the double helix, using each strand as a template to synthesize a new complementary strand, resulting in two identical DNA molecules. Signup and view all the answers

Discuss the three phases of interphase and what occurs in each phase.

The three phases of interphase are G1 (growth), S (DNA synthesis), and G2 (growth and preparation for mitosis). During G1, the cell grows and performs normal functions. During S, DNA is replicated. During G2, the cell prepares for mitosis by synthesizing proteins and organelles. Signup and view all the answers

Distinguish between the process of mitosis and cytokinesis.

Mitosis is the division of the nucleus, resulting in two identical nuclei. Cytokinesis is the division of the cytoplasm, resulting in two separate daughter cells. Signup and view all the answers

Describe the four phases of mitosis and be able to explain what occurs in each of the phases.

The four phases of mitosis are prophase, metaphase, anaphase, and telophase. During prophase, chromosomes condense and the nuclear envelope breaks down. During metaphase, chromosomes align at the metaphase plate. During anaphase, sister chromatids separate and move to opposite poles. During telophase, chromosomes decondense, and nuclear envelopes reform. Signup and view all the answers

Discuss factors that would inhibit or promote cell division.

Factors that promote cell division include growth factors, hormones, and adequate nutrient supply. Factors that inhibit cell division include contact inhibition, DNA damage, and lack of necessary growth factors. Signup and view all the answers

Flashcards

DNA Structure

DNA is composed of two strands forming a double helix, with a sugar-phosphate backbone and nitrogenous bases.

Chromosome Formation

DNA wraps around histone proteins to form nucleosomes, which coil into chromatin fibers, further condensing into chromosomes.

DNA Nucleotide

A DNA nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

Base Pairing

Purines (Adenine and Guanine) pair with pyrimidines (Thymine and Cytosine) via hydrogen bonds (A-T, G-C).