Chapter 17

Question 1

What is the central dogma of molecular biology?

Answer 1

The central dogma of molecular biology describes the flow of genetic information in cells from DNA to RNA to protein. It involves two main processes: transcription (DNA to RNA) and translation (RNA to protein).

Question 2

What is transcription and where does it occur in eukaryotic cells?

Answer 2

Transcription is the process of synthesizing RNA from a DNA template. In eukaryotic cells, transcription occurs in the nucleus.

Question 3

What enzyme is responsible for synthesizing RNA during transcription?

Answer 3

RNA polymerase is the enzyme responsible for synthesizing RNA during transcription.

Question 4

What are the three main stages of transcription?

Answer 4

The three main stages of transcription are initiation, elongation, and termination.

Question 5

What is the role of the promoter in transcription?

Answer 5

The promoter is a specific DNA sequence that signals the start of transcription. It is where RNA polymerase binds to initiate transcription.

Question 6

What is the TATA box and its significance in eukaryotic transcription?

Answer 6

The TATA box is a DNA sequence found in the promoter region of many eukaryotic genes. It is crucial for the binding of transcription factors and RNA polymerase II, facilitating the initiation of transcription.

Question 7

Describe the process of elongation in transcription.

Answer 7

During elongation, RNA polymerase moves along the DNA template, unwinding the DNA and synthesizing RNA by adding complementary RNA nucleotides in the 5’ to 3’ direction.

Question 8

How does termination of transcription occur in bacteria?

Answer 8

In bacteria, termination occurs when RNA polymerase transcribes a terminator sequence, causing the RNA transcript to be released and the polymerase to detach from the DNA.

Question 9

What is the polyadenylation signal sequence in eukaryotic transcription?

Answer 9

The polyadenylation signal sequence (AAUAAA) is a sequence in the pre-mRNA that signals the addition of a poly-A tail at the 3’ end, which is important for mRNA stability and export from the nucleus.

Question 10

What are the three main modifications made to eukaryotic pre-mRNA before it becomes mature mRNA?

Answer 10

The three main modifications are the addition of a 5’ cap, the addition of a poly-A tail at the 3’ end, and RNA splicing to remove introns and join exons.

Question 11

What is the function of the 5’ cap in mRNA processing?

Answer 11

The 5’ cap protects the mRNA from degradation, aids in ribosome binding during translation, and facilitates the export of mRNA from the nucleus

Question 12

What is RNA splicing and why is it important?

Answer 12

RNA splicing is the process of removing introns (non-coding regions) from pre-mRNA and joining exons (coding regions) together. It is important for producing a continuous coding sequence that can be translated into a functional protein.

Question 13

What is the role of the spliceosome in RNA splicing?

Answer 13

The spliceosome is a complex of proteins and small nuclear RNAs (snRNAs) that catalyzes the removal of introns and the joining of exons during RNA splicing.

Question 14

What is alternative RNA splicing and its significance?

Answer 14

Alternative RNA splicing allows a single gene to produce multiple protein variants by splicing the pre-mRNA in different ways. This increases the diversity of proteins that can be produced from a single gene.

Question 15

What is translation and where does it occur in the cell?

Answer 15

Translation is the process of synthesizing a polypeptide (protein) from an mRNA template. It occurs in the cytoplasm on ribosomes.

Question 16

What are the three main stages of translation?

Answer 16

The three main stages of translation are initiation, elongation, and termination.

Question 17

What is the role of tRNA in translation?

Answer 17

Transfer RNA (tRNA) brings the appropriate amino acids to the ribosome by matching its anticodon with the codon on the mRNA during translation.

Question 18

Describe the structure of a ribosome and its function in translation.

Answer 18

A ribosome is composed of two subunits (large and small) made of ribosomal RNA (rRNA) and proteins. It facilitates the binding of tRNA and mRNA, catalyzes peptide bond formation, and ensures the correct assembly of the polypeptide chain.

Question 19

What is the significance of the start codon in translation?

Answer 19

The start codon (AUG) signals the beginning of translation and specifies the amino acid methionine, which is the first amino acid in the newly synthesized polypeptide.

Question 20

How does termination of translation occur?

Answer 20

Termination occurs when a stop codon (UAA, UAG, or UGA) is reached on the mRNA. A release factor binds to the stop codon, causing the ribosome to release the completed polypeptide and disassemble.

Question 21

What are polyribosomes and their role in protein synthesis?

Answer 21

Polyribosomes (or polysomes) are clusters of ribosomes simultaneously translating a single mRNA molecule. They increase the efficiency of protein synthesis by producing multiple copies of a polypeptide from one mRNA.

Question 22

What are point mutations and their potential effects on protein synthesis?

Answer 22

Point mutations are changes in a single nucleotide pair in a gene. They can result in silent mutations (no effect), missense mutations (change in one amino acid), or nonsense mutations (premature stop codon).

Question 23

What are frameshift mutations and their impact on protein synthesis?

Answer 23

Frameshift mutations occur due to insertions or deletions of nucleotides that are not in multiples of three. They alter the reading frame of the mRNA, leading to extensive missense or nonsense mutations and often resulting in nonfunctional proteins.

Question 24

What is the role of the signal recognition particle (SRP) in targeting proteins to the ER?

Answer 24

The SRP recognizes the signal peptide on a newly synthesized polypeptide and directs the ribosome to the ER membrane, where translation continues and the polypeptide is translocated into the ER.

Question 25

How do mutations contribute to genetic diversity and evolution?

Answer 25

Mutations introduce genetic variation by altering DNA sequences. While most mutations are neutral or harmful, some can provide beneficial traits that enhance survival and reproduction, driving evolution through natural selection.