DNA to gene expression

Question 1

What is the structure of DNA?

Answer 1

DNA has a double helix structure composed of two complementary strands of nucleotides, with a sugar-phosphate backbone and nitrogenous bases.

Question 2

What are the differences between purines and pyrimidines?

Answer 2

Purines (adenine and guanine) have a double-ring structure, while pyrimidines (cytosine and thymine) have a single-ring structure.

Question 3

What are the steps involved in DNA replication?

Answer 3

The steps are:
Replication fork formation
Primer binding
Elongation
Termination
Coiling into a double helix

Question 4

What is the role of DNA polymerase during replication?

Answer 4

DNA polymerase adds new base pairs to the growing DNA strand, facilitating the synthesis of new DNA.

Question 5

How does RNA differ from DNA in terms of structure?

Answer 5

RNA is single-stranded and contains ribose sugar instead of deoxyribose, and uracil replaces thymine as a nitrogenous base.

Question 6

What are the main steps of transcription?

Answer 6

The steps are:
Initiation
Promoter clearance
Elongation
Termination

Question 7

What is mRNA processing in eukaryotes?

Answer 7

mRNA processing involves capping at the 5’ end, addition of a poly-A tail at the 3’ end, and splicing to remove introns.

Question 8

What is the function of tRNA during translation?

Answer 8

tRNA delivers amino acids to the ribosome and pairs its anticodon with the corresponding mRNA codon to facilitate protein synthesis.

Question 9

What are the stages of translation?

Answer 9

The stages are:
Initiation
Elongation
Termination

Question 10

What occurs during protein folding in the endoplasmic reticulum?

Answer 10

Proteins fold into their proper structures, undergo glycosylation, and are assembled into multi-subunit proteins before being packaged into vesicles for transport.

Question 11

What is the difference between constitutive and inducible genes?

Answer 11

Constitutive genes are always active, while inducible genes are off until stimulated by a signal.

Question 12

How does epigenetic control affect gene expression?

Answer 12

Epigenetic control alters chromosomal structure and access to genes through mechanisms like DNA methylation and histone modification, impacting gene expression.

Question 13

What is the role of transcription factors in gene regulation?

Answer 13

Transcription factors bind to DNA promoters to switch genes on or off, responding to external stimuli to determine gene expression.

Question 14

What are the key steps in post-transcriptional control?

Answer 14

Post-transcriptional control can occur during mRNA processing, transport from the nucleus to the cytoplasm, and binding to ribosomes.

Question 15

What role do Okazaki fragments play in DNA replication?

Answer 15

Okazaki fragments are short DNA segments synthesized on the lagging strand, allowing for discontinuous replication due to the antiparallel nature of DNA strands.

Question 16

How does RNA polymerase know where to start transcription?

Answer 16

RNA polymerase binds to the promoter region of a gene, which contains specific DNA sequences that signal the start of transcription.

Question 17

What is the significance of splicing in mRNA processing?

Answer 17

Splicing removes introns (non-coding regions) and joins exons (coding regions) together, allowing for the creation of a mature mRNA that can be translated into a protein.

Question 18

What are codons and why are they important?

Answer 18

Codons are sequences of three nucleotides in mRNA that specify a particular amino acid. They are essential for translating the genetic code into proteins.

Question 19

What is the role of the poly-A tail in mRNA?

Answer 19

The poly-A tail enhances the stability of mRNA, facilitates its export from the nucleus, and assists in the initiation of translation.

Question 20

What is gene expression?

Answer 20

Gene expression is the process by which information from a gene is used to synthesize a functional gene product, typically a protein.

Question 21

How can environmental factors influence gene expression?

Answer 21

Environmental factors such as temperature, nutrients, and stress can impact gene expression by activating or repressing specific transcription factors or signalling pathways.

Question 22

What is a transcription factor and its role in gene regulation?

Answer 22

A transcription factor is a protein that binds to specific DNA sequences to regulate the transcription of genes, acting as either an activator or repressor.

Question 23

What is the difference between transcriptional and post-transcriptional control?

Answer 23

Transcriptional control regulates gene expression at the level of transcription initiation, while post-transcriptional control affects the processing, stability, and translation of mRNA after it has been synthesized.

Question 24

What is the significance of epigenetic modifications in gene expression?

Answer 24

Epigenetic modifications, such as DNA methylation and histone acetylation, can alter chromatin structure and accessibility, influencing whether genes are expressed or silenced without changing the underlying DNA sequence.

Question 25

What is the purpose of the 5’ cap on mRNA?

Answer 25

The 5’ cap protects mRNA from degradation, helps with ribosome binding during translation, and plays a role in the export of mRNA from the nucleus.

Question 26

How does DNA replication ensure accuracy?

Answer 26

DNA polymerases have proofreading abilities that check and correct errors during base pairing, significantly reducing the error rate during replication.

Question 27

What is meant by ‘gene regulation’?

Answer 27

Gene regulation refers to the mechanisms that control the expression of genes, determining when and how much of a gene product is produced in response to internal and external signals.

Question 28

What happens during the process of termination in translation?

Answer 28

When the ribosome encounters a stop codon (UAA, UAG, or UGA), release factors bind to the ribosome, prompting the release of the newly synthesized protein and the disassembly of the ribosomal subunits.

Question 29

How do environmental stimuli affect the expression of inducible genes?

Answer 29

Inducible genes are typically turned off and are activated in response to specific environmental stimuli, such as hormones or nutrients, allowing the cell to adapt to changing conditions.

Question 30

What are enhancers and silencers in gene regulation?

Answer 30

Enhancers are DNA sequences that promote transcription when bound by specific transcription factors, while silencers inhibit transcription when bound by repressor proteins.

Question 31

What is the significance of chromatin remodelling in gene expression?

Answer 31

Chromatin remodelling alters the structure of chromatin, making certain regions of DNA more accessible for transcription, thereby regulating gene expression in response to cellular needs.

Question 32

How can epigenetic changes be inherited?

Answer 32

Epigenetic changes, such as DNA methylation patterns and histone modifications, can be passed on during cell division, potentially influencing gene expression in offspring without altering the underlying DNA sequence.