Gene expression regulation

Question 1

What is gene expression?

Answer 1

The process by which genetic information is used to produce
proteins.

Question 2

Why do cells regulate gene expression?

Answer 2

To conserve resources and adapt to environmental changes.

Question 3

What are the two major steps in gene expression?

Answer 3

Transcription and translation.

Question 4

Do all cells express the same genes?

Answer 4

No; different cell types express different sets of genes.

Question 5

What is the significance of differential gene expression?

Answer 5

It allows cell specialization in multicellular organisms.

Question 6

Give an example of gene regulation in response to environment.

Answer 6

Arctic hares turn off pigment genes in winter, resulting in white fur.

Question 7

Why is gene regulation important in simple organisms like yeast?

Answer 7

To avoid wasting energy or macromolecules on unneeded metabolic pathways.

Question 8

How is gene expression linked to metabolism?

Answer 8

Genes that encode enzymes are turned on or off based on metabolic needs.

Question 9

What term describes all proteins expressed in a cell?

Answer 9

The proteome.

Question 10

What internal signals can trigger gene regulation?

Answer 10

Hormones, feedback from metabolic products, or developmental cues (very briefly introduced).

Question 11

What are operons?

Answer 11

Clusters of prokaryotic genes regulated together by a single promoter.

Question 12

Do eukaryotes have operons?

Answer 12

No; their genes are generally regulated individually.

Question 13

What percent of the human genome is coding DNA?

Answer 13

Less than 2%.

Question 14

What is the role of non-coding DNA?

Answer 14

It includes regulatory sequences and introns.

Question 15

Where does transcription occur in eukaryotes?

Answer 15

In the nucleus.

Question 16

Where does transcription occur in prokaryotes?

Answer 16

In the cytoplasm.

Question 17

How are plasmids important in prokaryotes?

Answer 17

They can carry genes for antibiotic resistance (extra traits) and be transferred between cells.

Question 18

What is horizontal gene transfer?

Answer 18

Transfer of genetic material between organisms without reproduction.

Question 19

What are the physical differences in chromosomes between the two groups?

Answer 19

Prokaryotes have a single circular chromosome; eukaryotes have multiple linear chromosomes.

Question 20

Why is genome size not always correlated with organism complexity?

Answer 20

Because much of genome size is due to non-coding DNA.

Question 21

What are the two main levels of metabolic regulation?

Answer 21

Enzyme activity and gene expression.

Question 22

What is feedback inhibition?

Answer 22

When the end product of a pathway inhibits an early enzyme.

Question 23

What regulates enzyme activity quickly?

Answer 23

Allosteric inhibition by pathway products.

Question 24

How do cells regulate gene expression in response to metabolites?

Answer 24

By turning off transcription of enzymes no longer needed.

Question 25

Which is faster: regulating enzymes or gene expression?

Answer 25

Enzyme activity regulation is faster.

Question 26

Why is gene regulation slower?

Answer 26

Because it involves transcription and translation.

Question 27

What is the benefit of enzyme regulation?

Answer 27

Immediate adjustment to changing cellular needs.

Question 28

What is the benefit of gene regulation?

Answer 28

Long-term energy savings.

Question 29

What kind of regulation is feedback inhibition?

Answer 29

Allosteric regulation.

Question 30

What is an example of gene expression regulation in bacteria?

Answer 30

Turning off tryptophan synthesis when it is abundant.

Question 31

What is an operon?

Answer 31

A cluster of genes regulated together by one promoter.

Question 32

What is negative regulation?

Answer 32

Regulation by a repressor protein that blocks transcription.

Question 33

What is positive regulation?

Answer 33

Regulation by an activator that promotes transcription.

Question 34

What is an inducible operon?

Answer 34

An operon usually OFF but activated by a molecule (e.g., lactose) because the repressor is active by default.

Question 35

What is a repressible operon?

Answer 35

An operon usually ON but repressed by a product (e.g., tryptophan) because the repressor is inactive by default, and needs a co-repressor.

Question 36

What does the lac operon do?

Answer 36

Encodes enzymes to digest lactose in E. coli.

Question 37

What molecule induces the lac operon?

Answer 37

Allolactose.

Question 38

What represses the trp operon?

Answer 38

Tryptophan, acting as a co-repressor.

Question 39

What is the role of CAP-cAMP in lac operon?

Answer 39

It enhances transcription when glucose is low.

Question 40

How does glucose level affect cAMP?

Answer 40

Low glucose = high cAMP = more transcription.

Question 41

What is differential gene expression?

Answer 41

The selective expression of genes in different cell types.

Question 42

Do muscle and nerve cells have the same DNA?

Answer 42

Yes, but they express different genes.

Question 43

What controls tissue-specific gene expression?

Answer 43

Enhancers, silencers, and transcription factors.

Question 44

What do enhancers do?

Answer 44

They increase transcription from a distance.

Question 45

What do silencers do?

Answer 45

They decrease or prevent transcription.

Question 46

How is gene expression regulated during development?

Answer 46

Through signaling pathways and gradients of regulatory proteins.

Question 47

What are morphogens?

Answer 47

Signaling molecules that guide tissue development.

Question 48

What is a proteome?

Answer 48

The full set of proteins expressed by a cell.

Question 49

What role does gene regulation play in organ formation?

Answer 49

It ensures the right genes are active to build each structure.

Question 50

Can the same gene be used in different tissues?

Answer 50

Yes, depending on which enhancers are active.

Question 51

What are homeotic genes?

Answer 51

Genes that regulate the development of anatomical structures.

Question 52

In what organisms are Hox genes found?

Answer 52

In nearly all animals, from fruit flies to humans.

Question 53

What happens if a Hox gene is mutated?

Answer 53

Body parts can develop in the wrong location.

Question 54

What does pleiotropy mean?

Answer 54

One gene affects multiple traits.

Question 55

Are homeotic genes pleiotropic?

Answer 55

Yes, because they influence many developmental pathways.

Question 56

Give an example of a pleiotropic gene in humans.

Answer 56

The gene responsible for Marfan syndrome affects connective tissue, eyes, and the heart.

Question 57

What kind of proteins do homeotic genes encode?

Answer 57

Transcription factors.

Question 58

Why are homeotic genes important for evolution?

Answer 58

Small changes in them can lead to major changes in body plans.

Question 59

What opens chromatin for transcription?

Answer 59

Histone acetylation.

Question 60

What proteins assist RNA polymerase binding?

Answer 60

Transcription factors.

Question 61

What is alternative splicing?

Answer 61

Different ways of joining exons to produce varied proteins.

Question 62

How is mRNA lifespan regulated?

Answer 62

By sequences in the 3’ UTR and regulatory RNAs.

Question 63

What are microRNAs?

Answer 63

Small RNAs that block or degrade mRNA.

Question 64

What is the role of ubiquitin?

Answer 64

It tags proteins for degradation.

Question 65

What regulates translation?

Answer 65

RNA-binding proteins and regulatory RNAs.

Question 66

What is chromatin remodeling?

Answer 66

Structural changes to chromatin that allow or block transcription.

Question 67

What are epigenetic modifications?

Answer 67

Heritable changes like DNA methylation and histone acetylation that affect gene expression without altering DNA.

Question 68

How does DNA methylation affect gene expression?

Answer 68

It typically silences genes by preventing transcription.

Question 69

What is epistasis?

Answer 69

A genetic interaction where one gene modifies the effect of another gene.

Question 70

Why is multilayered regulation important?

Answer 70

It allows fine-tuned, reversible, and cell-specific gene control.