CHAPTER 16

Question 1

Epigenetics

Answer 1

the study of mechanisms that lead to changes in gene expression that:
-can be passed from cell to cell
-reversible
-do not involve a change in the sequence of DNA

Question 2

Epigenetic inheritance

Answer 2

involves epigenetic changes that are passed from parent to offspring, like X-chromosome inactivation and genomic imprinting

Question 3

types of molecular change underlie epigenetic regulation

Answer 3

• DNA methylation
• Chromatin remodeling
• Covalent histone modification
• Localization of histone variants
• Feedback loops

Question 4

Cis-epigenetic changes; where is it maintained and how many genes does it impact?

Answer 4

maintained only at a specific site, may affect only one copy of a gene but not
the other copy

Question 5

Trans-epigenetic changes; where is it maintained and how many genes does it impact?

Answer 5

maintained by diffusible factors, such as transcription factors, affect both copies of a gene

Question 6

General categories of epigenetic gene regulation

Answer 6

programmed developmental change and environmental agents

Question 7

programmed developmental change

Answer 7

• Genomic imprinting (silencing of a paternal or maternal allele)
• X chromosome inactivation (Barr body)
• Cell differentiation (specialization

Question 8

environmental agents

Answer 8

• Temperature (cold temperatures required for future growth)
• Diet (royal jelly and queen bees)
• Toxins (tobacco smoke alters DNA methylation)

Question 9

Chromatin

Answer 9

Chromatin is the complex of DNA, proteins, and non-coding RNAs that package chromosomal DNA in eukaryotic cells.

Question 10

Chromatin’s Basic Unit

Answer 10

It is the nucleosome, consisting of DNA wrapped around an octamer of histone proteins.

Question 11

Two types of chromatin

Answer 11

1. Euchromatin
2. Heterochromatin

Question 12

Euchromatin

Answer 12

-non-compacted
-transcriptionally active

Question 13

Heterochromatin

Answer 13

-highly compacted
-gene expression inhibited

Question 14

What is the role of heterochromatin in gene regulation?

Answer 14

Heterochromatin silences gene expression, prevents transposable element movement, and inhibits viral proliferation.

Question 15

What is the difference between constitutive and facultative heterochromatin?

Answer 15

-Constitutive heterochromatin is permanently heterochromatic at the same location in all cell types
-Facultative heterochromatin varies among cell types and developmental stages

Question 16

What are the characteristics of constitutive heterochromatin?

Answer 16

-Stable formation
-high condensation
-found near centromeres/telomeres
-consists of repeat sequences
-highly methylated
-specific histone modifications

Question 17

What are the characteristics of facultative heterochromatin?

Answer 17

-Reversible formation
-located at various sites
-involves LINE-type repeats
-methylation at CpG islands
-shares some histone modifications with constitutive heterochromatin.

Question 18

What molecular events lead to heterochromatin formation?

Answer 18

-Histone post-translational modifications (PTMs)
-Protein binding to nucleosomes,
-Chromatin remodeling
-DNA methylation
-Binding of non-coding RNAs

Question 19

How is heterochromatin maintained during cell division?

Answer 19

Epigenetic marks like DNA methylation and histone modifications are preserved in daughter cells, ensuring the inheritance of heterochromatin patterns.

Question 20

Genomic Imprinting

Answer 20

A form of gene regulation where only one allele of a gene is expressed, depending on the parent from whom it is inherited.

Question 21

X-chromosome inactivation

Answer 21

A process during early embryonic development in female mammals where one X chromosome is randomly inactivated to achieve dosage compensation.

Question 22

What role does the Trithorax group (TrxG) protein play in development?

Answer 22

TrxG is involved in gene activation
-regulating epigenetic changes during cell differentiation

Question 23

What role does the Polycomb group (PcG) protein play in development?

Answer 23

PcG is involved in gene repression
-regulating epigenetic changes during cell differentiation

Question 24

How do environmental agents influence epigenetics?

Answer 24

Dietary factors and toxins can cause epigenetic changes, as seen in examples like the Agouti gene in mice and the development of honeybee queens due to royal jelly.