chapter 13

Question 1

What is genetics?

Answer 1

The study of inheritance

Genetics focuses on how traits are passed from parents to offspring through genes.

Question 2

What is epigenetics?

Answer 2

The study of traits above inheritance

Epigenetics examines how environmental factors can influence gene expression without altering the DNA sequence.

Question 3

True or False: Lamarckism suggests that traits acquired during an organism’s lifetime can be passed onto offspring.

Answer 3

True

Lamarckism is often contrasted with Darwinian evolution, which emphasizes natural selection.

Question 4

How do Lamarckism and epigenetics differ?

Answer 4

They differ in their mechanisms and scientific validity

While both suggest that acquired traits can be inherited, epigenetics is supported by more contemporary scientific research.

Question 5

Fill in the blank: _______ involves the idea that traits acquired during an organism’s lifetime can be passed onto offspring.

Answer 5

Lamarckism

This concept has historical significance in the study of evolutionary biology.

Question 6

What gene modification leads to yellow coat color and extreme obesity in mice?

Answer 6

Modified agouti gene

The modified agouti gene results in a yellow coat color and obesity phenotype in mice.

Question 7

What effect does a certain diet during gestation have on female mice offspring with a modified agouti gene?

Answer 7

Leads to wild-type offspring

The diet rich in methyl factors silences the modified agouti gene, resulting in wild-type offspring.

Question 8

What is the key characteristic of the modified diet that affects the offspring of female mice?

Answer 8

Rich in methyl factors

Methyl factors contribute to increased methylation and gene silencing.

Question 9

What long-term health risks are associated with Dutch citizens who survived the World War 2 famine?

Answer 9

Increased risk of heart disease, diabetes, and obesity

Studies show that those who experienced famine have higher rates of these conditions.

Question 10

How does the methylation of the IGF2 gene differ in citizens born during the famine compared to those not born during it?

Answer 10

Less methylated in citizens born during the famine

This suggests a potential link between famine exposure and altered gene expression.

Question 11

What is the methylation status of IGF2 in siblings born after the famine?

Answer 11

Higher methylation of IGF2

Siblings born after the famine exhibit a different methylation pattern compared to those born during it.

Question 12

What are the five features of epigenetic modifications?

Answer 12

• Alter chromatin structure
• Transmissible during cell division
• Reversible
• Associated with gene transcription
• Do not alter DNA sequence

Epigenetic modifications involve changes to chromatin that affect gene expression without changing the underlying DNA sequence.

Question 13

True or False: Epigenetic modifications can lead to mutations in the DNA sequence.

Answer 13

False

Epigenetic modifications do not cause mutations; they remodel chromatin structure.

Question 14

What is euchromatin?

Answer 14

Loosely compacted genomic regions that are more transcriptionally active

Euchromatin allows for easier access to the DNA for transcriptional machinery.

Question 15

What is heterochromatin?

Answer 15

Densely compacted chromatin that is less transcriptionally active

Heterochromatin is typically associated with gene silencing.

Question 16

What is constitutive heterochromatin?

Answer 16

Genomic regions that are always heterochromatin

These regions are usually located near centromeres and telomeres.

Question 17

What is facultative heterochromatin?

Answer 17

Genomic regions that can switch between euchromatin and heterochromatin

This switching can be influenced by developmental cues or environmental factors.

Question 18

What are position effects?

Answer 18

Genomic regions can be transcriptional hotspots or coldspots, varying in genomic effects

Position effects are important for understanding gene expression regulation.

Question 19

What is a nucleosome?

Answer 19

A structure consisting of DNA wound around 8 histone proteins (H2A-H2B dimer + H3-H4 tetramer)

Nucleosomes are the fundamental units of chromatin.

Question 20

How do histone proteins affect DNA?

Answer 20

Histone proteins enable DNA to coil around them

This coiling results in the formation of chromatin, which impacts gene accessibility.

Question 21

What is the relationship between nucleosomes and chromatin structure?

Answer 21

Nucleosomes condense DNA into chromatin

The level of compaction affects the transcriptional activity of the associated genes.

Question 22

Fill in the blank: Euchromatin is _______ compacted compared to heterochromatin.

Answer 22

less

Question 23

True or False: Heterochromatin is more transcriptionally active than euchromatin.

Answer 23

False

Question 24

What is the effect of acetylation on histone/DNA interaction?

Answer 24

It relaxes histone/DNA interaction by neutralizing positively charged histones

Question 25

What are Histone Acetyltransferases (HATs) responsible for?

Answer 25

They add acetyl groups to histones, leading to euchromatin

Question 26

What is the role of Histone Deacetylases (HDACs)?

Answer 26

They remove acetyl groups from histones, leading to heterochromatin

Question 27

How does methylation typically affect chromatin structure?

Answer 27

It is typically associated with heterochromatin, but can also lead to euchromatin

Question 28

What do Histone Methyltransferases (HMTs) do?

Answer 28

They add methyl groups to histones

Question 29

What is the function of Histone Demethylases (HDMTs)?

Answer 29

They remove methyl groups from histones

Question 30

What is Position Effect Variegation (PEV)?

Answer 30

It occurs when heterochromatic areas spread to euchromatin, silencing transcription of genes

Question 31

What organism was used to first discover Position Effect Variegation?

Answer 31

Drosophila

Question 32

What genetic event was involved in the discovery of PEV?

Answer 32

An inversion on the X chromosome placed the white gene near the centromere

Question 33

What phenotype is associated with the wild-type allele for the white gene in Drosophila?

Answer 33

Red eyes

Question 34

What was the result of the inversion that led to PEV in Drosophila?

Answer 34

It created a mosaic where some cells in the fly compound eye were wild-type and others mutated

Question 35

True or False: The flies affected by PEV were genotypically wild-type.

Answer 35

True

Question 36

What do E(var) mutations stand for?

Answer 36

Enhancers of position effect variegation

Question 37

What is the effect of E(var) mutations on mutant phenotypes?

Answer 37

They enhance mutant phenotypes by encouraging spread of heterochromatic

Question 38

What do Sur(var) mutations stand for?

Answer 38

Suppressors of position effect variegation

Question 39

What is the effect of Sur(var) mutations on heterochromatic spread?

Answer 39

They restrict heterochromatic spread

Question 40

What phenotype do Sur(var) mutations encourage?

Answer 40

Wild-type phenotype

Question 41

Fill in the blank: E(var) mutations lean towards _______.

Answer 41

mutant

Question 42

Fill in the blank: Sur(var) mutations lean towards _______.

Answer 42

wild-type

Question 43

What is variegated eye expression in Drosophila similar to?

Answer 43

X-inactivation

Question 44

In which organisms does X-inactivation occur?

Answer 44

Female placental mammals

Question 45

When does X-inactivation occur during development?

Answer 45

Early in embryonic development

Question 46

How does a given cell decide which X chromosome to inactivate?

Answer 46

Random basis

Question 47

What does X-inactivation result in for female cells?

Answer 47

Mosaics of two cell types

Question 48

What are the two cell types resulting from X-inactivation?

Answer 48

One expresses the maternal X chromosome, the other expresses the paternal X chromosome

Question 49

What is another term for X-inactivation?

Answer 49

Epigenetic phenomenon

Question 50

What is long noncoding RNA (Inc RNA)?

Answer 50

Long RNA that lack open reading frames

Question 51

What role does long noncoding RNA play in cells?

Answer 51

Gene regulation in eukaryotic cells

Question 52

In which type of cells has Inc RNA been studied?

Answer 52

Stem cells of mice embryos

Question 53

What is the proposed function of Inc RNA?

Answer 53

Act as scaffolds linking to regulatory proteins, affecting chromatin structure

Question 54

What is an example of Inc RNA involved in X-inactivation?

Answer 54

X-inactivation-specific transcript (Xist)

Question 55

Where is the Xist gene located?

Answer 55

In the X-inactivation center (XIC) on the X chromosome

Question 56

What is the activity status of Xist in the heterochromatic X chromosome?

Answer 56

Active

Question 57

What is the activity status of Xist in the euchromatic X chromosome?

Answer 57

Inactive

Question 58

What does Xist RNA do during the inactivation process?

Answer 58

Coats X chromosome + spreads, causing silencing and deacetylation

Question 59

What is the result of Xist RNA spreading along the chromosome?

Answer 59

Inactivation of almost all genes, silencing the chromosome

Question 60

What is genomic imprinting?

Answer 60

An example of an epigenetic phenomenon that is heritable.

Question 61

How does the expression of certain genes in offspring depend on the parent?

Answer 61

It depends on which parent passed the gene on.

Question 62

What occurs during maternal imprinting?

Answer 62

The allele passed on by the mother is inactivated; offspring express the allele from the father.

Question 63

What occurs during paternal imprinting?

Answer 63

The allele passed on by the father is inactivated; offspring express the allele from the mother.

Question 64

Can genomic imprinting be x-linked or autosomal?

Answer 64

Yes.

Question 65

What happens to imprinting when offspring produce their own gametes?

Answer 65

The previous imprinting is erased to ensure their gametes are imprinted one way.

Question 66

In maternal imprinting, which gender switches alleles off when passing them on?

Answer 66

Only females.

Question 67

What is the outcome of maternal imprinting in the context of a dominant allele causing a disease?

Answer 67

Children may not be affected.

Question 68

What chromosomes are IGF2 and H19 located on?

Answer 68

Both are located on chromosome 11.

Question 69

Which gene is only expressed on the maternally inherited chromosome?

Answer 69

H19.

Question 70

Which gene is only expressed on the paternally inherited chromosome?

Answer 70

IGF2 (insulin growth factor 2).

Question 71

What syndrome occurs when both chromosomes display maternal expression patterns?

Answer 71

Russell-Silver Syndrome.

Question 72

What characterizes infants with Russell-Silver Syndrome?

Answer 72

They tend to be born underweight.

Question 73

What syndrome results when both chromosomes display paternal expression patterns?

Answer 73

Beckwith-Wiedemann syndrome.

Question 74

What condition is associated with Beckwith-Wiedemann syndrome?

Answer 74

Involves overgrowth of tissue.