Lecture 21 Chapter 21

Question 1

epigenesis

Answer 1

how an embryo develops

Question 2

genetics

Answer 2

the study of genes and heredity

Question 3

epigenetics

Answer 3

○ Heritable modification that does not involve changes in DNA

Question 4

thrifty hypothesis

Answer 4

assumes that when environmental conditions are poor for the parent, they are likely to also be poor for the offspring. Therefore, when the parent experiences food shortage, biochemical modifcations allow pre-adaptations to produce offspring that are metabolically thrifty, eating as much as possible, minimizing energy expenditure, and hoarding/conserving calories

Question 5

DNA methylation

Answer 5

addition of methyl groups to nucleotide bases

most common: methylation of cytosine to produce 5-methylcytosine

generally methylated cytosines are associated with gene repression

stably maintained through DNA replication

Question 6

Acetylated histones

Answer 6

generally acetylated histones are associated with gene activity

Question 7

What are some types of histone modifications?

Answer 7

• more than 100 different posttranslational modifications of histone proteins

modifications include addition of:

• phosphates
• methyl groups
• Acetyl groups
• ubiquitin

Question 8

What are some epigenetic effects by RNA molecules?

Answer 8

examples

• X inactivation by Xist
• Paramutation in corn by siRNAs

Question 9

Paramutation

Answer 9

an interaction between two alleles that leads to a heritable change in expression of one of the alleles

Question 10

Behavioral epigenetics

Answer 10

life experiences, especially early in life, have long-lasting effects on behavior

Question 11

genomic imprinting

Answer 11

the expression of an allele depends on whether it is inherited from the male or female parent

• certain genes are expressed in a parent-of-origin manner

Question 12

Uniparental disomy

Answer 12

inheriting 2 copies of a chromosome from one parent

Question 13

Epigenome

Answer 13

Overall pattern of chromatin modifications possessed by each individual organism

Question 14

detecting DNA methylation

Answer 14

• restriction endonucleases
• Bisulfate sequencing
• –treat DNA with bisulphate converts cytosine residues to uracil but leaves 5-methylcytosine residues unaffected; comparison of treated vs untreated sequences reveals the unmethylated Cs

Question 15

detecting histone modifications

Answer 15

ChIP (chromatin immuno-precipitation + next gene sequencing)
- combines chromatin immunoprecipitation with massively parallel DNA sequencing to identify the binding sites if DNA-associated proteins

methylated DNA is precipitated using an antibody that binds methylated DNA called MeDIp (methylated DNA immunoprecipitation)

Question 16

Which of the following is true of CpG Islands?

a. they are methylated near promoters of actively transcribed genes
b. they are unmethylated near promoters of actively transcribed genes
c. Acetylation of CpG islands leads to repression of transcription
d. CpG islands code for RNA molecules that activate transcription

Answer 16

b. they are unmethylated near promoters of actively transcribed genes

Question 17

Which is not a major mechanism of epigenetic change?

a. DNA methylation
b. Alteration of a DNA base sequence in a promoter
c. Histone acetylation
d. Action of RNA molecules

Answer 17

b. Alteration of a DNA base sequence in a promoter

Question 18

Which is a characteristic of paramutation?

a. one allele is able to alter another allele when both are present in a heterozygote
b. altered alleles must be passed on to future generations
c. altered alleles must be capable of altering other alleles in future generations
d. all of the above

Answer 18

d. all of the above

Question 19

What degree differences would you expect to see in the DNA base sequences and epigenetic marks of monozygotic twins?
a. similar differences in DNA base sequence and epigenetic marks
b. greater differences in DNA base sequence than epigenetic marks
c. Greater differences in epigenetic marks than DNA base sequence
d, no differences in either DNA base sequence or epigenetic marks

Answer 19

c. Greater differences in epigenetic marks than DNA base sequence

Question 20

What would be the effect of introducing into a female cell siRNAs that degrade Xist RNA?

Answer 20

No Xist RNA would be present to coat the X chromosome, and I inactivation would not occur. Both X chromosomes would remain active

Question 21

What is true of genomic imprinting?

a. the sex of the parent that transmits an allele effects the expression of the allele in the offspring
b. the sex of the offspring affects the expression of an allele inherited from one of the parents.
c. the sex of the parent affects how an allele is transmitted to the offspring
d. the sex of the offspring affects which allele is inherited from the parent

Answer 21

a. the sex of the parent that transmits an allele effects the expression of the allele in the offspring

Question 22

civilization diseases

Answer 22

chronic metabolic and degenerative disorders and diseases that are initiated and/or influenced by non-optimal epigenomic programming
- often takes place early in life

Question 23

Pathways that are altered by epigenetic reprogamming result in what?

Answer 23

disregulation of important physiological functions

Question 24

ChIP-Seq

Answer 24

chromatin immuno-precipitation + next gene sequencing

• combines chromatin immunoprecipitation with massively parallel DNA sequencing to ID the binding sites of DNA-associated proteins
• methylated DNA is precipitated using an Ab that binds methylated DNA called MeDIp (methylated DNA immunoprecipitation)

Question 25

List 3 molecular mechanisms that alter chromatin structure

Answer 25

1) changes in patterns of DNA methylation
2) chemical modification of histone proteins
3) RNA molecules that affect chromatin structure and gene expression

Question 26

What are the 4 types of histone modifications?

Answer 26

• Phosphates
• Methyl groups
• Acetyl groups
• ubiquitin

Question 27

When one of the two X chromosomes in somatic cells in mammalian females are randomly inactivate during development, what is the highly condensed structure called?

Answer 27

“Barr” body