Lecture 21 Chapter 21 Flashcards

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1
Q

epigenesis

A

how an embryo develops

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2
Q

genetics

A

the study of genes and heredity

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3
Q

epigenetics

A

○ Heritable modification that does not involve changes in DNA

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4
Q

thrifty hypothesis

A

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

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5
Q

DNA methylation

A

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

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6
Q

Acetylated histones

A

generally acetylated histones are associated with gene activity

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7
Q

What are some types of histone modifications?

A
  • more than 100 different posttranslational modifications of histone proteins

modifications include addition of:

  • phosphates
  • methyl groups
  • Acetyl groups
  • ubiquitin
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8
Q

What are some epigenetic effects by RNA molecules?

A

examples

  • X inactivation by Xist
  • Paramutation in corn by siRNAs
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9
Q

Paramutation

A

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

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10
Q

Behavioral epigenetics

A

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

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11
Q

genomic imprinting

A

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
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12
Q

Uniparental disomy

A

inheriting 2 copies of a chromosome from one parent

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13
Q

Epigenome

A

Overall pattern of chromatin modifications possessed by each individual organism

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14
Q

detecting DNA methylation

A
  • 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
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15
Q

detecting histone modifications

A

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)

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16
Q

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

A

b. they are unmethylated near promoters of actively transcribed genes

17
Q

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

A

b. Alteration of a DNA base sequence in a promoter

18
Q

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

A

d. all of the above

19
Q

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

A

c. Greater differences in epigenetic marks than DNA base sequence

20
Q

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

A

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

21
Q

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

A

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

22
Q

civilization diseases

A

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

23
Q

Pathways that are altered by epigenetic reprogamming result in what?

A

disregulation of important physiological functions

24
Q

ChIP-Seq

A

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)
25
Q

List 3 molecular mechanisms that alter chromatin structure

A

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

26
Q

What are the 4 types of histone modifications?

A
  • Phosphates
  • Methyl groups
  • Acetyl groups
  • ubiquitin
27
Q

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?

A

“Barr” body