PCB Exam 4

What term explains the variation of gene expression that is not related to the variation of the DNA, is transmissible and is reversible?

epigenetics

By looking at many different proteins and the genes that encode them in a variety of eukaryotic organisms, scientists have determined that a protein domain tends to be encoded by one or a few (usually adjacent) _________

exons

The genetic material inherited in an organelle, such as a mitochondria or a chloroplast, exhibits ____ inheritance.

extranuclear, cytoplasmic

In DNA _____, an individual is characterized based on the repetitive sequences in his or her genome.

fingerprinting or profiling

A large, healthy, natural population typically exhibits a ____ level of SNPs.

high

Even though offspring receive two alleles, one maternal and one paternal, during genomic imprinting only one allele is expressed. What is this phenomenon called?

monoallelic expression

Deme

one of several local populations that make up a large population

Splicing of pre-mRNA, altering mRNA stability and controlling the rate of translation are all examples of ____

posttranscriptional gene regulation

mutation rate

probability that a gene will be altered as a result of a mutation

Mutations occur when the DNA of an organism changes. Changes often happen in gene ______, but may also involve the structure and number of chromosomes.

sequences

AU-rich elements (AREs) are typically found in the 3' UTR of mRNAs with ___

short half-lives

Which type of RNA might originate in a virus?

siRNA

SNP

single-nucleotide polymorphism

Binding of IRP to the 3' UTR ____

stabilizes the transferrin receptor mRNA

Epigenetics

variation of gene expression that is not related to the variation of the DNA

What are the two ways that miRNA and siRNA regulate gene expression?

-by inducing the binding of RISC which may direct degradation of the mRNA -by inducing the binding of RISC which may inhibit translation

Select the following events that occur following the binding of Xist RNAs to the Xi. 1. recruitment of protein complexes to Xi 2. histone variant macroH2A is incorporated into the nucleosomes along the Xi 3. recruitment of DNa methyltransferases to Xi 4. covalent modification of specific sites in histone tails 5. activation of Tsix and subsequent inhibition of Xist

1, 2, 3, 4

Which of the following are true? 1. variations of gene expression are unrelated to DNA variants 2. epigenetic changes may be transmitted to offspring 3. variations of gene expression result from mutations 4. epigenetic changes are transmissible from cell to cell 5. variations are reversible from one generation to the next

1, 2, 4, 5

probability of fixation

= 1/(2n)

T/F regarding X inactivation: Pluripotency factors inhibit the expression of Tsix

False

T/F: Epigenetic changes due to PcG complexes are transient and only present during development

False

T/F: Gene regulation may be related to epigenetic events such as the binding of transcription factors to certain genes, which induce permanent mutations in the DNA.

False

T/F: The epigenetic modifications that lead to silencing of an X chromosome are lost and reestablished following each cell division.

False

Which two complexes are the key regulators of epigenetic changes that occur during development?

Polycomb group (PcG) Trithorax Group

How do noncoding RNAs regulate gene expression in plants?

RNA-dependent DNA methylation forms bridges between specific sites in DNA and protein, altering the chromatin structure

T/F regarding X inactivation: Expression of Tsix from both X chromosomes inhibits the expression of Xist

True

T/F regarding X inactivation: When the Xist gene is inactive the X chromosome is active

True

The term genetic ____ refers to any random change in the frequencies of alleles in a population.

drift

X chromosome inactivation is an epigenetic event that occurs during ___

embryogenesis

The inactivation of the X chromosome is a(n) ____

epigenetic event

Select all of the posttranscriptional mechanisms that regulate gene expression. -controlling mRNA stability -regulation of mRNA translation -DNA methylation -splicing of pre-mRNA -histone modification

-controlling mRNA stability -regulation of mRNA translation -splicing of pre-mRNA

The lgf2 gene will be expressed if

-the lgf2 gene can be stimulated by the enhancer -the ICR and DMR are methylated

Place in correct sequence the events of X chromosome inactivation: 1. X chromosomes pair briefly beginning at the Tsix gene 2. Xist RNA recruits proteins that epigenetically modify specific sites within the Xi 3. The Tsix gene of the chromosome without pluripotency factors and CTCFs is inhibited; the inactivated chromosome is coated with Xist RNA 4. a symmetry break shifts all pluripotency factors and CTCFs to a single chromosome

1 -> 4 -> 3 -> 2

List the steps of how a gene may be targeted for silencing by PcG and TrxG complexes.

1. PRE-binding protein binds to PRE and recruits PRC2 2. PRC2 catalyzes trimethylation of lysine 27 in histone H3 3. Transcription is inhibited by preventing binding of RNA polymerase and PRC1 may be recruited to inhibit transcription in various ways

List the steps of RNA interference

1. Pre-miRNAs and pre-siRNAs are cleaved by dicer 2. Double-stranded RNA associates with proteins to form the RNA-induced silencing complex (RISC) 3. One strand of the dsRNA is degraded 4. Single-stranded miRNA or siRNA allows RISC to bind to complementary mRNA sequences 5. RISC may inhibit translation or direct degradation of the mRNA

What are the conditions of Hardy Weinberg Equilibrium?

1. organisms are diploid and sexually reproducing 2. large population 3. random mating 4. no natural selection 5. no mutations or migration

How does iron regulatory protein exert its effect on ferritin mRNA?

IRP binds to IRE in the 5' UTR, and thus inhibits ferritin translation

In mammals, females (XX) and males (XY) express genes on the X chromosome at the same levels because of ___

X chromosome inactivation

Which two areas of the X chromosome play a key role in X inactivation?

Xist Tsix

What happens when pluripotency factors stimulate the expression of Tsix?

Xist is inhibited

Repetitive sequences are composed of a certain sequence that is repeated many times throughout the genome of a species. What is the typical size of the sequence that is being repeated?

a few to a few thousand base pairs

What is the result of exon shuffling?

a novel gene that may encode a protein with a novel combination of functional domains

Which type of exon may or may not be present in mature mRNA? constitutive or alternative

alternative exon

Epigenetic changes due to the actions of PcG complexes ____

are maintained in subsequent cell divisions

From the list below choose features of populations that can change from one generation to the next. a. species diversity b. geographic location c. genetic composition d. size

b. geographic location c. genetic composition d. size

Select all that are involved in the regulation of alternative splicing. a. CpG islands b. splicing factors c. histone modification d. SR proteins

b. splicing factors d. SR proteins

The _____ effect is observed when a population's size is dramatically reduced due to natural events or human destruction of habitat.

bottleneck

Most mutations are

deleterious or neutral

The binding of the polyA-binding protein to the polyA tail ____

enhances RNA stability

DNA methylation, chromatin remodeling, covalent histone modification and localization of histone variants are all examples of ____

epigenetics

The ___ ____ of a population consists of all of the alleles of every gene in all of the individuals of that population.

gene pool

______ occurs when two genetically related individuals mate.

inbreeding

MicroRNAs influence gene expression by

inhibiting translation of mRNA

proteins called ___ ____ are involved in the regulation of alternative splicing.

SR proteins

T/F regarding X inactivation: Xist RNA is inhibited by RNA interference

True

The term for the mechanism that enables two or more different polypeptide sequences to be produced from a single gene is _____

alternative splicing

In mice, slightly different forms of alpha-tropomyosin may be produced from the same gene depending on cell type. What accounts for this?

alternative splicing of the alpha-tropomyosin gene transcript

For random mating to occur, individuals must choose their mates irrespective of their genotype/phenotype. When this condition is violated, non-random mating is occurring, also known as _____ mating.

assortative

The methylation of hemimethylated sites is called ____

maintenance methylation

Which phenomena is responsible for introducing new genetic variation in a population?

mutation

The transfer of genetic material from one species to another is called

horizontal gene transfer

Order the events that a population undergoing inbreeding depression might experience. a. the population size decreases even more, possibly leading to extinction b. the mean fitness of the population decreases, which leads to a decrease in its reproductive success c. the population experiences high level of inbreeding due to its small size d. population size is dramatically reduced by habitat destruction

d -> c -> b -> a

What accounts for the molecular mechanism of imprinting of the lgf2 gene?

differential methylation during oogenesis and spermatogenesis