Ch. 11

Question 1

Epigenetic Modifications

Answer 1

Heritable chemical modifications to DNA and its associated proteins that alter gene expression, without changing the nucleotide sequence

is reversible

includes DNA methylation, histone modifications, miRNA-mediated gene silencing

Question 2

What does gene structure include?

Answer 2

5’ enhancer- promoter (regulatory region)- TSS - gene body (contains exons, introns, and regulatory sequences) - TTS 3’

TSS: transcription start site
TTS: transcription termination site

Question 3

Gene regulatory region

Answer 3

segment of DNA capable of increasing or decreasing expression of specific genes (enhancers & promoters)

Question 4

Promoter

Answer 4

region of DNA that initiates transcription of particular gene

Question 5

TATA Box

Answer 5

signature sequence at promoters

consensus sequence: 5’-TATA(A/T)A(A/T)-3’

Question 6

Enhancer

Answer 6

short region of DNA that can be bound by proteins (transcription factors) to increase transcription likelihood of gene

Question 7

Histone modification

Answer 7

expose DNA when and where it is to be transcribed and shield it when it is to be silenced

Question 8

How does acetylated histones allow transcription to begin?

Answer 8

acetyl binding can subtly shift histone interactions to ease transcription

on lysine residues (ONLY gene transcription activation)

Question 9

MicroRNA

Answer 9

prevents translation when microRNA binds to target mRNA
ex. cancer treatment & concussion markers

Question 10

Maximizing Genetic Info

Answer 10

proteins > genes
- chromatin remodeling b4 transcription
- alternative splicing (circular RNA) after transcription
- use of introns
- protein modification
- cutting of a precursor protein into 2 proteins

Question 11

Maximizing Genetic Info

Alternative splicing

Answer 11

alternative splicing of exons and introns may encode several isoforms (possible protein products) of protein

create different transcripts

Question 12

Maximizing Genetic Info

An intron encoding one isoform

Answer 12

is an exon in another

Question 13

Maximizing Genetic Info

An intron on one DNA strand

Answer 13

is an exon on the other

Question 14

Maximizing Genetic Info

Post-Translational Modifications

Answer 14

addition of sugars + lipids to create glycoproteins and lipoproteins

Question 15

All genes are expressed continuously at the same levels.

Answer 15

False; Different genes vary in the timing and the level of gene expression.

Question 16

Epigenetic changes alter the base sequence of a DNA molecule.

Answer 16

False

Question 17

Epigenetic changes affect molecules that associate with DNA

Answer 17

True; such as proteins and RNA molecules.

Question 18

When a cell divides, epigenetic changes are transmitted to its daughter cells.

Answer 18

True; Epigenetic modifications are passed to daughter cells, but are generally not passed on to offspring.

Question 19

Epigenetic changes result in modification of gene expression.

Answer 19

True

Question 20

MicroRNAs are typically about ___ bases long.

Answer 20

21

Question 21

MicroRNAs regulate gene expression at the level of

Answer 21

translation

Question 22

MicroRNAs are an example of ___ RNAs.

Answer 22

noncoding

Question 23

The human genome contains approximately ___ distinct sequences of microRNAs.

Answer 23

2500

Question 24

MicroRNAs regulate approximately ___ of the protein-encoding genes in the human genome.

Answer 24

1/3

Question 25

___ explains how one gene can specify multiple mRNAs.

Answer 25

alternative splicing

Question 26

You are studying two proteins that play a role in cell wall formation in plants. You are interested in determining the genomic location of the genes that encode these proteins. You are surprised to find that the two proteins appear to be encoded by the same gene, and that the sequence encoding one appears immediately before the other one, in frame, although they do not have overlapping sequence.

Which mechanism for maximizing genetic information do you suspect is at play here?

Answer 26

Precursor protein is cut to yield two proteins; Because these proteins appear to be encoded by the same gene, we can rule out that the proteins are encoded on opposite strands. Because there is no overlap in the sequence of the proteins, it seems unlikely that alternative splicing is at play here. In alternative splicing at least the first exon of the gene would be in common. Given that the two proteins are encoded by one gene and are in frame with one another, the most likely explanation is that a precursor protein is cut to yield two proteins.

Question 27

The collection of all mRNAs in a cell is called a(n)

Answer 27

transcriptome