W9

Question 1

What is the first level of control for gene expression?

Answer 1

At the chromosome. The coiled state of the the chromatin can inhibit physical access of the proteins necessary for transcription, therefor regulating whether a gene is expressed

Question 2

Define chromatin

Answer 2

A complex of DNA, RNA and proteins that gives chromosomes their structure

Question 3

What is chromatin remodeling?

Answer 3

The process in which nucleosomes are re positioned to expose different stretches of DNA to the nuclear environment

Question 4

Ways in which chromatin remodeling can occur?

Answer 4

• Chemical modification of the histones

- Chemical modification of certain bases in the DNA

Question 5

Explain the chemical modifications of histones as a way of chromatin remodeling

Answer 5

Individual amino acids in histone tails can be modified by the addition (or later removal) of different chemical groups (methyl or acetyl groups). The pattern of modifications of the histone tail constitutes a histone code that affects chromatin structure.

Question 6

Explain the chemical modification of certain bases in the DNA as a way of chromatin remodeling

Answer 6

The most common is the addition of a methyl group to a cytosine base.DNA methylation recruits proteins that affect changes in chromatin structure, histone modification and nucleosome positioning that restrict access of transcription factors to gene promoters

Question 7

Where does the methylation of cytosine bases usually occur?

Answer 7

In CpG islands, which are clusters of adjacent GC nucleotides located in or near the promoter of the gene

Question 8

Define epigenetic

Answer 8

Descries the effect on gene description due to differences in DNA packaging, such as modifications in histones, or chromatin structures

Question 9

True or false, epigenetic modifications can be inherited?

Answer 9

True. If they are present in sperm or eggs, they can transported from parents to offspring.

Question 10

What is an example of an epigenetic form of gene regulation?

Answer 10

The manner in which mammals equalize the expression of X linked genes in XX females and XY males.

Question 11

What is the relationship between gene dosage and gene expression?

Answer 11

The direct relationship means that as the number of copies of genes increases so does the expression of that gene because each copy of the gene is regulated independently

Question 12

What is dosage compensation?

Answer 12

The differential regulation of X chromosomal genes in both females and males

Question 13

What is X-Inactivation?

Answer 13

The process in mammals in which dosage compensation occurs through the inactivation of one X chromosome in each cell in females

Question 14

What is the XIST gene?

Answer 14

X-inactivation specific transcript. A gene found in the XIC

Question 15

What is the XIC (X inactivation center)

Answer 15

A small region on the X chromosome

Question 16

What are the steps in X inactivation

Answer 16

1. The Xist gene is transcribed and spliced, and Xist non-coding RNA binds with the Xic.
2. Transcription of Xist continues and the X chromosome becomes coated in Xist RNA
3. Eventually the entire chromosome becomes coated in Xist RNA
4. Presence of Xist RNA triggers DNA methylation and other changes associated with transcriptional activity.

Question 17

What is transcriptional regulation?

Answer 17

The mechanism that collectively regulates whether or not transcription occurs

Question 18

What does transitional regulation in eukaryotic cells require ?

Answer 18

The coordinated action of many proteins that interact with one another and the DNA sequences near the gene

Question 19

What are enhancers?

Answer 19

DNA sequenced that Regulatory transcription factors bind to that stimulate transcription.

Question 20

What are silencers?

Answer 20

DNA sequences that regulatory transcriptions bind to that repress transcriptions

Question 21

True or false a typical gene may be regulated by multiple enhancers and silencers of different types, each with one or more regulatory transcription factors that can bind with it?

Answer 21

True

Question 22

Define combination control

Answer 22

Regulation of gene transcription by means of multiple transcription factors acting together

Question 23

How does RNA processing contribute to gene regulation?

Answer 23

RNA splicing provides an opportunity for regulating gene expression because the same primary transcript can be spliced in different ways to yield different proteins in a process known as alternative splicing.

Question 24

Why does alternative splicing occur?

Answer 24

Because what the spliceosome recognizes as an exon in some primary transcripts, it recognizes as an intron in others.

Question 25

What is another way RNA can affect gene expression?

Answer 25

some RNA molecules can become a substrate for enzymes that modify particular bases in RNA, therefor changing its sequence and what i codes for