Chapter 15

Question 1

Operator

Answer 1

The “on-off switch! Of a segment of DNA

• positioned within the promoter
• controls the access of RNA polymerase to the genes

Question 2

Operon

Answer 2

A unit of genetic function found in bacteria and phases consisting of a promoter, an operator and a coordinated regulated cluster of genes.

Question 3

Represser

Answer 3

A protein that inhibits gene transcription.

In prok. Repressors bind to the DNA or near the promoter.
In euk. Repressors May bind to control elements within enhancers, to activators or other proteins to block activators from binding to DNA.

Blocks attachment of RNA polymerase

Question 4

Regulatory gene

Answer 4

A gene that codes for a protein, such as a repressors, that’s controls the transcription of another gene or group of genes.

Question 5

Some facts about repressors

Answer 5

Reversible
Operator alternates between repressive bound and non-repressors (bound is longer)
Repressors are allosteric (two alternative shapes)
Produced continuously with own promoter

Question 6

Co repressors

Answer 6

A small molecule that binds to a bacterial repressors protein and changes the proteins shape, allowing it to bind to the operator and switch operon off

Question 7

Inducer

Answer 7

A specific small molecule that binds to a bacterial repressors protein and changes the repressors shale so that I can not bind to an operator, thus switching operon on

Question 8

Cyclic AMP

Answer 8

A ring-shaped molecule made from ATP that is a common intracellular signalling molecule in euk, cells, it is also a regulator of some bacterial operons.

Question 9

Activator

Answer 9

A protein that binds to DNA and stimulates gene transcription. In prok. Activators bind in or near the promoter. In euk. Activators bind to control elements in enhancers.

Increases RNA POL affinity for the promoter

Question 10

A typical human cell might express how much of its protein coding genes at any time?

Answer 10

20%

Question 11

Differential gene expression

Answer 11

The expression of different sets of genes by cells with the same genome.

Question 12

Histone acetylation

Answer 12

The attachment of an acetyl group to certain amino acids of histone proteins.

Question 13

DNA methylation

Answer 13

The presence of methyl groups on the DNA bases (usually cytosine) or adding methyl groups to bases.

Question 14

Epigenetic inheritance

Answer 14

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence of a genome.

Can be altered, DNA methylation erased and reestablished on gametes

Methylation patterns inherited by parents

Question 15

Control elements

Answer 15

A segment of non coding DNA that helps regulate transcription of a gene by serving as a binding site for a regulatory proteins such as transcription factor. Multiple control elements are on euk. Enhancers.

Can be anywhere, even in introns (distal enhancer)

Question 16

Enhancers

Answer 16

A segment of euk. DNA. Containing multiple control elements, usually located far from the gene who transcription it regulates.

Question 17

Specific transcription factors can function as repressors by

Answer 17

Binding directly to control elements to block activator

Interfere with activator itself

Question 18

Alternative RNA splicing

Answer 18

A type of euk. Gene regulation at the RNA- processing level in which different mRNA molecules are produced from the same pre-mRNA depending on which RNA segments are treated as exons and which as introns.

Question 19

MicroRNA (miRNA)

Answer 19

Small single stranded RNA, can degrade or prevent translation of an mRNA wi5 a complementary sequence

Question 20

Small interfering RNA (siRNA)

Answer 20

Degrade or prevent translation of an mRNA with complementary sequence. Can also block transcription by promoting chromatin mod.

Block gene expression
Condensing of DNA

Question 21

Reverse Transcriptase-Polymerase chain reaction

Answer 21

A technique for determining expression of a particular gene. It uses reverse transcriptase and DNA pol. To synthesize cDNA from the mRNA in a sample and then subjects the cDNA to PCR amplification.

mRNA —DNA—double stand—copied DNA —PCR to amplify

Question 22

DNA microarray assays

Answer 22

A method to detect and measure the expression of thousands of genes at one time. Tiny amounts of a large number of single stranded DNA fragments are fixed to glass slide and tested for hybridization with samples of labelled cDNA.

Question 23

Negative gene regulation

Answer 23

REPRESSORS!
And inducible operon

Repressor+co repressor= off

Determines if transcription is on or off

Question 24

Positive gene regulation

Answer 24

ACTIVATORS

Determines rate at which transcription happens

Question 25

Duel control

Answer 25

Genes with both positive and negative control

Question 26

Co ordinated control

Answer 26

Interaction of multiple gene products is needed for appropriate control of transcription.

Ex: glucose is down= active CRP

Question 27

Regulation of chromatin structure includes

Answer 27

• location of nucleosome
• degree of condensation (eu or hetero chromatin)
• chemical mod of DNA and histones

Question 28

Methylation causes

While

Acetylation causes

Answer 28

Increases chromatin condensation= decrease transcription

Decreases condensation= increase transcription

Question 29

Genes that are unexpressed and Barr bodies have high degree of what?

Answer 29

Methylation

Question 30

General vs specific transcription factors

Answer 30

Low level rates of transcription on their own

Bind to control elements and act as either an activator or repressor

Question 31

Piwi-associated RNA

Answer 31

Induce formation of heterochromatin to block expression

Used in reestablishing methylation patterns in gametes