Unit 4 lecture 2 part 1 11/9/22

Question 1

Gene expression in bacteria is controlled by a mechanism described as the __________

Answer 1

Operon model

Question 2

The regulatory “switch” is a segment of DNA called an __________ usually positioned within the __________

Answer 2

operator
promoter

Question 3

An __________ is the entire stretch of DNA that includes the operator, the promoter, and the genes that they control

Answer 3

operon

Question 4

The operon can be switched off by a __________

Answer 4

protein repressor

Question 5

The __________ prevents gene transcription by binding to the __________ and blocking __________

Answer 5

repressor
operator
RNA polymerase

Question 6

The repressor can be in an __________ or __________ form, depending on the presence of other molecules

Answer 6

active
inactive

Question 7

A __________ is a molecule that cooperates with a repressor protein to switch an operon off

Answer 7

corepressor

Question 8

When tryptophan is __________ , it binds to the trp repressor protein, which then turns the __________

Answer 8

present
operon off

Question 9

A __________ is one that is usually on; binding of a repressor to the operator shuts off transcription

Answer 9

repressible operon

Question 10

An __________ is one that is usually off; a molecule called an inducer inactivates the repressor and turns on transcription

Answer 10

inducible operon

Question 11

The __________ is an inducible operon and contains genes that code for enzymes used in the hydrolysis and metabolism of __________

Answer 11

lac operon
lactose

Question 12

A molecule called an __________ inactivates the repressor to turn the lac operon on

Answer 12

inducer

Question 13

For the lac operon, the inducer is __________ , formed from lactose that enters the cell

Answer 13

allolactose

Question 14

Enzymes of the lactose pathway are called __________

Answer 14

inducible enzymes

Question 15

__________ usually function in __________ ; their synthesis is induced by a chemical signal

Answer 15

inducible enzymes
catabolic pathways

Question 16

__________ usually function in __________ ; their synthesis is repressed by high levels of the end product

Answer 16

repressible enzymes
anabolic pathways

Question 17

Regulation of the trp and lac operons involves __________ of genes because operons are switched off by the active form of the repressor

Answer 17

negative control

Question 18

E. coli will preferentially use __________ when it is present in the environment

Answer 18

glucose

Question 19

When glucose is scarce, __________ __________ acts as an activator of transcription

Answer 19

CAP(catabolite activator protein)

Question 20

CAP is activated by binding with __________ __________

Answer 20

cyclic AMP(cAMP)

Question 21

Activated CAP attaches to the __________ of the lac operon and increases the affinity of __________ , thus accelerating transcription

Answer 21

promoter
RNA polymerase

Question 22

When glucose levels __________ , CAP detaches from the lac operon, and transcription proceeds at a very low rate, even if lactose is present

Answer 22

increase

Question 23

In multicellular organisms, regulation of gene expression is essential for __________

Answer 23

cell specialization

Question 24

Differences between cell types result from __________ __________ , the expression of different genes by cells with the same genome

Answer 24

differential gene expression

Question 25

In all organisms, a common control point for gene expression is at __________

Answer 25

transcription

Question 26

The structural organization of __________ packs DNA into a compact form and also helps regulate gene expression in several ways

Answer 26

chromatin

Question 27

The location of a __________ relative to __________ and __________ or __________ attachment sites can influence gene transcription

Answer 27

gene promoter
nucleosomes
scaffold
lamina

Question 28

Chemical modifications to __________ and __________ can influence chromatin structure and gene expression

Answer 28

histone proteins
DNA

Question 29

In __________ __________ , acetyl groups are attached to positively charged lysines in histone tails

Answer 29

histone acetylation

Question 30

The addition of __________ __________ can condense chromatin and lead to reduced transcription

Answer 30

methyl groups (methylation)

Question 31

__________ is the addition of methyl groups to certain bases in DNA, usually __________

Answer 31

DNA methylation
cytosine

Question 32

After replication, enzymes methylate the correct daughter strand so that the methylation pattern is __________

Answer 32

inherited

Question 33

Though chromatin modifications __________ alter DNA sequence, they may be passed to future generations of cells

Answer 33

do not

Question 34

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called __________

Answer 34

epigenetic inheritance

Question 35

__________ __________ provide initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery 

Answer 35

Chromatin modifitying enzymes