gene expression 7.4, 7.5

Question 1

what do prokaryotes and eukaryotes do to save energy?

Answer 1

they regulate making proteins to save energy

Question 2

what is the lac operon?

Answer 2

the lac operon is a cluster of genes that contain DNA sequences to regulate the breakdown of lactose

Question 3

what does the lac operon contain?

Answer 3

1. promoter sites
2. operator regions
3. coding region

Question 4

what happens in the promoter site?

Answer 4

DNA transcription begins

Question 5

what do operator regions do?

Answer 5

regulatory factors bind to this region

Question 6

what are coding regions for?

Answer 6

coding regions are for enzymes that metabolize (break down) glucose

Question 7

what is upstream from the operon?

Answer 7

a gene that codes for the repressor protein (protein produced from lac1 gene) and it binds to the operator to stop gene transcription

Question 8

what are the genes in coding regions?

Answer 8

1. lac Z
2. lac Y
3. lac A

Question 9

what is lac Z

Answer 9

lac Z codes for enzyme: beta galactosidase which hydrolyzes or cleaves lactose into glucose and galactose

Question 10

what is lac Y

Answer 10

lac Y codes for enzyme permease which transports lactose across bacterial cell membrane

Question 11

what is lac A

Answer 11

lac A codes for enzyme transacetylase

Question 12

what happens when there is an increase in lactose?

Answer 12

• activates the lac operon by fitting in allosteric site of repressor molecule, rendering it inactive
• RNA polymerase now can transcribe genes to break down lactose

Question 13

what happens when there is a decrease in lactose?

Answer 13

• there would be nothing to bind the repressor molecule
• thus it will bind to the operator and inhibit RNA polymerase from starting transcription

Question 14

what is the trp operon

Answer 14

the trp operon has the same structure as the lac operon

Question 15

what composes the trp operon

Answer 15

a promoter and an operator that make gene coding for tryptophan-synthesizing enzymes

Question 16

what happens when tryptophan is not present

Answer 16

repressor proteins become inactive and doesn’t bind to the operator

Question 17

what enzyme is able to make trp

Answer 17

RNA polymerase is able to transcribe genes responsible for trp production

Question 18

what happens when there are increased tryptophan levels

Answer 18

• it binds to repressor molecule and activates it
• the repressor molecule binds to the operator stopping RNA polymerase from transcribing genes
• preserves energy

Question 19

what are the four genes control mechanisms in eukaryotes?

Answer 19

1. transcriptional
2. post-transcriptional
3. translational
4. post-translational

Question 20

what is transcriptional gene control

Answer 20

it regulates which genes are transcribed from DNA to RNA

Question 21

what happens in post-transcriptional

Answer 21

mRNA molecules undergo changes in the nucleus

Question 22

what is translation

Answer 22

controls how often/rapid mRNA transcripts are translated to proteins

Question 23

what is post-translation

Answer 23

controls when proteins become fully functional (and for how long) and when they’re degraded

Question 24

what are mutations

Answer 24

mutations are spontaneous rearrangement of genetic material resulting from DNA replication errors

Question 25

what are causes of mutations

Answer 25

- synthetic chemicals - radiation - incorrect replication - random

Question 26

what are point mutations and the types

Answer 26

it is a change in one nucleotide of a gene 1. substitution 2. insertion or deletion 3. inversion

Question 27

what is missense mutation

Answer 27

it changes a single amino acid thus altering protein

Question 28

what is nonsense mutation

Answer 28

mutation that results in a premature stop codon

Question 29

what is silent mutation

Answer 29

the change of one or more base pairs and does not affect gene function

Question 30

what is a frameshift mutation

Answer 30

a shift in the reading frame resulting in missense or nonsense effects

Question 31

what is base deletion

Answer 31

a mutation where a nucleotide is lost from the DNA sequence

Question 32

what is base insertion

Answer 32

a mutation where an extra nucleotide is added to the DNA sequence

Question 33

what are the two large scale mutations

Answer 33

1. translocation 2. inversion

Question 34

what is translocation

Answer 34

genes are moved from one chromosome to another

Question 35

inversion

Answer 35

a portion of DNA molecules reserves its direction

Question 36

what is spontaneous mutation

Answer 36

caused by inaccurate DNA replication

Question 37

what is induced mutation

Answer 37

mutation caused by an environmental agent

Question 38

what is a mutagen

Answer 38

an environmental agent that alters DNA - high temperatures - some viruses - industrial chemicals - radiation