Molecular Genetics

Question 1

CUT the PY

Answer 1

• cytosine, uracil, and thymine are pyrimidines
• pyrimidines are single ring

Question 2

PUR As Gold

Answer 2

• adenine and guanine are purines
• purines are double-ringed

Question 3

nucleosomes

Answer 3

complexes of DNA wrapped around histone proteins

Question 4

how many histones does each nucleosome contain?

Answer 4

9 histones

Question 5

central core

Answer 5

2 of each histone: H2A, H2B, H3 & H4

Question 6

outside

Answer 6

single histone, H1, holds DNA in place

Question 7

chromatin

Answer 7

overall packaging of DNA and histones

Question 8

euchromatin

Answer 8

loosely packed therefore DNA transcription occurs easily

Question 9

heterochromatin

Answer 9

tightly packed therefore DNA mostly inactive

Question 10

what allows for proper binding?

Answer 10

DNA is negatively charged while histones are positively charged

Question 11

acetylation

Answer 11

removes positive charge relaxing DNA-histone attractions allowing for more transcription

Question 12

deacetylation

Answer 12

increases positive charges tightening attractions thus decreasing transcription
deacetylation decreases transcription

Question 13

methylation

Answer 13

adds methyl groups either increasing/decreasing transcription

Question 14

DNA replication steps

Answer 14

initiation, elongation, termination

Question 15

initiation

Answer 15

origins of replication at A-T because easier to split

Question 16

elongation

Answer 16

producing new DNA strands using a variety of enzymes

Question 17

helicase

Answer 17

unzips DNA by breaking H bonds to create replication fork; leads to supercoiling

Question 18

single-stranded binding proteins

Answer 18

bind to uncoiled DNA strands preventing reattachment of strands

Question 19

topoisomerase

Answer 19

nicks DNA double helix

Question 20

primase

Answer 20

adds RNA primers at origin to create 3’ ends for nucleotide addition

Question 21

sliding clamp proteins

Answer 21

hold DNA polymerase on template strand

Question 22

DNA polymerase

Answer 22

adds free nucleoside triphosphates to 3’ ends

Question 23

leading strand

Answer 23

produced continuously because 3’ end faces replication fork

Question 24

lagging strand

Answer 24

produced discontinuously because 3’ end faces away replication fork
- need many RNA primers to produce Okazaki fragments

Question 25

termination

Answer 25

replication fork can’t continue therefore ending replication

Question 26

telomerase

Answer 26

extends telomeres to prevent DNA loss

Question 27

where does transcription and translation occur in prokaryotes?

Answer 27

cytosol

Question 28

initiation

transcription

Answer 28

promotoer next to gene attracts RNA polymerase to transcribe gene

Question 29

elongation

transcription

Answer 29

transcription bubble forms
* RNA 3’ –> 5’ on template strand but extends RNA 5’ –> 3’

Question 30

termination

transcription

Answer 30

termination sequence/terminator signals RNA polymerase to stop transcribing

Question 31

RNA polymerase holoenzyme

Answer 31

sigma factor + prokaryotic RNA polymerase

Question 32

rho-independent termination

Answer 32

termination sequence reached and RNA transcript folds into hairpin loop making RNA polymerase fall off to end it

Question 33

rho-dependent

Answer 33

Rho protein binds to RNA transcript moving 5’ –> 3’ to catch up and displace RNA polymerase

Question 34

operon

Answer 34

group of genes that function as a single unit and controlled by single promoter

Question 35

repressors

Answer 35

bind to operator regions

Question 36

activators

Answer 36

bind to promoter sites

Question 37

lac operon

Answer 37

inducible operon aka must be activated

Question 38

lac operon genes

Answer 38

lac Z, lac A, lac Y required for lactose metabolism

Question 39

when is the lac operon induced

Answer 39

when lactose is available and glucose isn’t

Question 40

DNA methylation

Answer 40

decrease transcription