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DAT BIOLOGY > ch 6- molecular genetics > Flashcards

ch 6- molecular genetics Flashcards

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1
Q

diff between RNA and DNA

A

RNA- 2 OHs

DNA- only one OH on the 3’

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2
Q

in DNA with higher proportion of G-C bonds,

A

higher temperature is needed to break apart the strands

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3
Q

how many origins of replication are there

A

circular DNA- only one

linear DNA- multiple

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4
Q

semi conservative meaning

A

each new strand of DNA has one old strand and one new

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5
Q

5’ and 3’ end of DNA

A

5’ - phosphate

3’ - hydroxyl

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6
Q

what is the initiation step of DNA replication

A
  • origin of replication created at AT rich segments using helicase - replication fork created which leads to supercoiling up ahead
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7
Q

single strand binding protein

A

bind to uncoiled DNA during ELONGATION to prevent it from reattaching

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8
Q

topoisomerase

A

nicks DNA double helix ahead to relieve build up tension and supercoiling

also called DNA gyrase

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9
Q

primase

A

places RNA primers at the origin of replication

creates 3’ end

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10
Q

sliding clamp proteins

A

holds DNA polymerase to the template strand

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11
Q

leading vs lagging strand

A

leading- produced continuously bc it has a 3’ end that faces the repliaction fork

laggin strand- produced discontinously bc its 3’ end is facing away from the replication fork
- needs many RNA primers to produce okazaki fragments

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12
Q

what happens to the rNA primers

A

replaced by another DNA polymerase with DNA

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13
Q

DNA ligase

A

glues separated fragments of DNA together

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14
Q

telomeres

A

non coding repeated nucleotide sequences at the ends of linear chromosomes

important in euk bc when the replication fork reaches the end of a chromosome, a small segment of DNA from the telomere is not replicated and lost (no RNA primer is present to help produce another Okazaki fragment).

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15
Q

telomerase

A

enzyme that extends telomeres to prevent DNA loss (adds repeatitive DNA)

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16
Q

DNA polymerrase

A

class of enzymes that extends DNA from the 5’ to 3’ direction

some have proofreading abilities

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17
Q

nucleosomes

A

DNA complexes wrapped around histone proteins

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18
Q

histones

A

positively charged

negatively charged DNA wraps around them

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19
Q

euchromatin vs heterochromatin

A

euchromatin- loosely packed nucleosomes - DNA accesible for transcription

heterochromatin- tightly bound chromatin so DNA is mostly inactive

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20
Q

acetylation

A

removing positive charges of DNA relaxing the nucleosomes
- ALLOWS MORE TRANSCRIPTION TO OCCUR

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21
Q

deacetylation

A

increases positive charge- more tight binding of histones to DNA

decreases transcription

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22
Q

methylation

A

adds methyl groups

can either increase or decrease transcription

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23
Q

steps of transcription

A

initiation- promoter attracts RNA polymerase to gene

elongation- transcription bubble is formed- RNA pol travels 3’ to 5’ direction on the template strand extending rNA in 5’ to 3’ direction

temination- termination sequence signals RNA pol to stop transcribing

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24
Q

another name for template strand

A

antisense
noncoding

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25
Q

what is the coding/ sense strand

A

it isnt the template

it will have a sequence that is nearly identical to DNA but the T will be U

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26
Q

R factor

A

extra chromosomal peices of DNA that form plastids

contain ANTIBIOTIC RESISTANCE GENES

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27
Q

transduction

A

transfer of DNA between bacteria through viruses

occurs when virus enters lysogenic cycle- carriers bact dna with its own when it goes back to lytic cycle

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28
Q

transformation

A

bact take up extracellular DNA

bact that can do that are called competent

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29
Q

how to make bact competent

A

electoporation

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30
Q

conjugation

A

bac use cytoplasmic bridge- pili to copy and transfer the F plasmid (F+) if it doesnt have this it is F-

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31
Q

how do bacteria increase genetic diversity

A

through horizontal gene transfer

conjugation
tranformation
transduction

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32
Q

prohpages

A

bacteriophage genome that has been integrated into the host genome

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33
Q

what is the viral replication cycle

A

attachment-

penetration

uncoating- viral capsid removed and degraded by host enzymes

replication

assembly - viral capsid components assemble to form the viral capsid

release

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34
Q

why are viruses not living

A

because they must infect livinh cells to multiply

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35
Q

capsid

A

viral protein that is made of capsomere subunitsl

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36
Q

lysogenic cycle

A

visu considred dormant

inserts its own genome into host genome

does not harm host

37
Q

lytic cycle

A

virus takes over host to replicate and does cayse harm

38
Q

retrovirus example

A

HIV

39
Q

retroviruses

A

Retroviruses (e.g., HIV) have an RNA genome that infects host cells. They contain an enzyme called reverse transcriptase, which converts their RNA into cDNA (complementary DNA). The cDNA can integrate into the host genome and enter the lysogenic cycle.

40
Q

operon

A

group of gnees that functions as a single unit controlled by one promoter

41
Q

how are operons promoters regulated

A

repressors or activators bind

42
Q

what kind of operon is the lac operon

A

inducible operon

contains lac Z, Y, A

encodes lactose metabolism

only induced when glucose not available

43
Q

how is the lac prootein regulated - first

A

the lac repressor protein - constituitively expressed- always turning off the lac protein expression

when lactose is present - converted to allolactose which binds to the REPRESSOR and prevents it binding to operator

44
Q

how is the lac operon regulated- second

A

CAMP- inversely related to glucose. high when glucose is low

it binds to CAP- binds near lac operon promoter attracting RNA polymerase

45
Q

what happens when lactose is present and glucose is present

A

moderate transcription of the lac operon

repressor not bound

CAP not bound

46
Q

what does CAP stand for

A

catabolite activator protein

47
Q

what happens when lactose is present and glucose is absent

A

high transcription of lac operon

repressor not bound

CAP bound

48
Q

what happens when lactose is absent and glucose is present

A

no transcription of lac operon

repressor is bound and CAP is not bound

49
Q

when happens when both lactose and glucose are absent

A

no transcriptino of lac operon

repressor is bound and CAP is bound

50
Q

what is the trp operon

A

responsible for producing the tryptophan amino acid

its repressible - encodes for tryptophan synthetase and always active unless trp is present in enviroment

51
Q

how is the trp operon regulated

A

trp binds to the trp repressor protein which attaches to teh operator

52
Q

what RNA pol is used by eyk

A

RNA pol II

53
Q

what do transcription factors do

A

needed in EUK to help RNA pol to bind to promoter

TFs bind to the TATA box in promoters

54
Q

enhancers

A

DNA sites that activator proteins bind to to inc transcription

55
Q

silencers

A

DNA sites that repressor proteins bind to to decrease transcription of a gene

56
Q

where are enhancers and silences

A

far upstream or downstream so DNA probably loops around to colocalize with RNA polymerase

57
Q

where is the poly A signal found

A

within the terminator

stimulates polyadenylation - addition of adenine nucleotides to the 3’ end of mRNA

58
Q

conversion of premRNA to processed mRNA

A

occurs after post transcriptional modification

processed mRNA leaves the nucleus

59
Q

post transcriptional modification

A

5’ capping - 7 methylguanosine cap added to 5’ end DURING ELONGATION

polyadenylation of 3’ end

splicing out introns- using spliceosomes (signalled by splice signals)

60
Q

what is the benifit of 5’ cap

A

prevent degradation

61
Q

benifit of polyadenylation

A

prevent degradation

62
Q

how many protein coding genes do we have

A

20,000

more non coding DNA than coding

63
Q

miRNA

A

(micro RNA) are small RNA molecules that
silence mRNA expression as a method of
post-transcriptional gene regulation by base-pairing with parts of sequences on the mRNA transcript that inhibits their translation.

64
Q

snRNA

A

make the functinal part of the spliceos0me

65
Q

what are snRNPs

A

small nuclear ribonucleoproteins

spliceosome with snRNA

66
Q

where are 30s and 50s ribosome subunits assembled

A

in the nucleoid

67
Q

64 codons but 20 aa means what

A

there is degeneracy

68
Q

start codon

A

AUG

69
Q

stop codons

A

UAA
UAG
UGA

70
Q

open reading frame

A

stretch of DNA between the start and stop codon

71
Q

aminoacyl tRNA

A

tRNA bound to amino acid

aa attatched to tRNA using aminoacyl-tRNA synthetase (enzyme) using energy from ATP

72
Q

ribosome binding sites for tRNA

A
  1. A site: A for aminoacyl-tRNA, which first enters at this site.
  2. P site: P for peptidyl-tRNA, which carries the growing polypeptide. The polypeptide chain moves from the P site to the tRNA on the A site during peptide bond formation.
  3. E site: E for exit site. The tRNA from the P site is sent here and released from the ribosome.
73
Q

what catalyzes the formatino of a peptide bond between the polypeptide in the P sie and the newly added aa in the A site

A

the ribosome

74
Q

translocation

A

occurs in which the tRNA molecule at the A site moves to the P site, and the tRNA at the P site moves to the E site (A → P → E)

75
Q

chaperonins

A

Specialized proteins known as chaperonins are found
in both eukaryotic and prokaryotic organisms and
function in assisting newly synthesized polypeptides
to fold into their correct shape.

76
Q

translocation

A

A piece of one chromosome
breaks off and attaches to another chromosome. Translocation increases chromosomal arm length and results in an abnormal banding pattern. This is the only mutation that affects both chromosomes.

77
Q

inversion

A

A portion of the chromosome becomes
inverted on the arm of the chromosome. Results in an abnormal banding pattern, but does not affect the length of the chromosome.

78
Q

duplication

A

A piece of the chromosome is
duplicated, resulting in a larger chromosomal arm and an atypical banding pattern.

79
Q

deletion

A

A portion of the chromosome is deleted,
resulting in a shorter chromosomal arm.

80
Q

what are the types of chromosomal muations

A

occur and affect the entire
chromosome rather than individual nucleotides. There
are four types:

81
Q

null mutation

A

non functional allele. is produced

lacks the functino of the normal wild-type allele

82
Q

types of base substitutions

A

silent mutations

missense mutations

nonsense mutation

83
Q

sielnt mutation

A

no change in amino acid sequence due to third base wobble due to degeneracy

84
Q

missense mutations

A

single change in aa sequence

conservative- similar aa
non conservative- different aa

85
Q

frameshirt

A

mutatinos that result in shift of reading frame

insertions
deletions

86
Q

what are the factors that contribute to DNA mutations

A

DNA pol errors

loss of DNA durign meiosis crossing over

chemical damage from drugs

radation

transposons

87
Q

what are transposons

A

jumping genes

DNA sequences in PROKARYOTES and EUKARYOTES that can move and
integrate into different places in the genome.

88
Q

what factors prevent DNA mutations

A

DNA pol proofreading

mismatch repair - macheinery that checks uncaught erros

nucleotide excision repair- that cuts out damaged DNA and replaces it with correct DNA using complementary base pairing.

DAT BIOLOGY (32 decks)

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