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Genetics > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

what enzymes and proteins are essential to DNA synthesis?

A

DNA polymerase 3, SSBPs, DNA gyrase, DNA helicase, and RNA primers

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2
Q

DNA polymerase 3

A

elongates and edits

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3
Q

SSBPs

A

single stranded binding proteins; keeps ssDNA template ss

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4
Q

DNA gyrase

A

relieves the coiling tension created by unwinding

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5
Q

DNA helicase

A

pushes open the replication fork; unwinds to create single strands to be used as templates

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6
Q

RNA primers

A

polymerase needs a 3’ end to add onto

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7
Q

what features are similar in eukaryotic and bacterial DNA replication?

A
  • dsDNA unwounded at ORI
  • replication fork formed
  • bidirectional synthesis creates leading and lagging strands
  • eukaryotic polymerases also require 4 deozyribonucleoside triphosphates
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8
Q

how does eukaryotic DNA differ from bacterial DNA?

A
  • more DNA
  • DNA is complexed with nucleosomes
  • linear chromosomes
  • have multiple ORIs
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9
Q

bacterial and viral chromosomes

A
  • single nucleic acid molecule
  • largely devoid of associated proteins
  • much smaller
  • contain less genetic information
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10
Q

viral chromosomes

A
  • DNA or RNA; ds or ss
  • circular or linear
  • genetic material is nactive until released into host
  • packages long DNA into a small volume
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11
Q

bacterial chromosomes

A
  • circular, ds DNA
  • associated with histone proteins
  • readily replicated and transcribed
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12
Q

supercoiled DNA

A
  • closed-circular molecules

- more compact

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13
Q

topoisomerases

A
  • enzymes that cut one or both DNA strands

- wind or unwind helix before releases strands

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14
Q

histones

A

-positively charged proteins associated with chromosomal DNA in eukaryotes

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15
Q

at what phase can DNA make RNA?

A

when the chromatin is a relaxed structure; when it is tightly wound no transcription can be occur

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16
Q

methylation

A

activates genes
can also repress genes
depends on what chemistry you are altering

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17
Q

phosphorylation

A

can promote demethylation

-can recruit proteins, those proteins can bind to this region and undo the work of the methyl group

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18
Q

acetylation

A

represses genes

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19
Q

euchromatin

A

-uncoiled and active

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20
Q

heterochromatin

A

condensed areas, mostly inactive

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21
Q

pseudogenes

A

single copy noncoding regions

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22
Q

codon

A

triplet code, every three ribonucleotides

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23
Q

what does unambiguous mean in the genetic code?

A

each triplet codon specifies for only one amino acid

24
Q

what does degenerate mean in the genetic code?

A

a given amino acid can be specified by more than one triplet codon

25
Q

what does commaless in genetic code mean?

A

once translation begins, there are no breaks in codons

26
Q

mRNA

A

messenger RNA

serves as intermediate in transferring genetic information from DNA to proteins

27
Q

how many codons are there? how many code for amino acids? what do the others do?

A
  • 64 codons
  • 61 coding
  • the other 3 are termination signals
28
Q

how many amino acids do the codons code for?

A

20

29
Q

frameshift mutation

A

-insertions or deletions shift the reading frame and change the codons downstream

30
Q

what are termination codons?

A

UAG, UAA, and UGA

31
Q

reading frame

A

-contiguous sequence of nucleotides

32
Q

nonoverlapping

A
  • genetic code reads three nucleotides at a time in a continuous, linear manner
  • during translation, genetic code is nonoverlapping
33
Q

triple binding assay

A
  • developed by Nitenberg and Leder
  • ribosomes bind to a single codon of three nucleotides
  • complementary amino acid charged tRNA can bind
34
Q

how does the genetic code show order?

A

chemically similar amino acids share one or two middle bases in triplets encoding them

35
Q

wobble hypothesis

A
  • the initial two ribonucleotides of triplet codons are often more critical than the third
  • the third position is less spatially constrained; need not adhere as strictly to established base-pairing rules
36
Q

initiation codons

A
  • methionine (AUG)
  • initial amino acid incorporated into all proteins
  • AUG is the only one to code for methionine
37
Q

overlapping genes

A
  • single mRNA has multiple initiation points
  • creates different reading frames
  • specifies more than one polypeptide
38
Q

Open Reading Frame (ORF)

A
  • overlapping genes
  • DNA sequence produces RNA with start and stop
  • series of triplet codons specify amino acids to make a polypeptide
39
Q

transcription

A
  • RNA synthesized on DNA template
  • genetic info stored in DNA transferred to RNA
  • serves as intermediate molecule between DNA and proteins
  • each triplet codon is complementary to anticodon of tRNA
40
Q

what does transcription result in?

A
  • in ssRNA
  • template is transcribed
  • transcription begins with template binding by RNA polymerase at promoter
  • alpha subunit is responsible for promoter recognition
41
Q

promoter

A

specific DNA sequences in 5’ region upstream of initial transcription point

42
Q

RNA polymerase

A
  • enzyme directs synthesis of RNA using DNA template
  • nucleotides contain ribose
  • no primer needed for initiation
43
Q

transcription start site

A
  • DNA double helix is unwound to make template strand accessible for RNA pol
  • interaction of promoter and RNA polymerase regulates efficiency of transcription
44
Q

how does transcription differ in eukaryotes?

A
  • occurs within a nucleus
  • mRNA must leave nucleus for translation
  • chromatin remodeling
  • RNA polymerase rely on transcription factors to scan/bind to DNA
  • enhancers and silencers control transcription regulation
45
Q

chromatin remodeling

A

chromatin must uncoil to make DNA accessible to RNA pol

46
Q

what are the three forms of RNA pol in eukaryotes?

A

RNA Polymerases 1,2,3

47
Q

RNA Polymerase 2

A

-responsible for transcription of wide range of genes in euk
-activity of RNAP2 is dependent on cis-acting elements and trans-acting transcription factors
RNAP2 core-promoter determines where RNAP2 binds to DNA

48
Q

what are the regulation sequences that influence the efficiency of transcription by RNAP2?

A
  • proximal-promoter elements
  • enhancers
  • silencers
49
Q

TATA box

A
  • core promoter element

- determines start transcription site

50
Q

enhancers

A
  • binds activators

- increase transcription levels

51
Q

silencers

A
  • binds repressors

- decrease transcription factors

52
Q

enhancers and silencers

A
  • found unpstream, within, or downstream of a gene

- modulate transcription from a distance

53
Q

posttranscriptional factors

A
  • addition of 5’ cap (7-mG cap)
  • addition of 3’ tail (poly-A tail)
  • excision of introns
54
Q

introns

A
  • regions of initial RNA transcript not expressed in amino acid sequence of protein
  • DNA sequence not represented in final mRNA product
  • prokaryotes do not have them
55
Q

heteroduplexes

A

introns present in DNA but not mRNA loop out

56
Q

splicing

A
  • introns are removed by splicing
  • exons are joined together in mature mRNA
  • mature mRNA is smaller than initial RNA

Genetics (11 decks)

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