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DAT BIOLOGY > ch 6- molecular genetics > Flashcards

ch 6- molecular genetics Flashcards

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
what is the coding/ sense strand
it isnt the template it will have a sequence that is nearly identical to DNA but the T will be U
26
R factor
extra chromosomal peices of DNA that form plastids contain ANTIBIOTIC RESISTANCE GENES
27
transduction
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
28
transformation
bact take up extracellular DNA bact that can do that are called competent
29
how to make bact competent
electoporation
30
conjugation
bac use cytoplasmic bridge- pili to copy and transfer the F plasmid (F+) if it doesnt have this it is F-
31
how do bacteria increase genetic diversity
through horizontal gene transfer conjugation tranformation transduction
32
prohpages
bacteriophage genome that has been integrated into the host genome
33
what is the viral replication cycle
attachment- penetration uncoating- viral capsid removed and degraded by host enzymes replication assembly - viral capsid components assemble to form the viral capsid release
34
why are viruses not living
because they must infect livinh cells to multiply
35
capsid
viral protein that is made of capsomere subunitsl
36
lysogenic cycle
visu considred dormant inserts its own genome into host genome does not harm host
37
lytic cycle
virus takes over host to replicate and does cayse harm
38
retrovirus example
HIV
39
retroviruses
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
operon
group of gnees that functions as a single unit controlled by one promoter
41
how are operons promoters regulated
repressors or activators bind
42
what kind of operon is the lac operon
inducible operon contains lac Z, Y, A encodes lactose metabolism only induced when glucose not available
43
how is the lac prootein regulated - first
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
how is the lac operon regulated- second
CAMP- inversely related to glucose. high when glucose is low it binds to CAP- binds near lac operon promoter attracting RNA polymerase
45
what happens when lactose is present and glucose is present
moderate transcription of the lac operon repressor not bound CAP not bound
46
what does CAP stand for
catabolite activator protein
47
what happens when lactose is present and glucose is absent
high transcription of lac operon repressor not bound CAP bound
48
what happens when lactose is absent and glucose is present
no transcription of lac operon repressor is bound and CAP is not bound
49
when happens when both lactose and glucose are absent
no transcriptino of lac operon repressor is bound and CAP is bound
50
what is the trp operon
responsible for producing the tryptophan amino acid its repressible - encodes for tryptophan synthetase and always active unless trp is present in enviroment
51
how is the trp operon regulated
trp binds to the trp repressor protein which attaches to teh operator
52
what RNA pol is used by eyk
RNA pol II
53
what do transcription factors do
needed in EUK to help RNA pol to bind to promoter TFs bind to the TATA box in promoters
54
enhancers
DNA sites that activator proteins bind to to inc transcription
55
silencers
DNA sites that repressor proteins bind to to decrease transcription of a gene
56
where are enhancers and silences
far upstream or downstream so DNA probably loops around to colocalize with RNA polymerase
57
where is the poly A signal found
within the terminator stimulates polyadenylation - addition of adenine nucleotides to the 3' end of mRNA
58
conversion of premRNA to processed mRNA
occurs after post transcriptional modification processed mRNA leaves the nucleus
59
post transcriptional modification
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
what is the benifit of 5' cap
prevent degradation
61
benifit of polyadenylation
prevent degradation
62
how many protein coding genes do we have
20,000 more non coding DNA than coding
63
miRNA
(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
snRNA
make the functinal part of the spliceos0me
65
what are snRNPs
small nuclear ribonucleoproteins spliceosome with snRNA
66
where are 30s and 50s ribosome subunits assembled
in the nucleoid
67
64 codons but 20 aa means what
there is degeneracy
68
start codon
AUG
69
stop codons
UAA UAG UGA
70
open reading frame
stretch of DNA between the start and stop codon
71
aminoacyl tRNA
tRNA bound to amino acid aa attatched to tRNA using aminoacyl-tRNA synthetase (enzyme) using energy from ATP
72
ribosome binding sites for tRNA
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
what catalyzes the formatino of a peptide bond between the polypeptide in the P sie and the newly added aa in the A site
the ribosome
74
translocation
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
chaperonins
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
translocation
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
inversion
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
duplication
A piece of the chromosome is duplicated, resulting in a larger chromosomal arm and an atypical banding pattern.
79
deletion
A portion of the chromosome is deleted, resulting in a shorter chromosomal arm.
80
what are the types of chromosomal muations
occur and affect the entire chromosome rather than individual nucleotides. There are four types:
81
null mutation
non functional allele. is produced lacks the functino of the normal wild-type allele
82
types of base substitutions
silent mutations missense mutations nonsense mutation
83
sielnt mutation
no change in amino acid sequence due to third base wobble due to degeneracy
84
missense mutations
single change in aa sequence conservative- similar aa non conservative- different aa
85
frameshirt
mutatinos that result in shift of reading frame insertions deletions
86
what are the factors that contribute to DNA mutations
DNA pol errors loss of DNA durign meiosis crossing over chemical damage from drugs radation transposons
87
what are transposons
jumping genes DNA sequences in PROKARYOTES and EUKARYOTES that can move and integrate into different places in the genome.
88
what factors prevent DNA mutations
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.

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