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genetics Flashcards

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Biology 101 flashcards
1
Q

purines and pyrimidines

A

purines = AG (2 bonds, 2 rings). pyrimidines = CT (3 bonds, 1 ring)

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2
Q

telomeres

A

only in eukaryotes, reads TTAGGG…

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3
Q

stop codons

A

UAA, UGA, UAG

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4
Q

nucleotide structure

A

triphosphate on 5’ of sugar. deoxy on 2’. nitrogenous base on 1’. Free hydroxyl end on 3’.

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5
Q

point mutation

A

single substitution of NT. May result in missense, nonsense, or silent mutation.

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6
Q

frameshift mutation

A

very serious. NTs inserted or deleted not in multiple of 3

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7
Q

UV ray mutation

A

causes pyrimidines to fuse into dimer. Distorts helix backbone

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8
Q

X ray mutation

A

can break covalent bonds, such as break backbone

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9
Q

intrastrand and interstrand crosslinking

A

form of endogenous DNA damage

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10
Q

if transposon is put in intergenic region

A

no effect

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11
Q

if transposon put in coding region

A

mutation

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12
Q

mismatch repair pathway

A

during or soon after replication to correct a single mismatched bp. Identify parent strand by its methylation to correct daughter

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13
Q

NT excision repair

A

can occur anytime; replace the bad base with correct one

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14
Q

homologous recombination

A

must occur BEFORE replication, you use the other sister chromatid as a template to correct chromosomal DSBs

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15
Q

non homology end joining

A

can occur anytime; just use ligase to join broken ends of a chromosome (this is the option before S phase when there’s no sister chromatid as reference)

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16
Q

theta replication

A

occurs in prokaryotes’ circular DNA, beginning at a single Ori. proks have 5 DNA polymerases

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17
Q

DNA pol III

A

very fast. It is the main replicase enzyme. No repair function.
Also has 3’ to 5’ exonuclease activity (when it backs up a NT and lops it off if wrong. This is called the proofreading function that can ONLY occur during replication)

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18
Q

DNA pol I

A

slower than pol III. Like III, it has 3’ to 5’ exonuclease activity where it can proofread too. Unlike III, it can remove RNA primers in 5’ to 3’ direction. it performs excision repair

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19
Q

telomerase

A

extends telomeres (reverse transcriptase ability because it copies its RNA template to make DNA)

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20
Q

DNA pol II

A

backup for DNA pol III. Also possesses proofreading function and also has repair mechanisms.

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21
Q

DNA pol IV and V

A

quite error prone

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22
Q

hnRNA

A

heterogeneous nuclear RNA. Large pre-mRNAs that must be further processed before entering cytoplasm

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23
Q

siRNA

A

short interfering RNA. It is double stranded and exogenous, taken up by cells

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24
Q

miRNA

A

micro RNA, single stranded and endogenous

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25
Q

Compare prok and euk transcription

A

Prok: translation occurs simultaneously with transcription; no processing of mRNA, only 1 RNA pol.
No introns, no splicing.

Euk: translation occurs in cytoplasm; mRNA needs to be mature, 3 RNA pol types

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26
Q

Poly vs monocistronic

A

In prokaryotes, many proteins can come from 1 mRNA transcript

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27
Q

aminoacyl tRNA synthetase

A

matches tRNA to its amino acid. Takes 2 ATP.

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28
Q

Wobble theory

A

though the first 2 NTs of the codon pair correctly, the 3rd has some leeway, permitting the same tRNA to match with multiple codons that vary in the 3rd letter. This reduces number of tRNA types needed

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29
Q

Translation energy requirements

A

takes 4ATP per 1 amino acid

30
Q

release factor

A

binds to stop codon to release growing peptide from ribosome

31
Q

Shine-Dalgarno sequence

A

sequence in mRNA, upstream of AUG, that helps find and bind ribosome. ONLY PROKARYOTES

32
Q

photoreactivation

A

visible light can recruit enzymes to repair pyrimidine dimer mutations formed by UV

33
Q

gyrases

A

only exist in prokaryotes; they maintain the helix coil shape

34
Q

splicing

A

hnRNA -> mRNA. Occurs in nucleus.

35
Q

metacentric

A

p and q arms equal in length

36
Q

submetacentric

A

p and q arms almost equal; q still longer

37
Q

acrocentric

A

p arms VERY VERY short

38
Q

Kozak sequence

A

sequence in eukaryotic mRNA (not prok) by which ribosomes can recognize it. They also recognize 5’ cap

39
Q

telocentric

A

p arms shorter even than acrocentric; barely there

40
Q

2 DNA strand types?

A 
coding = sense
template = antisense = the one being 'read' by RNA pol
41
Q

heterochromatin

A

has more histones, very compact. mostly noncoding regions; euchromatin: more often transcribed

42
Q

kinetochores

A

multi protein complexes that attach spindle fibers (of mitosis) to the centromeres of chromosomes

43
Q

types of genomic variation

A

single nucleotide polymorphisms, copy-number variations, and tandem repeats (which are rich in heterochromatin, centromeres, telomeres)

44
Q

SSBPs

A

bind to exposed DNA to prevent reannealing

45
Q

nucleophile

A

the 3’ hydroxyl during replication is the nucleophile

46
Q

ethidium bromide

A

a mutagen that inserts itself between bp (intercalating) thus causing errors in replication

47
Q

inversion

A

chromosomal mutation where a segment is flipped

48
Q

amplification

A

chromosomal mutation where segment is duplicated

49
Q

translocation

A

chromosomal mutation where segment is moved to another chromosome altogether

50
Q

transposons

A

all contain a gene coding for transposase (that has cut and paste activity)
IS element - simplest type; merely transposase flanked by repeats
Complex transposon - IS element followed by genes
Composite transposon - central region flanked by IS elements

51
Q

hemizygous

A

when there is only one gene copy in a diploid organism. Quite dangerous, because having 2 copies protects from mutations

52
Q

haploinsufficiency

A

diploid organism has only a single functional copy of a gene

53
Q

ncRNA

A

non coding RNA includes tRNA and rRNA. Also a type call long ncRNAs that control basal transcription level by regulating initiation complex assembly. Also work on post transcriptional regulation and have a function in X-inactivation

54
Q

rRNA

A

some rRNA serves a catalytic function, thus called RIBOZYMES

55
Q

snRNA

A

associate with proteins to form snRNP which do splicing. They also regulate transcription factors and maintain telomeres

56
Q

miRNA and siRNA

A

both bind specific mRNA to serve as post transcriptional regulation

57
Q

piRNA

A

PIWI-interacting RNA are single stranded and short. they work with the PIWI protein class to prevent transposon movement

58
Q

Pribnow box

A

a sequence in the bacterial promoter region (prok only) which is recognized by holoenzyme component of RNA pol

59
Q

RNA pol I

A

makes most rRNA

60
Q

RNA pol II

A

makes most hnRNA -> mRNA. Remember that transcription is MORE ERROR PRONE than replication

61
Q

RNA pol III

A

makes tRNA, siRNA, miRNA, and certain rRNA

62
Q

steps of translation

A
  1. amino acid + ATP –> aminoacyl AMP + PPi
  2. cleaving of PPi is extremely favored. this provides energy for tRNA loading (unfavourable).
  3. tRNA loading is where aminoacyl AMP and tRNA become aminoacyl-tRNA, with the AMP discarded
63
Q

aminoacyl tRNA synthetase enzymes

A

AT LEAST one for each amino acid type

64
Q

eIF proteins

A

essential to initiate translation. One binds the smaller ribosome subunit, another binds the 5’ mG cap of mRNA

65
Q

cap-independent translation

A

long believed that euk could only translate start at the 5’ cap, sometimes they begin in the middle of the transcript

66
Q

where does each process occur?

A

transcription, splicing, polyadenylation, 5’ cap adding = nucleus
translation = cytoplasm

67
Q

lac operon

A

P region - promoter site on DNA
O region - operator site to which the lac repressor binds
Z gene - codes for beta galactosidase, which digests lactose
Y gene - codes for permease, so lactose may enter
A gene - transacetylase, not strictly required for lactose metabolism

crp gene - located elsewhere, codes for CAP, the glucose-dependent promoter protein
I gene - also elsewhere, codes for Lac repressor protein. The repressor typically sits on the O region, blocking transcription, till binding a lactose makes it fall off

68
Q

trp operon

A

for making tryptophan

trpR gene - codes for repressor. The repressor binds trp when present and in turn turns the operon off

69
Q

post transcriptional control

A

miRNAs and siRNAs can inactivate mRNA
cells also monitor quality of mRNA and degrade defective ones
mRNA is also transported to correct location in cell BEFORE translated

70
Q

post translational modification

A

chaperones fold proteins
covalent modification (functional groups added, like sugars, phosphates, etc)
cleavage

71
Q

formyl-methionine

A

only used by prok; euk have regular methionine

Bio/Biochem (9 decks)

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