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MCAT bio > Molecular biology > Flashcards

Molecular biology Flashcards

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MCAT flashcards Biology 101 flashcards
1
Q

nucleic acids are..

A

found in the nucleus and possess many acidic phosphate groups

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2
Q

What are nucleotides built from

A

a sugar, an aromatic nitrogenous base, and 1-3 phosphate groups

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3
Q

What is the variable part of the DNA building block

A

the base

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4
Q

Watson crick dna model

A

cellular DNA is a right handed, antiparallel double helix held together by hydrogen bonds between bases

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5
Q

What is true about dna structure

A

It is also coiled and the double helix is stabilized by van Der Waals interactions between bases

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6
Q

What are prokaryotic genomes composed of

A

A single circular chromosome

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7
Q

What does dna gyrase do?

A

type of topoisomerase that uses energy of ATP to reduce strains and create super coils of double stranded DNA

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8
Q

How is dna packed

A

It is wrapped around histones to form nucleosomes which compose chromatin.

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9
Q

kinetochores

A

act as anchor attachment sites for spindle fibers

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10
Q

telomere function

A

they are the ends of linear chromosomes,

prevents chromosome deterioration and prevents fusion with neighboring chromosomes

They are eventually consumed and shorten during cell division

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11
Q

single nucleotide polymorphisms

A

mutations

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12
Q

Copy-number variations

A

structural variations in the genome that lead to different copies of DNA sections

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13
Q

tandem repeats

A

where short sequences of nucleotides are repeated one right after the other

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14
Q

Central Dogma

A

DNA leads to RNA via transcription and this RNA is used as a template during translation through ribosomes to create proteins

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15
Q

Degeneracy and (un) Ambiguity

A

Degenerate - multiple codons can code for the same amino acid

unambiguity- each codon specifies only a single amino acid

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16
Q

Meselson and Stahl experiment

A

showed that replication is semiconservative, meaning one strand of the helix is parental and one is newly synthesized daughter DNA.

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17
Q

origin of replication

A

specific place where helices begins to unwind the double helix

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18
Q

topoisomerase

A

cuts one or both of the strands and unwrap the helix to release excess tension created by helicases

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19
Q

single strand binding proteins

A

protects unpackaged DNA in preparation for replication and helps keep strand separated

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20
Q

primase

A

synthesizes RNA primer

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21
Q

DNA polymerase

A

catalyzes elongation of daughter strand using parental template

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22
Q

Where does polymerization occur?

A

Always in the 5 to 3 direction

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23
Q

What does DNA pol require

A

A template and a primer

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24
Q

lagging strands

A

wait until the replication fork widens before beginning to polymerize, comprised of Okazaki fragments discontinuous replication compared to continuous replication of leading strand

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25
Q

What direction do replication forks grow?

A

Away from the origin in both directions

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26
Q

What are RNA primers replaced by and how are fragments joined?

A

They are replaced by DNA and the fragments are joined by DNA ligase.

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27
Q

DNA polymerase III

A

does very fast elongation of leading strand, has proofreading function

28
Q

DNA polymerase I

A

adds nucleotides at RNA primer, slower than III, capable of proofreading, also important for excision repair

29
Q

theta replication

A

Replication of prokaryotes

30
Q

telomerase

A

adds repetitive nucleotide sequences to ends of chromosomes

31
Q

mutagens

A

any compound that can cause mutations

32
Q

point mutations

A

single base pair substitutions

33
Q

missense mutation

A

causes one amino acid to be replaced by another

34
Q

nonsense mutation

A

stop codon replaces a regular codon and prematurely shortens the protein

35
Q

silent mutation

A

codon is changed into a new codon for the same amino acid, causing no change

36
Q

frameshift mutation

A

mutations that cause a change in reading frame

37
Q

inversion

A

a segment of a chromosome is reversed end to end

38
Q

Chromosome amplification

A

when a segment of a chromosome is duplicated

39
Q

translocations

A

when recombination occurs between nonhomologous chromosomes

40
Q

transposons

A

can jump around the genome through the cut and paste activity of transposase

41
Q

hemizygosity

A

haploid expression in a diploid organisms can lead to increased effect of mutation on chromosomes

42
Q

homology dependent repair pathways

A

Mutations on one strand of DNA can be repaired using the undamaged complementary info on the other strand

happens before dna replication (excision repair) or after dna replication (post replication repair)

43
Q

mismatch repair pathway

A

targets mismatched watson crick base pairs that weren’t repaired by DNA polymerase proofreading during replication

44
Q

Rna characteristics

A

single stranded, contains uracil instead of thymine, pentose ring is ribose

45
Q

mRNA

A

carries genetic info to ribosome

46
Q

monocistrionic

A

each piece of mRNA encodes only one polypeptide

47
Q

tRNA

A

responsible for translating the genetic code

48
Q

rRNA

A

major component of the ribosome

49
Q

promoter

A

sequence of nucleotides on a chromosome that activates RNA polymerase to begin the process of transcription

50
Q

sigma factor

A

required along with core enzyme to form holoenzyme that is responsible for initiation of prokaryotic transcription

helps polymerase find promoter

51
Q

Three stages of transcription

A

initiation, elongation, termination

52
Q

Eukaryotic vs prokaryotic transcription

A

Eukaryotic - takes place in nucleus, splicing out of introns by splieceosome, addition of 5’cap and 3’ poly A tail

primary transcript of prokaryotic transcription is mRNA ready to be translated.

53
Q

The three rna polymerases

A

RNAP I - transcribes most rRNA
II - transcribes hnRNA (mRNA), most snRNA, and some miRNA
III - transcribes tRNA, long ncRNA, siRNA, some miRNA, and a subset of rRNA

54
Q

anticodon

A

sequence of three ribonucleotides which is complementary to the mRNA codon the tRNA translates

55
Q

amino acid acceptor site

A

where the amino acid is attached to the tRNA

56
Q

wobble hypothesis

A

states that the first two codon-anticodon pairs obey normal base pairing rules but the third position is more flexible

57
Q

trna loading/ amino acid activation

A

hydrolyzing two high energy phosphate bonds to provide the energy to attach an amino acids to its tRNA molecule

58
Q

Ribosome binding sites

A

A site - where each new tRNA delivers its amino acid
P site - where the growing polypeptide chain is still attached to a tRNA
E site - exit tRNA site

tRNA moves from A to P to E

59
Q

Shine Dalgarno sequence

A

the ribosome binding site of prokaryotic translation

60
Q

prokaryotic translation steps

A
  1. initiation - small ribosomal subunits binds two initiation proteins
  2. elongation - has three steps, last step is translocation where an empty tRNA moves into the E site, tRNA with the growing polypeptide moves to the P site, and the next codon to be translated moves to the A site
  3. termination - stop codon appears in the A site
61
Q

cap independent translation

A

when eukaryotes can start translation in the middle of an mRNA molecule

62
Q

epigenetic

A

changes in gene expression not due to changes in DNA sequences, includes dna methylation, chromatin remodeling, and rna interference

63
Q

genomic imprinting

A

when only one allele of a gene is expressed

64
Q

lac operon vs trp operon

A

lac operon is inducible, since it codes for catabolic enzymes and trp is repressible since it codes for an enzyme that mediates anabolism.

lac operon only has high transcription when lactose is present and glucose is absent

trp genes are off in presence of tryptophan

65
Q

transcription factors

A

crucial in transcription regulation

66
Q

chaperones

A

fold proteins into their correct 3D shape

67
Q

What is the reading direction of translation

A

5 to 3 on RNA template

MCAT bio (11 decks)

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