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Genetics final exam > genetics final exam > Flashcards

genetics final exam Flashcards

1
Q

gene linkage

A

when two or more genes located on the same chromosome are so close that their alleles are unable to assort independently

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2
Q

recombinant genes

A

different from parental genotypes; crossing over occurred

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3
Q

parental genes

A

same as parental genotype; no crossing over

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4
Q

how do you know if there is gene linkage?

A

if the parental genotypes are the most frequent in the progeny

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5
Q

how do you know if there is no genetic linkage?

A

if gametes occur in a 1:1:1:1 ratio.

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6
Q

complete genetic linkage vs incomplete genetic linkage?

A

Complete: ONLY parental gametes observed
Incomplete: parental and recombinant gametes are observed in the progeny

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7
Q

what increases the chances of crossing over?

A

greater length apart on a chromosome (further apart = increased chance of crossing over)

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8
Q

steps in constructing a gene map?

A
  1. identify the progeny classes (parental; most frequent, double cross overs; least frequent, single cross overs)
  2. determine gene order by comparing parental to double crossovers
  3. determine distance between each gene by calculating recombination frequency
  4. calculate coefficient of coincidence and interference
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9
Q

what kind of bonds are nucleotides joined by in DNA?

A

covalent phosphodiester bonds

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10
Q

what type of bonds are nucleotide pairs held together by?
How many bonds between each?

A

hydrogen bonds
-A to T: 2
-G to C: 3

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11
Q

what are the three components of nucleotides?

A
  1. A deoxyribose sugar
  2. one of four nitrogenous bases
  3. up to three phosphate groups
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12
Q

what are the two shapes of nitrogenous bases?

A

Pyrimidine, purine

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13
Q

Pyrimidine

A

Single ringed bases.
Includes cytosine and thymine (one six-ringed structure)

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14
Q

Purine

A

Double-ringed bases.
Included adenine and guanine (six ring and five ringed structure)

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15
Q

Meselson-Stahl experiment

A

Used to decipher the mechanism of DNA replication

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16
Q

Method to meselson-stahl experiment?

A

-tube is filled with CsCl and subjected to high ultracentrifuge speeds, separating them and creating a density gradient
-the parental strands contain N^15 nitrogen duplexes, which are mixed with an N^14 duplex.
-the density gradient shows how these isotopes are dispersed

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17
Q

what are the three models created by the meselson-stahl experiment? which one is accepted?

A

conservative, semiconservative, and dispersive replication
-semiconservative is accepted (each progeny retains one parental strand)

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18
Q

where is DNA replication initiated ?

A

at a DNA sequence called the replicator
-includes the origin of replication (region where double helix denatures)

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19
Q

how long does DNA replication take in humans?

A

over an hour (at 50 base pairs per second)

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20
Q

What are the enzymes involved in DNA replication? (8)

A

-histones
-DNA topisomerase
-DNA helicase
-single stranded binding protein (SSB)
-primase
-DNA polymerase III
-DNA polymerase I
-DNA ligase

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21
Q

histones

A

responsible for supercoiling of DNA

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22
Q

DNA topoisomerase

A

relaxes supercoiling of DNA during replication

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23
Q

DNA helicase

A

unwinds the double helix during replication
-recruits DNA primase

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24
Q

single standed binding protein (SSB)

A

binds to single stranded DNA to stabilize it and prevent re-annealing

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25
Q

primase

A

synthesizes RNA primers (substrates for DNA polymerase III)

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26
Q

DNA polymerase III

A

synthesizes daughter strands (adds new nucleotides)
-complete in leading strand, incomplete in lagging

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27
Q

DNA polymerase I

A

removes + replaces RNA primer with DNA

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28
Q

DNA ligase

A

joins the Okazaki fragments

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29
Q

which direction is DNA synthesized in?

A

5’ to 3’
-template strand is 3’ to 5’

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30
Q

End replication problem (telomeres)

A

-linear chromosomes are unable to replicate right to their ends. Therefore, they get progressively shorter with each replication cycle
-issue is resolved by the presence of hundreds to thousands of telomeres at the end of chromosomes
-telomeres do not contain protein-coding genes
-chromosome shorting occurs in most somatic cells but not germ cells

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31
Q

Polymerase chain reaction (PCR)

A

automated version of DNA replication
-also known as “amplification”; product known as “amplified DNA”

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32
Q

what does PCR require?

A
  1. double stranded DNA template (to be copied)
  2. DNA nucleotides (dNTPs)
  3. DNA polymerase (heat stable; called Taq polymerase)
  4. DNA primers (single stranded)
  5. a buffer solution
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33
Q

how many cycles is ran during PCR?

A

-30-35 cycles
-each double the number of copies of the targeted DNA sequence

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34
Q

what are the steps of PCR?

A
  1. denaturation (mixture is heated to 94ºC, causing DNA to denature into single strands. Takes roughly 1 minute)
  2. Annealing: temp is reduced to 54ºC to allow for primer annealing. Takes roughly 45 seconds.
  3. Extension: temp is raised to 72ºC to allow for primer extension, during which Taq polymerase synthesizes the DNA. Takes roughly 2 minutes.
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35
Q

automated DNA sequencing

A

each nucleotide is labelled with a fluorescent marker
-then used with gel electrophoresis to separate DNA fragments

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36
Q

Agarose gel electrophoresis

A

method for separating different protein/nucleic acid molecules/fragments from one another using an electric field
-charge is applied which separate the molecules based on charge, shape, and size.

37
Q

what are the steps of gel electrophoresis?

A
  1. pour agarose gel into the plastic casting tray
  2. allow gel to solidify
  3. remove comb; wells are left in the gel
  4. remove gel from casting tray, place in a buffered solution with electrodes
  5. add biological samples to wells, apply currents. Samples migrate towards the positive charge.
38
Q

Sanger sequencing

A

-also known as dideoxynucleotide DNA sequencing
-used to determine DNA sequences

39
Q

process of sanger sequencing?

A

-small amounts of dideoxynucleotide triphosphate (ddNTP) is added to large amounts of the four standard dexoynucleotides (dNTP) of DNA (A,T,G,C)
-after the reactions, the components of each reaction are loaded into separate lanes of a DNA gel electrophoresis gel
-components are separated by length
-DNA fragments towards bottom of gel are shorter than those higher up

39
Q

how is the product of sanger sequencing read?

A

Read from the bottom (5’) to the top (3’).

40
Q

how is RNA different from DNA?

A
  1. has a ribose sugar instead of deoxyribose
  2. usually single stranded
  3. Uracil instead of Thymine
41
Q

what are the five types of RNA?

A
  1. messenger RNA (mRNA)
  2. Transfer RNA (tRNA)
  3. Ribosomal RNA (rRNA)
  4. Small nuclear RNA (snRNA)
  5. Micro RNA (miRNA)
42
Q

messenger RNA

A

encodes amino acid sequence
-short lived, intermediary between DNA and protein
-only type of RNA that undergoes translation

43
Q

ribosomal RNA

A

makes up ribosomes with ribosomal proteins

44
Q

transfer RNA

A

brings amino acids to ribosomes during translation
-each bind to a specific aa
-at 3’ ends, all have: 5’—–

45
Q

small nuclear RNA

A

makes complexes (and proteins) that are used in RNA processing

46
Q

micro RNA

A

involved in post-transcriptional regulation of DNA

47
Q

small interacting RNA (siRNA)

A

protects plants and animals from production of viruses and movement of transposons

48
Q

what are the two steps of protein coding?

A
  1. transcription (DNA –> RNA)
  2. translation (RNA –> protein)
49
Q

transcription

A

transfer of genetic information from double stranded DNA template into single stranded RNA

50
Q

translation

A

conversion of RNA base sequence info into amino acid sequence of a polypeptide

51
Q

gene expression

A

the base pair sequences that are being transcribed (only some DNA transcribed at a time)

52
Q

gene regulatory elements

A

base pair sequences associated with each gene that are involved with its expression

53
Q

template, RNA, and nontemplate strands of RNA synthesis

A

template stand: 3’ to 5’ DNA strand
RNA: 5’ to 3’ RNA strand made from template DNA
nontemplate: 5’ to 3’ complementary DNA strand. Same polarity as RNA.

54
Q

steps of transcription

A
  1. the RNA polymerase core enzyme and sigma subunit bind to -10 and -35 promoter consensus sequence
  2. DNA unwinds near the transcription site to form the open promoter complex
  3. RNA polymerase holoenzyme initiates transcription and begins RNA synthesis
  4. Core enzyme synthesizes until it reaches a termination sequence
  5. transcription terminates, the core enzyme + RNA transcript are released
55
Q

where does transcription and translation occur in eukaryotes? Prokaryotes?

A

Eukaryotes: transcription in nucleus, translation in cytoplasm
Prokaryotes: both occur in cytoplasm

56
Q

what are the three sequences protein coding genes are made up of?

A
  1. promoter: starting point for transcription
  2. RNA coding sequence: codes for single stranded mRNA
  3. Terminator: ending point of transcription
57
Q

cloverleaf model of tRNA

A

-complementary base-pairing between different sections of the tRNA molecules form 4 base-pair stems separated by four loops (I, II, III, IV).
-loop II contains the anticodon which pairs with a codon during translation, and ensures correct amino acid sequencing

58
Q

what are the three steps in translation?

A
  1. initiation
  2. elongation
  3. termination
59
Q

what are the two main types of mutations?

A
  1. point/base pair mutations
  2. chromosomal mutations
60
Q

point mutations

A

mutations which substitute, add, or delete one or more DNA base pairs
-occur at a specific, identifiable position in the gene or genome

61
Q

types of point mutations?

A
  1. base-pair substitution mutations
  2. transition mutations
  3. transversion mutations
62
Q

base pair substitution mutations

A

the replacement of one or more nucleotide base pairs
-three types: synonymous mutations, missense mutations, nonsense mutations

63
Q

transition mutations

A

one purine replaces another, or one pyrimidine replaces another

64
Q

transversion mutation

A

one pyrimidine replaces a purine, or vice versa

65
Q

synonymous mutation

A

a base pair change that does not alter the resulting amino acid (codes for the same protein)

66
Q

missense mutation

A

a base pair change that results in a different amino acid (new protein is made)

67
Q

nonsense mutation

A

creates a pre-mature stop codon

68
Q

frameshift mutation

A

insertion or deletion of one or more basepairs, causing the entire sequence to shift

69
Q

chromosomal mutations

A

mutations which change the number or structure of chromosomes

70
Q

types of chromosomal mutations

A
  1. structure (deletion, duplication, inversion, translocation)
  2. number (aneuploidy, euploidy)
71
Q

structure chromosomal mutations

A

caused by one or more breaks in chromosomes
-types: deletions, duplications, inversions, translocations

72
Q

deletion structural chromosomal mutations

A

involves the loss of a chromosomal segment
-causes: heat, radiation, viruses, chemicals
-consequences depend on which genes/parts are lost
-may cause recessive disorders to be expressed if the dominant allele is lost

73
Q

duplication structural chromosomal mutations

A

involves the doubling of a segment of chromosome

74
Q

inversion structural chromosomal mutations

A

no change in the amount of DNA, but changes the arrangement of a chromosomal segment
-two types: pericentric inversion, paracentric inversion

75
Q

Piericentric inversion vs Paracentric inversion

A

Piericentric: includes centromere
Paracentric: does not include centromere

76
Q

translocation structural chromosomal mutations

A

change in the location of one or more DNA segments
-sometimes the cause of tumours

77
Q

number chromosomal mutations types

A

aneuploidy, euploidy

78
Q

Aneuploidy

A

one or more chromosomes added/removed from a normal set
-usually lethal in animals

79
Q

Trisomy, example

A

A form of aneuploidy when an n+1 gamete is fertilized by an n gamete
-ex: trisomy 21 (3 copies of chromosome 21)

80
Q

euploidy

A

involves changes in complete sets of chromosomes
-results from nondisjunction during meiosis
-lethal for most animals

81
Q

polyploids

A

organisms with more than two basic sets of chromosomes
-3x: triploid
-4x: tetraploid
-5x: pentaploid
-6x: hexaploid
-ex: wheat. x=7, 2n=6x=42.

82
Q

monoploids

A

arise spontaneously in natural populations
-found in males of some wasps, bees, ants, etc.

83
Q

how many lethal gametes does nondisjunction of meiosis I result in? meiosis II?

A

meiosis I: two lethal gametes
meiosis II: one lethal gamete

84
Q

what are the types of polyploidy in plants?

A
  1. autopolyploids
  2. allopolyploids
85
Q

autopolyploid

A

composed of multiple sets of chromosomes from ONE species
-arise from duplication of existing genomes within the organism

86
Q

allopolyploid

A

composed of multiple sets of chromosomes from DIFFERENT species (inbreds)
-organism with one haploid (n) set of each parent’s chromosomes, then doubled

87
Q
A
88
Q
A

Genetics final exam (4 decks)

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