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Cells, Organisms & Systems > Genetics > Flashcards

Genetics Flashcards

1
Q

Define mutation

A

A change in the DNA sequence

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2
Q

How are mistakes fixed in DNA replication

A

DNA repair processes

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3
Q

What is the name of the process that corrects mistakes during DNA replication

A

proofreading

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4
Q

What is proofreading

A

a DNA repair process in which they can recognise mistakes and remove the incorrect base before they persist in the DNA (during replication)

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5
Q

What is the name of the process that corrects mistakes after DNA replication

A

mismatch repair

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6
Q

What is mismatch repair

A

a DNA repair process in which enzymes remove the incorrect base and replace with the correct one (after replication)

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7
Q

Briefly outline DNA replication

A
  1. Helicase unwinds double helix
  2. DNA polymerase links nucleotides to form new strands
  3. DNA molecules each rewind to form double helix
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8
Q

What are the 2 main ways mutation can arise from

A

DNA replication & DNA damage

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9
Q

What is base excision repair

A

when cells repair damaged DNA during DNA replication

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10
Q

Explain the importance of fine-tuned mutation rates

A
  • too many mutations are detrimental to survival
  • enough is needed for genetic diversity for evolution
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11
Q

What is transition mutations

A

they are a type of DNA substitution mutation involving the exchange of bases of similar shapes

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12
Q

What is an example of transition mutations

A

(A & G) + (C&T)

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13
Q

What is a transversion mutation

A

A type of DNA substitution which involves the exchange of one ring & two-ring structure

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14
Q

What is an example of transversion mutation

A

(A&C) (C&G) (A&T) (T&G)

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15
Q

What are the 3 types of single base pair substitutions mutations

A
  • silent
  • nonsense
  • missense
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16
Q

What is a silent mutation

A

when the change in the DNA sequence doesn’t affect the sequence of amino acids that make up the protein

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17
Q

What is a nonsense mutation

A

when the single change results in a stop codon, terminating the protein synthesis prematurely

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18
Q

What is a missense mutation

A

when one of the DNA base pairs is changed and the DNA encodes for a different amino acid

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19
Q

Explain frameshift mutations

A

It involves an insertion or deletion of fragment of DNA that causes a shift in the reading frame –> a change in amino acid sequence + abnormal protein

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20
Q

What are the consequences of a frameshift mutation

A
  • stop codon generated
  • protein may be shorter or longer
  • protein is not functional
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21
Q

What is the relationship between DNA and evolutionary relatedness

A
  • the more similar DNA is, the more recently organisms diverged
  • the less similar DNA is, the further ago they diverged
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22
Q

Why are harmful mutations lost from the gene pool

A

Organisms that carry them reproduce and survive less

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23
Q

Why are sequences with vital functions conserved

A

It makes them better adapted to their environment, thus increases survival and reproduction rate

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24
Q

Are beneficial and harmless mutations conserved

A

Yes

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25
Q

What are sources of genetic diversity

A
  • mutation
  • chromosomal changes
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26
Q

What is evolutionary conservation

A

the presence of genes in different species which reflects common origin and important functional property of the conserved gene

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27
Q

What is the purpose of karyotype

A
  • shows number of chromosomes
  • identify gender
  • identify genetic abnormalities
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28
Q

Genome instability is the hallmark of what disease

A

cancer

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29
Q

What are Mendel’s main findings

A
  • law of segregation
  • law of dominance
  • law of independent assortment
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30
Q

Explain the law of segregation

A

offspring acquire only one of the 2 alleles from each parent

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31
Q

Explain the law of independent assortment

A

the alleles of 2 or more differents genes get sorted into gametes independently of one another

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32
Q

Explain the law of dominace

A

alleles can be dominant or recessive

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33
Q

What is an allele

A

different version of a gene

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34
Q

What does phenotype mean

A

trait controlled by the genotype (what you look like based on genes)

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35
Q

What does genotype mean

A

the combination of alleles present in a person

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36
Q

What does dominant allele mean

A

determines trait if individual only has one copy of this allele

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37
Q

What does recessive allele mean

A

determines trait only if the individual has 2 copies of this allele

38
Q

What is co-dominance

A

pairs of alleles which are both expressed

39
Q

What is pleiotropy

A

single gene mutation that can cause a range of phenotypes

40
Q

What is genetic heterogeneity

A

same phenotype can be caused by a range of different genes

41
Q

What is a polygenic trait

A

a trait controlled by more than 1 gene

42
Q

What factor influences polygenic traits

A

the environment

43
Q

How can polygenic traits be represented (stats)

A

continuous variation

44
Q

What is a dihybrid cross

A

cross between organisms that are both heterozygous for two different features

45
Q

What are homologous chromosomes

A

pair of chromosomes that have the same length, shape and they contain the same gene in the same location

46
Q

What happens in G1 of interphase

A

cellular contents except for DNA is replicated

47
Q

What happens in the S phase of interphase

A

DNA is replicated

48
Q

What happens in the G2 phase of interphase

A

the cell double-checks for errors, making any repairs needed

49
Q

What is the synaptonemal complex

A

a highly structurally conserved protein structure that forms between 2 homologous chromosomes during meiosis

50
Q

What is the function of the synaptonemal complex

A

It facilitates crossover between non-sister chromatids at the chiasma

51
Q

When does crossing over occur

A

Prophase I

52
Q

What happens during crossing over

A

the exchange of genetic material between the 2 non-sister chromatids at the chiasm

53
Q

What is the purpose of crossing over

A

give rise to genetic diversity

54
Q

What are linked genes

A

genes that are carried on the same chromosome

55
Q

What are non-linked genes

A

genes that are carried on different chromosomes OR on the same but far apart from one another

56
Q

Why are they called “linked” genes

A

they usually inherited together

57
Q

What is the fault in Mendel’s law of independent assortment

A
  • it is only true for unliked genes
  • the inheritance of one linked gene affects the other
58
Q

How can linked genes be separated

A

cross overs

59
Q

What is recombination frequency

A

it determines how closely linked genes are
- large recombination frequency = far apart

60
Q

What are wild type alleles

A

allele that encodes for the phenotype most common in a population

61
Q

What is a mutant allele

A

allele that encodes for the phenotype that differs from the normal population and phenotype

62
Q

How to calculate allele frequency

A

number of copies of allele A in population/ total number of alleles in population

63
Q

What is the purpose of the Hardy-Weinberg

A
  • a way to measure if a population is evolving or not
  • to compare allele frequencies in a population over time
64
Q

What are some Hardy-Weinberg assumptions

A
  • no mutation
  • no migration
  • population size is big
  • mating is random
  • no selection
65
Q

What are the different types of natural selection

A
  • stabilising selection
  • directional selection
  • disruptive selection
66
Q

Explain stabilising selection

A
  • genetic diversity decreases as the population stabilises on a particular trait
  • intermediate phenotypes have the highest fitness
67
Q

What does the graph of stabilising selection look like

A

a skinny bell curve

68
Q

Explain directional selection

A
  • a single phenotype is favoured causing the allele frequency to shift in one direction
  • one of the extreme phenotypes has the highest fitness
69
Q

What does the graph of direction selection look like

A

the bell curve is sifted to towards one side

70
Q

Explain disruptive selection

A

extreme values for a trait are favoured over intermediate values

71
Q

What does the graph of disruptive selection look like

A

the bell curve has 2 peaks

72
Q

What is a genetic drift

A

a mechanism of evolution where frequencies of population change due to random events that are not linked to adaptation

73
Q

What are population bottlenecks

A

a large population declines and the gene pool of the reduced population does not represent the original population

74
Q

What is an example of a cause of a population bottleneck

A

natural disasters

75
Q

What are the consequences of population bottlenecks

A
  • reduced genetic variation
  • population may not be able to adapt to new selection pressure
76
Q

What is the founder effect

A

a few individuals colonise a new location and their gene pool is not representative of the original location

77
Q

What is the main consequence of the founder effect

A

reduced genetic variation from orginal population

78
Q

What are the different types of non-random mating

A
  • assortative mating
  • positive assortative mating
  • negative assortative mating
79
Q

What is assortative mating

A

mates chosen based on genotype/phenotype

80
Q

What is positive assortative mating

A

mates are chosen based on similar genotype/phenotype

81
Q

What is negative assortative mating

A

mates are chosen based on dissimilar genotype/phenotype

82
Q

What is aneuploidy

A

presence of an abnormal number of chromosomes in a cell

83
Q

What is it called when one chromosome is missing

A

Monosomy

84
Q

What is it called when there is an extra chromosome that joins a pair

A

Trisomy

85
Q

What is the main general consequence of aneuploidies on autosomal chromosomes

A

They are incompatible with life

86
Q

Relationship between aneuploidy and maternal age

A

woman’s age increases so does the risk of producing eggs with aneuploidy

87
Q

How is a diagnosis of aneuploidy achieved

A

karyotype

88
Q

What is the SRY gene

A

the protein produced by this gene is involved in male-typical sexual characteristics + prevents female reproductive structures

89
Q

What is the Human Genome project

A

they worked out the entire genetic material of human

90
Q

What is the purpose of the Human Genome Project

A
  • understand inherited disorders
  • search for genes linked to diseases
91
Q

What is nanopore sequencing

A

technology that enables real-time analysis of long DNA fragments

92
Q

What is Next Generation Sequencing

A

technology that is used for DNA and RNA sequencing and mutation detection

Cells, Organisms & Systems (5 decks)

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