Evo Devo Flashcards
1
Q
Nucleotide =
A
sugar + phosphate + base
2
Q
Pyrimidines
A
Cytosine and thymine
3
Q
Purines
A
Adenine and guanine
4
Q
Transcription
A
mRNA is transcribed from the DNA in the nucleus
5
Q
Translation
A
Amino acid sequence is read off the mRNA sequence in the ribosomes
6
Q
what percentage of DNA codes for genes?
A
5%
7
Q
Uses of HWE
A
Simple conceptual model; estimation of variables; null hypothesis
8
Q
what would cause a deviation from HWE
A
Non-random mating (assortative, disassortative or no mating)
9
Q
Assortative mating
A
like genotypes preferentially mate; result is a deficit of heterozygotes
10
Q
Disassortative mating
A
different genotypes preferentially mate; result is excess of heterozygotes
11
Q
Forces of genetic change
A
natural selection, genetic drift, mutation and migration
12
Q
response to natural selection is determined by variation in…
A
fitness
13
Q
Fitness (w)
A
relative survival and reproductive success of a genotype
14
Q
selection coefficient (s)
A
relative selective intensity against a genotype/reduction in fitness relative to the best genotype (1-w)
15
Q
Balance of selection and mutation
A
selection can never eliminate deleterious alleles because they keep re-appearing by mutation
16
Q
why do chromosome heterozygotes have higher fitness
A
Dominance: Chromosomal heterozygotes mask deleterious recessives at many loci
17
Q
example of single locus heterozygote advantage
A
Sickle cell anemia polymorphism in humans (anemia selects against SS, malaria selects against AA)
18
Q
Why are there not many examples of single locus heterozygote advantage
A
not common; hard to detect; theoretical problem of genetic load
19
Q
positive frequency dependence
A
fitness increases with frequency, results in monomorphism
20
Q
negative frequency dependence
A
fitness decreases with frequency, result is polymorphism
21
Q
examples of negative frequency dependence
A
predation, mate choice, niche variation
22
Q
causes of genetic drift
A
mendelian segregation, finite population size
23
Q
principles of genetic drift
A
- The direction of genetic drift in unpredictable
- The magnitude of genetic drift depends on population size
- The long-term effect is to reduce variation within a population
- Genetic drift causes populations to diverge from one another
- causes heterozygosity to decrease over time
24
Q
factors that affect effective population size
A
unequal sex ratio; variation in population size; variation in family size; mitochondrial DNA
25
founder effect
Establishment of a new population by a few original founders
26
population bottleneck
population is suddenly reduced in size
27
identical by state
functionally equivalent alleles
28
identical by descent
pairs of alleles that trace to the same copy
29
inbreeding coefficient (F)
probability that two copies of a gene are identical by descent
30
effective population size (Ne)
the number that when substituted for N in equations based on ideal populations, describes the drift experienced by the actual population
31
what is mutation
any heritable change in genetic material
32
types of mutation
chromosomal; point; indels; gene duplications
33
chromosomal mutations
- Change in the number or structure of chromosomes
- Aneuploidy – extra or missing chromosomes
- Polyploidy – entire sets of chromosomes duplicates
- Inversions – chromosome breaks and is flipped 180 degrees
- Translocations – chromosome breaks and attaches to a non-homologous chromosome
34
point mutations
A change in a single nucleotide in a DNA sequence
35
Indels
Insertions or deletions in the DNA sequence caused by errors in DNA replication
36
Gene duplication
New copies of a gene or groups of genes
37
why does sexual reproduction exist
theories
- genetic constraint
- sex can accelerate evolution
- coevolution of hosts and parasites
- mutational theory
38
genetic constraint
Mutations to produce asexual reproduction have not occurred so we are ‘stuck with it’ (unlikely because mutation for asexual reproduction is not difficult, it has arisen many times)
39
coevolution of hosts and parasites
- Sex likely to be advantageous in changing environments
- Coevolution between hosts and parasites can generate rapid ‘environmental’ change
- Arms race between hosts resistance mechanism and parasites method of penetrating defences
40
sex can accelerate evolution
Beneficial mutation, at separate loci, can be combined in a single individual faster with sex
41
mutational theory
Sex exists because it enhances the power of selection against deleterious mutation
42
inbreeding
positive assortative mating for relatedness; mating between related individuals
43
how does inbreeding differ from assortative mating
it affects all genes, not just those controlling that trait which mating preference is based
44
what does inbreeding result in
excess of homozygotes and deficiency of heterozygotes
45
autozygous
Alleles that are ibd are derived by replication from a single allele
46
allozygous
Alleles that are not ibd are called
47
Inbreeding depression
increased appearance of lethal and deleterious traits with inbreeding
48
Does inbreeding ‘purge’ deleterious recessive alleles?
If deleterious recessives are responsible for inbreeding depression, then populations that habitually inbred should have higher frequencies of fitter wild-type alleles
49
population subdivision
Most populations are grouped into smaller subpopulations where random mating usually occurs (genetic neighbourhood)
50
reduction in heterozygosity due to population subdivision
wahlund effect
51
why is it important to know F statistic for conserving genetic variation
- When a population has no population structure (FST close or equal to 0), there is no variation in allele frequencies between subpopulations, therefore genetic resources can be conserved by protecting one or two large populations
- If FST is large, there is a high population structure and most genetic variation exists between subpopulations rather than within subpopulations, in these species it is necessary to protect as many subpopulations as possible to conserve genetic diversity
52
gene flow
The movement of genes between subpopulations within a species
53
Homogenising force
holds the gene pools of subpopulations together and limits how much genetic divergence takes place
54
genetic variation has two impacts on island populations:
- Reduces genetic variation within populations
- Increases genetic variation between populations
55
stepping stone model
Recognizes that gene flow is likely to be greater among demes (populations) closer together
56
polygenic
traits that are controlled by multiple genes (e.g. height)
57
coadaptation
allele favoured by selection if it is in the same individual as a particular allele at another locus
58
haplotype
combinations of alleles at different loci
59
linkage equilibrium
When alleles at different loci combine independently
60
linkage disequilibrium
when haplotype frequencies deviate from linkage equilibrium
61
recombination frequency
the frequency of recombination between two loci (range 0-0.5)
62
significance of linkage equilibrium
- Simplest model for 2 loci (HWE for single locus)
- Deviations can indicate that something interesting is happening (i.e. one of the assumptions is not met)
- Lets us know if more complex two-locus theory is needed
63
causes of linkage disequilibrium
linkage; genetic drift; non-random mating; mutation; natural selection
64
linkage disequilibrium mapping
Associations between traits and molecular markers are used to identify genes controlling traits
65
species concepts
biological; recognition; ecological; phenetic; phylogenetic
66
biological species concept
Groups of interbreeding natural populations that are reproductively isolated from other groups (no gene flow)
67
recognition species concept
Group of individuals with shared specific mate recognition systems
68
ecological species concept
Defines a species as a set of individuals with shared ecological attributes
69
phenetic species concept
Defines a species as a set of individuals with shared morphological attributes
70
phylogenetic species concept
Species are identified by estimating the phylogeny of closely related populations and finding the smallest monophyletic group
71
what stops species interbreeding
Reproductive isolating barrier (pre or post zygotic) are evolved characters that prevent interbreeding between species
72
how does reproductive isolation evolve?
- allopatric speciation model (geographical isolation)
- sympatric speciation model
73
genetic correlation can exist for two reasons:
- Pleiotrophy – one gene influences more than one trait
- Hitch-hiking – natural selection favours one locus, genes at other loci also increase
74
qualitative vs quantitative traits
- qualitative: discrete categories
- quantitative: needs to be measured
75
quantitative traits
Depend on genes whose individual effects are small in relation to variation attributed to other causes
76
common property of quantitative traits
sibling resemblance (generally, the closer the relationship, the closer the resemblance)
77
breeder's equation
- Proportion of total phenotypic variance that is due to genetic causes
78
method for quantifying resemblance between parents and offspring
parent-offspring regression
79
paternal half siblings
A powerful method for testing for additive genetic effects based on the covariance among paternal half siblings
80
basic principle of paternal half siblings
where males provide no resources at reproduction other than genes, and phenotypic similarity among his offspring from different females must be due to those offspring sharing the same paternal genes
81
the fitness function
Describes the strength and form of selection acting on the phenotype
82
direct selection
causal relationship between relative fitness and phenotype
83
indirect selection
when there is a correlation between the focal trait and another one that experiences direct selection
84
correlational selection
When two traits interact to determine fitness
85
applications of quantitative genetics in the wild
medicine; conservation; selective breeding; disease resistance
86
additive genetic variation
the variation that causes offspring to resemble their parents
87
allelic diversity
the variation discernable through molecular genetic techniques
88
fisher's fundamental theorem
- at each generation, only a subset of fitness related alleles pass on to the next generation
- There should be very little genetic variation for traits that are closely related to fitness
89
mutation:selection balance
Selection and drift must be balanced by mutation and other mechanisms that maintain genetic variation
90
whether mutations can supply enough genetic variation depends on:
- the genomic mutation rate
- the intensity of selection
- the number of genes involved
91
how can variation be maintained in variable environments
When generations overlap or environmental heterogeneity is spatial, genetic variation can be maintained by migration between the ‘patches’
92
disruptive selection
- Short term increases in heritability
- Practice: natural selection
93
theory of selection for heterozygotes
- where the optimum phenotype is the heterozygote
- Practice: mate choice in Antarctic fur seals
94
theory of frequency dependent selection
- rare genotypes have higher fitness than common ones, creating ‘negative’ frequency dependent selection
- Practice: frequency dependent selection on male phenotype in a species of guppy
95
theory of antagonistic pleiotrophy
- Genes that enhance the fitness pay-off from one aspect of life-history reduce the pay-off from another
- Practice: attractiveness and male survival in the guppy
96
