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SEMESTER 1 > BIO genetics and evolution > Flashcards

BIO genetics and evolution Flashcards

1
Q

Definition of dominant

A

an allele that is always expressed in the phenotype

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2
Q

definition of recessive

A

an allele that is only expressed if homozygous

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3
Q

Definition of genotype

A

genetic composition of an organism(which two alleles they have for a gene)

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4
Q

definition of phenotype

A

characteristic of an organism due to expression of genotype and environment

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5
Q

Definition of gene

A

small section of DNA which codes for a polypeptide

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6
Q

Definition of allele

A

alternative form of a gene

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7
Q

what is dihybrid crosses?

A

genetic cross where inheritance of two genes is considered at same time

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8
Q

in a dihybrid cross, both the parents are heterozygous so what would the ratio be normally and if not why?

A

9:3:3:1 unless autosomal linkage or crossing over in meiosis

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9
Q

what does crossing over result in?

A

new combination of alleles in gametes

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10
Q

what is autosomal linkage?

A

when 2 genes are located on same chromosome not x or y

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11
Q

if you do not observe the ratio that you expected what does this mean?

A

crossing over has occurred

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12
Q

what does crossing over in meiosis do?

A

new combination of alleles in gametes

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13
Q

what are codominant allies?

A

both alleles expressed in phenotype

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14
Q

what is locus?

A

position of gene on chromosome

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15
Q

homozygous definition

A

both alleles being the same

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16
Q

heterozygous defintion

A

both alleles differing

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17
Q

multiple alleles definition

A

more than 2 alleles of a particular gene (only 2 in genotype)

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18
Q

what is a sex-linked gene?

A

gene carried out only on one type of sex chromosome usually x

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19
Q

what is menders monohybrid ratio?

A

3:1
Tt Tt genotypes
T+t, T+t gametes
TT Tt Tt tt F2 genotyoes
tall tall tall dwarf phenotypes

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20
Q

is probability pf blue eyes 1/4 and blonde hair is 1/4 what is probability of both blue eyes and blonde hair?

A

1/16

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21
Q

what are autosomes?

A

non-sex chromosomes 22 pairs

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22
Q

why are recessive conditions caused by females?

A

as males do not carry alleles on Y which is why makes can’t be heterozygous

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23
Q

why can’t a man passed a sex linked condition to his son?

A

males have a Y chromosome which could only come from father so x chromosome must have come from mothers

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24
Q

why might observed and expected not be similar?

A

small sample size-if low number of offspring then sampling error is greater
fusion of gametes at fertilisation is random

25
Definition of species
exists as one or more populations individuals of same species can breed together to make fertile offspring
26
Definition of population
group of organisms of same species occupying particular space at a particular time that can potentially interbreed
27
Definition of gene pool
all alleles in a population
28
definition of allelic frequency
number of times an allele of a particular genes occurs within the gene pool
29
what does the hardy-weinburg principle predict?
predicts that allele frequencies in a population will not change from gen to gen if -population is large and isolated -mating with population is random -no mutations of gene occur - no selection
30
hardy-weinburh equation?
p^2 +2PQ + q^2
31
variation=
genetic and environmental factors
32
what is the primary source of genetic variation?
mutation. meiosis and random fertilisation of gametes during sexual reproduction produce further genetic variation
33
what are the types of genetic factors that can occur?
gene mutations, crossing over, independent segregation of chromosomes, random fertilisation of gametes
34
what are the characteristics mainly influenced by genetic factors with little or no environmental influence?
controlled by one or two genes, expressed as distinct phenotypes with no intermediates, are represented as distinct groups on bar charts/pie
35
what characteristics that are significantly influenced by the environment?
controlled by many genes (polygenic), no separate categories or types but have range of intermediates between two extremes, produce a curve of normal distribution when plotted on a graph
36
37
in natural selection all organisms are subject to selection pressures, what are they?
predation, disease and competition
38
what happens when there is a change in environment in organisms with particular phenotype?
being better adapted to this environment surviving and reproducing while those that are less adapted do not
39
what is survival of some organisms of a population that go on to reproducing known as?
differential survival and differential reproductive success
40
what happens when frequency of a selected phenotype increases?
frequency of favourable alleles in gene pool increases
41
what is the method for natural selection?
1. variation exists due to mutations and genetic recombination 2-some individuals have advantageous alleles increasing chances of reproduction 3- individuals pass on beneficial to next gen 4-frequency of advantagaous alleles increases in populations 5. leads to change in population genetic composition over time 6.process is called evolution by natural selection
42
what are types of natural selection?
directional selection, stabilising selection, disruptive selection
43
what is directional selection?
- one of the extremes has selective advantage -occurs when there is a change in environment -modal trait changes
44
what is stabilising selection?
-modal trait has selective advantage -occurs when no change in environment -modal trait remains same -standard deviation decreases as individuals with extreme trait decreases
45
what is disruptive selection?
- individuals which have alleles coding for extreme trait more likely to survive and pass on their alleles -allele frequency will change and more individuals possess allele for extreme trait + model ratio become less frequent -continued disruptive selection can ultimately lead to speciation
46
what is speciation?
evolution of new species from existing ones
47
what is species group of?
group of individuals capable of breeding with one another to make fertile-offspring
48
why does evolution occur?
as a result of change in allele frequencies in a population
49
how does speciation occur?
happened when 1 organically population of same species reproductively isolated so 2 populations of same species can't breed this results in accumulation of differences in their gene pools to extent that that 2 populations would be unable to interbreed to make fertile offspring
50
what are the different ways speculation can occur?
allopatric , sympatric and genetic drift
51
how does allopatric speciation occur?
1.separated geographically eg by earth quake,(geographically isolated) so unable to produce due to geographic barrier leads to reproductive isolation 2. both populations continue to accumulate different beneficial mutations + different selection pressures in each environment causes GENETIC variation 3. due to this accumulation of DNA differences over time populations become so genetically different (genetic divergence) due to NATRUAL SELECTION + GENETIC drift 4. unable to interbreed to create fertile offspring so classes as 2 different species
52
what is sympatric speciation?
1. random mutation within same population impacts reproductive behaviour 2. unable to perform different courtship rituals to fertile at different times of year 3. individuals can't produce together due to reproductive isolation so no gene flow 4. overtime become reproductively isolated so accumulate different mutations to extent that DNA is so different they can't interbreed to create fertile offspring 5. classed as 2 different species
53
what is a genetic drift?
change in allele frequency within a population between generations
54
what does continual substantial genetic drift result in?
evolution
55
does genetic drift impact big populations?
no so the smaller a population is the bigger allele frequency changes have proportionally so evolution occurs ore rapidly in smaller populations
56
does genetic drift rely on natural selection?
no by chance, allele of particular gene is passed on to offspring more often than other alleles of same gene so frequency of this allele increases in susccesivve gens greater effect on smaller populations as likely to be small variety of a;;eyes in gene pool
57
what is crossing over?
during meiosis exchange of alleles of same genes results in new combo of alleles
58
what is independent segregation of chromosomes?
during first meiotic division separation of two members of homologous pair of chromosomes happened independently of the separation of other homologous pairs

SEMESTER 1 (8 decks)

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