Patterns Of Inheritance 2 Flashcards

1
Q

Evolution

A

The change in inherited characteristics of a group of organisms over time
Occurs due to change in frequency of different alleles within population

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2
Q

Gene pool

A

Sum of all genes in a population at any given time

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3
Q

Allele frequency

A

The relative frequency of a particular allele in a population

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4
Q

Allele frequency

A

P + q = 1
P^2 + 2pq + q^2 =1
P^2= frequency of homo dominant
Q^2= frequency of homo recessive
2PQ= frequency of heterozygous

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5
Q

Factors affecting evolution

A

Mutation
Sexual selection
Gene flow- movement of alleles between populations
Genetic drift- change in allele frequency due to random mutation ( greater in smaller pop)
Natural selection

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6
Q

Limiting factors

A

Density dependent- dependent on population size eg disease predation etc
Density independent- affect all sizes of pop eg climate change and natural disasters

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7
Q

Bottlenecks

A

Large reduction in population size
Gene pool greatly reduced

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8
Q

Founder effect

A

Establishment of new colonies by a few isolated individuals
Small populations have a far smaller gene pool
If carried to new population freq of alleles that were rare in original pop will be much higher in the new - much bigger impact during natural selection

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9
Q

Stabilising selection

A

The norm or average is selected for and the extremes are selected against
Increase in frequency of average alleles

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10
Q

Directional selection

A

Change in the environment and the less common extreme phenotypes are positive selected - allele frequency of this increases

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11
Q

Disruptive selection

A

Extremes are selected for and the norm selected against
Eg blue lazuli birds
Brown non threatening not compete pop increase
Blue too threatening not compete pop increases
Mix compete pop fall

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12
Q

Speciation

A

Formation of a new species through the process of evolution
Not able to interbreed to produce fertile offspring

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13
Q

Events that lead to speciation

A

Members become isolated and no longer interbreed resulting in no gene flow
Alleles within the groups undergo random mutations
Accumulation of mutations and changes in allele frequencies over many generations lead to large changes in phenotype - no longer able to interbreed

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14
Q

Allopatric speciation

A

When members of population separated from main by a physical barrier eg sea
Different selection pressures thus different adaptions - founder effect/ generic drift

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15
Q

Sympatric speciation

A

Within population that shares the same habitat
When members of 2 different species interbreed and form fertile offspring
Different No of chromo to parents and may longer not be able to breed w parental population

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16
Q

Artificial selection/selective breeding

A

Selection of plants or animals with desirable characteristics by farmers or breeders

17
Q

Inbreeding and it’s problems

A

Breeding closely related individuals
-decreases genetic diversity and adaptability
- recessive genetic disorders more common
- less biologically fit - less likely to survive and produce offspring

18
Q

Seed banks

A

Alleles are used to increase genetic diversity by outbreeding
Reduces homozygous recessive and increase potential to adapt

19
Q

Chlorosis

A

Plants have a lack of chlorophyll
Not a genetic disorder which alters phenotype - environmental factors
- lack of light
- mineral deficiency
- virus infections

20
Q

Animal body mass

A

Controlled by genetics and environment
Obesity= environment
However can be genetic eg mice mutation on chromo 7 fat deposition is different

21
Q

Continuous variation

A

Polygenic
Take any value within a range
Genetic and environmental
Eg skin colour

22
Q

Discontinuous variation

A

Only appear in specific discrete values/ catergories
Monogenetic
Eg blood group

23
Q

Monogenic inheritance

A

Inheritance of a single gene
Eg parents Gg and Gg for green pods
Form GG Ggx2 and gg (yellow pod)

24
Q

Codominance

A

When two alleles of the same gene are equally dominant
Both are expressed
Eg snap dragons white x red = pink
Upper and lower case not used

25
Multiple alleles
Eg blood group Ia and Ib are codominant however Io is recessive
26
Sex linkage
Genes carried on sex chrosomomes- sex linked As the Y is much smaller than X doesn’t hold all copies from X If X holds recessive allele characteristic is more commonly shown in men eg colour blindness and haemophilia
27
Haemophilia
Sex linked genetic disorder V slow blood clotting due to the absence of a protein blood clotting factor
28
Dihybrid inheritance
Show the inheritance of 2 genes Heterozygous = 9:3:3:1
29
Linkage
Ratios in dihybrid crosses differ significantly from those expected. - due to linkage genes on same chromo
30
Autosomal linkage
When the genes that are linked are found on the same chromosome Linked genes are inherited as one unit - no independent assortment 3:1 if not this ratio crossing over would have occurred
31
Recombinant offspring
Different combinations of alleles than either parent
32
Proximity of genes effect
Closer the genes on a chromosome the less likely they are to be separated during crossing over and fewer recombinant
33
Recombinant frequency
Amount of crossing over No of recombinant offspring/ total No of offspring 50% indicates no linkage Less than 50% there is linkage and independent assortment has been hindered
34
Chi squared
Sum of((observed-expected)^2/expected) If greater than critical value reject null hypothesis sig diff vice versa
35
Epistasis
Interaction of genes at different loci Dominant or recessive epistasis
36
Dominant epistasis
If dominant allele has an effect on the expression of another gene masking it
37
Recessive epistasis
If both alleles recessive blocks the expression of another gene