Patterns Of Inheritance 2

Question 1

Evolution

Answer 1

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

Question 2

Gene pool

Answer 2

Sum of all genes in a population at any given time

Question 3

Allele frequency

Answer 3

The relative frequency of a particular allele in a population

Question 4

Allele frequency

Answer 4

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

Question 5

Factors affecting evolution

Answer 5

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

Question 6

Limiting factors

Answer 6

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

Question 7

Bottlenecks

Answer 7

Large reduction in population size
Gene pool greatly reduced

Question 8

Founder effect

Answer 8

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

Question 9

Stabilising selection

Answer 9

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

Question 10

Directional selection

Answer 10

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

Question 11

Disruptive selection

Answer 11

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

Question 12

Speciation

Answer 12

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

Question 13

Events that lead to speciation

Answer 13

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

Question 14

Allopatric speciation

Answer 14

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

Question 15

Sympatric speciation

Answer 15

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

Question 16

Artificial selection/selective breeding

Answer 16

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

Question 17

Inbreeding and it’s problems

Answer 17

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

Question 18

Seed banks

Answer 18

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

Question 19

Chlorosis

Answer 19

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

Question 20

Animal body mass

Answer 20

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

Question 21

Continuous variation

Answer 21

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

Question 22

Discontinuous variation

Answer 22

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

Question 23

Monogenic inheritance

Answer 23

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

Question 24

Codominance

Answer 24

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

Question 25

Multiple alleles

Answer 25

Eg blood group Ia and Ib are codominant however Io is recessive

Question 26

Sex linkage

Answer 26

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

Question 27

Haemophilia

Answer 27

Sex linked genetic disorder
V slow blood clotting due to the absence of a protein blood clotting factor

Question 28

Dihybrid inheritance

Answer 28

Show the inheritance of 2 genes
Heterozygous = 9:3:3:1

Question 29

Linkage

Answer 29

Ratios in dihybrid crosses differ significantly from those expected. - due to linkage genes on same chromo

Question 30

Autosomal linkage

Answer 30

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

Question 31

Recombinant offspring

Answer 31

Different combinations of alleles than either parent

Question 32

Proximity of genes effect

Answer 32

Closer the genes on a chromosome the less likely they are to be separated during crossing over and fewer recombinant

Question 33

Recombinant frequency

Answer 33

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

Question 34

Chi squared

Answer 34

Sum of((observed-expected)^2/expected)
If greater than critical value reject null hypothesis sig diff vice versa

Question 35

Epistasis

Answer 35

Interaction of genes at different loci
Dominant or recessive epistasis

Question 36

Dominant epistasis

Answer 36

If dominant allele has an effect on the expression of another gene masking it

Question 37

Recessive epistasis

Answer 37

If both alleles recessive blocks the expression of another gene