Patterns Of Inheritance

Question 1

3 conditions needed for speciation to occur?

Answer 1

Mutations
Different selection pressures
Natural/directional selection

Question 2

Why is genetic drift more concerning in smaller populations?

Answer 2

• Random changes in allele frequencies cause larger % changes in small populations
• Alleles will be lost from the population

Question 3

Ethical consideration surrounding artificial selection?

Answer 3

Selective breeding leads to ‘inbreeding’ which is breeding animals closely related to eachother - reduces gene pool (reduced no. Alleles in a population) - known as inbreeding depression
Due to limited size of gene pool:
- increased chance of genetic defect (as there is a higher chance of harmful recessive alleles combining and being expressed)
- more vulnerable to new diseases (as less chance of resistant alleles being present in the reduced genes pool)

Question 4

E.g of dog breeds that suffer due to a long history of artificial selection?

Answer 4

Bulldogs and Pekinese - breathing problems bc of extremely shortened snouts
Sait Bernards and Great Danes can suffer frm hip dysplasia
Golden retrievers can suffer from malignant blood vessel tumours

Question 5

Allopatric speciation?

Answer 5

1. Populations of a species become Seperated by geographical barriers (e.g body of water/mountain range or motorway)
2. Creates 2 populations of same species that are reproductively isolated so no gene flow between them
3. Different Selection pressures act on the populations
4. Mutations can occur + natural selection favours different alleles in each environment (so the pops experience different directional selection) and genetic drift can occur (if populations are small)
5. Over time allele frequencies in a population changes causing genetic divergence (as the gene pools are being increasingly different)
6. The 2 populations evolve separately + they can no longer breed to prodcue fertile offspring - new species

Question 6

Sympratic speciation?

Answer 6

Ecological/behavioral separation mechanisms (e.g different habitat preference, mate selection) lead to groups becoming reproductively isolated
Reproductive isolation prevents gene flow
Different selection pressures act on the 2 populations
Natural selection acts on each group and favours different alleles + also genetic drift occurs (if the groups are small)
This leads to genetic divergence
Causes the populations to evolve separately + new species formed (the 2 groups cannot reproduce to produce fertile offspring)

Question 7

Genetic divergence?

Answer 7

Process where 2 or more populations of the same species become genetically different over time

Question 8

Reproductive isolation?

Answer 8

Occurs when 2 populations of the same species can no longer interbreed to produce fertile offspring

Question 9

What factors lead to genetic divergence?

Answer 9

Mutations
Natural/directional selection (caused by selection pressures)
Genetic drift

Question 10

Importance of maiantining a resource of genetic material for use in sleelctive breeding?

Answer 10

Important to maintain a resource of genetic material that is close to the original wild type (of the organism you’re selectively breeding)
- ensure gene pool for organism doesn’t get too small

Question 11

E.g of maintaining genetic resources ?

Answer 11

Outbreeding
Maize has been inbred heavily
- led to smaller/weaker maize plants due to inbreeding depression
Inbreeding depression increases chance of harmful recessive alleles combining/being expressed in phenotype/leads to decreased growth and survivability

Outbreeding wild type varieties of maize involves breeding induviduals that are not closely related
- produce taller/healthier maize plants
Reduces chances of harmful recessive alleles combining/being expressed in phenotype /lead to increased growth