Inheritance, population genetics and speciation

Define genotype:

All of the alleles an organism carries on its chromosomes

define phenotype:

physical characteristics of an organism due to the expression of its gene and environmental factors

When is the chi-squared test used?

• compare observed values and expected values

• Data falls into discrete categories

definition of species

• group of organisms that can produce fertile offspring

Definition of population

group of organisms of the same species living in the same environment at the same time

what is a gene pool;

All the alleles in a population

What is allele frequency?

the frequency of an allele in an ecosystem

what does the Hardy-Weinberg principle show?

The allele frequency does not change from one generation to the next

assumptions of the Hardy-Weinberg principle:

• no mutation

• No selection

• Mating is completely random

• Population is large

what is the Hardy Weinberg equation?

p² + pq + q² = 1

What is the source of genetic variation?

• crossing over

• Mutation

• Independent assortment

what are the effects of stabilising selection:

• favours one extremity

what is the effect of directional selection?

• favours the average phenotype

what is the effect of disruptive selection?

• favours either extremities, decreases frequency of average phenotype

• May lead to speciation

Describe allopatric speciation:

• geographical barrier separates species

• Prevents gene flow

• Random genetic mutation accumulates in the two sub species

• Different environmental factors may accelerate speciation

• Until population becomes reproductively isolated

describe sympatric speciation:

• occur in the same environment

• Mutation causes difference in hormone/ physiological/ behavioural difference

• Reproductive separation so no gene flow

• Different alleles passed on

• Disruptive selection

• Leads to different species that cannot produce fertile offspring (reproductive isolation)

what is genetic drift?

Change in frequency of an allele in a population due to random chance rather than natural selection

Meiosis results in cells that have the halploid number of chromosomes and show genetic variation. Explain how.

• Homologous chromosomes pair up along equator

• Crossing over occurs to form new combination of alleles

• Chromosome separates at random into two separate cells

• Chromosome line up in a random order

• Chromatids splits into separate cells