6.1.2 Patterns Of Inheritance Flashcards
What are the different patterns of inheritence
Codominance- two different alleles which are neither dominant nor recessive, both expressed in phenotype
Multiple alleles- more than two allelelic forms
Sex linkage- genes carried on X or Y chromosome
Autosomal linkage- genes located on same chromosome, likely to be inherited together.
What affects autosomal linkage?
Autosomal linkage effects expected ratio of offspring phenotypes, however this can become less of an effect due to crossing over. The further apart the alleles are located on the gene the more likely they are to be separated via crossing over, this alleles the expected gametes to be produced. When genes are linked there are less recombinant offspring so less variation.
What is epistasis?
When the presence of one gene will mask the expression of another
Can be recessive or dominant.
What is evolution?
Process of phenotypes of a population changing over many generations. Occurs as a result of variations in allelic frequency of populations.
What is a gene pool?
Complete set of genetic material in a population.
What is genetic drift?
Random changes in allele frequencies of a population due to chance events. Has a bigger impact on small populations, can eliminate whole alleles. Decreases genetic diversity.
What is gene flow?
The transfer of alleles between different populations.
What is the bottleneck effect?
Dramatic event occurs to reduce population size drastically. Leads to a reduced gene pool and genetic diversity. Can cause inbreeding and reduced fertility. Mutations are more prevalent. New gene pool is not representative of the old one.
What is the founder effect?
A small group from original population seperate, leading to an smaller gene pool and decreased genetic diversity. Rare alleles can be more common in new population (extreme genetic drift).
What are the different types of natural selection?
Stabilising- modal phenotypes is selected for and extremes are selected against. Happens when environment is stable.
Directional- selects for one extreme phenotypes and against the other extreme. Causes mean phenotypes to shift to one extreme.
Disruptive- both extreme phenotypes are selected for but the mean phenotypes is selected against.
What are the assumptions of the hardy-weinberg principle?
no mutations
Random mating
Large population
No migration or immigration
No natural selection pressures
What is allopatric speciation?
Populations are separated by a geographical barrier. Exposes populations to different environmental selection pressures. Involves prezygotic barriers. Interrupts gene flow between populations. Over many generations populations become too genetically different that they can no longer breed to produce fertile offspring.
What is sympatric speciation?
Populations become reproductively isolated. Ecological or behavioural mechanisms isolate groups. (Habitat, mate selection and chromosomal changes) most common in plants.
Whatvare the different types of variation?
Discontinuous- distinct subgroups, often monogenic traits. Represented by bar charts
Continuous- no distin t subgroups, often polygenic and influenced by environment (etiolation, diet and height)
