Inheritance And Selection Flashcards
What is a genotype?
The genetic composition of an organism
All alleles in an organism
What is a phenotype?
The characteristics of an organism, often visible, resulting from its genotype and the environment
What is a gene?
A section of DNA that is a sequence of nucleotides that determine a singular characteristic
Codes for a specific amino acid
What is an allele?
One of the different forms of a gene
What is a dominant allele?
An allele that is always expressed in the phenotype
What is a recessive allele?
When the allele is only expressed if it is homozygous or diploid as it is masked by the dominant
What are co-dominant alleles?
When two alleles are equally dominant and do contribute to the phenotype
What is monohybrid inheritance?
The inheritance of a single gene
What are the sex chromosomes for male and female?
Male - XY
Female - XX
How are sex linked diseases inherited?
For most of the X chromosome there is no equivalent portion of the Y chromosome
Recessive alleles on the non-homologous portion of the X chromosome will appear more frequently in males
Because there is not dominant allele to stop the recessive allele being expressed
In sex linked diseases who is the disease inherited from?
A male inherits it from his mother as his father will have a Y chromosome and so cannot pas an allele on
But a father can pass it to a daughter on the X chromosome
What are the blood groups and which ones are recessive or dominant?
A - AA or AO
B - BB or BO
AB - AB
O - OO
A and B are co dominant and O is recessive
What five conditions are assumed when calculating Hardy-Weinberg?
No mutations An isolated population Mating is random No selection The population is large
What does the Hardy-Weinberg principle predict?
That the proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next
What is directional selection?
If the environmental conditions change so that those with phenotype a further away from the mean are more adapted for the new conditions
What is stabilising selection?
When environmental conditions stay stable so individuals with phenotypes closer to the mean are favoured
What is speciation?
The evolution of a new species from existing species
Stages of geographical isolation
When a physical barrier prevents two populations from breeding
Climate change creates two different conditions, one hot, one cold
Those with advantageous phenotypes survive and breed passing on the allele for it
Others not adapted die
Allele type and frequency in the gene pools become more different until they are different species
They will not be able to breed to produce fertile offspring
