Inheritance Flashcards
Define genotype.
The complete set of genes of an organism.
Define phenotype.
The expression of an organism’s genetic constitution, combined with it’s interaction with the environment.
What is meant by a dominant allele?
An allele whose characteristic will always appear in the phenotype, whether one or two are present.
What is meant by a recessive allele?
An allele whose characteristic only appears in the phenotype if no dominant allele is present.
What is meant by codominant alleles?
Two dominant alleles that both contribute to the phenotype, either by showing a blend of both characteristics, or the characteristics appearing together.
Define monohybrid inheritance.
Where one phenotypic characteristic is controlled by a single gene.
Define dihybrid inheritance.
Where two phenotypic characteristics are determined by two different genes present on two different chromosomes at the same time.
What is meant by sex linkage?
Where an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual.
Why are males more likely to express a recessive sex-linked allele?
Males only get one copy of the allele, so they will express this characteristic even if it is recessive.
Which parent do males inherit sex-linked characteristics from?
Their mother as the Y chromosome can only come from their father. Therefore if the mother is heterozygous for sex linked alleles, she is a carrier and may pass the trait on.
What is meant by autosomal linkage?
Where two or more genes are located on the same (non-sex) chromosome. In this case, only one homologous pair is needed for all four alleles to be present. For genes that aren’t linked, two homologous pairs are needed.
What is meant by epistasis?
Where two non-linked genes interact with one gene either masking or suppressing the other gene.
Define the two types of epistasis.
Recessive epistasis = where two homozygous recessive alleles mask expression of another allele
Dominant epistasis = where one dominant allele masks expression of multiple other alleles.
What is the chi squared test?
A statistical test to find out whether the difference between observed and expected data is due to chance or a real effect.
What are the criteria for the chi squared test?
- data placed in discrete categories
- large sample size
- only raw count data allowed e.g. not percentages
- no data values equal zero
