Inheritance Flashcards
Sex chromosomes are also called:
Heterosomes
All non-sex chromosomes are also called:
Autosomes
Which chromosome is longer, X or Y?
The X chromosome is much longer
The male genotype is:
The female genotype is:
Male = XY Female = XX
Give two examples of sex-linked recessive disorders
a) Colour blindness
b) Haemophilia
Why do far more males than females have sex-linked recessive disorders?
Males are XX, females are XY. Therefore, for males, it only takes one recessive allele for the disorder to be expressed in the phenotype. However, females have two X chromosomes, therefore it takes two recessive alleles which is half the likelihood
How can you tell if a condition is recessive, looking at a pedigree chart?
If both parents don’t have the condition but one child does, the condition is recessive
Define discontinuous variation
Differences in phenotype fall into distinct categories
Define continuous variation
No distinct categories, gradual change over a range
Define polygenes
Several genes that work together to control a characteristic
Define a polygenic characteristic
A characteristic controlled by several genes
Define a monogenic characteristic
A characteristic controlled by a single gene
Define epistasis
Epistasis is where two genes at different loci control the same, single characteristic, but one of the genes can mask the effect of the other
Epistatic gene =
The gene which supresses the expression of a gene at a different locus
Hypostatic gene =
The gene that is supressed
