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
Epistasis _______ the number of phenotypes for a characteristic, usually a ::: ratio
Epistasis REDUCES the number of phenotypes for a characteristic, usually a 9:3:3:1 ratio
State the ratio for dominant epistasis and define it
Dominant epistasis = 12:3:1
= The presence of a dominant allele at the first locus prevents the expression of the allele at the second locus
State an example of dominant epistasis
Fruit colour in squash plants
State the ratio for recessive epistasis and define it
Recessive epistasis = 9:3:4
= The presence of a homozygous recessive allele prevents the expression of the alleles at the second locus
Give an example of recessive epistasis
Coat colour in mice
If your Chi Squared value ≥ the critical value…
If Chi Squared value ≥ the critical value…
a) There is a significant difference between O & E
b) Reject the H0
If your Chi Squared value ≤ the critical value…
If Chi Squared value ≤ the critical value…
a) There is NO significant difference between O & E
b) Accept the H0 (Fail to reject)
