Inheritance Flashcards
Monohybrid Inheritance Definition and F1 and F2 ratios
One phenotypic characteristic is controlled by a single gene.
F1: 100% heterozygous
F2: 1:2:1
Dihybrid Inheritance and the Heterozygous Genotype Cross Phenotypic Ratio
When two phenotypic characteristic are determined by two different genes on two different chromosomes at the same time.
9:3:3:1
Codominance
Two dominant alleles which both contribute to the phenotype.
Multiple Alleles (Blood Group)
A gene may have more than two alleles, e.g. blood groups.
A and B are codominant and O is recessive to both. Therefore possible phenotypes are A, B, AB, and O
Sex Linkage
A gene that is located on a sex chromosome
Which chromosome are most sex linked alleles found on?
X chromosome
Who’s more likely to express recessive sex linked alleles and why?
Males, X chromosome shorter so most alleles on X don’t have a corresponding Y, so if recessive allele on X then it will be expressed, in females both X chromosomes must have recessive allele which is less likely.
Which parent do males inherit sex linked characteristics from
Mother, X chromosome comes from mother and Y comes from father
Sex-linked genetic cross between heterozygous female and unaffected male ratios
X^H X^h x X^H Y
1 unaffected female: 1 carrier female: 1 affected male: 1 unaffected male
Autosomal Linkage
If two or more genes are located on the same chromosome.
Possible gametes: AB and ab only
Cross gives 1:2:1 ratio of AABB:AaBb:aabb
Autosomal Linkage and Crossing Over
During meiosis, crossing over may cause the genes to be separated, which may result in recombination
The closer the genes are on the chromosome, the less likely it is for recombination.
Epistasis
When two non linked genes interact whit one supressing or masking the other
A dominant allele can mask or homozygous recessive can mask
