CBG12 Flashcards
What is an autosome?
chromosome that is not a sex chromosome
what is hemizygous
A chromosome in a diploid organism is hemizygous when only one copy is present. Hemizygosity is also observed when one copy of a gene is deleted, or in the heterogametic sex when a gene is located on a sex chromosome.
What is a recessive lethal gene? give an example
can cause organism to die only when present in homozygous 1/4 of offspring die in hetergozygous cross eg. manx cat with no tail hetero= tailess homo = normal recessive = die in utero ratio 2:1 not 3:1
How many genotypes and phenotypes are there in human blood groups?
6 genotypes 4 phenotypes A B O AB complete and codominance occur
What is an example of incomplete/partial dominance
eg. sna drgaon homozygotes are red/white hetero= pink more red than white. red homo partially dominates looks like blending but not often due to haplo insufficiency - 1 copy of red allele not enough for phenotype
What is codominance give an example
2 alleles encode different gene products contributions of both alleles are visible in phenotype eg. 2 forms of glycoprotein (M or N) on RBC L^M or L^N alleles at locus chromosome 4 mating between heterozygotes gets 1:2 :1 ratio
What is an example of 2 genes effected a single trait? eg. dihybrid cross 9:3:3:1 phenotypes
can be seen in skin pigmentation in corn snakes 2- independent genes 4 phenotypes camoflage, orange, black, albino
What is epistasis?
effect of one gene being dependent on presence of another. epistatic gene interferes with phenotypic expression of other - hypostatic gene
What is dominant epistasis?
WwYy selfing leadings to mendalin genotype F2 ratio 9:3:3:1 and 12:3:1 phenotype eg. in fruit colour in summer squash presence of W/Y effects and W dom to Y epistatically.
What is polygenic inheritance/additive?
when phenotypic effects of alleles and poly genes are additive. eg. kernal colour in wheat 2 genes each with 2 alleles with additive gene action each A/B add oone unit of colour each a/b add 0 phenotypic sum of additive colour eg. AABB =4 darkest.
How many phenotypic classes would do polygenes give?
5 classes eg. AABB aaBB Aabb AaBb AABb more genes gives more classes giving continuous distribution
What is penetrance?
% of individual in population exhibiting phenotype associated with their allele
What is expressivity?
degree to which a given alle is expressed at the phenotypic level
What does variable pentetrance, expressivity and penetrance and expressivity look like?

What happens in autosomal recessive?
males and females equally effected
skips generation