Transmission genetics Flashcards
when are reccessive alleles expressed?
If homozygous
What is P1, F1, F2
Parental generation, First filial generation, second filial gen
What does progeny mean
Offspring
advantages of studying pea plant (pisum sativum)
- different discrete traits can be studied
- self fertilizer
- quickly reproduces
What’s Mendel’s first postulate? UNIT FACTORS IN PAIRS
One aspect of a trait comes from one parent and another aspect of a trait comes from the other parent
What’s Mendel’s second postulate? Dominance/recessive
If two alleles are heterozygous then the dominant one will determine the appearance and the recessive doesn’t have any noticeable effect
if crossed Tt and Tt in the F1 gen, what would the F2 gen look like?
1/4 TT
2/4 Tt
1/4 tt
Mendel’s third postulate (first law) SEGREGATION
If heterozygous then 50% gametes contain one allele type and 50% the other. If homozygous then alleles identical then so are all the gametes.
What’s the phenotypic ratio in F2 MONOHYBRID
3(dominant):1(recessive)
Genotypic ratio in complete dominance in F2
1 (Dominant): 2 (heterozygous): 1(recessive)
What’s dihybrid inheitance?
2 genes on different chromosomes each with 2 alleles. looking at 2 phenotypes at the same time. in ON
Mendels 4th postulate (second law) INDEPENDENT ASSORTMENT
a pair of traits segregates independently of another pair during gamete formation.
different traits get equal opportunity to occur together.
What’s the phenotypic ratio in F2 DIHYDRBRID
9(a dominant pheno):3(the otuer dom pheno):3(recessive):1(recessive)
in ON
What is incomplete dominance
E.g red flower (RR) and White flower (rr) makes pink Rr instead of just red.
No complete dominance
What’s the F2 ratio in incomplete dominance
1:2:1
RR:Rr:rr
What blood type can accept blood from any donor? Often referred to as universal recipients
AB
What blood type can donate blood to any recipient? Often referred to as universal donors
O
Codominance
Includes phenotypes of both homozygous parents.
E.g blood type AB
What does a ratio of 2:1 suggest?
Lethality, lost a 1/4 of the offspring
What are Dihybrid gene interactions
Two separate genes each with two alleles. They both give a single phenotype together.
Normally would expect a 9:3:3:1 but can get really weird ratios.
What’s recessive epistasis
Ratio = 9:3:4
E.g Labrador dogs, can get black brown and yellow
Dominant A allele produces Black, recessive a produces brown, dominant. Dominant B allows the pigment of the colour to show.
in ON
