GENES - INHERITANCE pt.2 Flashcards
what is codominance and what is an example
— both alleles are expressed in the phenotype,
neither one is recessive. One example in humans is the allele for sickle-cell anaemia:
what are people who are homozygous (HnHn) for the normal haemoglobin
People wh o are homozygous for normal haemoglobin
(FINH N) don’t have the disease
what are people who are homozygous
(HsHs)
People wh o are homozygous for sickle haemoglobin
(HSHS) have sickle-cell anaemia — all their blood
cells are sickle-shaped (crescent-shaped).
what are people who are heterozygous (HnHs)
People who are heterozygous (H NHS) have an
in-between phenotype, called the sickle-cell trait
— they have some normal haemoglobin and some
sickle haemoglobin. The two alleles are codominant
because they’re both expressed in the phenotype.
In the A B O blood group system in humans there are three alleles for blood type what are they
1° is the allele for blood group O .
IA is the allele for blood group A.
IB is the allele for blood group B.
what alleles are recessive
Allele 1° is recessive.
what alleles are codominant
Alleles lA and Is are codominant
what alleles do people with blood type AB have
people with genotype lA lB will have blood group AB.
what parents do monohybrids have
homozygous d om in an t
x homozygous recessive
(e.g. RR xrr)
what parents do dihybrids have
homozygous dominant
x homozygous recessive
(e g . R R Y Y x rryy)
what parents do codominants have
homozygous for one allele
x homozygous for the
other allele
(e.g. H NH N x H !H S)
what phenotyic ratios in F1 do monohybrids have
All heterozygous offspring
(e.g. Rr)
what phenotypic ratios in F1 do dihybrids have
All heterozygous offspring
(e.g. RrYy)
what phenotypic ratios in F1 do codominants have
All heterozygous offspring
(e.g. H NH S)
what phenotypic ratios in F2 do monohybrids have
3 : 1
d o m in a n t: recessive
