Homework Sourse1 A dominant gene H produces wirehaired texture in dogs its
1. A dominant gene (H) produces wire-haired texture in dogs; its recessive allele (h) produces smooth hair. Two heterozygous wire-haired individuals were crossed and their F1 progeny testcrossed. Determine the expected genotype and phenotype rations among the testcross progeny. Note: in a testcross, an individual with an unknown genotype is crossed with a homozygous recessive individual.
2. A white guinea pig, whose parents were black, is closed with a black guinea pig whose male parent was white and whose female parent was black. Two white offspring result. Determine the genotypes of all individuals mentioned. About which individuals is there some doubt?
Solution
Answer:
1)
HH: Homozygous dominant (wire-haired individua)
Hh: Heterozygous dominant (wire-haired individua)
hh: Homozygous recessive (Smooth haired)
Two heterozygous wire-haired individuals were crossed
Hh x Hh
F1 = The possible genotype: HH, Hh, hH, hh
F1 progeny is testcrossed,so genotype is crossed with a homozygous recessive individual
1) HH x hh
possible genotypes are : Hh, Hh. Hh,Hh
Hh: All genotypes are heterozygous dominant (wire-haired )
2) Hh x hh
Possible genotypes are Hh, Hh, hh, hh
Hh (50%)= wired haired , hh= smooth haired
3) hh x hh
Possible genotype are hh, hh, hh, hh
hh= all are smooth haired
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2) White guinea pig: ww (Recessive), parents are Black (WW or Ww)
Male parent was white (ww) and whose female parent was black (Ww, WW)
so, two chances
1) ww x Ww, possible genotype are = wW, ww, wW,ww
wW (50%)= Black, ww (50%)= white
2) ww x WW, possible genotypes are Ww, Ww,Ww,Ww,
all are Black
so, black guinea pig genotype is Ww from the above cross
white guinea pig (ww) x black guinea pig(Ww)
Possible Genotype are : Ww, ww, wW, ww
Ww (50%)= Black Guinea pig
ww (50%) = White Guinea pig
