Categories
Biology

Dihybrid cross

The study of cross involving the inheritance pattern of two characters each of which is

determined by two alleles of a gene for instance, pea plant with  seed colour and seed shape are used in garden pea plant , round seed (RR) is dominant  over wrinkled seed (rr)  , yellow seed (Y)  is dominant over the green seed (y).

When a pure stock of plants having round yellow seeds is crossed with a pure stock  of wrinkled and  seeds, the F1 general offspring all round and yellow.

When a pure stock of plants having round yellow seeds is crossed with a pure stock  of wrinkled and  seeds     , the F1 general offspring all round and yellow.

Parents  ____  Round and yellow  X wrinkled and green

RYRY         x       ryry

Gametes     RY                                      ry

F1                                               RYry   (All round and yellow)

F2 is arranged in prunnet table as follow

RY, ry ,   X  RYry

Gametes :  RY, RY, ry , ry  X   RY  , RY, RY, ry

 RYRYryry
RYRYRYRYRYRYrYRYrg
RyRyRyRyrYRyrY Ryry
RyRYrYRyrYRyrYrYry
RyRYryRyryrYryryry

Analysis of phenotype ratio

Round and yellow9
Round and green3
Wrinkled and yellow3
Wrinkled and green1

Analysis of genotyptic ratio

Homozygons romo yellow1
Homozygons romo green1
Homozygons wrinkled yellow1
Homozygons wrinkled green1
Homozygons Romo, heterozygons yellow2
Homozygons romo yellow, Homozygons green2
Homozygons wrinkled, Homozygons yellow2
Homozygons romo and yellow4

Questions

(1)    A man with heterozygous  genotype for blood group B marries a woman with heterozygous

  1. what percentage of their children be universal donor?

2.The alternative form of a gene that represents constrasting character is  a/an (A)allele (B)diploid (C)haploid (D)homologue

(3)  If two parents are sickle cell carrier their genotype  would be (A)      Hb  HbA  and  Hbs Hbs  (b)  HbsHbs and  Hbs Hbs  (c)  HbA Hbs and  Hb A Hbs  (D)  Hba HbA  and  HbA HbA

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