Question

38. In Mendel's experiments, tall pea plants (T) are
dominant over dwarf pea plants (t).
() What is the phenotype and genotype of the
F, generation if a homozygous tall plant is
crossed with a homozygous dwarf plant?
(1) Draw a Punnett square board to show the
gametes and offspring when both the
parents are heterozygous for tallness.
(in) What is the phenotypic ratio and genotypic
ratio of the above cross in (ii) ?
(iv) State Mendel's Law of Dominance.
(1) What is a Dihybrid Cross ?
[ICSE 2019)​

Answer 1

Explanation:

38 ) A cross between two homozygous varieties always obtains all dominant offspring.

• During a cross between homozygous tall (TT) and homozygous dwarf (tt), the tall parent produces all gametes with “T allele” and dwarf parent produces all gametes with “t allele”.
• Random fusion of gametes carrying “T” and “t” produces all zygotes carrying “Tt” genotype.
• According to the law of dominance, the presence of one copy of allele for tallness (“T”, the dominant allele) is sufficient to mask the expression of an allele of dwarfism (“t”, the recessive allele). Therefore, the progeny with “Tt” genotype would exhibit tall phenotype.

Mendel's law of dominance

1. states that in a heterozygote, one trait will conceal the presence of another trait for the same characteristic. Rather than both alleles contributing to a phenotype, the dominant allele will be expressed exclusively.

Dihybrid cross

• A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits. A hybrid organism is one that is heterozygous, which means that is carries two different alleles at a particular genetic position, or locus.

Answer 2

Answer:

2

Explanation:

1+1=2

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