In pea plants (*Pisum sativum*), seed shape (round R dominant to wrinkled r) and seed colo… — JAMB UTME

In pea plants (*Pisum sativum*), seed shape (round $R$ dominant to wrinkled $r$ ) and seed color (yellow $Y$ dominant to green $y$ ) inherit independently according to Mendel's Second Law. Match each parental genetic cross on the left with its corresponding phenotypic ratio of offspring on the right.

Cross between two heterozygous dihybrids ( $RrYy \times RrYy$ ) $9 : 3 : 3 : 1$ (Round Yellow : Round Green : Wrinkled Yellow : Wrinkled Green)
Dihybrid test cross ( $RrYy \times rryy$ ) $1 : 1 : 1 : 1$ (Round Yellow : Round Green : Wrinkled Yellow : Wrinkled Green)
Cross between $RrYy$ and $Rryy$ $3 : 3 : 1 : 1$ (Round Yellow : Round Green : Wrinkled Yellow : Wrinkled Green)
Cross between $RrYY$ and $RrYy$ $3 : 1$ (Round Yellow : Wrinkled Yellow)

Cevap

Cross between two heterozygous dihybrids (

RrYy \times RrYy

) matches

9 : 3 : 3 : 1

; Dihybrid test cross (

RrYy \times rryy

) matches

1 : 1 : 1 : 1

; Cross between

RrYy

and

Rryy

matches

3 : 3 : 1 : 1

; Cross between

RrYY

and

RrYy

matches

3 : 1

(Round Yellow : Wrinkled Yellow).

Each cross produces a specific phenotypic distribution based on independent assortment during meiosis.

RrYy \times RrYy

gives the classical

9:3:3:1

dihybrid F2 ratio.

RrYy \times rryy

gives the equal

1:1:1:1

test cross ratio.

RrYy \times Rryy

produces

3:3:1:1

across all four phenotypes.

RrYY \times RrYy

produces only yellow seeds in a

3:1

ratio of round to wrinkled.

Adım Adım Çözüm

Determine gamete combinations for each parent in the cross.

Identify the types and frequency of gametes produced via independent assortment.

Mendel's Law of Independent Assortment states that alleles for different traits segregate independently during gamete formation.

Construct Punnett squares or calculate product rule probabilities for each parental cross pair.

Obtain the genotypic frequencies and translate them into phenotypic ratios.

Crosses involving different combinations of homozygous and heterozygous loci produce characteristic phenotypic frequency distributions.

Match each cross with its calculated phenotypic ratio.

RrYy \times RrYy \rightarrow 9:3:3:1

RrYy \times rryy \rightarrow 1:1:1:1

RrYy \times Rryy \rightarrow 3:3:1:1

, and

RrYY \times RrYy \rightarrow 3:1

Comparing predicted proportions to the listed choices establishes the accurate pairings.

Anahtar Kavram

Mendel's Law of Independent Assortment and Dihybrid Phenotypic Ratios

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Adım Adım Çözüm

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