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Zorluk: KolayMendel's Second Law and Dihybrid Inheritance

In a dihybrid organism with the genotype AaBbAaBb, the two gene pairs assort independently during meiosis according to Mendel's Second Law. What is the expected phenotypic or genotypic ratio of the gametes produced by this individual?

  1. 1 AB:1 Ab:1 aB:1 ab1\ AB : 1\ Ab : 1\ aB : 1\ abCevap
  2. B
    9 AB:3 Ab:3 aB:1 ab9\ AB : 3\ Ab : 3\ aB : 1\ ab
  3. C
    3 AB:1 ab3\ AB : 1\ ab
  4. D
    1 Aa:1 Bb1\ Aa : 1\ Bb

Cevap

The expected ratio of gametes produced is 1 AB : 1 Ab : 1 aB : 1 ab.
The correct answer states a 1:1:1:1 ratio of ABAB, AbAb, aBaB, and abab. A dihybrid organism heterozygous for two unlinked genes (AaBbAaBb) undergoes independent assortment during meiosis. Allele AA or aa has a 50% chance of combining with allele BB or bb, generating four distinct haploid gametes in equal proportions (25% each).

Adım Adım Çözüm

1
Determine the possible allele combinations for gamete formation from genotype AaBbAaBb.
Gene AA produces alleles AA and aa; Gene BB produces alleles BB and bb.
Meiosis separates homologous chromosomes so each gamete receives one allele per gene.
2
Apply Mendel's Law of Independent Assortment to combine alleles from both genes.
The four possible gamete combinations are ABAB, AbAb, aBaB, and abab.
Alleles of unlinked genes segregate independently into gametes.
3
Calculate the probability of each gamete combination.
Each combination has a probability of 12×12=14\frac{1}{2} \times \frac{1}{2} = \frac{1}{4}, yielding a ratio of 1:1:1:11 : 1 : 1 : 1.
Since segregation of each allele pair is equally likely, all four gamete types occur in equal frequencies.

Anahtar Kavram

Mendel's Law of Independent Assortment states that alleles of different genes segregate independently of one another during gamete formation, resulting in equal proportions of all possible haploid allele combinations.
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Mendel's Second Law and Dihybrid Inheritance

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