Biology benchmark 2 semester exam fall 24

Question

Dihbrid crosses can be conducted with two organisms that are heterozygous for two different traits: SsYyxSsYy for example. Which genotype ratio shows that genes in dihybid crosses are inherited according to the principle of independent assortment
25:25:25:25
50:50
3:1
9:3:3:1

Answer 1

In dihybrid crosses, the principle of independent assortment states that the alleles for different traits segregate independently of one another during gamete formation. When two organisms that are heterozygous for two traits (such as SsYy) are crossed, the expected genotype ratio of the offspring is 9:3:3:1.

This means:

• 9 offspring will show both dominant traits (SSYY or SSYy or SsYY or SsYy)
• 3 offspring will show the dominant trait for the first gene and the recessive trait for the second (SSyy or Ssyy)
• 3 offspring will show the recessive trait for the first gene and the dominant trait for the second (ssYY or ssYy)
• 1 offspring will show both recessive traits (ssyy)

Therefore, the genotype ratio that shows that genes in dihybrid crosses are inherited according to the principle of independent assortment is 9:3:3:1.