Dihybrid cross
what is the phenotype distribution of each: Dominant green seeds
Recessive yellow seeds
Dominant purple flowers
Recessive white flowers ?
To determine the phenotype distribution of each trait in a dihybrid cross, we need to understand the principles of Mendelian genetics and the laws of segregation and independent assortment.
Here's a step-by-step explanation of how to determine the phenotype distribution for each trait:
1. Identify the genotypes of the parents: Let's assume the two parents are heterozygous for both traits. For example:
- Dominant green seeds (GgYy)
- Recessive yellow seeds (ggyy)
- Dominant purple flowers (PPww)
- Recessive white flowers (ppWW)
2. Determine the possible gametes: Each parent produces gametes through the process of meiosis. In this case, the possible gametes are:
- For the green seed trait: The green-seeded parent can produce two types of gametes, one containing the dominant allele (G) and the other containing the recessive allele (g).
- For the yellow seed trait: The yellow-seeded parent can produce only one type of gamete, which contains the recessive allele (y).
- For the purple flower trait: The purple flower parent can produce only one type of gamete, which contains the dominant allele (P).
- For the white flower trait: The white flower parent can produce two types of gametes, one containing the dominant allele (W) and the other containing the recessive allele (w).
3. Write out the Punnett square: A Punnett square is a visual representation that shows all the potential combinations of gametes from both parents.
Dominant green seeds (GgYy) crossed with Recessive yellow seeds (ggyy):
| g | g |
-----|---------|-------|
G | GgYg | GgYg |
g | ggYg | ggYg |
Dominant purple flowers (PPww) crossed with Recessive white flowers (ppWW):
| w | W |
-----|---------|-------|
P | PwW | PWw |
p | pwW | pWw |
4. Determine the phenotype distribution: Look at each square of the Punnett square and determine the phenotype based on the dominant and recessive alleles.
- Phenotype distribution for dominant green seeds (GgYy) crossed with recessive yellow seeds (ggyy):
- The dominant green seeds will result from the combinations GgYg and GgYg, so there will be 4 dominant green seeded offspring in total.
- The recessive yellow seeds will result from the combination ggYg, so there will be 2 recessive yellow seeded offspring in total.
- Phenotype distribution for dominant purple flowers (PPww) crossed with recessive white flowers (ppWW):
- The dominant purple flowers will result from the combinations PwW and PWw, so there will be 2 dominant purple flowered offspring in total.
- The recessive white flowers will result from the combinations pwW and pWw, so there will be 2 recessive white flowered offspring in total.
Therefore, the phenotype distribution for each trait in the dihybrid cross is as follows:
- Dominant green seeds: 4 offspring
- Recessive yellow seeds: 2 offspring
- Dominant purple flowers: 2 offspring
- Recessive white flowers: 2 offspring