If curly hair is dominant to straight hair, what letters will we use to show these genes? 2. If a heterozygous curly haired male marries a straight haired female, how would we represent the parents of the cross using the letters above? . 3. What alleles would be in the gametes for the male parent? . 4. What alleles would be in the gametes for the female parent? 5. Now, complete a Punnett square to be able to answer the questions. Mother’s gametes go on top and fathers on the left side. Genotypic Ratio Phenotypic Ratio 6. What are the chances of the offspring being homozygous curly haired?
The Correct Answer and Explanation is :
Explanation and Solution:
- Dominance and Representation of Genes
If curly hair (C) is dominant to straight hair (c), we use C to represent the dominant allele (curly hair) and c to represent the recessive allele (straight hair). - Parents’ Genotypes
- A heterozygous curly-haired male would have the genotype Cc (one dominant allele for curly hair and one recessive allele for straight hair).
- A straight-haired female, being homozygous recessive, would have the genotype cc.
- Gametes for the Male Parent (Cc)
The male can produce two types of gametes: C and c (as he has one dominant and one recessive allele). - Gametes for the Female Parent (cc)
The female can only produce one type of gamete: c, as she has two recessive alleles. - Punnett Square
Let’s construct a Punnett square with the male’s gametes on the left and the female’s gametes on the top.
| c (female gamete) | c (female gamete) | |
|---|---|---|
| C (male gamete) | Cc | Cc |
| c (male gamete) | cc | cc |
- Genotypic Ratio:
- 2 Cc (heterozygous curly-haired)
- 2 cc (homozygous straight-haired)
Ratio: 2:2 or 1:1 - Phenotypic Ratio:
- 2 curly-haired (dominant trait expressed in Cc)
- 2 straight-haired (recessive trait expressed in cc)
Ratio: 2:2 or 1:1
- Probability of Homozygous Curly-Haired Offspring
Homozygous curly-haired offspring would have the genotype CC, which is not present in this cross.
- Probability = 0%
Conclusion (300 words)
In this cross, curly hair (C) is dominant, while straight hair (c) is recessive. The heterozygous male (Cc) produces two types of gametes, C and c, while the homozygous recessive female (cc) only produces gametes with c. The Punnett square analysis reveals that offspring will have either a heterozygous genotype (Cc, curly hair) or a homozygous recessive genotype (cc, straight hair). Thus, the genotypic ratio is 1:1, and the phenotypic ratio is also 1:1, reflecting equal chances of curly and straight hair. Importantly, there is no chance of homozygous curly-haired (CC) offspring in this particular genetic cross.