Final answer:
The allele for straight hair, which is recessive, would be represented by the lowercase letter 'h' as the uppercase 'H' represents the dominant allele for curly hair. Correct answer is b) h.
Step-by-step explanation:
In genetics, alleles for a gene are often represented by letters, where dominant allele is denoted by an uppercase letter and the recessive allele by a lowercase letter. Since curly hair is the dominant trait represented by the letter H, the allele for the recessive trait, which in this case is straight hair, would be best represented by h. This convention helps to distinguish the dominant trait from the recessive one clearly. Therefore, the correct answer to which letter represents the allele for straight hair is b) h.
As is the case in other examples like the pea plant flower color and the cat coat genetics, heterozygous individuals carry one dominant and one recessive allele, represented as Hh, whereas homozygous dominant or recessive individuals would carry HH or hh, respectively. In order for a trait to be expressed as the recessive phenotype, an individual must be homozygous recessive (hh).