In fruit flies, the genes for wing shape and body stripes are linked. In a fly whose genotype is WwSs, W is linked to S, and w is linked to s. Show how this fly can produce gametes containing four different combinations of alleles.
Which are parental-type gametes?
Which are recombinant gametes? How are the recombinants produced?

Verified step by step guidance

1. Understand the concept of linked genes: Linked genes are located close together on the same chromosome and tend to be inherited together. In this case, W (wing shape) is linked to S (body stripes), and w is linked to s.
2. Determine the possible gametes: Since the fly has the genotype WwSs, it can produce gametes with combinations of alleles. Parental-type gametes are those that retain the original linkage (WS and ws), while recombinant gametes are those that result from crossing over (Ws and wS).
3. Explain how crossing over occurs: During meiosis, homologous chromosomes can exchange genetic material in a process called crossing over. This exchange can break the linkage between W and S or w and s, creating recombinant gametes (Ws and wS).
4. List the four possible gametes: The fly can produce gametes with the following combinations of alleles: WS (parental type), ws (parental type), Ws (recombinant type), and wS (recombinant type).
5. Clarify the distinction between parental and recombinant gametes: Parental-type gametes (WS and ws) maintain the original linkage of alleles, while recombinant gametes (Ws and wS) result from crossing over during meiosis, which reshuffles the alleles.

Key Concepts

Linked Genes

Linked genes are genes that are located close to each other on the same chromosome and tend to be inherited together during meiosis. This linkage affects the assortment of alleles into gametes, as they do not assort independently like unlinked genes. In the case of the fruit fly, the genes for wing shape (W/w) and body stripes (S/s) are linked, influencing the combinations of alleles in the gametes produced.

Gamete Formation and Allele Combinations

During gamete formation, specifically meiosis, alleles segregate into different gametes. For the genotype WwSs, the possible combinations of alleles in the gametes can be determined by considering the parental alleles and their linkage. The four gametes produced from this genotype are WS, Ws, wS, and ws, representing different combinations of the alleles for wing shape and body stripes.

Parental and Recombinant Gametes

Parental-type gametes are those that contain the same allele combinations as the parents, while recombinant gametes have new combinations of alleles due to crossing over during meiosis. In this scenario, WS and ws are parental-type gametes, while Ws and wS are recombinant gametes. Recombinants are produced when homologous chromosomes exchange segments during prophase I of meiosis, leading to new allele combinations.