In a diploid species of plant, the genes for plant height and fruit shape are syntenic and separated by 18 m.u. Allele D produces tall plants and is dominant to d for short plants, and allele R produces round fruit and is dominant to r for oval fruit. A plant with the genotype DR/dr produces gametes. Identify gamete genotypes, label parental and recombinant gametes, and give the frequency of each gamete genotype.

Verified step by step guidance

1. Identify the parental gametes based on the given genotype DR/dr. The parental gametes are DR and dr.
2. Determine the recombinant gametes. Since the genes are syntenic and separated by 18 map units, the recombinant gametes are Dr and dR.
3. Calculate the frequency of recombinant gametes. Since 1 map unit corresponds to 1% recombination frequency, 18 map units correspond to 18% recombination frequency. Therefore, the frequency of each recombinant gamete (Dr and dR) is 9%.
4. Calculate the frequency of parental gametes. Since the total recombination frequency is 18%, the remaining 82% is for parental gametes. Therefore, the frequency of each parental gamete (DR and dr) is 41%.
5. Summarize the gamete genotypes and their frequencies: Parental gametes DR and dr each have a frequency of 41%, while recombinant gametes Dr and dR each have a frequency of 9%.

Key Concepts

Synteny

Synteny refers to the conservation of gene order on chromosomes between different species or within the same species. In this context, the genes for plant height and fruit shape are located on the same chromosome, which affects how they are inherited together. Understanding synteny is crucial for predicting gamete formation and the inheritance patterns of linked traits.

Gamete Formation and Recombinant Types

Gamete formation involves the segregation of alleles during meiosis, leading to the production of haploid cells. In this scenario, the parental gametes are those that carry the original combinations of alleles (DR and dr), while recombinant gametes arise from crossing over and carry new combinations (Dr and dR). Identifying these types is essential for calculating their frequencies and understanding genetic variation.

Map Units and Genetic Linkage

Map units (m.u.) are a measure of genetic distance that reflects the frequency of recombination between genes on a chromosome. An 18 m.u. distance indicates that 18% of the gametes will be recombinant due to crossing over. This concept is vital for determining the expected frequencies of each gamete genotype and understanding the strength of linkage between the traits in question.