wwxxyy: Gamete Types and Inheritance Meaning
The keyword wwxxyy is a compact way to write a genotype at three loci: \(w\) locus: ww, \(x\) locus: xx, \(y\) locus: yy. Each locus is homozygous, so the same allele is present on both homologous chromosomes.
Homozygous at every locus means there is no allele choice during meiosis for those genes.
Step 1: Interpret the genotype by locus
Separate the string into pairs (one pair per locus): ww, xx, yy. At each locus, a gamete receives one allele.
Step 2: Apply the meiosis rule for gamete variety
A useful counting rule in Mendelian genetics is:
\[ \text{number of distinct gamete types} = 2^n \]
where \(n\) is the number of heterozygous loci (loci with two different alleles, such as \(Ww\)). For wwxxyy, every locus is homozygous, so \(n = 0\).
\[ 2^0 = 1 \]
Step 3: Write the only possible gamete genotype
Because each locus has only one allele available, every gamete must carry:
- \(w\) from ww
- \(x\) from xx
- \(y\) from yy
Therefore, the only gamete genotype is wxy, and its probability is: \[ P(\text{wxy}) = 1 \]
Summary table
| Locus | Parent genotype | Allele available to pass | Allele in every gamete |
|---|---|---|---|
| \(w\) | ww | \(w\) only | w |
| \(x\) | xx | \(x\) only | x |
| \(y\) | yy | \(y\) only | y |