Question

Explain how the alleles were passed from parents to offspring.

Answer 1

Short answer
- Each parent contributes one allele for each gene to its offspring. During meiosis a parent’s two alleles segregate so each gamete (sperm or egg) carries one allele; fertilization reunites one allele from each parent to make the offspring’s genotype.

A bit more detail (Mendelian case)
- A diploid parent has two alleles per gene (e.g., A and a).
- Law of Segregation: the two alleles separate into different gametes so each gamete contains only one allele.
- Fertilization joins two gametes (one from each parent) → offspring genotype (e.g., AA, Aa, or aa).
- If the trait is simply dominant/recessive, phenotype follows the dominant allele (Aa shows the dominant trait).
- Example: Aa × Aa → gametes A and a from each parent; Punnett square gives genotypes 1/4 AA : 1/2 Aa : 1/4 aa, so 3/4 show the dominant phenotype and 1/4 the recessive.

Other important cases
- Independent assortment: different genes on different chromosomes assort independently, producing predictable dihybrid ratios (9:3:3:1) for unlinked genes.
- Linkage and crossing-over: genes close together on the same chromosome tend to be inherited together unless recombination breaks them up, altering expected ratios.
- Sex-linked inheritance: genes on sex chromosomes (e.g., X-linked) show different patterns in males and females because males are hemizygous for X.
- Non‑Mendelian patterns: incomplete dominance (heterozygote intermediate), codominance (both alleles expressed), mitochondrial (maternal-only) inheritance, genomic imprinting, etc.

If you give the parents’ genotypes (or the trait type and whether genes are linked or sex‑linked), I can show the exact cross and expected offspring genotypes/phenotypes.