Gametes are haploid, and therefore contain only one copy of each gene. If a person is homozygous, then the genotype of all the gametes is the same. If they are heterozygous, then half of thier gametes contain the other allele.
There is an equal chance of any gamete from one parent fusing with any gamete from the other. The genetic diagram shows the different genotypes that can arise in the offspring, and the relative chances of the genotype occuring.
Offspring ratios predicted by genetic diagrams are only probabilities, and the actually results may not be ezactly the same, especially if small numbers are involved.
In a sitution involng dominance, if two heterzygous organisms are crossed we could expect a 3:1 ratio of offspring showing the dominant characteristic to those showing the recessive characteristic in thier phenotype. If a heterozygous organism was crossed with a homozygous recessive one, then we would expect a 1:1 ratio in the offspring
in humans, sex is determined by the X and Y chromosomes. Genotype ** produces females, and XY produces males
Numerous genes that are found on the X chromosome are not found on the Y chromosome. These are called sex linked genes.
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