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Human Inheritance (Patterns of Human Inheritance (single genes with two…
Human Inheritance
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The Sex Chromosomes
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Girl or Boy?
Sex chromosomes are the only chromosme pair that do not always match. If you are a female, your chromosomes match (XX), and if you are a male your chromosomes do not match (XY).
If you are a female, you have two X chromosomes. If you are a male, you have one X chromosome and one Y chromosome. The Y chromosome is much smaller than the X chromosome.
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Sex-Linked Genes
Genes for some human traits are carried on sex chromosomes. That being said, genes on the X and Y chromosomes are often called sex-linked genes because their alleles are passed on from parent to child on a sex chromosome.
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The X and Y chromosomes in a male have different genes. Most genes that are on the X chromosomes are not on the Y chromosome.
Sex-linked genes can have dominant and recessive alleles. In females, a dominant allele on one X chromosome will mask the recessive allele on the other X chromosome. In males, there is usually no matching allele on the Y chromosome to mask the X chromosome. That means that a recessive allele on the X chromosome in a male will show up no matter what
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