Extensions of Mendelian inheritance - Genes on sex chromosomes

7 important questions on Extensions of Mendelian inheritance - Genes on sex chromosomes

What is X-linked inheritance?

X-linked inheritance is an inheritance pattern in certain species that involves genes that are located only on the X chromosome.

What features of this pedigree indicate that the allele for Duchenne muscular dystrophy is X-linked?

The key feature of the pedigree that points to X-linked inheritance is that only males are affected with the disorder. Also carrier females often have affected brothers.

Explain why the reciprocal cross yields a different result from the first cross.

The reciprocal cross yields a different result because females carry two copies of an X-linked gene, whereas males have only one.
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What is a sex-linked gene?

A sex-linked gene is a gene that is found on one of the two types of sex chromosomes but not on both.

What are holandric genes? What is an example?

Holandric genes are genes that are only present on the Y chromosome.
An example of a holandric gene is the the SRY gene in mammals. The SRY gene is necessary for proper male development.

What is pseudoautosomal inheritance?

Pseudoautosomal inheritance is the inheritance pattern of genes that are found on both the X and Y chromosomes. Even though such genes are located physically on the sex chromosomes, their pattern of inheritance is identical to that of autosomal genes.

Why are the homologous regions of the X and Y chromosome important during meiosis?

Homologous regions of the X and Y chromosome are important for chromosome synapsis (pairing) during meiosis.

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