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Meiosis and Sex-linked traits

Meiosis and Sex-linked traits. Ch. 10.4-10.5. Objectives. Explain chromosome theory of inheritance Understand genetic linkage Explain sex-linked genes and why more common in males. Chromosome Theory of Inheritance. Mendel’s findings were not widely accepted at first

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Meiosis and Sex-linked traits

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  1. Meiosis and Sex-linked traits Ch. 10.4-10.5

  2. Objectives • Explain chromosome theory of inheritance • Understand genetic linkage • Explain sex-linked genes and why more common in males

  3. Chromosome Theory of Inheritance • Mendel’s findings were not widely accepted at first • During the 1900’s, parallels discovered between genes and chromosomes • This is referred to as the chromosome theory of inheritance: • Chromosome Theory of Inheritance: • Genes located on chromosomes • accounts for inheritance patterns

  4. Chromosome Theory of Inheritance • Remember, diploid individuals have 2 sets of homologous chromosomes • One from mom, one from dad • Gene locus: • Alleles of a gene reside at same location

  5. Genetic Linkage and Crossing Over • Genetic Linkage: • Tendency for alleles on one chromosome to be inherited together • Closer the genes, the greater the genetic linkage • Farther apart, greater chance of separation

  6. Sex Linked Genes • What two sex chromosomes make up a male? Female? • Male = XY, Female = XX • Which chromosome is physically larger? • The X. It can hold a lot more genetic info • Sex linked gene: • Any gene on a sex chromosome

  7. Sex-linked Disorders • Many sex-linked disorders are recessive alleles • Let’s say that white eyes in fruit fly is an example • Disorders always carried on X chromosome (Y doesn’t have any room, too small) • What does all this mean?

  8. Sex-linked Disorders • If disease is recessive and always carried on X chromosome, then females (XX), will most likely have dominant form of allele on other chromosome --> don’t get disorder. • If males (XY) have allele for disorder on their X chromosome, they will get disorder because Y chromosome doesn’t carry alleles.

  9. Rare!

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