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Bell Work

Bell Work. Chapter 12 Patterns of Heredity and Human Genetics. Two copies of each autosomal gene affect phenotype. Mendel studied autosomal gene traits, like hair texture. (dominant). Mendel’s rules of inheritance apply to autosomal genetic disorders.

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Bell Work

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  1. Bell Work

  2. Chapter 12 Patterns of Heredity and Human Genetics

  3. Two copies of each autosomal gene affect phenotype. • Mendel studied autosomal gene traits, like hair texture.

  4. (dominant) • Mendel’s rules of inheritance apply to autosomal genetic disorders. • A heterozygote for a recessive disorder is a carrier. • Disorders caused by dominant alleles are uncommon.

  5. Males and females can differ in sex-linked traits. • Genes on sex chromosomes are called sex-linked genes. • Y chromosome genes in mammals are responsible for male characteristics. • X chromosome genes in mammals affect many traits.

  6. Male mammals have an XY genotype. • All of a male’s sex-linked genes are expressed. • Males have no second copies of sex-linked genes.

  7. Eye color in fruit flies is sex-linked (also called X-linked) • R – dominant allele for red eyes • r – mutant and recessive allele for white eyes • What are the probabilities for offspring phenotypes?

  8. Practice

  9. Practice

  10. A pedigree is a chart for tracing genes in a family. • Phenotypes are used to infer genotypes on a pedigree. • Autosomal genes show different patterns on a pedigree than sex-linked genes.

  11. Pedigrees • Identify males • Identify females • Identify “affected” individuals • Identify “carriers” • What is a carrier? • Heterozygous not always marked

  12. If the phenotype is more common in males, the gene is likely sex-linked.

  13. (dominant) Inheritance patterns • Simple dominance

  14. Phenotype can depend on interactions of alleles. • In incomplete dominance, neither allele is completely dominant nor completely recessive. • Heterozygous phenotype is intermediate between the two homozygous phenotypes

  15. Codominant alleles are neither dominant nor recessive. • Codominant alleles will both be completely expressed.

  16. What is it? Regular dominance, Incomplete dominance or Codominance?

  17. Alleles also written with superscripts • Many genes have more than two alleles.

  18. Color vision is an X-linked and colorblindness is recessive

  19. Complex Inheritance Multiple Alleles • The ABO blood group is an example of a single gene with multiple alleles in humans. • Blood types: A, B, AB, and O • Gene I has three alleles: IA, IB and i A and B are codominant; while the i allele is recessive.

  20. Order of dominance: brown > green > blue. Many genes may interact to produce one trait. • Polygenic traits are produced by two or more genes.

  21. An epistatic gene can interfere with other genes.

  22. The environment interacts with genotype. • Phenotype is a combination of genotype and environment. • The sex of sea turtles depends on both genes and the environment • Height is an example of a phenotype strongly affected by the environment.

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