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1 Review What are autosomes Explain What determines whether a person is male or female

1 Review What are autosomes Explain What determines whether a person is male or female Propose a Solution How can you use a karyotype to identify a species 2 Review Explain how sex linked traits work

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1 Review What are autosomes Explain What determines whether a person is male or female

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  1. 1 Review What are autosomes Explain What determines whether a person is male or female Propose a Solution How can you use a karyotype to identify a species 2 Review Explain how sex linked traits work Infer Why would the Y chromosome be unlikely to contain any of the genes that are absolutely necessary for survival

  2. Ch 14 Human Heredity 14.1 Human Chromosomes

  3. Shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size. Karyotypes

  4. Genome • Full set of genetic information that an organism carries.

  5. Two of the 46 chromosomes determine sex Females are XX Males XY. Sex Chromosomes

  6. X chromosome contains 1200 genes Y chromosome contains 140 genes Most are associated with male development.

  7. Autosomal Chromosomes • Remaining 44 human chromosomes.

  8. Transmission of Human Traits • Many traits have a pattern of simple dominance • Many are also codominant.

  9. Dominant and Recessive Alleles • Rhesus, or Rh blood group • Rh+ and Rh- • Rh+ is dominant so heterozygous individual is Rh+ • Rh- individuals need to have both negatives.

  10. Human blood types Determined by a gene with three alleles: IA, IB, and i. Codominant and Multiple Alleles

  11. Codominant and Multiple Alleles • Alleles IA and IBare codominant • Produce molecules known as antigens on the surface of red blood cells • Individuals with alleles IAand IBproduce both A and B antigens • Blood type AB • The i allele is recessive • Homozygous for the i allele (ii) produce no antigen and are type O.

  12. Sex Linked Gene • Gene located on a sex chromosome • Genes on Y chromosomes only pass from father to son • Genes on X chromosome are found in both sexes • Remember males only have one.

  13. Sex-Linked Inheritance • Three genes responsible for color vision all are on the X chromosome • Males only have one X so if they have one recessive allele they will have some form of color blindness, 1 in 12 • Females have 2 X chromosomes so they would need both copies of a recessive allele, 1 in 200.

  14. Females really only need to use 1 X chromosome (males make it work) The second X chromosome is turned off Barr Body Inactivated x chromosome that gets shoved off to the side. X-Chromosome Inactivation

  15. Also occurs in other mammals like cats One X chromosome has an allele for orange spots Other X chromosome has an allele for black spots Some cells has one X chromosome switched off other cells turns off the other. X-Chromosome Inactivation

  16. Pedigree • Shows the presence or absence of a trait according to the relationships between parents, siblings, and offspring.

  17. This pedigree shows how a white lock of hair just above the forehead passes through three generations of a family White lock is dominant.

  18. Grandfather has trait • Two of his three children inherited the trait • Three grandchildren have the trait, but two do not.

  19. All family members lacking this trait must have homozygous recessive alleles One of the grandfather’s children lacks the white forelock trait, so the grandfather must be heterozygous.

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