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

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

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

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

11. Codominant and Multiple Alleles
Alleles IA and IB are codominant
Produce molecules known as antigens on the surface of red blood cells
Individuals with alleles IA and IB produce 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. X-Chromosome Inactivation
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.

15. X-Chromosome Inactivation
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.

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.

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

20. 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.