Biology - 1 sex linked traits

1. Biology - 1sex linked traits • Objectives: a) Types of cells &Types of Chromosomes b) Sex linked traits c) Sex Influenced traits

2. Cells • We have 2 types of cells • 1. Somatic Cells (2n) – body cells • 2. Sex Cells (n) – sperm and egg

3. Chromosomes We have 2 types of Chromosomes: • Autosomal chromosomes • pairs 1 through 22 in humans (non-sex chromosomes) • Sex chromosomes – xx or XY

4. Sex-linked Traits

5. Definition • Sex-linked traits are traits that are controlled by genes on the sex chromosomes • The X and Y chromosomes

6. Are they controlled by both sex chromosomes? • Most sex-linked traits are controlled by genes on the X chromosome. • This is because an X chromosome is much larger than a Y chromosome. • A few traits are controlled by genes on the Y chromosome.

7. Different Forms of Sex-linked Inheritance • There are three different forms of sex-linked inheritance that we will be examining: • X-linked recessiveinheritance • X-linked dominantinheritance • Y-linkedinheritance

8. X-linked Recessive Inheritance • X-linked recessive traits are traits resulting from a recessive allele on the X chromosome. • X-linked recessive alleles are represented by an X , superscript lower case letter or a plus/minus (+/-)

9. X-linked Recessive Inheritance • These traits tend to show up in males more than females. • Why?

10. X-linked Recessive Inheritance Example #1: Colorblindness • The allele that controls colorblindness is found on the X chromosome and is recessive . • What genotype must a female have to be diagnosed as colorblind?

11. Are you colorblind? Normal Color Vision:A: 29, B: 45, C: --, D: 26 Red-Green Color-Blind:A: 70, B: --, C: 5, D: --3. Red Color-blind:A: 70, B: --, C: 5, D: 64. Green Color-Blind:A: 70, B: --, C: 5, D: 2

12. Try this problem! • What is the probability that the sons of a homozygous recessive mother would be colorblind? • Represent colorblindness with a “c”

13. X-linked Recessive Inheritance • Example #2: Hemophilia • Hemophilia is a serious ailment in which the blood lacks a clotting factor, and therefore when an individual is injured, they cannot stop bleeding. • Hemophilia is also controlled by recessive alleles on the X chromosome.

14. Try this problem • A woman who is heterozygous (a carrier) for hemophilia marries a normal man: • a. What are the genotypes of the parents? • b. Make a Punnett square for the above cross. • c. What is the probability that a male offspring will have hemophilia? ________ • d. What is the probability of having a hemophiliac female offspring? _________

15. X-linked Dominant Inheritance • X-linked dominant traits result from the presence of a dominant allele on the X chromosome. • Unlike X-linked recessive traits, females and males both require only ONE dominant allele in order to express the trait. • X-linked dominant traits are represented by an X, superscript capital letter or a (+)

16. X-linked Dominant Inheritance • Example: Faulty Tooth Enamel and Dental Discoloration • Individuals who have an X chromosome that carries a dominant allele for this trait will have dental discoloration.

17. Try these problems! • Would a heterozygous woman for dental discoloration display the trait? YES! Because this is a X-linked dominant trait, you only need to carry one dominant allele in order to express the trait.

18. Y-linked Inheritance • Y-linked traits are controlled by alleles on the Y chromosome • Another word for Y-linked traits is holandric traitsas they are “wholly male”.

19. Y-linked Inheritance • Do the words homozygous or heterozygous apply to Y-linked traits?Are females affected by Y-linked traits?

20. What is this?

21. Y-linked Inheritance • An example of a Y-linked trait is . . . . . HAIRY EARS!

22. Y-linked Inheritance • All of the sons of an affected male will display this Y-linked trait.