Warm Up (discussion only)

1. Warm Up (discussion only) • Which parent determines the biological sex of the baby? + why is that? • Candace has type B blood. Her husband Dan has type AB blood. Is it possible for Candace and Dan to have a child that has O blood? Explain why or why not (Hint: Punnett square!)

2. Sex-linked Traits7R

3. Let’s talk about sex! (kinda) • Recall: Humans have 23 pairs of chromosomes • Autosomes: the chromosomes that don’t determine sex (22 homologous pairs) • Sex Chromosomes: the chromosomes that determine the sex of an individual (1 pair) • Male: XY • Female: XX

4. What determines sex? • What kinds of gametes do males make? • What kinds of gametes do females make?

5. Sex-linked Inheritance • Sex chromosomes don’t just determine the sex of an individual, they also have other genes on them as well • Sex-linked traits: traits controlled by genes located on sex chromosomes

6. Sex-linked Inheritance • The two different alleles of the gene are represented as… • Superscripts of the X and Y symbols • Ex. XR or Xr (for a gene on the X chromosome) • Ex. YR or Yr (for a gene on the Y chromosome)

7. Sex-linked Inheritance • Remember!!: The X and Y chromosomes are NOT homologous!! • They don’t have the same genes on them • So if we are talking about a gene on the X chromosome (XR), the Y chromosome won’t have this gene so we leave the Y blank (Y) • Any recessive allele on the X chromosome in a male will NOT be masked by a chromosome on the Y • You will see the recessive phenotype!! ***

8. Let’s Stop and Think… • If the gene for eye color is on the X chromosome and the dominant allele is red (R) & recessive is white (r), what would be the eye color phenotype of these individuals? • XRXR - ? • XRY - ? • XRXr - ? • XrY -?

9. Check it out

10. Human example 1 • Hemophilia = problem with blood-clotting proteins (ruh-roh!) • Mostly affects males • WHY?!?! https://www.youtube.com/watch?v=h2xufrHWG3E- start at 2:24

11. Human example 2 • Even if neither parent expresses the recessive “disease” phenotype, a child (probably a male) might • IF 1 parent (usually the mom!) is a CARRIER • Ex: Red-green colorblindness

12. Just for funsies

13. Let’s Stop and Think… (top half of 7L) • In fruit flies, eye color is on the X chromosome. R = red, r = white • If a heterozygous red-eyed female is crossed with a red-eyed male, what would the phenotypes of the offspring be? • 1st, figure out the genotypes of the parents • Female: XRXr Male: XRY • 2nd, figure out the gametes of the parents • Female: XR and Xr Male: XR and Y

14. Let’s Stop and Think… (top half of 7L) • 3rd, create a Punnett Square: XR Xr XR XRXR XRXr XrY Y XRY

15. Let’s Stop and Think… (top half of 7L) • 4th, determine the phenotypes • Females: 100% red-eyed • Males: 50% red-eyed; 50% white-eyed XR Y 75% of the offspring will have red eyes; 25% white XRY XR XRXR XRXr XrY Xr

16. Calico Cat Challenge (bottom half of 7L) • Background: Calico is a coat color found in cats, caused by a Sex-Linked, Codominant allele. B=black, R=orange, B R=calico. ONLY females can be calico. • Challenge: Determine which combination of cat parents will probably create the most number of calico kittens.○ Good luck! Hint: first determine the possible genotypes!! There should be 5 ;)

17. BIG PICTURE PRACTICE • On each of the following slides, you’ll see a picture, a punnett square, or a scenario described. • You need to determine what pattern of inheritance is being shown & WHY: • Simple • Incomplete Dominance • Codominance • Polygenetic • Sex-linked

18. Pattern of inheritance + why?

19. Pattern of inheritance + why?

20. Pattern of inheritance + why?

21. Pattern of inheritance + why?

22. Pattern of inheritance + why?