1. Cool organism of the day… One of the only mammals to lay eggs (other is echidna) The egg develops inside the female for 28 days, then develops for 10 days outside the female in an egg Milk is released through pores in the skin Platypuses also have ankle spurs that release venom! Duck billed platypus

3. Topic 4 – Wearing your genes Read pages 37 - 45

4. Why do some people have brown eyes? Why do some people have red hair? Why do some people need glasses? Why are some people shorter than others?

5. Genetics genetics is the study of heredity (traits passed on from parent to offspring) we inherit our traits from our parents because of genetics we get half of our DNA from our mother (23 chromosomes) and the other half from our father (23 chromosomes)

6. Remember this is called….fertilization

8. There are two types of variation I.Continuous Variation there are a wide variety of possible outcomes these traits have a lot of “in- between” possibilities Examples: weight, height, skin colour, hair colour, eye colour

12. There are two types of variation II.Discrete Variation there are a limited number of possible outcomes there are NO “in-betweens” for these traits

13. Examples of discrete variation Tongue rolling vs. non-rolling

14. Examples of discrete variation Hitch-hiker thumb vs. straight thumb

15. Examples of discrete variation Widows peak vs. smooth hairline

16. Examples of discrete variation Detached earlobe vs. attached earlobe

17. Examples of discrete variation Blood type (A, B, AB, O)

18. Dominant or recessive? Dominant if a dominant and a recessive trait are both inherited then the dominant trait will over- ride the recessive trait Examples: – Brown eyes (are dominant to blue eyes) – Hitchhiker thumb(is dominant to straight thumb)

19. Dominant or recessive? Recessive trait the recessive trait will be overpowered by a dominant trait the off-spring will inherit a recessive trait only if both parents pass on the recessive trait Examples: – Blue eyes – Straight thumb

20. Example Tongue rolling is a dominant trait If both of your parents can roll his/her tongue, then you should be able to roll your tongue too. Your parents might also have the dominant or recessive gene. If you cannot roll your tongue, it means that neither of your parents have the dominant gene for tongue rolling.

21. e.g. colour blindness Colour blindness is recessive. You would have to get two recessive genes to be colour blind.

22. Punnett Square A punnett square can be used to predict how many offspring will get a certain trait from the parents A dominant trait is represented by a capital letter (e.g. brown eyes – B) A recessive trait is represented by a small letter (e.g. blue eyes  b)

23. Punnett Square Mother (brown eyes) father (brown eyes) Bb B b BBBb bb

24. Bb B b BBBb bb mother father BB – brown eyes (1/4) offspring Bb – brown eyes (1/2) bb – blue eyes (1/4) 75% of offspring will have brown eyes 25 % of offspring will have blue eyes

26. Dominance vs. frequency Many people assume that if a trait is widespread (common) then it must be dominant However, dominance is not the same as frequency E.g. some populations have a high frequency of blonde hair and blue eyes even though these are recessive traits

27. Dominance vs. frequency Having six fingers (polydactyly) is a dominant trait but it is relatively rare in human populations.

28. Nature vs. Nurture (genes vs. environment) Not all characteristics are inherited - some characteristics are learned. Some of our behaviours are the result of our environment. Examples: – Personality – Being a good athlete – Weight, eating disorder

29. Nature vs. Nurture It is very complex – most traits involve a combination of both nature and nurture

30. Nature vs. Nurture Scientists look at identical twins who are separated at birth to help them figure out if traits are caused by genes or the environment. Identical twins share the same DNA so they have the same inherited traits.

32. Changing our Genetic Information Sometimes our DNA and genetic information can change because of external factors. These changes are called mutations. Some of the causes of mutations are: X-rays, drinking alcohol, taking drugs, UV rays mutagens (chemicals)

33. Example Thalidomide baby – given to mothers to prevent morning sickness – Caused major birth defects in babies – Thalidomide is a mutagen

34. Cancer Some cancers are the result of a genetic mutation in a few isolated cells. Cancerous cells divide uncontrollably

36. Check your understanding Do questions #1 – 6 on page 45 Do questions #1 – 8 on the worksheet in your notes