Chapter 14

1. Chapter 14

2. Thomas Hunt Morgan (1933) • Used fruit flies (Drosophilia melanogaster) • Females had 8 paired chromosomes while males have 3 pairs and 1 mismatched pair

3. How is sex determined? • Sex Chromosomes – mismatched chroms that determine sex • In humans, X or Y - Always a 50:50 chance of a boy or a girl with males determining sex of child • Humans have 46 chrom/body cell. Last two are sex chroms. 22 autosomes & 2 sex chroms

4. Sex Linkage • Morgan noticed that some traits in fruit flies were inherited differently in males than in females. Males seem to inherit certain traits w/ a greater frequency than females. P1: Wild type female X White eyed male F1: Wild type F2: 75% Wild type 25% White males (All females & ½ (Only males) of the males)

5. How was the gene for eye color related to being a male? • Conclusion: The gene for eye color is carried on the X chromosomes. The Y chromosome is shorter than the X and has no corresponding gene for eye color.

6. Normal female Carrier femaleFemale w/ traitNormal maleMale w/trait

7. Crosses: Cross a carrier red-eyed female w/ a white eyed male. • XRXr x XrY PR: • Cross a red eyed male w/ a carrier red eyed female. • XRY x XRXr

8. Can a female have white eyes? • Cross a Carrier red eyed female with a white eyed male. • XRXr x XrY PR:

9. Sex-linked traits in humans • Red-Green color blindness – recessive. Can’t distinquish between colors • Muscular dystrophy- recessive – weakens then destroys muscle tissue • Hemophilia – recessive – lacks ability to produce clotting factor – bleeders • Ran rampant through the royal families of Europe – “Royal Hemophilia”

10. . Here is a test for you. Look at the figures below and write down what you see. Do not talk or make any comments during this test! 4. If you could not see the 29, 45, 56, 6 or 8, you are color blind!! 12 – 20% of the population has this trait. How colorblind people see colors

13. Sex Linked Problems

14. Cross a colorblind male with a carrier female

15. What percent of the boys may have hemophilia if their mother is pure normal and their father is a hemophiliac?

16. If both parents are normal vision, show the cross that could result in a colorblind son

17. If 2 parents are normal and nd their son has MD, what must have been the genotypes of the parents?

18. In humans, the gene for color vision is dominant to the gene for red-green colorblindness. XNXN, XNY = Normalcolor vision XNXn = Carrier for colorblindness but normalvision XnXn, XnY = Colorblind • Show the cross between a normal visioned carrier female and a normal male. • What is the likelihood of them having a colorblind son? Daughter?

19. Show the cross between a carrier mother and a colorblind father. What is the probability of them having a son that is colorblind? A daughter?

20. In humans, the dominant allele for a rare form of rickets (Vitamin D deficiency), is located on the X chromosome. This condition can be successfully treated with Vitamin D therapy. Let “R” = the rickets allele & “r” = the normal allele XR XR, XR Y = Affected female, male XR Xr = Affected female Xr Xr , Xr Y = normal female, male A couple goes to a genetic counselor to find out the chances of them having children with rickets. The wife is normal, without any family history while the husband is affected by this disease. Phenotype: ________________________________________ Genotype: ________________________________________

21. What if the wife were affected (but had a normal father) & the husband was normal? Phenotype: ___________________________________ Genotype: ___________________________________

22. In cats, the black coat pigment (R) is codominant with the orange coat pigment (O). These two alleles are found only on the X chromosome. XB XB , XB Y = Black coated female, Black male XO XO, XO Y = Orange coated female, Orange male XB XO = Tortoiseshell coat (intermingled black and orange in fur) Notice, only females can have tortoiseshell coats. A female tortoiseshell cat mated with an unknown male cat giving birth to 6 kittens (2 orange females, 1 tortoise female, 1 black male and 2 orange males. What was the genotype and phenotype of the father? Phenotype: ____________________ Genotype: _________

23. The owner of a black female cat wants to know which cat fathered her two tortoiseshell female and 2 black male kittens. Was it the same male cat from above?

25. Pedigrees - like a flow chart of a family’s genetic history. Traces a family’s genes

26. Roman numerals show each Generation

27. This pedigree chart shows inheritance of the gene that causes albinism (autosomal recessive trait). N = Normal pigmentation n = Albino gene

28. A pedigree chart for the inheritance of achondroplasia (ay-kon-druh-play-zhuh), a form of dwarfism. Dwarfism is a dominant autosomal trait D = Dwarfism d = normal height

31. Karyotypes Diagrams or photo of how chromosomes are arranged and which ones are present from an individual. Chromosome smear Karyotypes can be used to determine abnormalities in chromosome makeup.

32. A Normal female

33. A Normal Male

34. Amniocentesis • Method of extracting amniotic fluid w/ fetal cells. Can give sex of child and also a karyotype is produced.

35. Mutations – aka: what can go wrong.Changes in the genetic material of a cell Types: • Gene mutation – affects gametes therefore inheritable – Point & frameshift • Chromosomal mutations – involves segments, whole chroms or an entire set of chroms • Somatic mutations – affect body cells. Not inheritable. Cancers (skin, etc)

36. Nondisjuction • Involves a whole chromosome or an entire set of chromosomes that fail to separate during meiosis. Gametes may contain extra chromosomes (or missing chromosomes) • Another animation

38. If Sex chromosomes fail to separate properly • a. Turner’s Syndrome - 45 XO #1280 • Sterile, underdeveloped, short, webbed neck, low hairline • May have learning problems • 1/2500 births • b. Klinefelter’s syndrome – 47 XXY#1281 • Underdeveloped, sterile, female characteristics but is a male. • 1/1000 births • 45YO – Dead – need an X chromosome to survive • 47XXX – Triple female – normal mental capacity. Tend to be lighter than normal. Very passive. Are fertile. 1/1000 • 47XYY – Triple males. 1/1000. Very physical. Fertile. Tends to be more aggressive. 2% of convicts of violent crimes

39. 46XX 45X0 47XXY 46XY Descriptions

40. If Autosomes fail to separate • Trisomy 21(or other type of trisomy) – aka; Down’s syndrome • Extra #21 chromosome • Mild to serious mental deficiency • 1/800 births

41. Down’s Syndromeor Trisomy 21

42. Extra #21 chromosome

43. Klinefelter’s syndrome 47XXY

44. Turner’s Syndrome - 45XO

45. Polyploidy • Entire set or sets of chromosomes fail to separate • Fatal in animals • In plants, leads to larger, hardier plants • 3N, 4N

46. Polyploidy • An entire set of chromosomes fails to separate. • Fatal in animals • In plants, leads to larger, hardier plants • 3N, 4N…

47. Chromosomal mutations • Deletions – loss of a part of a chromosome #1178 • Additions – gain of a part of a chromosome (duplication) • Inversions – Part of a chrom becomes oriented in the reverse of its normal direction • Translocation - crossing over of nonhomologous chroms