Chapter 10: Patterns of Inheritance

1. Chapter 10: Patterns of Inheritance PowerPoint

3. Rosalind Franklin Franklin, at 37 yeas old, died in 1956, 3 years after Watson and Crick published their work on DNA structure. She never received credit until 1968 with the publishing of the book “The Double Helix”. Famous Photo 51: X-ray revealing the helix shape shown to Watson and Crick by Franklin’s discontented collaborator, Maurice Wilkins.

4. Brown Eye Blue Eye B b Chromosomes are in homologous pairs... 23 in humans. Each chromosome has alleles or versions of a gene pair.  

5. Genotype – The actual genes/alleles an individual contains for a specific trait Example: Bb Phenotype– The physical traits an individual has a result of its genotype. Example: Brown hair

6. Dominant - expressed trait B Recessive - hidden trait b Homozygous – alleles for a trait are the same Example: BB or bb Heterozygous – alleles are different Example: Bb

7. Tongue Rolling: possibly a dominant trait. Jury still out, but most likely a combination of genetics and environment. Clover shaped Tongue... Just kinda weird

8. Hitchhiker’s Thumb Recessive = hh This kid doesn’t have it

9. Widow’s Peak Dominant too WW - Homozygous Dominant Ww - Heterozygous

10. Free Earlobes Dominant EE or Ee Attached Earlobes Recessive ee

11. A Long Second Toe is Dominant

12. Gregor Mendel The Father of Genetics Monastery Garden in Brunn, Moravia

13. From the monastery garden, Mendel grew pea plants. He studied 7 variations and predicted their inheritance

14. 1865... Gregor Mendel published his work

15. Mendel’s Three Laws • Principle of Dominance • Principle of Segregation • Principle of Independent Assortment

16. Principle of Dominance: When two forms of the same gene are present, the dominant allele will be expressed Principle of Segregation: In meiosis, two alleles separate so each gamete receives only one form of the gene Principle of Independent Assortment: Each trait is inherited independent of other traits

17. Punnett Square

19. Ais a dominant characteristic. ais a recessive characteristic. This bird has two genes for orange feathers:AA. This bird has two genes for blue feathers:aa. Offspring are heterozygous Aa and phenotypically red

20. Now suppose that two individuals from the Bird’s F1 generation become parents. These parents are both heterozygous. What will their offspring be? Will the offspring all be the same?

21. Cross a heterozygous smooth pea (male) and a wrinkled pea. Smooth is dominant S = smooth; s = wrinkled • Step One: write a gene symbol Male = Ss Female = ss • Step Two: parent genotypes s s • Step Three: Punnett Square S S S s s s s s s s • Step Four: Ratios Genotypic = 0:2:2 Phenotypic = 2:2

22. Ratios Bb bb Bb bb Determining the Genotypic Ratio: B b Bb count all homozygous dominant (BB) B BB next all heterozygous (Bb) Bb bb b then count homozygous recessive (bb) : : 1 2 1 B b What is the genotypic ratio? b 0 : 2: 2 b

23. Ratios Bb Bb bb bb B b Determining the Phenotypic Ratio: Bb B BB B is black guinea pig hair and b is white guinea pig hair Bb bb b count those with black hair... BB / Bb count those with white hair... bb : 3 1 What is the Phenotypic ratio? 2: 2

24. Mendel’s Patterns of Inheritance followed the Principle of Dominance, as we have seen. Here is a list of Non-Mendelian Patterns of Inheritance • Intermediate Inheritance also known as Incomplete Dominance • Multiple Alleles • Sex-linked Traits • 4. Polygenic Inheritance

25. Incomplete Dominance – Both Alleles contribute to the phenotype of a heterozygous individual to produce a trait unlike either parent R R RR WW W RW RW RW Example: Snapdragon flowers that have a pure red parent and a pure white parent produce an intermediate pink W RW RW

26. Do the Cross Between Two Pink Snapdragons Genotypic Ratio = 1:2:1 Phenotypic Ratio = 1:2:1 RW RR WW R RR RW RW W RW WW RR RW RW WW

27. B b B Bb BB b Bb bb

28. Codominance – When a trait is controlled by more than two alleles ABO Blood Types are an example A gene is dominant (IA) B gene is dominant (IB) O gene is recessive (iO) Type A Blood can be IAIA; IAiO Type B Blood can be IBIB; IBiO Type O is iOiO Type AB is IAIB

29. IA iO IAIB IBiO IB IAiO iO iOiO Cross a Heterozygous Type A female with a Heterozygous Type B Male Genotypic Ratio 1:1:1:1 AB Phenotypic Ratio 1:1:1:1 B A O

30. Father = IAiO Mother = IAIB Using the Four Steps show the cross between a heterozygous type A male and a female who is AB. IA = A gene IB = B gene iO = O gene IA IB IA IAIA IAIB Genotypic = 1:1:1:1 Phenotypic = 1:2:1 iO IAiO IBiO

31. A Sex-Linked Trait is a trait controlled by genes on the Sex Chromosome. • If Found on the X Sex Chromosome it is an X-Linked Gene; • If on the Y Sex Chromosome it is Y-Linked Hemophilia and Red/Green Colorblindness are X-Linked Traits

32. Sex-Linked Genes Sex Chromosomes in fruit flies studied by T.H. Morgan in 1900’s X Y X X

33. Hemophilia is due to a X-linked recessive gene (h) Genes on the X Chromosome, but NOT on the Y Chromosome H h Y X X

34. XHXH = Female normal XHXh = Female carrier XhXh = Female hemophiliac (very rare) XHY= Male normal XhY= Male hemophiliac

35. Queen Victoria: Queen of England from 1837 -1901 Hemophilia in Royal Family

36. Show the Punnett Square Cross Between Queen Victoria and Prince Albert • Victoria was a carrier of hemophilia, XHXh H = normal blood clotting factors h = hemophilia • Albert was a normal male XHY XH Xh 75% phenotypically normal 25% hemophiliac XH XHXH XHXh 50% of females genotypic carriers 50% females normal Y XHY XhY

37. Polygenic or Multiple Gene Inheritance • When two or more independent genes affect one characteristic Human characteristics such as skin, eye, and hair color all involve more than a single pair of genes. The combinations of all the genes involved provides the rich variations we see in the human population.

39. Dihybrid Cross Cross a heterozygous two eyed triangular alien with another heterozygous two eyed triangular alien E = two eyes e = one eye T = triangle t = hexagon EeTt x EeTt

40. ET Et eT et Et et eT ET E = two eyes; e = one eye T = triangle; t = hexagon

41. Genetic Corn A = purple smooth; B = purple wrinkled C = yellow smooth; D = yellow wrinkled