Unit 6: Genetics & Heredity Ch 8: Heredity & Ch 11: Human Genetics

1. Unit 6: Genetics & HeredityCh 8: Heredity & Ch 11: Human Genetics • What is genetics? • __________________ = the passing of traits from parents to offspring • Why is your combination of genes unique? heredity

2. Gregor Mendel – the Father of Genetics1822-1884

3. Mendel’s Experiments 7 • Studied garden peas – _____ different traits with clearly different forms • Tried to determine how these traits were transmitted from parent to offspring

4. Male & female parts in same flower Normally Self pollinate Produce pure offspring ______ parents produce______ offspring ______ parents produce _________ offspring Mendel’s Experiments purple purple white white

5. Mendel’s Experiments • Cross pollination of pure purple parent & pure white parent (parent generation) • Purple offspring (________ ____________ generation) • Hybrids (genes for both purple & white in all offspring) F1 or first filial

6. Mendel’s Experiments • Offspring allowed to self pollinate • New offspring (F2, second filial, generation) weren’t all purple • _______ • _______ Parent 3 purple 1 white First filial Crossed 2 F1 plants to get F2 Second Filial

7. Mendel’s Principle of Dominance • Mendel noted that for each trait one form dominates the other • In other words, the __________ trait prevents the expression of the _______________ trait. • Ex. In peas, purple x white gives all purple offspring • ____________________ • ____________________ dominant recessive Purple = dominant white = recessive

8. Punnett Squares • Helps to predict the results of crosses • all possible resulting offspring • & the probability of each offspring’s genes • Ea. parent can contribute 1 of 2 genes for a trait (______)- found on homologous chromosomes • Represent with letters • ________________= dominant gene • ________________ = recessive gene • ________________ – alleles same • ex. AA or aa • ________________ – alleles different • ex. Aa allele CAPITAL lowercase homozygous heterozygous

10. Genotype vs. Phenotype genotype • ____________________ = actual genetic make-up of individual • represented by letters • __________ = outward (physical) expression of the genotype • (due to) the protein that is produced • Ex. Let P = purple & p = white • Genotypes PP & Pp both have the same phenotype (purple) • PP = ________________ dominant • Pp = ________________________ • Genotype pp has (white) phenotype: • pp = ________________ recessive phenotype homozygous heterozygous homozygous

12. Mendel’s Principle of Segregation B A b B a b • During gamete formation, the pair of genes responsible for each trait separates so that each gamete receives only 1 gene for each trait. • happens during meiosis I when homologous chromosomes line up (randomly) @ equator (metaphase 1) & separate (anaphase 1)

13. Mendel’s Principle of Segregation

14. Mendel’s Principle of Segregation • tested segregation using heterozygous purple flower & homozygous white flower • Predicted ______ purple & ______ white offspring b/c: • P gene would combine w/ p gene _______ the time • producing ___________ _____________ flowers • p gene would combine w/ p gene _______ the time • producing ___________ _____________ flowers ½ ½ ½ heterozygous purple ½ homozygous white

15. Mendel’s Principle of Independent Assortment • Genes for different traits segregate independently during gamete formation when they are located on different chromosomes… • What if they are on the same chromosome? Genes on same chromosome meiosis Genes on same chromosome

17. Probability • The chance an event will occur • What is the chance of getting heads? Tails? • If you flip two coins, of getting 2 heads? 2 tails? • What is the chance of a couple having a boy? A girl? Of having four boys? Five girls?

18. Ratios genotypic ratio • _______________________ = probable ratio of genotypes in offspring of a cross • Ex. If cross Pp & Pp • 1PP : 2Pp : 1 pp • _______________________ = probable ratio of phenotypes resulting from the genotypic ratio • Ex. If cross Pp & Pp • 3 purple : 1 white • ________________________ = ratio expected based on probability (Punnett Square) • ___________________ = what actually occurs • Why would these be different? phenotypic ratio expected ratio observed ratio

19. Phenotype genotype P p p P Pp Pp Pp Phenotype genotype Pp

20. Monohybrid Cross only one characteristic • a cross where __________________________ _______________________ (gene) is studied • ex. only height, flower color, eye color, etc... T t

21. Dihybrid Cross 2 traits • involves study of inheritance patterns for organisms differing in _____ (each w/ 2 forms). • Mendel  determine if different traits of pea plants, such as flower color & seed shape, were inherited independently. Dihybrid Cross Animation

22. Dihybrid Cross 2 traits with 2 forms

23. Test Cross unknown genotype • Used to determine __________________ of dominant phenotype • Cross ______________ phenotype w/ ________ phenotype • If any offspring show recessive trait, unknown parent  heterozygous • If all show dominant trait, then parent  homozygous dominant dominant Show as P_ recessive

24. Dominant/Recessive is Not Always the Mode of Inheritance • Traits are not always as clearly defined as the 7 pea plant traits Mendel studied • Incomplete dominance • Codominance • Multiple alleles • Sex-linked inheritance • Polygenic inheritance • Continuous variation

25. Incomplete Dominance dominant over another • No allele is ________ __________________ • results in _ phenotypes – ________________, ___________ (mixed), __________________. • Genotypic & phenotypic ratios same • ___________________ • ___________________ • Ex. Pink four o’clock flowers 3 “dominant” 1 intermediate “dominant” 2 1 CRCR: 2 CRCW:1 CWCW 1 red : 2 pink :1 white

26. heterozygote displays the protein products of both alleles __________ Ex. Roan cow has a mixture of both red & white hairs. Codominance equally

27. Multiple Alleles 2 • More than ______ different forms of an allele exist, but individual still has just 2. • Ex. alleles that code for human blood types • A = ______ • B = ______ • O = ______ • exhibit both codominance & multiple alleles • (____ = ____) > _____ IA IB i i IA IB • How many possible genotypes are there? • How many phenotypes? • Can you spot the blood type that is a product of codominance?

28. antigen antigen antigens No antigens

29. Multiple Alleles • Agouti rabbits • 4 alleles: C, cch, ch, c • w/ dominance relationship to one another: _________________________________ • agouti rabbit (wild type) • Phenotype: brown, Genotype: CC, Ccch, Cch, or Cc • “Chinchilla” (mutant) • Phenotype: silvery gray, Genotype: cchcch, cchch, or cchc • “Himalayan” (mutant): • Phenotype: white w/ black points, Genotype: chch orchc • “Albino” (mutant) • Phenotype: white, Genotype: cc C > cch > ch > c

30. Sex Determination autosomes • In humans chromosomes: • Pairs 1 – 22 = _____________________________ • 23rd pair determine gender = __________________ • ______________ = female • ______________ = male sex chromosomes XX XY What is the probability of having a son? A daughter?

31. Sex-linked Inheritance • X & Y chromosomes not fully homologous • X is bigger & carries more genes • Males will have _____________________ for traits carried only on X • called _______________________________ • Ex.: • In Drosophila (fruit flies) eye color • In humans  ______________________________ & ___________________________________________ • X-linked traits more common in males • Why??? only 1 allele X-linked or sex-linked hemophilia colorblindness

32. Sex-linked Inheritance • Predictions made using Punnett square • Include sex of each parent • Consider the sex chromosomes & genes they carry together as a unit… • ex. XG (= dominant gene), Xg (= recessive gene), Y (= no gene) XG female Xg XG XG XG Xg XG Y Xg Y XG Male Y

33. Sex-linked Inheritance • Ex. In Drosophila (fruit flies) eye color • What are the sex, genotype, & phenotype of each offspring? • Are there any female carriers for the white eye gene? Heterozygous red-eyed carrier for white eye allele P generation genotypes were XRXR & XwY red-eyed

34. Sex-linked Inheritance • Hemophilia is X-linked recessive • If mother is carrier & father has hemophilia: • genotypic ratio? • phenotypic ratio? • If mother is carrier & father is normal: • Make a Punnett square • genotypic ratio? • phenotypic ratio?

35. Sex-linked Inheritance • pedigree chart showing inheritance of hemophilia • Does hemophilia affect one gender more often? • Why?

36. Sex-linked Inheritance • Colorblindness is X-linked recessive • In this Punnett square, what are the genotypes & phenotypes of the parents? Ishihara test for red- green color blindness

37. Polygenic Inheritance Many genes • ______________ affect a single trait • shows range of phenotypes from one extreme to another (_______ _____________) • Ex. in humans: hair color, height, skin color continuous variation

38. Expression of Genes interact w/ one another • Genes can ________________________ to control various other patterns of inheritance • Most characteristics that make up individual’s phenotype not inherited in Mendelian patterns • Ex. Modifier genes affect eye color • influence amount, intensity, & distribution of melanin (color pigment) in eye cells

39. Expression of Genes Environment • ______________ in which organism develops is another factor that affects expression • Probably due to how enzymes (proteins) operate at different temperature • Higher temps may “deactivate” enzyme & prevent a reaction form occurring (therefore, changing phenotype) • Examples: • temp & size of fruit fly wings: Warmer temps = larger wings & colder temps = smaller wings • __________: Low altitudes = taller & high altitudes = shorter • ____: Poor soil or drought may produce shorter (or no) ears • _______________: Green (dominant) & albino (recessive)… • however green color is also affected by environment • No sunlight green color cannot be expressed due to lack of chlorophyll production • Put in light green will appear b/c chlorophyll being produced trees corn tobaccoseedlings

40. Human Genetic Disorders

41. Pedigree Charts • A family tree (chart) of genetic history of family over several generations • Scientist or a genetic counselor would find out about your family history & make this chart to analyze. • used to find out probability of a child having a disorder in a particular family • To begin to interpret a pedigree, determine if the disease or condition is autosomal or X-linked and dominant or recessive.

42. Pedigree Chart Square = male Circle = female Shaded = studied trait Marriage = horizontal line Offspring = vertical line

43. Human Genetic Disorders • Due to DNA mutation (usually recessive) or chromosome abnormalities (# or structure) • Causes production of abnormal proteins • Examples: • Autosomal recessive (***most genetic disorders) • Cystic Fibrosis • Sickle-cell Anemia • Tay-Sachs Disease • Autosomal dominant • Huntington’s Disease • Sex-linked • Hemophilia • Color Blindness • Chromosomal abnormality • Down Syndrome (trisomy 21) • Klinefelter’s Syndrome

44. Autosomal Recessive • Must be homozygous b/c allele needed to produce trait is recessive • Cystic Fibrosis • Sickle-cell Anemia • Tay-Sachs Disease Afemale S A Male S

45. Autosomal Dominant • Can be homozygous or heterozygous b/c allele needed to produce trait is dominant • Huntington’s Disease

46. Sex-linked Disorders • Hemophilia • Color blindness

47. Chromosomal Abnormalities • Affects # or structure of chromosomes • #: • Down Syndrome (trisomy 21… 3 copies of chromosome # 21) • Cause  non-disjunction (failure of paired chromosomes to separate during meiosis 1 or meiosis 2)

48. Detecting Abnormalities • Klinefelter’s Syndrome • Sex chromosome disorder • Males have extra copy of the X chromosome *XXY (or 47, XXY b/c 47 total chromosomes) • Cause  non-disjunction (failure of paired chromosomes to separate during meiosis 1 or meiosis 2)

49. Chromosomal Abnormalities • Affects # or structure of chromosomes • Structure: • Added, deleted, inverted, or translocated pieces

50. Detecting Abnormalities • Karyotyping • “picture of human chromosomes” • From blood sample • Can detect extra chromosomes or chromosomal abnormalities (additions, deletions, inversions, translocations)