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` HEREDITY = The passing of traits from parents to offspring. x Transmitted by means of information stored in molecules of DNA.

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Presentation on theme: "` HEREDITY = The passing of traits from parents to offspring. x Transmitted by means of information stored in molecules of DNA."— Presentation transcript:

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2 ` HEREDITY = The passing of traits from parents to offspring. x Transmitted by means of information stored in molecules of DNA.

3 ` GENEITCS =Scientific study of heredity x Based on knowledge that traits are transmitted by chromosomes. x Chromosomes carry units of hereditary information called genes.

4 ` Since an organism receives genes from both parents it is not exactly like either parent but like each parent in some ways.

5 ` ENVIRONMENT = All the outside forces that act on an organism. x Affects the development, later life, and the expression of hereditary traits of an organism.

6 ` WHAT MAKES YOU WHO YOU ARE TODAY? ◦ HEREDITY & ENVIRONMENT--are the two great influences, acting together all through you life.

7 ` Genetic messages determine what organisms may become. ` The interaction of messages and the environment determines what organisms do become.

8 ` Organisms inherit genetic messages, not traits! ` Traits develop when genetic messages interact with the environment.

9 ` GREGOR MENDEL -“Father of Genetics” - (1865) Austrian monk x His research with garden peas led to the discovery of the basic principles of heredity. x Did a statistical study of traits in garden peas over an eight year period.

10 ` Garden peas were a good choice for experimentation because: 1. They can be cultivated quickly. 2. They display several traits in one of two contrasting forms: Height—tall/short Seed color—yellow/green 3. They are normally self-pollinating plants and are very easy to cross- pollinate.

11 ` Mendel used logical experimental methods and kept careful records. ` He used his math principles of probability to interpret results.

12 ` Mendel studied pea traits, each of which had a dominant & a recessive form (alleles). ` The dominant (shows up most often) gene or allele is represented with a capital letter, & the recessive gene with a lower case of that same letter (ex: B, b).

13 ` Mendel's traits included: a. Seed shape --- Round (R) or Wrinkled (r) b. Seed Color ---- Yellow (Y) or Green (y) c. Pod Shape --- Smooth (S) or wrinkled (s) d. Pod Color --- Green (G) or Yellow (g) e. Seed Coat Color --- Gray (G) or White (g) f. Plant Height --- Tall (T) or Short (t) g. Flower color --- Purple (P) or white (p)

14 ` Trait = any characteristic that can be passed from parent to offspring ` Heredity = passing of traits from parent to offspring ` Genetics = study of heredity

15 ` Alleles = two forms of a gene (dominant & recessive)

16 ` Dominant = stronger of two genes expressed in the hybrid; represented by a capital letter (R) ` Recessive = gene that shows up less often in a cross; represented by a lowercase letter (r)

17 ` Genotype = gene combination for a trait (ex: RR, Rr, rr) ` Phenotype = the physical feature resulting from a genotype (e.g. tall, short)

18 ` Homozygous genotype = gene combination involving 2 dominant or 2 recessive genes (ex: RR or rr); also called pure ` Heterozygous genotype = gene combination of one dominant & one recessive allele(ex: Rr); also called hybrid

19 ` Monohybrid cross = cross involving a single trait ` Dihybrid cross = cross involving two traits

20 ` Punnett Square = used to solve genetics problems. (based on probability)

21 ` Humans each have two sets of 23 chromosomes in their somatic (body) cells. ◦ 46 chromosomes total.

22 ◦ Our chromosomes are made up of our genes, which are pieces of DNA that code for certain traits. x For example, both of our chromosomes might contain the genes for hair texture or height.

23 ` The different forms or types of a specific gene are called alleles. ◦ For example, a GENE for eye color might have a blue allele, a brown allele, and a green allele. ◦ In plants, a gene for flower color might have a yellow allele and a white allele.

24 ◦ Because our chromosomes are in two sets, we have two copies of each gene, one from our mom and one from our dad. ◦ If both of our parents gave us the same type of gene - the same allele - then we are:

25 ` HOMOZYGOUS or pure (on both sets of our chromosomes, on both sets of genes; the allele is the same).

26 ` If one parent gave us one type of gene and the other parent gave us a different type, then we are: x HETEROZYGOUS or hybrid - we have two different alleles.

27 ` With MENDELIAN traits (the type of traits that Mendel studied), heterozygotes DO NOT have a blend of the two alleles. x Instead, one type of allele dominates - x We show the characteristics of this allele only - it is the DOMINANT trait.

28 ` The other version of the trait is still there on half of our chromosomes (so we might still pass it on to our children, depending on meiosis) BUT it DOES NOT affect us right now—it is the RECESSIVE trait.

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30 ` Whether we are heterozygous, homozygous with the dominant trait, or homozygous with the recessive trait it is called our GENOTYPE (type of genes that we have). ` Which trait we physically show is our PHENOTYPE (the type of allele that is expressed).

31 ` For example, if the dominant allele of the eye color gene is brown and the recessive allele of the eye color gene is blue, then the person could have the following possibilities:

32 1. Two blue alleles, bb (one from mom, one from dad). ◦ Genotype would be homozygous recessive ◦ Phenotype would be blue-eyed.

33 2. Two brown alleles, BB (one from mom, one from dad). ◦ Genotype would be homozygous dominant ◦ Phenotype would be brown-eyed.

34 3. One brown and one blue allele, Bb (one from mom, one from dad). ◦ Genotype would be heterozygous ◦ Phenotype would be brown-eyed.

35 ` When only one trait is being studied in a genetic cross, it is called a monohybrid cross. ◦ When parent organisms, called the P generation, are crossed, the resulting offspring are the first filial, or F 1 generation. ◦ When organisms of the F1 generation are crossed, their offspring make up the second filial or, F 2 generation

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37 ` Mendel produced pure strains by allowing the plants to self-pollinate for several generations. ` These strains were called the parental generation or P 1 strain.

38 ` Mendel cross-pollinated two strains and tracked each trait through two generations. (ex: TT x tt ) x Trait = plant height x Alleles = T (tall),t (short)

39 ` P 1 cross = TT x tt t t T Tt Tt F 1 Genotypic ratio = 100% Tt F Phenotypic ratio = 1 100% Tall

40 T t Tt t TtTt The offspring of this cross were all hybrids showing ONLY the dominant trait & were called the First Filial or F 1 generation.

41 ` Mendel then crossed two of his F 1 plants and tracked their traits; known as an F 1 cross. x Trait = plant height x Alleles = T (tall),t (short)

42 ` F 1 cross = Tt x Tt T t TtTt TTTt Tttt F 2 Genotypic ratio = 1 TT: 2 Tt: 1 tt F 2 Phenotypic ratio = 3 Tall: 1 short

43 ` When 2 hybrids were crossed, 75% (3/4) of the offspring showed the dominant trait & 25% (1/4) showed the recessive trait ` Two hybrids ALWAYS create a 3 (dominant trait): 1 (recessive trait) ratio. ` The offspring of this cross were called the F 2 generation.

44 ` Inheritable factors or genes are responsible for all heritable characteristics. ` Phenotype is based on genotype.

45 ` Each trait is based on two genes, one from the mother and the other from the father. ` True-breeding individuals are homozygous (both alleles) are the same. ` Formulated 3 laws of heredity in the early 1860's.

46 1. Law of Dominance states that when different alleles for a characteristic are inherited (heterozygous), the trait of only one (the dominant one) will be expressed. The recessive trait's phenotype only appears in true- breeding (homozygous) individuals.

47 Trait: Pod Color Genotypes: Phenotype: Green Pod GG Green Pod Gg Yellow Pod gg

48 2. The Law of Segregation = states that each genetic trait is produced by a pair of alleles which separate (segregate) during reproduction. Rr Rr x Explains the disappearance of a specific trait in the F 1 generation and its reappearance in the F 2 generation

49 3. The Law of Independent Assortment = states that each factor (gene) is distributed (assorted) randomly and independently of one another in the formation of gametes (egg or sperm). RrYy RYRyrYry

50 ` Explains that different traits are inherited independently, if on different chromosomes ` Ex: wrinkled seeds do not have to be yellow. They can be green.

51 ` Ex: A gamete with RrYy ◦ R and r - separate into different gametes ◦ Y and y - Separate into different gametes ◦ They can then recombine 4 ways to form gametes: ` RY Ry rY ry

52 ` Dark hair/ Light hair ` Non-red hair/ Red hair ` Curly hair/ Straight hair ` Widows peak/ Straight or curved hairline ` White forelock/ normal hair ` Body hair/ Scant body hair ` Freckles/ Normal ` Dimples/ No dimples

53 ` Brown eyes/ gray or blue eyes ` Normal eyesight/ Nearsighted ` Large eyes/ Small eyes ` Long eyelashes/ Short eyelashes ` Broad nostrils/ Narrow nostrils ` Roman nose/ Straight nose

54 ` Large nose/ Small nose ` Free ear lobe/ Attached ear lobe ` Web fingers/ Normal fingers ` Bent little fingers/ Parallel little fingers ` Left over right thumb/ Right over left thumb

55 ` A or B blood/ O blood ` RH+ blood/ RH- blood ` Normal clotting/ Hemophilia ` Normal / Allergy ` Tongue roller/ Non-roller

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57 ` Identical twins develop from a single fertilized egg that splits shortly after fertilization x Since they developed from the same egg they have exactly the same genetic makeup

58 ` Fraternal twins develop from two eggs that are fertilized by different sperms x They are completely different people

59 ` By studying identical twins, geneticists have learned that genes seem to have a greater influence than the environment on such traits as height, weight, blood pressure, speech patterns, and gestures.

60 ` They have also discovered that genes play a role in some medical problems once thought to be caused only by environmental factors. ◦ For instance, genes can cause a susceptibility to diseases such as diabetes and certain types of cancer.

61 ` Infections and infectious diseases CANNOT be inherited ` Certain chemical conditions of the cells and body tissues important in resistance against infections may be inherited.

62 ` Diseases resulting from abnormal structure or function of body organs are more likely to be hereditary

63 ` Some diseases that may be associated with genes are: ◦ -diabetes - respiratory allergies - asthma - nearsightedness - farsightedness - night blindness

64 OR ? ` Sex chromosomes = determine the sex of an individual ◦ The X chromosomes (XX) produce a female ◦ An X chromosome paired with a Y chromosome (XY) produces a male

65 ` Since only a male can produce a gamete bearing a Y chromosome, the father determines the sex of the child x Note: the X chromosome contains additional genetic information that the Y chromosome does not have, therefore a male child actually inherits more genetic information from his mother than his father (a very tiny amount)

66 ` Traits that occur more frequently in one sex than another ◦ Males -color blindness and hemophilia

67 ` Occurs because other genes besides the alleles for sex are also located on the sex chromosomes ◦ They are recessive to the normal condition and the Y chromosomes appear to lack genes for these traits ◦ These traits generally do no show up in females

68 ` Use Punnett Squares to solve genetic problems!

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70 ` Black coat color in guinea pigs is dominant over white coat color. Using a Punnett square, show the results of crossing a hybrid black with pure white. Then show the results of crossing a hybrid black and a hybrid black.

71 Black Trait - B (dominant) White Trait - b (recessive) Hybrid black - Bb Pure white – bb

72 ` P 1 cross: Bb x bb b b BbBb Bbbb Genotypes of F 1 offspring 2 Bb : 2 bb Phenotypes of F 1 offspring- 2 black : 2 white (or 50% black and 50% white)

73 Black Trait - _B (dominant) White Trait - _ b (recessive) Bb Hybrid black - __ Hybrid black - ___Bb___

74 ` P 1 cross: B B Bb ____x b Bb ____ Genotypes of F 1 offspring 1BB: 2Bb: 1bb b BB Bb bb Phenotypes of F 1 offspring- 3Black: 1white

75 1.) In pigs, the white color (W) is dominant; the black color (w) is recessive. Using Punnett squares, show the expected results of the following crosses.

76 ` P cross: 1 WW x ww w W W Ww Genotypes of F 1 offspring 100% Ww Ww Phenotypes of F 1 offspring- w Ww 100% White

77 ` P cross: 1 Ww x Ww W W w WW Genotypes of F 1 offspring 1WW: 2Ww: 1ww Ww Phenotypes of F 1 offspring- w Wwww 3White: 1black

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79 ` Because each parent and offspring are using two traits, each one should have 4 alleles, 2 for each trait. ` Each gamete produced by the P 1 generations will contain 2 alleles, one for each trait.

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81 ` Example: A plant that is heterozygous for being tall and having green seeds is crossed with a homozygous yellow and short x Traits = seed color and plant height x Alleles G =green g = yellow Cross: _______ x T = tall t = short ttgg

82 ` Determine the gametes produced by each parent by using the FOIL method. ◦ TtGg produces 4 different gametes: TG Tg tG tg ◦ ttgg produces only 1 gamete: tg

83 TG Tg tG tg tg TtGgTtgg ttGgttgg Phenotypes: 4 tall/green seeds 4tall/yellow seeds 4short/green seeds 4short/yellow seeds TtGg Ttgg ttGg ttgg tg TtGg Ttgg ttGg ttgg TtGgTtgg ttGg ttgg Genotypes: 4TtGg: 4Ttgg: 4ttGg: ttgg

84 ` In a dihybrid cross, when two traits are considered, the number of possible combinations of the offspring increases. Suppose that black hair (B) is dominant over blonde hair (b) and brown eyes (E) are dominant over blue (e). ` What percent of offspring could be expected to have blonde hair and blue eyes if:

85 ` The father has black hair (heterozygous) and brown eyes (heterozygous) and the mother has blonde hair and blue eyes. ` Genotype of father = BbEe ` Genotype of mother = bbee ` Complete the cross using the Punnett square. Determine what percent of offspring will have blonde hair and blue eyes.

86 BE Be bEbe BbEeBbee bbEe bbee 25% (4/16) % blonde hair & blue eyes

87 ` Both parents have black hair (heterozygous) and brown eyes (heterozygous). BbEe ` Genotype of father = ________ BbEe ` Complete the Punnett square below. Determine what percent of offspring will have blonde hair and blue eyes.

88 BE Be bEbe BE BBEE BBEe BbEE BbEe Be bE be BBEe BBeeBbEe Bbee BbEE BbEE bbEE bbEe BbEeBbeebbEebbee 6.25% (1/16) % blonde hair & blue eyes


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