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Human Genetics Ch 12.

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Presentation on theme: "Human Genetics Ch 12."— Presentation transcript:

1 Human Genetics Ch 12

2 Chromosomal Mutations
Genetic Diseases….

3 Ultrasound Sonic picture of fetus Boy or girl?

4 Amniocentesis

5 Amniocentesis Remove amniotic fluid with baby’s cells
Observe karyotype 1% risk to fetus

6 Amniocentesis

7 Nondisjunction Failure of homologous chromosomes to separate properly during meiosis Karyotype will show extra or missing chromosomes





12 Diseases from Nondisjunction
Down’s syndrome extra 21 Trisomy 13 (Patau Syndrome) Klinefelter’s syndrome 47 XXY Turner Syndrome 45X Edwards Syndrome Trisomy 18 Cri-du-Chat Syndrome missing part of Chromosome # Link

13 Downs Syndrome Karyotype

14 Downs Syndrome 1/700 live births Extra chromosome #21
Mental retardation Short Heart defects Same facial features More frequent in mothers over 40

15 Downs Syndrome




19 Down’s Syndrome

20 Down’s Syndrome

21 Down’s Syndrome

22 Down’s syndrome

23 Trisomy 13

24 Trisomy 13 Patau syndrome rare 1/20,000 Extra #13 Not alert Deaf
Harelip Cleft palate Polydactyly Live ~6 months

25 Trisomy 13 (Patau)

26 Trisomy 13

27 Trisomy 13

28 Klinefelters Syndrome

29 Klinefelters 47 XXY 2/1000 male births Male but sterile

30 Turner’s Syndrome

31 Turners 45X_ Female, usually sterile and sexually immature
Short, webbed neck

32 Turners 47

33 Turners 17

34 Edward’s Syndrome(Trisomy 18)

35 Edwards Extra #18 Smaller Ears low and malformed Webbed neck
Receding chin Usually die of pneumonia or heart failure

36 Cri-du-chat (missing part of chromosome #5)

37 Cri-du-chat (missing part of chromosome #5)
Heart problems Mental retardation Abnormality in larynx - cries like a cat


39 Simple Recessive Heredity

40 1. Cystic Fibrosis (CF) Defective protein in plasma membrane
Mucus clogs lungs, liver, pancreas 1/20 white am. are carriers 1/2000 white americans born with CF Physical therapy, special diet, drug therapy, gene therapy raised life exp to adulthood




44 2. Tay Sachs Disease Missing enzyme that breaks down a lipid produced and stored in tissues of the central nervous system Newborns appear normal for 5 months Blind, paralyzed, mentally retarded, die before age 5 1/1600 Amish and Jews of Eastern European descent

45 Baby with Tay Sachs Video link

46 Children age 3-5 with Tay Sachs

47 3. Phenylketonuria (PKU)
Failure of brain to develop Absence of enzyme that converts phenylalanine to tyrosine, so amino acid builds up in the body Most common in people with ancestors from Norway or Sweden

48 Testing Can detect in newborns, appear normal at first, but milk is high in phenylalanine

49 Special diet Avoid foods with phenylalanine PKU warnings on diet foods

50 Mom with PKU Can have high phenylalanine in blood and can damage the fetus even if the fetus is normal Control diet

51 Simple Dominant Heredity
Six fingers Widow’s Peak Free earlobes Tongue rolling Usually lethal genetic disorders result in death before they can be passed on


53 Hapsburg Lip The above portrait is of Charles II, who was King of Spain from 1665 to 1700, and who displays this characteristic trait, a trait that was passed down through the Austro-Hungarian monarchy through successive inbreeding.ハ The Hapsburg lip deformity 
affected poor Charles II so badly that he could not chew his food.ハ Years of inbreeding had also taken its toll on his 
intelligence (he was retarded) and his powers of procreation (he was impotent).


55 1. Huntington’s Disease Causes the breakdown of the brain, mental deterioration and loss of muscle control Onset after age (after had kids!) Can test to see if carrier and can pass to kids and will develop the disease

56 Brain Deterioration


58 Huntington’s Disease 30,000 currently suffer in US
Over 150,000 have 50% risk of developing it

59 When Heredity Follows Different Patterns
1. Incomplete Dominance Neither allele is dominant, but combine to make a blended phenotype Ex: Red, white, pink carnations R = red pigment R’ = defective gene

60 Incomplete Dominance cont.
RR = Red RR’ = Pink R’R’ = White What would the offspring look like if you crossed Red and White? What would the offspring look like if you crossed Pink and Pink?


62 2. Codominance Both alleles are expressed in heterozygous offspring
No dominant or recessive No blending Ex: Chickens B = Black feathers W = white


64 2. Codominance What would a cross of a black chicken and a white chicken look like? BB x WW

65 BW = checkered chickens!

66 Codominance - Sickle Cell Anemia
Affects African Americans and (white Americans with Mediterranean Sea ancestors) 1/12 African Americans are heterozygous carriers

67 Codominance-Sickle Cell Anemia

68 SS = sickle cell anemia AS = sickle and normal cells and protection from Malaria


70 3. Sex-linked Inheritance
Genes on the sex chromosomes are passed on differently in men and women XX = female XY = male

71 3. Sex-linked Inheritance

72 3. Sex-linked Inheritance
Y doesn’t have the same alleles as X Ex: Color blindness, Duchenne’s Muscular Dystrophy, Hemophilia

73 Colorblindness

74 Colorblindness

75 Colorblindness

76 3. Sex-linked Inheritance
Color blindness: XN = Normal Xc = colorblind recessive No gene on Y XNXc x XNY? XNXc x XcY?

77 4. Polygenic Inheritance
Trait controlled by many genes Phenotypes have a continuous range of variability Ex: skin color, height Homozygous recessive = aabbcc Homozygous dominant = AABBCC Heterozygous = AaBbCc

78 Eye Color

79 Height



82 5. Multiple Phenotypes Trait controlled by multiple alleles in a population Each individual gets only 2 alleles Ex: Blood Types 3 Alleles: IA, IB, i

83 5. Multiple Phenotypes IA IA or IAi = A Blood IB IB or IBi = B Blood
IA IB =AB Blood i i = O Blood

84 Donating Blood Immune system destroys foreign proteins
Type AB can accept all blood types Type A can accept ? Type B? Type O?

85 Mother and Child Reunion
Beth Sarah Baby 1 Baby 2 Baby 3 Anti-A Anti-B Blood Type Possible Genotypes Actual Genotype

86 Questions 1. Which two babies are Beth’s twins?
2. Which baby is Sarah’s? 3. Now that you know the mother of each baby, can you narrow down each baby’s genotype? 4. What blood type is the twin’s father? 5. What are the possible blood types of the father of Sarah’s baby? Explain!

87 Environment Temp, light, nutrition, chemicals, and infections can all influence if a gene is actually expressed. Internal Environment changes with age or different hormones. Sex-Influenced trait: expressed differently in males and females

88 Sex-influenced Ex: Male Pattern Baldness Genotype Male Female
BB Bald Bald Bb Bald Not bald bb not not Ex: Horn size in mountain sheep, feather color in birds

89 Sex-Influenced trait BB or Bb Only BB











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