Beyond%20Mendel,%20Sex%20Linkage,%20Human%20Genetics

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Beyond Mendel, Sex Linkage, Human Genetics
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Mendel studied only simple inheritance
WELL-DEFINED, DOM/REC
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Non-Mendelian Inheritance Patterns
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Incomplete Dominance INTERMEDIATE HET (Rr
PINK)
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Homework - perform P, F1, F2 crossesUSING
SNAPDRAGONS
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Multiple Alleles some genes have MORE THAN TWO
ALLELES
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Understand A, B, O BLOOD TYPING
Phenotype Genotype
Type A
Type B
Type O
Type AB
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Understand A, B, O BLOOD TYPING
Phenotype Genotype
Type A AA or AO
Type B
Type O
Type AB
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Understand A, B, O BLOOD TYPING
Phenotype Genotype
Type A AA or AO
Type B BB or BO
Type O
Type AB
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Understand A, B, O BLOOD TYPING
Phenotype Genotype
Type A AA or AO
Type B BB or BO
Type O OO
Type AB
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Understand A, B, O BLOOD TYPING
Phenotype Genotype
Type A AA or AO
Type B BB or BO
Type O OO
Type AB AB
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Codominance both alleles EXPRESSED/DETECTED
(e.g. AB)
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Nature/Nurture environment INFLUENCES PHENOTYPE
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Morgan, Flies, Sex Linkage - 1910sGenes Shown on
Chromosomes
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By now, scientists could see CHROMOSOMES AND
MEIOSIS
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Drosophila melanogaster FRUIT FLY
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Autosomes (flies have 3 pairs) NOT GENDER
DETERMINING
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Sex Chromosomes (flies have 1 pair) GENDER
DETERMINING, X AND Y
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Wild Type DOMINANT (e.g. RED EYES)Mutant
RECESSIVE (e.g. WHITE EYES)
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Cross 1 True Parentals RED FEMALE X WHITE MALE
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At first, Morgan assumed eye color was
autosomal/Mendelian F1 Rr, F2 31
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But F2 was half unexpected where all females
red, MALES 5050 REDWHITE
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Morgan formed a new hypothesis GENE FOR EYE
COLOR ONLY ON X
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Rule Three For sex linkage, show alleles on Xs
(e.g. XR) - none on Ys. Prediction must include
gender. Use Mendelian letters for genes - not
Morgans (/-) naming system.
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Lets Show the P X P Cross to F1P Gametes
red/female X white/male



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Lets Show the P X P Cross to F1P Gametes
red/female X white/male
XR XR
Xr
Y
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Predictions 50 RED FEMALES50 RED MALES
XR XR
Xr XR Xr XR Xr
Y XRY XRY
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Lets Show the F1 X F1 Cross to F2F1 Gametes
Het/Female X Red/Male



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Lets Show the F1 X F1 Cross to F2 F1 Gametes
het/female X red/male
XR Xr
XR
Y
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Predictions 50 RED FEMALES25 RED MALES 25
WHITE MALESIs this consistent with observations?
XR Xr
XR XR XR Xr XR
Y XR Y Xr Y
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Some Human Genetics
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Pedigree Analysis MASTER ALL RULESMake sure
you define shaded trait OR write phenotype below
each person.
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The following FYI traits are NOT on exam.
Gene Dom Allele Rec Allele
Chin Dimple -
Free Ear Lobes -
Widows Peak -
Left Thumb Top -
Iris Pigmentation -
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• Sickle Cell Anemia
• REC AUTOSOMAL - SOME INC DOM
• African Americans - 1/400
• Carriers - 1/10
• Defective HEMOGLOBIN CHAIN
• Hom/Rec LETHAL Het WEAK
• Protects against tropical malaria - thus,
  selected among many equatorial races.

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• Cystic Fibrosis
• REC AUTOSOMAL
• European Caucasions - 1/2500
• Carriers - 1/24
• Defective Na/Cl TRANSPORTER
• High levels of secreted SALT, MUCUS
• If untreated, LETHAL BY AGE 5

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• Huntington Disease
• DOM AUTOSOMAL
• Unstable - EXPANDING MUTATION
• 30,000 HAVE, 150,000 AT RISK
• Gene function unclear
• Degenerative BRAIN FUNCTION
• No good treatment - LETHAL 35-45

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• Duchenne Muscular Dystrophy
• REC X-LINKED
• Male Bias - 1/3500
• Defective anchoring protein between
• CYTOSKELETON AND MEMBRANE
• Degenerative MUSCLE DISEASE
• No good treatment - LETHAL 20-25

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