Meet Harry Shields

Farmer/judge in KansasMy great-great grandfatherNotice:– Nose– Hairline– Inner eye canthus

We all have relatives characteristics!…sooo…?

“mommy. Where do babies…”

Early conceptions about reproduction…storks?What problems would you see in these?Discovery of egg and sperm leads to questions

Gregor Mendel

Childhood & schoolingApplied math? (stats)Simple experimentsSuccess??? Well???

MENDELIAN GENETICS

Introduction…blending vs particle theory?Mendel’s experiments…peas again!!His results…what do they mean?Some terminology to make genetics easierHow to solve monohybrid problems

Some terms to know

Homozygous…dominant & recessiveheterozygousallelesPunnett squareGenotypePhenotypeGene, gene locus

Incomplete dominance or codominanceMonohybrid crossDihybrid crossTest crossPleiotropyEpistasisPolygenic inheritance

Some terms to know

Crossing overSex-linked genesSex-influenced genesAutosomeGerm cellKaryotypeGene locuspolyploidy

Turners/Kleinfelters/XXXDown syndromeNondisjunctionAmniocentesisChorionic villus samplingLinked genes

BLENDING vs PARTICLE?

Evidence for blending…Consequences of blending theoryEvidence for particle…Consequences of particle theoryEvolution/natural selection seems to favor which theory???

Mendel’s “factors”

Believed in particulate theoryFelt that ‘factors’ were contributed equally from male/femaleThought these ‘factors’ separated during meiosis and recombined at zygote

Gene=location

Occur in pairs of alleles

One from maleOne from female

Mitosis vs meiosis

Garden peas & heredity

Blending vs particle theories…No real evidence for either, until…Science in the early 19th centuryMendels 7 traits!!

Mendel’s “lucky seven”

Seed shapeSeed colorPod shapePod colorFlower colorFlower positionPlant height

Quiz

What are purebreeding plants (homozygous)?What is a hybrid (heterozygous)?What is the ratio of dominant to recessive in the F1 generation?What is meant by segregation of alleles?What is meant by independent assortment of alleles?

Mendel’s pea experiment

‘pure breeding plants’Blend or…?F1 generation suggests what…?F2 generation is the real proof…!!conclusions

Results

Mathematical analysis solved mysteryF1 & F2 generationswhat did 3:1 ratio mean??Dominant/recessiveindependent assortmenttest crosses prove theory

quiz

What is the F2 phenotypic ratio of dom/rec plants?What is the genotypic ratio of the F2 generation?What is a test cross?Why was Mendel able to solve such a difficult problem when others failed?

Mendel’s ‘laws’

Segregation of alleles- remember meiosis?

Independent assortment

Dominance and recessiveness

How to do a punnett square

What is a test cross (back cross)

What if you know the phenotype but not the genotype?What genotype do you always know?Two predicted outcomes

Heterozygous Homozygous

Some problems??

If a brown-eyed man marries a blue-eyed woman and they have brown-eyed 10 kids (!) can you be certain that he is homozygous?What if the 11th is blue-eyed?A brown-eyed man, whose father was brown-eyed and whose mother was blue-eyed, marries a blue-eyed woman whose father and mother were brown-eyed have a blue-eyed son. Give the genotypes for all?

Multiple Alleles???

Replace lost blood???

Why didn’t it work?

Landsteiner solves the mystery (1900) by…

But how could genetics explain it with just 2 genes…?

“it’s in the blood”…?

‘mixed’ blood often agglutinates (thus death)But sometimes it doesn’t? Why?Landsteiner postulates 4 phenotypes based on unseen ‘antigens’ and antibodies in blood!

Blood Types?? Multiple alleles

But how to explain the genetics?

Each parent contributes an “element” (gene)The A and B genes are both dominant or said to be “codominant” and the o is recessive thusThree genes (taken only two at a time) code for blood type…producing 4 possible phenotypes and six genotypes…what are they?

The Simpsons and Nelsons

Both the Simpsons and Nelsons had baby boys the same day in the same hospital. Ricky went home with the Simpsons and Bart the Nelsons. Soon, odd behaviors in both households suggested that something was terribly wrong!! Could they have been switched at birth?? Blood tests were doneand…

The Simpsons and Nelsons

Homer both had type A while Marge had type B. Ricky had type o. (Oh No!!)…Ozzie and Harriet had type A. Bart had type B…Did a switch occur??…what happened next?

But what about pink carnations?

Red flower X white flower produces…Pink???

But what about pink carnations??

Incomplete dominance

Neither gene is dominantIntermediates resultF2 generation reveal the parental phenotypes…why?

Quiz…incomplete dominance

Use the example of snapdragons…a red (RR) flower is crossed with a white (WW) flowerWhat is the F1 phenotypic ratio of 2 hybrids (heterozygotes) mating?What is the genotypic ratio?

Sex determination in other species

Many animal systems have different mechanisms for determining sexSome are variable or changeable!! Why??

Male to female sex ratio

Sex determination

Sex-linked genes

Why are more boys than girls color-blind?What is color-blindness?What is a ‘sex-linked’ trait??

The retina has, normally, 3 kinds of cones…red, blue and green light sensitive…because of 3 different proteins…blue is on chr 7 but red/green on X chr are 98% similar and a mutation causes either the loss of red or green sensitivity

Genetics of Color-Blindness

A man and his wife have normal color vision, but a daughter with color-blindness. He sues his wife for divorce for infidelity. You be the judge!

Down Syndrome

Nondisjunction of 21st chromosomesVariable effectsAmniocentesis can detect trisomy 21 early…Difficult questions remain for the parents…