Dividing & DeducingTaking care of genetic information; figuring it out from a standing start

How? Why?

Lab 8

Q: What is a gene?

Q: What is an allele?

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Why Mendel Matters

The laws governing inheritance are for the most part unknown; no one can say why the same peculiarity in different individuals of the same species, or in different species, is sometimes inherited and sometimes not so; why the child often reverts in certain characteristics to its grandfather or grandmother or more remote ancestor; why a peculiarity is often transmitted from one sex to both sexes, or to one sex alone, more commonly but not exclusively to the like sex.”

--Charles Darwin, The Origin of Species

…Because Darwin sucked

Meiosis & Phenotype

Taking care of genetic information; figuring it out from a standing start

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Today...• We will figure out the dominant trait and

genotype for a set of individuals• There will be no luck, no guessing, no

random stabbing in the dark involved• We will generate and explore all possible

(simple) hypotheses and rule out those that do not fit, until only one viable one remains

Meiosis & PhenotypeToday we’ll:

• Refine problem-solving skills• Explore all strategies & outcomes to

determine the best one– And save hours on homework

Thinking it Through• Develop lines of ‘pure breeding’ traits

(green and yellow peas)• Cross them… ONLY yellow trait is

evident– TWO hypotheses?– One test?

Thinking it Through• Two Hypotheses• Make a prediction– IF ‘this’ is true, THEN…

• Model and test

Answer1) the green trait had been

destroyed, pushed out, eliminated

2) the green trait was silenced/hidden/overwhelmed

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Holmes had it rightWhen you have ruled out the impossible, that which remains, however improbable, must be the truth.

--Sir Arthur Conan Doyle

Basic principle of science--we work by listing hypotheses & trying to kill as many as possibleIf one survives, it’s our best description of the universe--provisionally

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Scaling

•A gene is ~1,000-100,000 basepairs*

•A chromosome is tens or hundreds of thousands of genes

*Includes control regions & stuff that won’t make it into the final product

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Blinding you with Science (jargon)

• Gene: A stretch of DNA that represents all the information for a product as well as when and where to make the product

• Allele: A version (or flavor) of a gene; two alleles of the same gene my differ by a nucleotide or dozens of them--generally a small number

• Dominant/recessive: Two alleles enter; one allele leaves (which version manifests in the organism)

– NOT which version is more common!

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The Bigger Picture• Which traits are dominant? What are individual

genotypes? You can use sex to find out!

• Today we’ll engage in some specific problem-solving techniques

– Combinatorial thinking

– Enumerating hypotheses

– ‘Last one standing’

– Orderly approaches & record keeping

Bang it out• You don’t know, but you can “*make sex” to

figure it out!

* that’s about as romantic as I get

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Blinding you with Science (symbols)

• Allele: A version (or flavor) of a gene; two alleles of the same gene my differ by a nucleotide or dozens of them

– Common symbolism: A vs. a or BLU vs. blu (etc.)

• Homozygous: ‘same-pairing’ = has identical alleles (AA, aa)

• Heterozygous: ‘different-pairing’ = has different alleles (Aa)

PRACTICE!!

• Punnett

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Puzzle: What’s dominant?• Imagine you are confronted with

two phenotypes (foot color)• Can you tell which is dominant• What crosses should you do to

quickly assign dominance & genotype?

• (FYI: these are actually two different species)

Blue: http://theadventuretravelcompany.files.wordpress.com/2009/02/blue-footed-booby2.jpgRed: http://farm3.static.flickr.com/2177/1621918794_be3a25433b.jpg

If you were trapped on the island of the boobies, could you figure out the

genetics?

How will you know what’s dominant?

• Two hypotheses? Blue is dominant vs red is dominant

• First: Blue Dom – which genos => dominant appearance

• Recessive phenotype• All possible blue x blue in Blue world?• All possible red x red in Blue world?

How will you know what’s dominant?

• Two hypotheses? Blue is dominant vs Green is dominant

• First: Blue Dom – which genos => dominant appearance

• Recessive phenotype• All possible blue x blue in Blue world?• All possible green x green in Blue world?

What crosses yield all blue?All red?

More Punnetts• Keep your blue work• Start ‘again’ in a RED World

Whatcha got?• Which models can explain all green

offspring?• Anything useful?• How useful to cross to ‘same’

organisms?– ‘need’ heterozygotes– How do you get them if you don’t know?

A better way?• Need more room? Open x_plorer• Graded exercise – show me ‘Total

Victory’ and explain what/why you won (100% or 0%)

MORE Vocab• Naming is hard. Your parents are their parents’

children. So what’s a parent & what’s a child?• In x_plorer: parents stay parents• Formally, you will hear P1, F1, F2 in crosses• P1: the initial parents for the events in question• F1: First filial (of pertaining to, or benefiting a son

or daughter)• F2: Second filial

x_Plorer• An exercise to guide you in thinking• Simultaneously consider two alternative

hypotheses about dominance (left half; right half)

• Work through BOTH cases until you have an ordered set of tests (algorithm) to distinguish (i.e. rule one OUT)

• Watch the lavender box for ‘what to do next’

Lab Instructor: Why ‘Total Victory’ ?

x_Plorer• If you cross Blue with Red and get…• Then….

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Believing what you read“The genetics of dimples is actually rather interesting. Dimples are a dominant trait, which means that it only takes one gene to inherit dimples. If neither of your parents has dimples, you shouldn't have them either, unless you experience a spontaneous mutation. If one of your parents has dimples, you have a 25-50% chance of inheriting the gene, since it means that parent inherited the gene from one or both parents. If both of your parents have dimples, you have a 50-100% chance of inheriting the gene, depending on how they inherited their dimple genes.”

http://www.wisegeek.com/what-are-dimples.htm

On desktops, with chalk!

Phenos to Genos

Deducing the latter from the former using only voyeurism

Phenos to GenosNOW the fun!!!!

MendelStar!• Given the outcome, can you predict the

genotype of the parents?• Observe, Hypothesize, Predict,

Model/Test• Have a plan• Write it down

MendelStar!• For practice purposes, use the ‘Just Mendel’ option• If NOT logged in, tutorial in main lab walks you

through ‘mating and sorting’ (Show Me... menu)• If all that color & such is bugging you, use the

‘Image Simplify’ menu to focus on 1 trait• When not logged in, go to the ‘Evaluate’ destination

for a list of the genotypes in play

Mate your own Butterflies!• Once logged in, choose ‘Find the Genotype’• Work through problems – Have a plan– Write it down! (IF this is TRUE…)– Saves time!

• After answering, hit submit; if score < 76 you’ll get a hint

• You can store at any time by submitting

Mate your own Butterflies!• Why 76 points ‘max’?• Yep, written part in dropbox• Really, have a plan

Genetic Disease Presentations

• -Semester Projects