Transcript Dividing & Deducing

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How?
Why?
Dividing & Deducing
Taking care of genetic information;
figuring it out from a standing start
Goals for today
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Refine problem-solving skills
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Explore all strategies & outcomes to determine the best one
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and save hours on homework!
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Mendel Mattered
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
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Today...
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We will figure out the dominant trait and genotype for a set of
individuals
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There will be no luck, no guessing needed
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We will generate and explore all (simple) hypotheses and rule
out those that do not fit, until only one viable one remains
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Thinking it through
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Developed lines of ‘pure breeding’ traits. Example: green &
yellow-colored peas
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Cross them. ONLY the yellow trait is evident
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Two hypotheses, please?
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One test, please?
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Scaling
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•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
Blinding you with
Science (jargon)
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Gene: A stretch of DNA that represents all the information for a product as
well as when and where to make the product
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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
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Dominant/recessive: Two alleles enter; one allele leaves (which version
manifests in the organism)
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NOT which version is more common!
Genotype/phenotype: Underlying cause; outward appearonce
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Phenos to Genos
Deducing the latter from the former using
only voyeurism
The Bigger Picture
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Which traits are dominant? What are individual
genotypes? You can use sex to find out!
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Today we’ll engage in some specific problem-solving
techniques
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Combinatorial thinking
Enumerating hypotheses
‘Last one standing’
Orderly approaches & record keeping
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Blinding you with
Science (symbols)
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Allele: A version (or flavor) of a gene; two alleles of the same gene
my differ by a nucleotide or dozens of them
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Common symbolism: A vs. a or BLU vs. blu (etc.)
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Homozygous: ‘same-pairing’ = has identical alleles (AA, aa)
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Heterozygous: ‘different-pairing’ = has different alleles (Aa)
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Puzzle: What’s dominant?
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Imagine you are confronted
with two phenotypes (foot color)
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Can you tell which is dominant
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What crosses should you do to
quickly assign dominance &
genotype?
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(FYI: these are actually two
different species)
Blue: http://theadventuretravelcompany.files.wordpress.com/2009/02/blue-footed-booby2.jpg
Red: http://farm3.static.flickr.com/2177/1621918794_be3a25433b.jpg
Occam says...
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What?
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“No more things should be presumed to exist than are
absolutely necessary.”
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So how many alleles should we assume, and what sort of
relationship?
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Review
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Where do sperm & eggs come from?
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Where do they go?
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What’s in them & why?
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Are babies, like, totally unpredictable or what?
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Today we’ll...
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How many blue booby genotypes in a blue-booby dominant
world
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What little boobies can occur in blue x blue?
Ways to make a red booby in a blue-booby dominant world?
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Figure out how to make little red boobies
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Do the same for the land of the dominant RED boobies
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Discover a sure path to the booby genotypes regardless of
which is the dominant booby color
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Path
Blue dominant world
Cross two blues: generally get all blue (ex. Bb x Bb)
cross 2 reds: always all red
Red dominant world
Cross two blues: always all blue
cross 2 reds: generally get all red (ex. Rr x Rr)
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How will you know what’s dominant?
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Two hypotheses: Blue is dominant vs. Red is dominant
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First: Blue Dom, which genos => dominant appearance
(pheno)?
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recessive phenotype?
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What are all possible blue x blue crosses in “Blue dom world?”
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What are all possible red x red crosses in “Blue dom world?”
Punnettopia
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Keep your ‘blue work’
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Clearly demarcate and explore red dom world
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Can we conclude...
anything??
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Which models can explain all red offspring?
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A better way
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If the same x same colored crosses aren’t working, what should
we explore?
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Out of room on your desk? Open x_plorer
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Today’s lab is a graded exercise--show me the ‘Total Victory’
stamp and explain what/why you won to receive 100% (or not,
which yields 0%)
Cross talk
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Naming is hard. Your parents are their parents’ children. So
what’s a parent & what’s a child?
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In x_plorer: parents stay parents
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Formally, you will hear P1, F1, F2 in crosses
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P1: the initial parents for the events in question
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F1: First filial (of pertaining to, or benefiting a son or daughter)
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F2: Second filial
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Thinking through it
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Load x_plorer: (an exercise to guide you in thinking through upcoming
homework)
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Simultaneously consider two alternative hypotheses about
dominance (left half; right half)
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Work through BOTH cases until you have an ordered set of
tests (algorithm) to distinguish (i.e. rule one OUT)
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Watch the lavender box for ‘what to do next’
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Phenos to Genos
Deducing the latter from the former using
only voyeurism
Driving Ms. MStar
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For practice purposes, use the ‘Just Mendel’ option
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If NOT logged in, tutorial in main lab walks you through ‘mating
and sorting’ (Show Me... menu)
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If all that color & such is bugging you, use the ‘Image Simplify’
menu to focus on 1 trait
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When not logged in, go to the ‘Evaluate’ destination for a list of
the genotypes in play
Butterflies
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Once logged in, choose ‘Find the Genotype’
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After answering, hit submit; you’ll see score and be offered a
hint if score ≠ 76 (and all 3 answered)
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You can store @ any time by submitting
Believing what you read
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“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
Homework
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