Transcript Lab 8: Meiosis & Phenotype Taking care of genetic information

Lab 8: Meiosis &
Phenotype
Taking care of genetic information;
figuring it out from a standing start
Meiosis & Phenotype
Today we’ll:
• Refine problem-solving skills
• Explore all strategies & outcomes
to determine the best one
– And save hours on homework
Today…
• We will figure out the dominant trait
and genotype for a set of individuals
• There will be no luck, no guessing
needed
• We will generate and explore all
(simple) hypotheses and rule out
those that do not fit, until only one
viable one remains
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
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
Vocab Revisited
• 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!
• Genotype/phenotype: Underlying cause; outward
appearance
Pheno to Geno
Deducing the latter
from the former
Working Through
• Which traits are
dominant? What are
individual genotypes?
You can use sex to find
out!
• Today we’ll engage in
some specific problemsolving techniques
•
•
•
•
Combinatorial thinking
Enumerating hypotheses
‘Last one standing’
Orderly approaches & record
keeping
Vocab and 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: B vs b or BLU vs blu
• Homozygous: ‘same pairing’ = has
identical alleles (AA, aa)
• Heterozygous: ‘different pairing’ = has
different alleles (Aa)
What’s Dominant?
• Imagine you are
confronted with two
phenotypes (color)
• Can you tell which is
dominant?
• What crosses should
you do to quickly
assign dominance &
genotype?
http://talkbudgies.com/showthread.php?t=41797
Occam’s Razor?
• What?
• “No more things should be
presumed to exist than are
absolutely necessary.”
• So, how many alleles should we
assume, and what sort of
relationship?
Remember When?
• Where do sperm and eggs come
from? (Process)
• How many alleles for each
trait/gene in each gamete?
– How to distribute?
• When doing Punnett squares, what
do the ‘letters’ represent?
Today we’ll…
• How many blue-budgie genotypes in a
‘blue-budgie’ dominant world?”
• What do your offspring look like from
blue x blue?
• Ways to make green in a ‘blue’ world?
• What if it’s a ‘green-budgie’ dominant
world
• Develop a sure path to the budgie
genotypes regardless of which ‘world’
How will you know
what’s dominant?
• Two hypotheses? Blue is dominant vs
Green is dominant
• First: Blue Dom – which genos =>
dominant appearance (pheno.)
• Recessive phenotype?
• All possible blue x blue in Blue world?
• All possible green x green in Blue
world?
How will you know
what’s dominant?
• Two hypotheses? Blue is dominant vs
Green is dominant
•What
First: Blue
Dom – which
=>
crosses
yieldgenos
all blue?
dominant appearance
All green?
• Recessive phenotype
• All possible blue x blue in Blue world?
• All possible green x green in Blue
world?
More Punnetts
• Keep your blue work
• Start ‘again’ in a Green dominant
World
Whatcha got?
• How explanatory are these
crosses?
• Anything useful?
• How useful to cross to ‘same’
organisms?
– ‘need’ heterozygotes
• If same X same not working, what
should we explore?
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’
x_Plorer
• If you cross Blue with Red and
get…
• Then….
Lab Instructor: Why ‘Total Victory’ ?
How ‘good’ is the Interweb?
“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 50100% chance of inheriting the gene, depending on
how they inherited their dimple genes.”
What do you have?
IF… THEN
http://www.wisegeek.com/what-are-dimples.htm
How ‘good’ is the Interweb?
“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 50100% chance of inheriting the gene, depending on
how they inherited their dimple genes.”
http://www.wisegeek.com/what-are-dimples.htm
Phenos to Genos
NOW 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
Part 5 of Presentation
• Due next week in dropbox
Meiosis & Phenotype