Nice animation, includes
recombination
http://www.johnkyrk.com/meiosis.html
Announcements
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Genetic Disease Presentations – sign up for a date
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Proposals graded – see comments and revise!
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Come to me with any questions regarding revision of
proposals after class today
All hemoglobin tutorials graded, see comments and answer key.
Downloadable from course software page
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Comments on
Citations
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You MUST cite any information used from an online website,
textbook or the lab manual EVEN if you put it in your own words
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Review citation format (journal of Ecology example)
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Citation Example
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Last initial. First name. (Year). Title of article. Journal. Volume:page numbers.
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Example:
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S. John, B. Anne, and R. Jordan. (2012). Assessing the effects of spatial
contingency and environmental filtering. Ecology. 93:114-125.
In text (Author last name, year)
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Example from above citation: (Smith et al., 2012).
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If more than two authors – et al., after first author (note: must state all
authors in citation at the end of the document, et al. is only for in text)
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If two authors, state both last names with ‘and’ in between
In text – superscript  after use of information from article, superscript the
number of the citation as it appears in the citation list at the end of the document
How?
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Why?
Dividing & Delivering
Distributing genetic information
Goals for today
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Scaling: Nucleotide, Gene, Chromosome--and how many of each
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Concept: Chromosomes are hugely long threads of DNA; some
regions are genes
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PURPOSES of ‘mitosis’ & ‘meiosis’ & how these dictate the
events
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Mixing and matching parental DNA made you. It provides hope
you’re better than them ;)
The birthday cake
gene
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You are a birthday cake-making company!
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A call comes in to order a cake. What information must you take?
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You’re an old fashioned mom-and-pop place; no photos
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Scaling
•A gene is ~1,000-100,000 basepairs*
•A chromosome is tens or hundreds of
thousands of genes
•A genome is 1-100s of chromosomes
•A genotype refers to the alleles present
in a given genome
• Human genome is ~3,000,000,000
basepairs
•Human genome is (currently
guesstimated at) ~20-30,000 genes**
•Human genome is ~1 meter of DNA
*Includes control regions & stuff that won’t
make it into the final product
**We keep finding stuff that matters
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!
More in the lab manual & Vocab exercises!
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Windows on the gene: eyes
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Find a brown- and a blue-eyed person. Look deep into their
eyes & try to figure out the difference
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What does it mean genetically when we say ‘brown eyes are
dominant’?
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One gene, two alleles
Why should that be so? What do brown alleles got that blue do
not?
Ripped from the headlines
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Blue eyes arise from a DNA change that prevents creation of
melanin in the eye specifically
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Mutation appears identical in all blue-eyed folks, suggesting
single origin
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Headline: Blue eyes result of ancient genetic ‘mutation’
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It’s not a ‘mutation’; it’s a mutation
[FYI]: On green eyes
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Touching mitosis &
meiosis
Meet the
Chromosomes
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Compare our bead
models with image
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What corresponds?
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Some data on PTC, hair, etc. (Source: Exploring Biology in the Laboratory, p. 205-7)
USE these to make the point that dominant <> predominant (and to give everybody
a break in which they think about their own phenotypes)
PTC paper: 70% can taste; tasting is dominant (SAVE for Pedigrees)
Bent little finger: bending inwards towards ring finger is dominant
Tongue rolling--ability to roll is dominant
Widow's peak--v-shaped hairline (think Paul Ryan). Means you are Devil's spawn, is
dominant
Dimpled chin--Dominant to have the dimple
Free earlobe: port is detached. Detached = dominant
Swing hands, clasp together. If left thumb over right, you've got the dominant trait
Bending your thumb away from your palm: INability to bend tip 60 degrees relative
to thumb is dominant
Hair on middle joint of finger is dominant
Dimpled cheeks is dominant
Ability to raise eyebrows is dominant
Ability to wiggle ears is dominant
second toe longer than big toe? Dominant
Curly hair dominant to straight
Freckles is dominant
Genotype, phenotype
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Pick two traits
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Pick a dominant & recessive outcome arising from
different alleles
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You all start off heterozygous
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bead = gene
Symbolism
Room 450
Room 460
Pay close attention
to the nipples!
String of beads = chromosome = double-stranded DNA
Room 430
Room 420
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Mitosis Manually
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Point at some of your cells that ‘do’ mitosis?
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What’s the goal/purpose of this thing called ‘mitosis’?
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So what must the first step be? Do it.
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Now what must be achieved?
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Any half? If not, how pick the appropriate half?
How do your final results compare with starting?
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Clear your mind
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Go outside & take a lap around the floor
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Yeah. Go
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Meiosis: the other
cell division
Throwing the dice
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“Sexual reproduction has been compared to a game of roulette in
which the players throw away half their chips at every spin of the
wheel.”
Jonathan Silverton, ‘An Orchard Invisible’ p. 22
Why have sex?
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Suppose I’m Jack Sprat; you’re my wife.
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I have the mutant form of the fat-eating gene; you of the
lean-eating gene
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If we reproduce asexually (mitotically), how long until some
descendant can eat a whole pig?
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If sexually, i.e. by taking parts of our holdings & throwing
them together in an offspring?
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Thinking it through
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How much are you ‘like’ your ma & pa?
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How much of your genome should you give your child if
he/she is not uni-parental?
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Why bother II-breaking DNA
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Just shuffle the chromosomes: all the genes on every
chromosome inherited together
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Recombine between homologs: one set of genes on a
chromosome inherited independently of another
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Homologous Recombination I
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Where should the circled site on Chromo1 recombine
with Chromo2?
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2
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Room 430
Room 420
Room 450
Room 460
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Dances with Genes
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First, make a copy--b/c that’s the way it happens
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Pair the pairs: duplicated mom’s & dad’s contributions pair
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Recombine (randomly)
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Dancing II
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Now we’ve recombined; how to separate?
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When you’re a gamete, go fuse with a classmate
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Stop by and show me the genotype
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Seeing & Believing
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Mitosis: Turning an onion into a squash
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Meiosis: Prepared grasshopper testes
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Genes on chromosomes
Blinding you with Science
(jargon) II
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Linked/Linkage: Referring to whether genes are tethered
to one another by virtue of being ‘close’ on a chromosome
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Linked: referring to the resulting behavior of traits encoded
by such genes
Think it over...
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No recombination: every chromosome is a linkage group
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recombination: new combinations every cross-over (= every
gamete)
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Fire it up
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Load Gameter
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Interface walk-through: designing the parentals
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A & B close together on Chromosome II, A further to the
right than B, A/A and b/B
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Sciencize it!
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Explore
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Observe
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Hypothesize
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A word on research
Tying the papers, the observations & your
interests together
Where it’s heading
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You’ll propose an answerable, interesting question
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It will reflect a causal view of the universe (i.e. not ‘does it go left or
right if I...’ but ‘since simple mazes can often be solved by keeping
your left hand on a wall, I hypothesize that the organism will have
an innate leftward bias that will manifest if I...’
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Clean up
Room 430
Room 420
Room 450
Room 460
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Homework
Gameter:
4 challenges worth 80 pts
Written portion worth 20 pts – see rubric
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