Transcript How do you get a `new` receptor?

“… And please let Mom, Dad, Rex, Ginger, Tucker,
me and all the rest of the family see color”
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comments
• To view my comments on your in class lab
assignments/homeworks…
Goals for Today:
• Understand properties of light and
molecules
• Dark side of recombination
• Develop skill at deducing genotype by
observation of phenotype and
inheritance patterns
What is “color”?
And how do we ‘see’ it?
Wavelengths (nm)
Gamma X-rays Ultrarays
violet
Shorter
wavelength
Infrare
d
Visible light
Microwaves
Radio
waves
Longer
wavelength
nm
Higher
energy
Lower
energy
Looking in at looking out
http://www.bio.miami.edu/dana/pix/retina.jpg
• Rods
• A Cone
http://www.sciencephoto.com/media/121458/enlarge
Looking Deeper
Where are we?
The difference between
2 and 3 receptors…
Or, the beautiful colors of fall
Can ~10 million American males be wrong?
http://www.rgblind.com/
http://www.rgblind.com/
http://www.rgblind.com/
What IS ‘color’?
Wavelengths (nm)
Gamma X-rays Ultrarays
violet
Shorter
wavelength
Infrare
d
Visible light
Microwaves
Radio
waves
Longer
wavelength
nm
Higher
energy
Lower
energy
The brain’s
interpretation of
the eye’s report
of (three)
samplings of a
narrow bit of the
electromagnetic
spectrum
Wavelengths (nm)
Gamma
rays
Shorter
wavelength
X-rays Ultraviolet
Infrared
Visible light
Microwaves
Radio
waves
Longer
wavelength
nm
Higher
energy
Lower
energy
If the light is
red (680 nm),
which
receptor do
you expect to
‘hear’ it
more loudly?
‘green’ receptor
Think Triangulation
Hypothesis A:
Near & Faint
Hypothesis B:
Far & Loud
You are allowed to make one additional
auditory observation
http://www.mediabistro.com/baynewser/bay_area_radio/
http://www.faqs.org/photo-dict/phrase/1715/ear.html
How do you get a ‘new’
receptor?
Fashioning a new gene using a hammer
What’s in an Opsin?
• Week 9 calendar: click on ‘Opsin’ link
• Retinal eats the photon -> changes
shape
– Change is directly transmitted to change in
opsin (which is holding retinal)
• Work through the page, “see” and
assemble opsin and retinal
Launch ‘Opsinize’
• Starting with “green-tuned” opsin (531
nm)
• Your objective: make a ‘red-tuned’ (as
close to 559) nm
• Your tool: mutating codon sequences
• From each menu you can mutate the
codon (which reflects changes in DNA)
3-Letter Code
• Leu: Leucine
• Ala: Alanine
• Arg: Arginine
• Lys: Lysine
• Asn: Asparagine
• Met: Methionine
• Asp: Aspartic Acid
• Phe: Phenylalanine
• Cys: Cysteine
• Pro: Proline
• Gln: Glutamine
• Ser: Serine
• Glu: Glutamic Acid
• Thr: Threonine
• Gly: Glycine
• Trp: Tryptophan
• His: Histidine
• Tyr: Tyrosine
• Ile: Isoleucine
• Val: Valine
Thinking it through…
• Shown: the only the only amino
acid differences between red and
green opsins
• DNA sequences would be… how
similar?
• What happens in meiosis when th
maternal and paternal
chromosomes pair?
• Think anything might ever go
wrong?
How do you get a ‘new’
receptor?
• What’s the ‘easiest’ way to get a
slightly different protein?
– Make a new segment of DNA that
happens to be similar
– Start with a random stretch of
existing DNA and randomly mutate
until…
– Copy the original gene and ‘tweek’
Remember Recombination?
Things don’t always go smoothly
Where to Recombine?
Oooooops
2
Genes for “Green” and
“Red” are 98% Similar*
•
•
•
•
What does this mean?
Recombination?
When things go “wrong”
R and G on the same chromosome
(23)
• “Blue” is on chromosome 7
*Howard Hughes Medical Institute
“New” Genes
• Green -> “Red” Opsin
• Myoglobin -> Hemoglobin
• Adult vs. Fetal Hemoglobin
What’s seX got to do with it?
• The “X” is big
• The “Y” not so
much
• What does this
mean?
What’s seX got to do with it?
• Autosomal: chromosome NOT X or Y
• Sex chromosome: X or Y (b/c of where each
joined together during meiosis)
• Symbolism: normally, we don’t care what
chromosome given allele is on; in sex, it
matters
– On the X, we designate : XA, Xa
– On the Y, generally designate: Y
a?
• Hemizygous
How come no A or
What’s seX got to do with it?
•
•
•
•
Consider A and a
How many genotypes for females? Males?
How many possible crosses?
Do the cross
– How can you tell it’s sex-linked?
– Compare sex-linked vs autosomal
It sucks to be XY
•
•
•
•
R/G Colorblind
Hemophilia
Different anemias
Duchenne Muscular Dystrophy
How is this useful?
Pedigrees!
PTC and parentage
•
•
•
•
WASH HANDS
Who can taste this?
Separate into haves, have-nots
Each: if trait is dominant, what can
you deduce about your parents?
• If trait is recessive?
Boys
vs
Girls
Makin’ Babies
Pair up, decide who’s the adult consenting
male & who the similarly conscientious
female
You’re both heterozygotes (recall:
‘different-pairing’)
Make the babies--hold an allele in each
hand, partner picks
How to determine the sex of the baby?
Pediducer
Deductions from Pedigrees
Pediducer
Rules and Conventions
• What assumption about randomly
selected, ‘healthy’ individual?
• Justification is “Outsider”
• REASON must be sufficient &
necessary
Pediducer
Rules and Conventions
• What does affected indiv. look like?
• You are TESTING models
– How many right for model to be right?
– How many wrong...
• Justification
• “Check me”
Two Phases
• Phase I: Assign genotypes and justify
• Phase II: Rule model “plausible” or
“out”
NO POINTS!!!!!
If you don’t rule models in/out
Round the Fourth
Preparing for next week
Reagents for glucose
(One solution per test
tube)
• 1% glucose
• 0.2% glucose
• water
Do it!
• Appendix C--the supplies are on
your benches
• Do the Benedict’s test on C-1
(substituting 0.1% glucose for the
1% starch indicated)
• Do the CO2 test on C-2
45
Homework
If you don’t rule models in/out
Pedid
comp
pedig
solve
plaus
out fo
three
hypot