Upload
teresa-posy-mclaughlin
View
215
Download
0
Tags:
Embed Size (px)
Citation preview
Interested in Being a Preceptor?
• Reinforce your understanding of Bio182 topics
• Help peers navigate 182L
• Help make the course better
• Learn teaching techniques while earning 3 credits
Interested in Being a Preceptor?
• Work with TAs to teach and develop labs
• Travel to exotic locations (okay, not that)
• Contact Kevin Baker ([email protected]) for more info (link on Bio182L homepage)
Lab 9: In a Family Way
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?
Higherenergy
Wavelengths (nm)
Gamma rays
X-rays Ultra-violet
Infrared
Micro-waves
Radiowaves
Shorterwavelength Visible light
Longerwavelength
Lowerenergy
nm
Looking in at looking out
http://www.bio.miami.edu/dana/pix/retina.jpg
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’?
The brain’s interpretation of the eye’s report of (three) samplings of a narrow bit of the electromagnetic spectrum
Higherenergy
Wavelengths (nm)
Gamma rays
X-rays Ultra-violet
Infrared
Micro-waves
Radiowaves
Shorterwavelength Visible light
Longerwavelength
Lowerenergy
nm
Higherenergy
Wavelengths (nm)
Gamma rays
X-rays Ultra-violet
Infrared Micro-waves
Radiowaves
Shorterwavelength Visible light
Longerwavelength
Lowerenergy
nm
If the light is red (680 nm), which receptor do you expect to ‘hear’ it more loudly?
‘gre
en
’ recep
tor
‘red
’ recep
tor
How do you get a ‘new’ receptor?
What’s in an Opsin
• Week 9 calendar: click on ‘Go_Opsin’ link
• Retinal eats the photon -> changes shape– Change is directly transmitted to change in
opsin (which is holding retinal)
• Work through the handout
Launch ‘Opsinize’• Starting with “red-tuned” opsin (559
nm)
• Your objective: make a ‘green-tuned’ (as close to 531) nm
• Your tool: mutating codon sequences
• From each menu you can mutate the codon (which reflects changes in DNA)
3-Letter Code• Ala: Alanine
• Arg: Arginine
• Asn: Asparagine
• Asp: Aspartic Acid
• Cys: Cysteine
• Gln: Glutamine
• Glu: Glutamic Acid
• Gly: Glycine
• His: Histidine
• Ile: Isoleucine
• Leu: Leucine
• Lys: Lysine
• Met: Methionine
• Phe: Phenylalanine
• Pro: Proline
• Ser: Serine
• Thr: Threonine
• Trp: Tryptophan
• Tyr: Tyrosine
• Val: Valine
Thinking it through…
• Shown: the only amino acid differences between red and green opsins
• DNA sequences would be… how similar?
• What happens in meiosis when the 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
G G
How do the restriction enzymes ‘know’ whereto cut and recombine?
G G
But….
G
G
So…..• Is it easier to make a gene, or tinker
with an existing one?
G
G
So what if this gamete
‘fertilized’ with...G
This one
G G
G
How many colors?
But what if you alteredthe protein to make it
sensitive to a different wavelengthR
NOW what do you have?
Red and green 98% similar.Why?
“New” Genes – Sound Familiar?
“New” Genes – Sound Familiar?
• 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 is
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 How come no A or a?
• Hemizygous
What’s seX got to do with it?• Consider A and a
• How many genotypes for females? Males?
• How many possible crosses?– How to distribute
What’s seX got to do with it?• Consider A and a• How many genotypes for females? Males?• How many possible crosses?
– How to distribute
• Do the cross– How can you tell it’s sex-linked?– Compare sex-linked crosses to corresponding
autosomal• What is the equivalent of Y?
It sucks to be XY• R/G Colorblind
• Hemophilia
• Different anemias
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 Girlsvs
Makin’ BabiesPair 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
Two Phases• Phase I: Assign genotypes and justify
• Phase II: Rule model “plausible” or “out”
PediducerRules and Conventions
• What assumption about randomly selected, ‘healthy’ individual?
• Justification is “Outsider”
• REASON must be sufficient & necessary
PediducerRules 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”
Explore• Menu progression: left to right
• If not logged in, first menu tells you what the ‘answer’ is
• Third menu specifies the model you are currently considering
• You are seeking to prove (how much data?) or disprove model (how many internal contradictions?)
NO POINTS!!!!!
If you don’t rule models in/out
Preparing for next week
Let me intreduce myself
• RHC=O + H2O => RCOOH + 2H+ + 2e-
• 2CU2+ + 2e- => 2Cu+
• 2Cu+ + 2OH- => Cu2O (red ppt.) + H2O
Who is oxidized (loses electron ownership--often to oxygen)?
Who is reduced?
Reagents for glucose (do all three)
• 1% glucose
• 0.2% glucose
• water
Capturing CO2
H2O + CO2 -> H2CO3
H2CO3 -> HCO3– -> CO3
2–
CO32– + Ba2+ ->BaCO3 (white ppt.)
53
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)
• Candidate solution = glucose
• Do the CO2 test on C-2– Place dry ice in flasks with appropriate tubes/stopper– Why dry ice?
If you don’t rule models in/out
Homework Pediducer: Three complete pedigrees solved to the plausible/ruled out for each of three hypotheses