1 A little knowledge is a dangerous thing. So is a lot. Albert Einstein Distribution of grades: Exam I 0 0.1 0.2 0.3 0.4 0.5 A B C D F Grade Percentage Genetics • If Huntington’s disease is a dominant trait, shouldn’t most people have Huntington’s? Genetics • How can O be the most common blood type if it is a recessive trait? 100% 70-79% 80-89% 90-99% Percent type O blood in Native Americans Genetics • Why don’t all traits have 3:1distribution in populations? – Why would we expect a 3:1 ratio? Genetics • Mendelian crosses • Population • Reproduction
7
Embed
Distribution of grades: Exam I - Central Michigan University
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
A little knowledgeis a dangerousthing.
So is a lot.
Albert Einstein
Distribution of grades: Exam I
0
0.1
0.2
0.3
0.4
0.5
A B C D F
Grade
Perc
enta
geGenetics
• If Huntington’s disease is a dominanttrait, shouldn’t most people haveHuntington’s?
Genetics
• How can O be the most common bloodtype if it is a recessive trait?
100%
70-79%80-89%90-99%
Percent type O bloodin Native Americans
Genetics
• Why don’t all traits have 3:1distributionin populations?– Why would we expect a 3:1 ratio?
Genetics
• Mendelian crosses• Population• Reproduction
2
General model population genetics Gene pool: f(A)=0.6, f(a)=0.4
Gene pool:f(A)=0.6,f(a)=0.4
Hardy-Weinberg: Derivation
• For 1 locus, 2 alleles:f(A)=pf(a)=q =1-p
• Genotype frequencies next generation:f’(AA)=pXp (=p2)f’(Aa)=pXq + qXp (=2pq)f’(aa)=qXq (=q2)
• (p+q)2 = p2 + 2pq + q2 = 1
Hardy-Weinberg: continued
• Allele frequencies next generation:p’=p2 + 0.5(2pq)
=p2+ pq=p(p+q)=p
– No change in allele frequencies
Hardy-Weinberg Equilibrium
• A way to predict the genotype frequencies in futuregenerations
• Assumptions– Diploid– Sexual– Non-overlapping generations– Random mating– Allele frequencies identical in males and females– Infinite population size– No migration– No mutation– No selection
3
What bloodygood is it???
Implications of Hardy-Weinberg
• No evolution, no change• Recessive traits not wiped out• Genotype frequencies can be predicted
from allele frequencies– (p2, 2pq and q2)
Using Hardy-Weinberg:
• Can determine frequency of rarerecessive alleles in population
• e.g. PKU (phenylketonuria)– can’t metabolize phenylalanine– frequency in population: 1/10,000-assuming HWE, what proportion of
population are asymptomatic carriers?
HaWeE
• Why do we use it?– It provides us with a representation of how alleles should
behave in the absence of evolutionary forces.– No evolutionary forces
Assumptions of Hardy-WeinbergB) Sexual reproduction
Send in the clones
C) DiploidyCan you do it for others?
D) Discrete generations
Clonaid has been able tofind living cells in a bodythat has been dead for 4months - there is hope!
Assumptions of Hardy-Weinberg
E) Infinite population size-finite pop’s = sampling error (genetic drift)-random fluctuations in allele and genotype frequencies-drift strength proportional to 1/(2N)-eventually one allele fixed, others lost
Assumptions of Hardy-Weinberg
F) Equal allele freqs between sexesG) No selectionH) No migrationI) No mutation
HaWee• Why do we use it?
– It provides us with a representation of how alleles should behave in theabsence of evolutionary forces.
• Null model for evolution– If frequencies are changing evolution is occurring.
– Can you maintain allele frequencies through generations but still have the genotype frequencieschanging?
– Prove it yes or no
– In conservation, provides a basis for the following:• detecting deviations from random mating• tests for selection• modeling the effects of inbreeding and selection