Class Notes (836,148)
Canada (509,657)
Biology (1,284)
BIOL 201 (86)
Lecture

The Hardy-Weinberg Principle

3 Pages
71 Views
Unlock Document

Department
Biology
Course
BIOL 201
Professor
Elaine Power
Semester
Fall

Description
The Hardy-Weinberg principle  Allele frequency → p (A) + q (a) = 1 (total gene pool)  Genotype frequency p2 (AA) + 2pq (Aa) + q2 (aa) = 1 (gene pool)  Allele frequency must be constant / population must be stable [EXAM] o Large population  Prevents large swings in frequencies  Anomalies and chance variation less significant o Random mating  Equal chance of alleles being passed on o No mutations / no immigration/emmigration / no natural selection  Prevents addition or removal of new alleles  Baseline by which to judge whether allele frequency of population's gene pool has changed  Gene pool: all the alleles in a population Selection and change of allele frequency Natural selection  New environmental factor affects survival rate of phenotype before reproduction o //otherwise population may become extinct  Organisms better adapted to the environment survive, reproduce, pass on their alleles/genes  Allele frequency of the advantageous gene increases  Changes frequencies of alleles in gene pool / phenotype in population  Population becomes adapted to environment Stabilising selection  Natural selection favours "average" organisms best adapted to that environment  Organisms with extreme forms of characteristics/mutations are selected against  Heaviest and lightest babies have highest mortality o Less likely to survive, reproduce, pass on their alleles  [Graph] Normal distribution curve with thinner bell-shaped curve Directional selection  Natural selection favours organisms with one extreme form of a characteristic  Pesticide resistance (warfarin - poison used to kill rats) o Resistant rats / need a lot of vitamin K / stabilising selection o New environmental effect: warfarin / kills normal rats o Resistant rats survived, reproduced, pass on resistance gene o New population forms by directional selection  Antibiotic resistance (penicillin resistance) o Resistant bacteria / unnecessary enzymes / selected against o New environmental factor: penicillin / kills normal bacteria o Resistant bacteria survived, reproduced, passed on resistance gene  [Graph] bell-shaped curve shifted to the right Disruptive selection  Natural selection favours organism with two extreme forms of a characteristic  Balanced polymorphism: equilibrium of non-carriers and carriers of a characteristic caused by natural selection  Sickle-cell anaemia o Abnormal Hb makes red blood cells sickle-shaped / stick in capillaries o People homozygous for this recessive allele die before reproducing o People heterozygous for the allele should be at
More Less

Related notes for BIOL 201

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit