Study Guides (248,007)
Canada (121,222)
Biology (1,525)

Quantitative Genetics.docx

15 Pages
Unlock Document

Biology 3466B
Yolanda Morbey

Quantitative Genetics Pages 73-94, 11-15, 319-355 A growing body of evolution, concluded by Darwin, 3.2 EVOLUTION BY NATURAL SELECTION indicated both fossilized and living organisms were derived from a common ancestor or a few. Darwin proposed that the descent of modification is the outcome of 4 postulates: 3.1 ARTIFICIAL SELECTION: DOMESTIC ANIMALS AND 1) Individuals within population are variable PLANTS 2) The variations among individuals are, at least in part, passed from parents to offspring Darwin studied mechanism of nature under 3) In every generation, some individuals are more domestication; method plant and animal breeders use to successful at surviving and reproducing than others modify crops and livestock 4) The survival and reproduction of individuals are not random; instead they are tied to variation among In order to refine a particular breed of pigeon that has, individuals. The individuals with the most favourable for example, taller feathers or feathers curl more variations, those who are better at surviving and elegantly, breeders employ artificial selection reproducing, are naturally selected They choose pigeons from the flock with the desirable If these 4 postulates are true, then the composition of the traits, let them mate to produce next generation population changes from one generation to the next. (The stronger individuals survive at higher rates) (pg.76 If the desirable traits are passed from parent to offspring, fig.3.4) the next generation will show the desirable traits in a higher proportion than existed in the previous -Darwinian evolution: gradual change in populations over generations flock time This theory helps to prove the descent of giant tomatoes -Selection happens to individuals, but what changes is versus small tomatoes populations. On chromosome 2 of tomatoes, a gene called fw2.2 is -When a particular trait survives and is passed on to the carried. This gene encodes a protein that represses cell next generation and the next generation has a higher division; high production of this protein, smaller the fruit percentage of this trait in the present generation than the one before, this is evolution by natural selection Changes in the fw2.2 promoter (on/off switch) alter the total production of protein -Darwinian fitness is the ability of an individual to survive and reproduce in its environment Large tomatoes fw2.2 promoter OFF, less protein production, cell division not repressed -Adaptation is a characteristic that increases the fitness of an individual compared to individuals without the trait Small tomatoes- fw2.2 promoter ON, more repressor protein production, cell division repressed Farmers take seeds of larger tomatoes and replant them, eliminating smaller tomatoes Quantitative Genetics Pages 73-94, 11-15, 319-355 3.3 THE EVOLUTION OF FLOWER COLOUR IN AN Testing Darwins Prediction: Did the Population Evolve? EXPERIMENTAL SNAPDRAGON POPULATION -Since bees selected white flowers over yellow and white -48 snapdragons were tested have higher reproductive success, and genes determine flower colour, there would be a higher proportion of Postulate 1: There is Variation among Individuals white flowers in the next generation -Snapdragons varied in flower colour (75% white with 2 yellow spots, 25% full yellow) -Experiment proved Darwins theory of evolution, proving all 4 postulates hold. Postulate 2: Some of the Variation is Heritable -Variation in colour was due to different genotypes. Genes SS and Ss have white flowers with 2 yellow spots, ss have full yellow flowers; 12/48 SS, 24/48 Ss, 12/48 ss Testing Postulate 3: Do Individuals Vary in Their Success at Surviving or Reproducing? -Bees pollinated these snapdragons and to monitor plants success at reproducing, the researchers counted the seeds produced from each fruit. rd -Consistent with Darwins 3 postulate, plants showed considerable variation in reproductive success (as pollen donors and seed mothers) Testing Postulate 4: Is Reproduction Nonrandom? -Bees were more attracted to white flowers wit 2 spots, and white flowers/2spots had higher success of pollen donation and seed production -Flowers that donated more pollen, had higher seed production th -Consistent with Darwins 4 postulate, reproductive success was no random. Through pollen donation and seed production, white plants had higher reproductive success than yellow plants Quantitative Genetics Pages 73-94, 11-15, 319-355 nd 3.4 THE EVOLUTION OF BEAK SHAPE IN GALAPAGOS -Darwins 2 postulate is met; a substantial fraction of FINCHES the variation in beak size is due to variation in genotype -The beak is the primary tool used by birds in feeding, and -It is experimentally seen that BMP4 (bone morphogenic the enormous range of beak morphologies among the protein 4), a signaling molecule that helps sculpt the Galapagos finches reflects the diversity of foods they eat shape of bird beaks, are in larger amounts and are produced earlier in development for birds with larger -Medium ground finches were studied in an experiment. beaks. These finches are mostly seedeaters, in general, birds with bigger beaks eat bigger seeds and birds with smaller beaks eat smaller seeds due to efficiency Testing Postulate 1: Is The Finch Population Variable? -Scientists weighed each finch, measured its wing length, tail length, beak width, beak depth and beak length. All these traits are variable. st -1 postulate is met; variation among individuals within populations is practically universal Testing Postulate 2: Is Some of the Variation among Individuals Heritable? -Variation in the amount of food that individual birds ate as a chick can lead to variation in beak depth among adults. Injuries or abrasion against hard seeds or rocks can also affect beak size and shape -To determine if variation among finch beaks is genetically based, scientists estimated heritability -Heritability of a trait is the proportion of the variation observed in a population that is due to variation in genes. Heritability ranges from 0-1 (because it is a proportion) -Based on collective data (fig.3.10, pg. 83), parents with shallow beaks tend to have chicks with shallow beaks and parents with deep beaks have chicks with deep beaks. -This proves large proportion of the observed variation in beak depth is genetically based and can be passed onto offspring
More Less

Related notes for Biology 3466B

Log In


Join OneClass

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

Sign up

Join to view


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.