Anthro 1/20/09 Assignment Example- Mom= Type B, Child= Type AB, what must dad have? Dad= AB or A (Phenotype) Genotype dad can be AA or AO Autosomal recessive Inheritance- needs 2 copies to be affected by the trait, 1 copy makes you a carrier Recessive Trait can sometimes skip a generation Examples of Recessive Traits- Cystic Fibrosis, Sickle Cell, Albinism Sex Linked Inheritance- These traits are on the X and Y chromosomes Most are on the X chromo rather than the Y Females have XX 1X affected= carrier, 2 X affected= Exhibit the trait Males= XY 1x affected= Exhibit the trait (b/c they only have one X) Dominant and Recessive not really at work in males Polygenic Traits- Trait that is continuous and is not measured on a ?present or absent? scale Example Hair color is continuous but present vs. absent would be hair on your knuckles Influenced by alleles at several locations Need high powered stats punnett squares= no Sometimes influenced by environment Pleiotropy- One gene affects several traits phenotype expression Human Blood Groups- ABO blood group system 3 alleles= A,B,O Blood type describes antigens (proteins) on Red Blood Cells Antigens respond to specific antibodies Causes clotting ? transfusion problems Co dominance- 2 alleles, neither one is recessive both alleles influence the phenotype Population Genetics ? Analyze blood from 50 individuals= 100 alleles b/c it?s a 2 allele system 20 A?s, 20 B?s, 60 O?s Calculate allele frequency- Will always add up to 1 F(A)= 20/100= .20 or 20% F(B)= 20/100= .20 or 60% F(O)= 60/100= .60 or 60% 25 years later a population geneticist looks at 50 more people from the same population 30 A?s, 30 B?s and 40 O?s .30, .30. .40= 1 This occurred because of evolution A change in allele frequencies over time Microevolution- Small scale changes Only occur over a few generations, can be detected within living populations, and constrained to one species Small changes alter your DNA chromos Overtime with enough changes, alleles won?t recognize each other anymore Macroevolution- large scale changes Require 100s of changes over time Fossil Records Population- A unit of evolutionary change Molecular DNA Cellular Cell level Individual Population Comprised of Individuals Fitness- Reproductive success Certain variations allow some individuals to be better adapted than others in certain environments Better adapted in one environment doesn?t mean you will be well adapted to another 4 major principles- Natural Selection All species will produce more offspring than environment can support resources now limited All populations vary internally no 2 are the same Because there are too many individuals for the environment they struggle and compete for resources, those with an advantage survive Those advantages are passed on to offspring Sickle Cell Anemia Carrier makes you resistant to Malaria Advantageous in certain environments Find high allele frequencies in West and Central Africa, Mediterranean, Middle East and India Mutation- Change in genetic material Provides the raw material for evolution New gene combo?s Only way to introduce new genes within an population Only evolutionarily important within sex cells b/c they are inherited Point Mutations- change in the 1 base Base= added, deleted, or substituted Most common type, occur during cell division If you get a different amino acid not necessarily given the same protein Sickle Cell Anemia Chromosomal Mutation- can affect all or part of the chromo Chromos can be duplicated, deleted of damaged If it affects your X or Y it can be fatal or not fatal Genetic Drift- Random Depends on breeding population size 1 individual contributes a disproportional amount of genes Can also occur because the population is small Low frequency alleles may not be passed down pretty much disappears from population Large population- little or no drift Small population- greatly affected by drift Founder effect- small group breaks off and starts a new population they interbreed Alleles that were in small amount in the larger population become a higher frequency in this new population Example- Ellis Van Cravel- amish
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