Study Guides (238,105)
Canada (114,924)
Biology (1,397)
Tom Haffie (259)

Biology notes 2 final.docx

59 Pages
Unlock Document

Western University
Biology 1001A
Tom Haffie

Biology notes for examLecture 12 1 Strategy to distinguish between a phenotype that results from codominance relative to incomplete dominanceIncomplete dominance occurs when the effects of recessive alleles can be detected to some extent in heterozygotesFor example in snapdragons when a red flower and a white flower cross they produce a pink flowerTwo red colour alleles are needed to make enough pigment to produce entirely red colour White alleles make no pigment whatsoeverOf course when crossed the pink flowers can produce both red and white flowersIn codominance the effects of different alleles are equally detectable in heterozygotesThe alleles have approximately equal effects in individualsHuman blood types A and B are codominantYou would not be able to distinguish between codominance and incomplete dominance by looking at the inheritance patterns because they are the same 2 Characteristics that identify a pleiotropic alleleIn pleiotropy two or more characters are affected by a single geneFor example sickle cell disease causes sickling of red blood cells which also causes anaemia fatigue kidney failure abdominal pain etcThese wideranging effects are caused by the single sickle cell gene 3 Conditions under which Hardy Weinberg Equilibrium is possible in a populationThe HardyWeinberg principle is a null model that describes how evolution does not occur It specifies the conditions for genetic equilibriumGenetic equilibrium in which allele frequencies and genotype frequencies do not change in succeeding generations is possible only if these conditions are met 1 No mutations are occurring2 The population is closed to migration from other populations3 The population is infinite in size 4 All genotypes in the population survive and reproduce equally well 5 Individuals in the population mate randomly with respect to genotypeUnder these condition microevolution does not occurThis model is used as a reference point to access condition in which microevolution does occur by identifying which conditions are not met Lecture 12 lecture 1 General pathway of eukaryotic membrane protein productionDNA in the nucleus is transcribed and the transcripts leave the nucleusRibosomes take those transcripts to the ER and they are translated on the ERThese translated proteins are packaged into vesicles that go to the Golgi complex then into new vesicles that send those proteins to the cell membrane 2 General physiology of skinhair pigmentationPigment production is determined by melanocytes which produce melanin packed into melanosomes which get exported into the skinhair cellsThere are two kinds of melanin black and redyellow melaninBrown is produced by a mixture of red and black melanin 3 Characteristics of dominant allelesThe dominant alleles do not inhibit the recessive alleles They simply mask the effects of the recessive alleles and determine the phenotypeAn allele isnt always dominant all the time A dominant over O blood type but codominant with B blood type It depends on the other allele present in the pair 4 Which allele in a heterozygote is dominant given the biochemical mechanism of action of allele productsDominance happens because of the interaction of the gene productsEx If a R allele and a W allele are paired the W allele will be dominant because the black melanin is sometimes produced and pigments the skinhairBut if a W allele and a B allele pair the B allele will be dominant because it produces black melanin all the time which determines the pigmentation 5 Factors that affect how allele frequencies change over time in a populationIf there is no naturalsexual selection equal fitness allele frequencies do not changeDominant alleles do not outcompete recessive alleles or vice versa in the absence of a difference in fitnessDominance in an allele by itself does not make it more evolutionarily fitIn a large population in the absence of selection the starting allele frequencies influences future allele frequenciesDiploidy dominancerecessive relationships inheritance are not in themselves sufficient to drive changes in allele frequency 6 Allele frequencies p and q given genotypic frequenciesAllele frequencies in a population can be anything not just 5050 22 If 60 of alleles in a population are p and 40 are q pppqqq and pq2pq7 Function of various MC1R allelesMC1R is a membrane receptor which produces black melanin if cyclic AMP levels are high High cyclic AMP stimulates production of black melanin
More Less

Related notes for Biology 1001A

Log In


Don't have an account?

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.