HMB265H1 Lecture : Notes taken during lecture

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redtermite204

21 Jan 2011

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Lecture 4: mendelian traits in humans and human pedigree analysis. Mendel"s laws of inheritance, how applied to dna level, dominance applied to dna to phenotype. Today how mendel"s laws apply to humans, how inheritance in humans studied via pedigrees. Drosophila cannot self-fertilize simply cross siblings for a number of generations longer until homozygotes achieved. Mammalian not as fast generation time as drosophila or elegans, but closer to humans in genes. Cannot self-fertilize mice can look at large numbers of offspring. Humans are poor genetic organisms cannot do controlled crosses by deciding breeding couples; not many offspring; using model organisms to understand humans: forward genetics start with phenotype and tyring to understand at. Follow pedigrees: few progeny too few to look at ratios, so focus on patterns instead, deceased not genetically relevant really, autosomal recessive. parents must have allele but not expressed therefore recessive. the non-diseased offspring a- meaning it is unknown whether aa or aa.

Related Questions

In pea plants, the appearance of flowers along the main stem isa dominant phenotype called "axial" and is controlled by an alleleT. The recessive phenotype, produced by an allele t, hasflowers only at the end of the stem and is called "terminal."

Pod form displays a dominant phenotype "inflated," controlled byan allele C, and a recessive "constricted" form, producedby the c allele.

A cross is made between a pure-breeding axial, constricted plantand a plant that is pure-breeding terminal, inflated.

Part A

The F1 progeny of this cross are allowed to self-fertilize. Whatis the expected phenotypic distribution among the F2 progeny?

*The answer for this one is 9:3:3:1. I understand this part.

Part B

Suppose that all of the F2 progeny with terminal flowers, i.e.,plants with terminal flowers and inflated pods and plants withterminal flowers and constricted pods, are saved and allowed toself-fertilize to produce a partial F3 generation. What is theexpected phenotypic distribution among these F3 plants?

(Remember to take into consideration the frequency of eachgenotype in the F2 as well as the probability of specific offspringthat result from self-fertilizing each F2 genotype.)

*I don't understand this part. It wants wants an answer in termsof "terminal inflated : terminal constricted."

Part C

If an F1 plant from the initial cross described above is crossedwith a plant that is terminal, constricted, what is the expecteddistribution among the resulting progeny?

*I understand this part. The answer is axial inflated : axialconstricted : terminal inflated : terminal constricted =1:1:1:1

Part D

If the plants with terminal flowers produced by the cross inPart C are saved and allowed to self-fertilize, what is theexpected phenotypic distribution among the progeny?

*I also don't understand this part. They want an answer in termsof "terminal inflated : terminal constricted."