BIOL 2040 Lecture Notes - Lecture 9: Meiosis, Chromosome, Wild Type

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Published on 1 Feb 2013
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BIOL 2040
Lecture 9
The Chromosome Theory of Inheritance
Initiated with discovery of meiosis
Direct correlation with Mendel
o Chromosomes are structures having to do with meiosis containing alleles that are
transmitted during sexual reproduction
Discovery of Sex Chromosomes
Specific combinations of chromosomes dictated the phenotype of gender
o Discovery of the chromosomes was done by Stevens and Vincent
o Animal Model is a meal worm
50% of the chromosomal make up is the same as in the egg
50% of the chromosome is like in the male cell
o In many organisms, the sex chromosomes are XX/XY
There is a talk about this on a previous lecture
Chromosomal Basis of Sex
Dictates who is male and female by chromosomes
o It is noted that males have 22 pairs and 1 mismactch
o It is noted that females have 23 matched pairs
Morgan’s Choice of Experimental Organisms
Worked with fruit flies
o Short generation time, high breeding rate
o 2 week generation time
Wild type or abnormal
o They have the system of dominant or recessive
Proved chromosomes, that X in this case, are the location of Mendel’s heritable
factors
“X-Linked inheritance
Principle of linkage
When doing this experiment he realized that there is not exactly a 3:1 ratio because of
mutations
o if the mutation is on the Y, all males will have this mutation
o thus, this explains it being on the X-chromosome
He had to prove this point though, so he showed it via a punnett square
With a normal male and carrier female, half the males will attain the
gene.
Morgan finally showed an association between phenotype and eye colour
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