PPT

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Review of relevant topics prior to “Linkage” lectures
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DNA as it exists in the cell- normally vs. metaphase; w/ respect to chromosomes
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DNA structure varies out of necessity- expose genes (encoding regions) for
transcription; keep organized structurally for replication and division of cell
o 2 key points here: gene expression and inheritance
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Have to visualize gene (locus)/alleles/chromosomes/metaphase/chromatids
segregating/gamete formation
1. Stretch of DNA that codes for a protein; in the middle of a bunch of bases
that are not encoding
2. The location of that gene (sequence) relative to the chromosome it exists
on
3. The specific copy of the gene; need to have a term to clarify the presence
of 2 copies of each gene- MAternal and Paternal
4. Mitosis vs. Meiosis
5. Primary germ cell  gametes: what are the chromosomes doing and how
are they segregating
6. How are the genes on those chromosomes segregating relative to each
other- THIS IS THE BASIS OF THE NEXT 2 LECTURES!
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Have to use letters, symbols, techniques to discuss genes and inheritance; but it’s
critical to be able to visualize what those symbols represent.
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Mendelian Genetics (inheritance)- those 3 postulates are very important:
1. 2 copies of each gene (i.e. 2 alleles)
2. Simple dominance
3. Random segregation and independent assortment
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Consider 2 genes: a dihybrid cross; if Mendelian, it’s like 2 monohybrid crosses b/c
of Postulate 3.
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Non-Mendelian Genetics (Inheritance)- everything else…
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Linkage (think in terms of meiosis, forming gametes, and inheriting genes)
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No longer have independent assortment of genes during gamete formation
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Buzz words: (non)parental chromosome, crossing over, recombination, recombination
frequency,
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Notes on slides:
o Skip 2 & 3, 20 & 21 (for now), 23-28 (for now)
o Don’t have to know 13,
o GO NO FURTHER THAN SLIDE 32 on Thursday
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