04BIS10110152013RecombinLect4

In other word eye color pr and wing monohybrid and

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Unformatted text preview: s test cross for an F1 expressing As 2 traits (dihybrid) produced a 1:1:1:1 ratio. However in the test cross below, Morgan found another exception to Mendel’’s s cross results. In the example below, the test cross to a homozygous (male) tester, produces the standard 1:1 ratio typical of a monohybrid cross. In other word, eye color (pr) and wing monohybrid and shape (vg) behave as one gene or “linked” genes. shape F1 pr + pr pr pr pr vg X + vg vg pr + vg (tester) vg vg + 1:1 ratio BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 10 Interchromosomal recombination (unlinked genes) ­ Independent Independent assortment (i.e., interchromosomal recombination) produces genotypes with new combinations of parental alleles. ­ Notice that the test Notice cross produces the typical 1:1:1:1 ratio observed by Mendel’s dihybrid cross. dihybrid BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 11 Intrachromosomal recombination (linked genes) ­ ­ ­ New combinations of New parental alleles can also be produced when genes are linked on the same chromosome. This can occur by This intrachromosomal or intrachromosomal meiotic recombination. Notice that the test cross does not produce the 1:1:1:1 ratio but something like, 0.8 : 0.8 : 0.2 : 0:2. 0.8 This is because This recombination is rare. recombination BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 12 Meiotic recombination during Prophase 1 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 13 Dihybrid (2-factor) cross and meiotic recombination ­ Some of the gametes produce by Morgan’s F 1 progeny have a different configuration of alleles as a result of rare crossing over between pr and vg +. result F1 BIS101­001, Spring 2013—Genes a...
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This note was uploaded on 02/12/2014 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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