BIOL 309 Lecture Notes - Lecture 5: Linkage Disequilibrium, Genetic Recombination, Prophase

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19 Nov 2018

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The genes le and v are 12 cm apart on chromosome 4. Since the genes are 12 cm apart, there is no genetic recombination going on because the alleles are linked. Le = plant height tt or tt x tt (long and short) V = pod shape ss or ss x ss (round and wrinkled) Since f1 is linked will be dd and will be recessive dd. Crossing over occurs during prophase 1 of meiosis 1. Recombination occurs between two molecules of dna that exchange their genetic information with each other. Yes, recombination could be seen in liver tissue: look at slide 5 from 9-10-18. If the recombination frequency is less than 50% we say the two loci are linked. You can tell if the traits are linked by looking at the offspring. Two identical daughter cells with 46 numbers of chromosomes (23) Yes, a parent produced 2 identical daughter cells.

Related Questions

The data below involve three mutations: brown eyes (be), black body (blk) and vestigial wings (vg). The wild-type alleles be⁺ (red eyes), blk⁺ (gray body), and vg⁺ (long wings) show complete dominance. In each cross, repulsion heterozygotes were mated to flies homozygous for the recessive alleles of the genes. The progeny were sorted as having either a parental phenotype or a recombinant phenotype.

Calculate the frequency of recombination for each cross:

		Parental	Recombinant	Recombination
Cross	Heterozygote	Progeny	Progeny	Frequency %
1	be blk⁺/be⁺ blk	1105	579
2	blk vg⁺/blk⁺ vg	1077	400
3	be vg⁺/be⁺ vg	1054	145

The alelles for all three mutations are linked. How would you know this?

Complete the four-part question.

If you have an organism in which the A allele is dominant to the a allele, a heterozygote will produce gametes of either A or a. This is what leads to two phenotypes among the offspring in an F2 cross (ie. Aa x Aa). In genetic terms this is called

a. dominant

b. recessive

c. segregation

d. independent assortment

e. none of the above

If you have an organism of genotype AaBb (A dominant to a, and B dominant to b), there will be 4 phenotypic classes among F2 progeny in a 9:3:3:1 ratio. In genetic terms this is an example of

a. dominant

b. recessive

c. segregation

d. independent assortment

e. none of the above

Which type of nuclear division produces diploid cells from diploid cells? Haploid cells from diploid cells?

a. fission, fusion

b. meiosis, mitosis

c. mitosis, meiosis

d. linkage, independent assortment

e. none of the above

If a pea plant shows a recessive phenotype

a. it can be either TT or Tt

b. it can be either Tt or tt

c. it can be only TT

d. it can only be tt

e. it can be TT, Tt ot tt

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4. Imagine you cross a plant homozygous for the recessive trait hairless leaves (h) with a plant homozygous for the recessive trait glossy stems (g). Wild-type plants have fuzzy (H) leaves and waxy (G) stems. Mapping studies have indicated that the two genes are linked.

What are the genotypes of the parental and recombinant gametes produced by the resulting F1 plant?

Parental Gametes: _______hh_____ and ______gg______; Recombinant Gametes: _____hg_______ and ______gh_______.

If these two genes are very close to each other on the chromosome:

Which of the four phenotypic classes of selfed progeny from the F1 plant will likely be absent in the F2 generation?

_________________________

What phenotype classes of progeny will be most common if the F1 plant is crossed with a hairless, glossy plant?

______________________________ and ______________________________

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BIOL 309 Lecture Notes - Lecture 5: Linkage Disequilibrium, Genetic Recombination, Prophase

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