BICD 100 Lecture Notes - Lecture 10: Green Leaves, Gene Mapping, Centimorgan

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coffeecamel142

1 Apr 2019

School

UCSD

Department

Biol/Genetics,Cellular & Develop

Course

BICD 100

Professor

Deborah Yelon

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Document Summary

Set up a test cross with the heterozygote. Flower color in a type of plant is due to the dominant allele r, which produces a red color. The recessive allele, r, when homozygous, produces white flowers. Leaf color (not flower color) is controlled by another gene with two alleles, y and y. The dominant y allele results in green color, whereas the homozygous presences of the recessive y allele causes the plant to appear yellow. In a testcross between a plant of unknown genotype and phenotype and a plant that is homozygous recessive for both traits, the following progeny were obtained: The only way to get red and green from a cross with ry is to have r and y alleles, meaning red and green. What is the map distance between r and y. Recombination serves as the basis for mapping genes to a chromosome.

Related Questions

In the tomato, red fruit (R) is dominant over yellow fruit (r), and yellow flowers (F) are dominant over white flowers (f). A cross was made between true-breeding plants with red fruit and yellow flowers, and plants with yellow fruit and white flowers. All F₁ offspring are heterozygotes for both traits. The F₁ female plants were then test crossed to males with yellow fruit and white flowers (homozygous recessive for both traits). The following results were obtained:

333 red fruit, yellow flowers

64 red fruit, white flowers

58 yellow fruit, yellow flowers

345 yellow fruit, white flowers

Total of 800

1. Conduct a Chi square analysis to see if the two genes are linked ( Check a solved problem S1, page 148 in the first edition text book, and page 150 in the second edition problem #1 for an idea)â¦follow the same steps)

a. Propose a hypothesis to be tested

b. Find the expected (predicted) number of offspring ( Hint what is the ratio of test cross results?)

c. Calculate and Interpret the Chi âsquare result

d. If the two genes (fruit color and flower color) are linked, calculate the map distance between the two genes.

2. Set a sample test cross, Explain the rationale behind a testcross, why is it necessary for one of the parents to be homozygous recessive for the genes of interest?

Hi I am studying for a biology exam and I have some questionsthat are on a review sheet that i am unsure about

1. In Tomatoes, the allele for red fruit is dominant over theallele for yellow fruit. If a plant that is homozygous for redfruit is crossed with a plant with yellow fruit â

a) what is/are the genotype(s) and the phenotype(s) of the fruitproduced in the F1 generation?

b) what is/are the genotype(s) and the phenotype(s) of the fruitproduced in the F2 generation?

c) what is the phenotypic ratio of the F2 fruit?

2. A plant with red flowers is crossed with a plant with whiteflowers. All the F1 plants produced red flowers. When the F1 plantsare allowed to self-pollinate, they produce 623 plants with redflowers and 198 plants with white flowers. What are the genotypesof the P and F1 generations?

3. In Tomatoes, the allele for red fruit isdominant over the allele for yellow fruit. Theallele for tall plants is dominant of the allele forshort plants. Find the genotypes and phenotypes ofthe F₁ and F₂ generations and the phenotypicratio of a cross between a homozygous dominant in both genes and ahomozygous recessive in both genes. The homozygous individuals arethe Parental generation.

4. In cocker spaniels, solid coat color is dominantover spotted coat. A veterinarian has a spaniel with a solidcoat. How can she unequivocally determine the genotype of thisanimal for coat color from a single breeding?

rubyserval737

My prof says this is done wrong as the break point is between R and Y. Could you please help me out? With explanation? Thank you!

10. In a certain plant, a dominant allele for one gene, R, produces round fruit and the recessive allele, r, produces oblong fruit. A dominant allele of a second gene, Y, produces yellow flowers and the recessive allele, y, produces white flowers. The two genes are linked on chromosome IV. A plant (r y/r y) with normal chromosomes is crossed to a plant (R Y/R Y) homozygous for a reciprocal translocation between chromosomes IV and VIII. The presence of the translocation causes semi-sterility. The F1 progeny are phenotypically yellow flowered with round fruit and are semi-sterile. A backcross to the parent with normal chromosomes yields the 750 progeny shown in the table below.

	Number of Progeny
	Fertile	Semi-sterile
Yellow, round	3	283
White, oblong	295	2
Yellow, oblong	73	12
White, round	10	72

a. From these data, draw a map showing all relevant map distances (in centimorgans) for the genes and the translocation breakpoint. Show your work.

Answer:

Cross over gametes: Yellow, oblong & White, round

Total number of Progeny = 381

Frequency of cross over gametes=

83 / 381 = .22 Morgans

22 cM

85 / 369 = .23 Morgans

23 cM

The genes are located on the same side of the chromosome.

Break point R Y

. . 22cM .

No; the breakpoint is located between the two genes. Also you muat use both classes of dluble crossovers to calculate the two intervals. Please redo

b. Briefly explain the basis of the semi-sterility of translocation-bearing plants.

Answer: The semi-sterility in F1 plants are caused by reciprocal translocation. As the organism is heterozygous for reciprocal translocation meaning that offsprings are produced less than normal. This reciprocal translocation may have occurred at meiosis during chromosome segregation. No; the translocation already existed.

Please read your text and redo 3/10

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BICD 100 Lecture Notes - Lecture 10: Green Leaves, Gene Mapping, Centimorgan

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