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Genetics problems

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Genetics problems

Postby jamesandrew » Fri Jan 18, 2013 7:20 am

I just needed some help with the following questions, I have no idea where to start! Some pointers would be great thanks :)


Question 1.
Pea pod shape is controlled by a one gene - two allele genetic system. Full pod shape is completely dominant to constricted pea pod shape. Pea plant size is also controlled by a one gene – two allele system with tall size being completely dominant to dwarf size. Given a plant was heterozygous for pod shape and homozygous recessive for plant size:

a. What is the phenotype of this plant?

b. If this plant was crossed to a dihybrid (heterozygote), what would be the phenotypic ratio of pod shape among the progeny?

c. What would be the phenotypic ratio of plant size?

d. What would be the phenotypic ratio of pod shape and plant size together?

Question 2.
A pure breeding, tall pea plant white flowers is crossed with a pure-breeding short plant with red flowers. The F1 plants are tall with red flowers. When allowed to self-fertilise themselves, these F1 plants produce the following F2: 326 tall, red; 104 tall, white; 117 short red and 29 short white. Explain these data; indicating genotypes of the parents and the different F2 phenotypes. What is the expected numbers in the various F2 classes? Test the goodness of fit between the data and your hypothesis using 2.
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Re: Genetics problems

Postby JackBean » Fri Jan 18, 2013 9:09 am

1.
a.
Given a plant was heterozygous for pod shape and homozygous recessive for plant size


b. do you know Punnett square?

c. the same as above

d. the same as above and above above, just combined

2. Pure breeding means they are homozygous (thus all progeny of self-breeding has the same phenotype, that's not possible for heterozygotes). Since F1 is tall red, the tall and red alleles should be dominant. Now you have to determine the ratio of F2 and compare with numbers from submission.
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby simina » Mon Mar 18, 2013 1:31 pm

Hii!!! I was wandering if a phenotype is expressed as a consequence of 2 different genes, are these genes part of an operon or are regulated by different promoters, meaning that can be located far away? ( in a prokaryotic organisms)??
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Postby JackBean » Mon Mar 18, 2013 11:04 pm

they can be far away
http://www.biolib.cz/en/main/

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