Help with a biology question

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I don't understand this question. Any help would be appreciated.

 

[IB`NOT`ez]

For the first question, gene linkage is occurring -- where the pairs of genes have their loci on the same chromosome. Unlike in unlinked genes, they do not assort independently as they are located on the same chromosome. This gives an explanation on conducting dihybrid crosses with linked genes: 

 

As the genes are linked, when TtRr is crossed with TtRr through a dihybrid cross, only the possible combinations can be had: TR and tr only for the first parent plant, and TR and tr only as well for the second parent plant (if genes are unlinked, which would result in the 1/16 short, wrinkled seeds, the possible combinations would also involve Tr and tR, as well as TR and tr). Basically, take the first letter of the first gene, combined with the first letter of the next gene, and second letter goes with second letter when genes are linked. Use the punnet square again and you should be getting 1/4 short, wrinkled seed plants.

For the second question, the statistical test is called the Chi Squared Test, which involves using degrees of freedom where observed values are compared against expected values. Expected values would for example be the 1/16 chance or 1/4 chance for a certain phenotype as from the Punnet Square, whereas the observed values are what you get experimentally. Since the question just asks you to outline the test, the first sentence of this paragraph should suffice for all the marks available. This video is useful in explaining Chi Squared Tests: 

 

Edited October 17, 2016 by IB`ez

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ah thank you so much! you're so sweet