Genetics - Analysis and Principles

Biology

Quiz 25 :

Genetics Basis of Cancer

Quiz 25 :

Genetics Basis of Cancer

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Discuss why heritability is an important phenomenon in agriculture. Discuss how it is misunderstood.
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Heritability is important in agriculture because, in selective breeding heritability plays a major role. The breeder selects the plants as breeding stock for next generation, whose heritability value is high to improve the desired traits.
People misunderstood the concept of heritability, by thinking that the variation of a trait is governs by genetics alone. But, Heritability is the amount of phenotypic variation is due to genetic variation in a particular population raised in a particular environment. Heritability depends on both genetical and environmental factors. Heritability does not describe the relative impact of the genetic variation and effect of environment on the outcome of a trait.

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If an r value equals 0.5 and N = 4, would you conclude that a positive correlation is found between the two variables Explain your answer. What if N = 500
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We know that, the r value ranges between -1 and +1. Here, r = 0.5 and N = 4, that indicates that there may be a weak positive correlation between the two variables by chance. There is a need to conduct more experimentation by taking many more pairs of individuals in to account to determine the r value is whether statistically significant or it occurred as a matter of random sampling errors.
In case N = 500, then the correlation would be statistically significant and the correlation may not occurred by chance.

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In one strain of cabbage, you conduct an RFLP analysis of head weight; you determine that seven QTLs affect this trait. In another strain of cabbage, you find that only four QTLs affect this trait. Note that both strains of cabbage are from the same species, although they may have been subjected to different degrees of inbreeding. Explain how one strain can have seven QTLs and another strain four QTLs for exactly the same trait. Is the second strain missing three genes
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We know that the phenotypic expression of a trait within a population is due to the genetic variation in the population. It is called heritability of the trait. In the given situation, the first strain with seven QTLs has at least 7 different genes in the form of multiple alleles that are influencing the phenotype of the trait (head weight in cabbage). The second strain with 4 QTLs also has the same type of 7 genes. But out of these 7 genes, 3 genes became monomorphic. So, these 3 genes do not have any influence on the head weight of cabbage. It is a common effect of inbreeding.

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Using the same strategy as the experiment of Figure 25.6, the following data are the survival of F 2 offspring obtained from backcrosses to insecticide-resistant and control strains: img Interpret these results with regard to the locations of QTLs.
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The variance for weight in a particular herd of cattle is 484 lb 2. The mean weight is 562 lb. How heavy would an animal have to be if it was in the top 2.5% of the herd The bottom 0.13%
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At the molecular level, explain why quantitative traits often exhibit a continuum of phenotypes within a population. How does the environment help produce this continuum
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What is a frequency distribution Explain how the graph is made for a quantitative trait that is continuous.
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You need to understand solved problem S5 before answering this question. The average weights for two varieties of cattle were 514 kg and 621 kg. The genetic variance for weight calculated for both strains was 382 kg 2. What is the minimum number of genes that affect weight variation in these two varieties of cattle
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What is heterosis Discuss whether it is caused by a single gene or several genes. Discuss the two major hypotheses proposed to explain heterosis. Which do you think is more likely to be correct
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What does it mean when a correlation coefficient is negative Can you think of examples
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From an experimental viewpoint, what does it mean to say that an RFLP is associated with a trait Let's suppose that two strains of pea plants differ in two RFLPs that are linked to two genes governing pea size. RFLP-1 is found in 2000-bp and 2700-bp bands, and RFLP-2 is found in 3000-bp and 4000-bp bands. The plants producing large peas have RFLP-1 (2000 bp) and RFLP-2 (3000 bp); those producing small peas have RFLP-1 (2700 bp) and RFLP-2 (4000 bp). A cross is made between these two strains, and the F 1 offspring are allowed to self-fertilize. Five phenotypic classes are observed: small peas, small-medium peas, medium peas, medium-large peas, and large peas. We assume that each of the two genes makes an equal contribution to pea size and that the genetic variance is additive. Draw a gel and explain what RFLP banding patterns you would expect to observe for these five phenotypic categories. Note: Certain phenotypic categories may have more than one possible banding pattern.
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Explain the difference between a continuous trait and a discontinuous trait. Give two examples of each. Are quantitative traits likely to be continuous or discontinuous Explain why.
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The abdomen length (in millimeters) was measured in 15 male Drosophila, and the following data were obtained: 1.9, 2.4, 2.1, 2.0, 2.2, 2.4, 1.7, 1.8, 2.0, 2.0, 2.3, 2.1, 1.6, 2.3, and 2.2. Calculate the mean, standard deviation, and variance for this population of male fruit flies.
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Outline the steps you would follow to determine the number of genes that influence the yield of rice. Describe the results you might get if rice yield is governed by variation in six different genes.
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From a biological viewpoint, speculate as to why many traits seem to fit a normal distribution. Students with a strong background in math and statistics may want to explain how a normal distribution is generated, and what it means. Can you think of biological examples that do not fit a normal distribution
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What is a normal distribution Discuss this curve with regard to quantitative traits within a population. What is the relationship between the standard deviation and the normal distribution
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Give several examples of quantitative traits. How are these quantitative traits described within groups of individuals
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Let's suppose that two strains of pigs differ in 500 RFLPs. One strain is much larger than the other. The pigs are crossed to each other, and the members of the F 1 generation are also crossed among themselves to produce an F 2 generation. Three distinct RFLPs are associated with F 2 pigs that are larger. How would you interpret these results
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Here are data for height and weight among 10 male college students. img A. Calculate the correlation coefficients for this group. B. Is the correlation coefficient statistically significant Explain.
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Two different varieties of potatoes both have the same mean weight of 1.5 pounds. One group has a very low variance, and the other has a much higher variance. A. Discuss the possible reasons for the differences in variance. B. If you were a potato farmer, would you rather raise a variety with a low or high variance Explain your answer from a practical point of view. C. If you were a potato breeder and you wanted to develop potatoes with a heavier weight, would you choose the variety with a low or high variance Explain your answer.
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