Problems 1 - 3. In 1999, Neal et al. (Animal Biotechnology 10:153-158) analyzed

ID: 207087 • Letter: P

Question

Problems 1 - 3. In 1999, Neal et al. (Animal Biotechnology 10:153-158) analyzed the chromosome constitution of embryos extracted from female pigs that were heterozygous for a reciprocal translocation between the X chromosome and chromosome 14. These female pigs had all mated with males whose chromosome constitution was normal. Neal et al. examined 38 embryos taken from the female pigs at two weeks of gestation and recorded the following data, which are numbered as three different classes of embryos Number of embryos Chromosome constitution of embryo Balanced, no translocation Balanced, translocation Unbalanced 12 1. Based on the predicted segregation ratios for reciprocal translocation heterozygotes, how many balanced embryos, without translocation, are expected? A. 4.875 B. 6.5 C. 9.5D. 19 E. 26 2. Using chi-square analysis, test the hypothesis that the results conform to the frequencies of embryos expected with typical chromosome segregations in a reciprocal translocation heterozygote What is your chi-square statistic? A. 1.16 B. 1.47 C. 3.38 D. 7.05 E. 23.91 3. One of the reasons that you might reject your hypothesis that the results conform to a typical segregation ratio for a reciprocal translocation heterozygote is because there are far fewer unbalanced embryos than expected. Neal et al. found that among the twelve unbalanced embryos, eleven were of one gender and only one of the opposite gender. They examined another set of embryos from this cross at four weeks gestation and found that all unbalanced embryos were of the same gender as the eleven unbalanced two-week embryos from the data set shown above. Which gender is most likely overrepresented in these unbalanced pig embryos? A. male B. female

Explanation / Answer

To find the ratio lets divide the given data will least number which is 10.

we will give 1.6: 1: 1.2 which is most likely equivalent to 1:2:1.

1)As there are total 38 embryos, So expected number of balanced embryos without translocation will be =

38 x (2/4) = 19

2) Now, here expected ratio is 1:2:1

Type of embryos

Observe (O)

Expected (E)

(O-E)

(O-E)2

(O-E)2/E

Unbalanced

9.5

2.5

6.25

0.657

Balanced, non-translocate

-3

0.474

Balanced, Translocate

9.5

0.5

0.25

0.026

Chi-square = sum of (O-E)2/E

1.157

so Chi-square value is = 1.157 = 1.16(approx.)

so option A is correct.