Question

1. An organism has a diploid chromosome number of 8. The paternal chromosomes differ from the maternal ones. If no crossing over occurs, how many different gametes are possible?
2. If a couple has 4 boys, what is the probability that the fifth child will be a boy?
3. You have performed some experiments, collected data, and calculated the chi-square values for 2 data sets. (The degrees of freedom = 1 for both data sets.)

4. The calculated chi-square value for data set #1 is 0.004.

   The calculated chi-square value for data set #2 is 10.83.

   a. Which data set will have the largest p-value?

           b. Which data set will have the smallest p-value?

           c. Which data set most strongly suggests that your results are due to random chance?

Answer 1

If an organism is diploid i.e. its ploidy will be 2n,then its gametes will be haploid when means gametes have ploidy 'n'.

For e.g:- In humans,they are diploid with 46 chromosomes while Spermatozoa/Ovum has haploid set of chromosome ie; a total of 23 chromosomes.

As per question, organism is diploid with chromosome Number (2n) = 8

and n = 8/2 = 4.

The paternal chromosomes differ from the maternal ones and  If no crossing over occurs between paternal and maternal chromosomes which means that during meiosis no exchange of genetic material between non-sister chromatids of homologous chromosomes occurs. No possible recombination will occur.

Number of possible gametes for paternal and maternal will be equal to n i.e. 4.

Which means paternal and maternal parent have 4 gametes each.

If a couple has 4 boys already,the probability of fifth boy is still 50% .

​​​​​​Nearly ,chances are around 50% for having a boy and 50% for having a girl.

Chi-square values for data actually tells about how well the observed distribution of data fits with the distribution that is expected if the variables are independent.

The p-value will tell us that if the test results are significant or not.

For set#1 having chi-square value (0.004) p-value lies between 0.95 and 0.90 probability value which means that difference between the actual and the expected count would occur between 90 and 95% of the time.

For set#2 having chi-square value (10.83),p-value exactly lies on 0.001 probability value which means that the difference between the actual and the expected count is 0.1% of the time.

a)​​​​ set#1 will have the largest p-value,i.e. 90 and 95%..

b) set #2 will have the lowest p-value i.e. 0.1%.

#*  In biology,its generally accepted that a p- value greater than 0.05 is acceptable,while a p-value lower than 0.05 would indicate that the results cannot be due to the random sampling and therefore do not fit the original prediction/hypothesis.

c) Data set#1 strongly suggest that our results are due to random chance because its value is greater than 0.05 which is acceptable.

For details check above #*

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