Please help, Genetics: Q1) For a period of several years, Hans Nachtsheim invest
ID: 56188 • Letter: P
Question
Please help,
Genetics:
Q1) For a period of several years, Hans Nachtsheim investigated an inherited anomaly of the white blood cells of rabbits. This anomaly, termed the Pelger anomaly, is the arrest of the segmentation of the nuclei of certain white cells. This anomaly does not appear to seriously inconvenience the rabbits.
A) When rabbits showing the typical Pelger anomaly were mated with rabbits from a true-breeding normal stock, Nachtsheim counted 217 offspring showing the Pelger anomaly and 237 normal progeny. What appears to be the genetic basis of the Pelger anomaly?
B) When rabbits with the Pelger anomaly were mated with each other, Nachtsheim found 223 normal progeny, 439 showing the Pelger anomaly, and 39 extremely abnormal progeny. These very abnormal progeny not only had defective white blood cells, but also showed severe deformities of the skeletal system; almost all of them died soon after birth. In genetic terms, what do you suppose these extremely defective rabbits represented? Why do you suppose there were only 39 of them?
C) What additional experimental evidence might you collect to support or disprove your answers to part b?
D) In Berlin, about 1 human in 1000 shows a Pelger anomaly of white blood cells very similar to that described for rabbits. The anomaly is inherited as a simple dominant, but the homozygous type has not been observed in humans. Can you suggest why, if you are permitted an analogy with the condition in rabbits?
Explanation / Answer
a)
Here, 231 (50%) offspring has normal phenotype and 217 (50%) has Pelger anomaly, so the ratio 1:1. Which states that it is a test this is a test cross here, the genetic basis of the Pelger anomaly is as follows:
Here, A/a is a Pelger individual and “a/a” is homozygous recessive (true-breeding normal stock).
b)
Based on the data, three phenotypes were resulted from selfing of two Pelger anomaly individual. In these individuals
So, form the progeny the genotypic ratio is 1: 2:1.
As we already know
So, extremely abnormal progeny genotype should be AA. There were only 39 extremely abnormal progeny, because almost all of them died soon after birth.