ompensation is necessa With regard to the numbers of sex chromosomes, explain wh

Question

ompensation is necessa With regard to the numbers of sex chromosomes, explain why dosage c ry A maternal effect gene exists in a dominant N (normal) allele and a recessive n (abnormal) alle What would be the ratios of genotypes and phenotypes for the offspring of the following crosses? A. nn female NN male B. NN female x nn male C. Nn female x Nn male How many Barr bodies would you expect to find in humans with the following abnormal compositions of sex chromosomes? A. XXY B. XYY C.XxX D. XO (a person with just a single X chromosome) The following X-linked recessive traits are found in fruit flies: vermilion eyes are recessive to red eyes miniature wings are recessive to long wings, and sable body is recessive to gray body. A cross was made between wild-type males with red eyes, long wings, and gray bodies to females with vermilion eyes, miniature wings, and sable bodies. The heterozygous females from this cross, which had red eyes, long wings, and gray bodies, were then crossed to males with vermilion eyes, miniature wings, and sable bodies. The following outcome was obtained: Males and Females 1320 vermilion eyes, miniature wings, sable body 1346 red eyes, long wings, gray body 102 vermilion eyes, miniature wings, gray body 90 red eyes, long wings, sable body 42 vermilion eyes, long wings, gray body 48 red eyes, miniature wings, sable body 2 vermilion eyes, long wings, sable body 1 red eyes, miniature wings, gray body A. Calculate the map distance between the three genes.

Explanation / Answer

1. Dosage compensation is a very important process which occurs in organisms to somehow equalize the expression of genes in various biological sexes. The number and type of chromosomes which determines the sex or the sex chromosomes vary across the species. To counter this variation species have acquired this process of dosage compensation to equalize Gene expression among different sex.

For example if we take the case of humans, in female the transcription of one X chromosome is silent thus the end expression in both male and female is from just one X chrmomosme though the number of X chrmomosme in both male and female vary. This shows the important role of dosage compensation.

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