1A. A line selected for high bristle number in Drosophila has a mean of 25 stern

Question

1A. A line selected for high bristle number in Drosophila has a mean of 25 sternopleural bristles, whereas a low-selected line has a mean of only 2 bristles. Marker stocks for the two large autosomes II and III are used to create stocks with various mixtures of chromosomes from the high (h) and low (l) lines. The mean number of bristles for each chromosomal combination is as follows:

What conclusion can you reach about the distribution of genetic factors and their actions from these data?

1B. You analyze chromosome X from the high bristle line in greater detail by generating recombinants between this chromosome and a chromosome that has the recessive visible marker mutations, v (vermillion colored eyes), cv (crossveinless or absence of a crossvein on the wing), and ct (cut or sniped wing edges). Importantly, these mutations do not impact bristle number. You analyze the following recombinant chromosome genotypes for the X chromosome in a genetic background that is otherwise constant for the other chromosomes (II, III, and IV). Assume that these three genes, v, cv, and ct, are equally distributed along the length of the X chromosome. These are your results:

(+ indicates a wild-type allele for the gene that is from the high bristle line X chromosome)

What conclusions can you draw from this data about potential number of genes and their distribution on the X chromosome that influence bristle number? Support your answer.

PLEASE answer both questions completely. I will be sure to leave positive feedback IF both questions are answered completely - thank you!

Line # Genotypes Mean Bristle # 1 v- cv- ct-/v- cv- ct- 2.3 2 + + +/+ + + 12.5 3 v- cv- ct-/+ + + 7.2 4 v- cv- ct-/v- + + 2.5 5 v- cv- ct-/v- cv- + 4.4 6 v- cv- ct-/+ cv- ct- 7.3 7 v- cv- ct-/+ + ct- 7.4 8 v- cv- ct-/+ cv- + 7.8 9 v- cv- ct-/v- + ct- 2.1

Explanation / Answer

1a). Here two pure lines represented one with autosomal homozygous pair of chomosome with "h" gene and the other with autosomal homozygous pair of chromosome with "l" gene stocks.

* Here in the stocks we observe linkage, recombination and crossing over of QTLs. deletion, duplication, Insertion and inversion of genes were oberserved in producing various stocks. i.e. mutation

2b). What conclusions can you draw from this data about potential number of genes and their distribution on the X chromosome that influence bristle number?

+ + +/+ + +........wild type with high bristle number

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