Genetics Take Home Quiz 1     Due The Week of April 7, 2003   Good Luck!


 1.)	A corn plant known to be heterozygous at three loci is testcrossed.
	The following results were obtained:
	
	+ + +	455
	a b c	470
	+ b c	45
	a + +	33
	+ + c	47
	a b +	35
	+ b +	460
	a + c	475

	Calculate the distances between the three genes, and draw a map of the
	chromosome on which they are located.  (5 points)

 2.)	Drosophila heterozygous for three traits ebony body (e), scarlet
	eyes (s), and spineless bristles (sp) were testcrossed with the
	following results:

	wild type			67
	ebony				8
	ebony, scarlet			68
	ebony, spineless		347
	eony, scarlet, spineless	78
	scarlet				368
	scarlet, spineless		10
	spineless			54


	Determine the relative order and map distance between the genes
	involved.  (5 points)
	
	Calculate Interference, if any exists.  (2 points)
	
	What are the phenotypes of the parents of the triply heterozygous
	flies?  (2 points)

 3.)	In politicians, the following genes responsible for
	character mutations have been localized to chromosome 14:  
	truthless (tl), double speak (dblspk), and shifty (shfty).  
	The distances between these genes are as follows:

	tl-shfty 10.0 map units
	dblspk-shfty 6.1 map units
	tl-dblspk 16.1 map units

	Construct a map of chromosome 14 based on these data.  (2 points)
	
	Calculate the probability of a double crossover between the genes
	involved.  (2 points)

 4.)	In corn, the alleles C and c result in colored versus colorless seeds,
	Wx and wx in nonwaxy versus waxy endosperm, Sh and sh in plump versus
	shrunken endosperm.  When plants grown from seeds heterozygous for each
	of these pairs of alleles were testcrossed with plants from colorless,
	waxy, shrunken seeds, the progeny seeds were as follows:

	84 colorless, nonwaxy, shrunken
	974 colorless, nonwaxy, plump
	20 colorless, waxy, shrunken
	2349 colorless, waxy, plump
	951 colored, waxy, shrunken
	99 colored, waxy, plump
	2216 colored, nonwaxy, shrunken
	15 colored, nonwaxy, plump

	Determine the relative order of the three genes and construct a linkage
	map showing the distances between the genes.  (5 points)

 5.)	In Drosophila, the genes ct (cut wing margin), y (yellow body), and v
	(vermilion eye color) are X-linked.  Females heterozygous for all three
	traits were mated with wild-type males, and the following male 
	offspring were obtained:   
	(Remember + means wild-type allele for that gene)

	ct	y	v	4
	ct	y	+	93
	ct	+	v	54
	ct	+	+	349
	+	y	v	331
	+	y	+	66
	+	+	v	97
	+	+	+	6

	What is the order of the genes?  (2 points)
	
	Calculate the recombination frequencies and the interference between
	the genes.  (5 points)
	
	Draw a genetic map of the X chromosome showing the relative positions
	of these genes  (1 point)
	
	Why were only male offspring counted?  (2 points)