BILD 1							Dr. Nigel Crawford
Winter 1997						Due: Th, Feb. 20, 1997
PROBLEM SET # 4

1.	We could describe the ploidy of a certain organism as 4N.
	a) What is n (define it)
	b) What is 4 in this case?
	c) What is the ploidy of a human?
	d) What is the n value for a human?

2.	You cross two related species of animal.  The progeny (offspring) are 
viable (survive) but sterile.  What do you conclude about mitosis & meiosis 
in the progeny (ie. are both normal or abnormal and if abnormal, why?).

3.	The gene specifying blood group determinants can occur in three 
alleles A, B, and O.  A and B are codominant, while O is the recessive allele.  
If a person's father was blood type B, and she herself is type A, what blood 
type(s), if any, could the mother not be?

4.	The crossing over frequency between genes X and Y is 5%; between Y 
and Z, 15%; between X and Z, 10%; between Z and P, 1%; and between Y and 
P, 14%.  What is the frequency of crossing over between X and P?

5.	Sketch an eukaryotic chromosome in:

A) interphase (show and label: histones, nucleosomes, DNA)
B) mitotic prophase (show and label: chromatid, centromere)
C) metaphase of meiosis I with cross over (show and label: Sister 
	chromatids, chiasma, centromere)

6.	For rabbits, long ears and brown fur are dominant over short ears 
and white fur.  Crosses of individuals heterozygous for ear and fur traits to 
homozygous recessives (a test cross) gave the following results:
	long, brown	11
	long, white	110
	short, brown	106
	short, white	13
Are these genes linked; if yes, how many map units apart are they?
7.	Haploid yeast can use nitrate as a nitrogen source for growth.  A 
mutant was found that could not use nitrate. This mutant also required 
alanine for growth.  The mutant was crossed to normal (wildtype) yeast; 
the number of resultant progeny were:
Grows on nitrate, requires no alanine			50
Does not grow on nitrate, requires alanine		52
Grows on nitrate, requires alanine				49
Does not grow on nitrate, requires no alanine		48
Are there one or two genes that are defective in this mutant?  If two, are 
they linked or unlinked, explain?

8.	Brown eye color is dominant in humans; blue is recessive.  If a 
brown-eyed woman marries a brown-eyed man and they have a brown-
eyed boy and a blue-eyed girl, what can you conclude about the genotypes 
of the parents (homozygous/heterozygous, sex-linked?)?

9.	Indicate at what stage of meiosis each of the following begins. If it is 
not a part of meiosis, state so.
	1) Homologous Chromosome Pairing
	2) Crossing Over
	3) Separation of Sister Chromatids (assume no crossing over)
	4) Separation of Nonsister Chromatids (assume no crossing over)
	5) Chromosome Condensation (packaging)
	6) Centriolar Movement
	7) Independent Assortment
	8) Chromosome Replication
	9) Reformation of Nuclear Envelope

10.	What is interphase, how is it divided and what cellular processes 
occur during interphase?

11.	What is the difference between maternal inheritance and the 
inheritance of a sex-linked trait?