2.6.E: Chromosomes, Mitosis, and Meiosis (Exercises)
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- Ying Liu
- City College of San Francisco
These are homework exercises to accompany Nickle and Barrette-Ng's " Online Open Genetics " TextMap. Genetics is the scientific study of heredity and the variation of inherited characteristics. It includes the study of genes, themselves, how they function, interact, and produce the visible and measurable characteristics we see in individuals and populations of species as they change from one generation to the next, over time, and in different environments.
2.1 Define chromatin. What is the difference between DNA, chromatin and chromosomes?
2.2 Species A has n=4 chromosomes and Species B has n=6 chromosomes. Can you tell from this information which species has more DNA? Can you tell which species has more genes?
2.3 The answer to question 2 implies that not all DNA within a chromosome encodes genes. Can you name any examples of chromosomal regions that contain relatively few genes?
2.4 a) How many centromeres does a typical chromosome have?
b) What would happen if there was more than one centromere per chromosome?
c) What if a chromosome had zero centromeres?
2.5 For a diploid with 2n=16 chromosomes, how many chromosomes and chromatids are per cell present in the gamete, and zygote and immediately following G 1 , S, G 2 , mitosis, and meiosis?
2.6 Bread wheat ( Triticum aestivum ) is a hexaploid. Using the nomenclature presented in class, an ovum cell of wheat has n=21 chromosomes. How many chromosomes in a zygote of bread wheat?
2.7 For a given gene:
a) What is the maximum number of alleles that can exist in a 2n cell of a given diploid individual?
b) What is the maximum number of alleles that can exist in a 1n cell of a tetraploid individual?
c) What is the maximum number of alleles that can exist in a 2n cell of a tetraploid individual?
d) What is the maximum number of alleles that can exist in a population?
2.8 a) Why is aneuploidy more often lethal than polyploidy?
b) Which is more likely to disrupt gene balance: polyploidy or duplication?
2.9 For a diploid organism with 2n=4 chromosomes, draw a diagram of all of the possible configurations of chromosomes during normal anaphase I, with the maternally and paternally derived chromosomes labelled.
2.10 For a triploid organism with 2n=3x=6 chromosomes, draw a diagram of all of the possible configurations of chromosomes at anaphase I (it is not necessary label maternal and paternal chromosomes).
2.11 For a tetraploid organism with 2n=4x=8 chromosomes, draw all of the possible configurations of chromosomes during a normal metaphase.
2.12 A simple mnemonic for leptotene, zygotene, pachytene, diplotene, & diakinesis is L ame Z ebras P ee D own D rains. Make another one yourself.