Download Mitoosis and Meiosis Practice Problems: Genetics and Chromosome Segregation and more Exams Genetics in PDF only on Docsity!
PRACTICE PROBLEMS 1
1. The diagram shows the nucleus of a diploid cell in G2. In this organism, N = 2;
chromosome 1 is metacentric with a knob near the end; and chromosome 2 is
acrocentric with no knob. Numbers 1-8 refer to centromeres.
(a) A line and the letters en represent the location of two copies of the en gene; draw
another line with en to indicate the location of the other two copies.
(b) Draw two arrows labelled sc pointing to any one pair of sister chromatids.
(c) Draw two arrows labelled hc pointing to any one pair of homologous
chromosomes.
(d) Which centromere(s) will segregate from the following centromeres at mitosis?
(e) Which centromere(s) will segregate from the following centromeres at meiosis I?
2. The diagram below depicts a microspore mother cell of maize in anaphase of meiosis
I, except that the chromosomes are missing. The maize plant is heterozygous at the C
locus on chromosome 9 and and the P locus on chromosome 10:
C c P p
โโโโoโโโโ โโโโoโโโโ โโโโoโ โโโโoโ
chromosome 9 chromosome 10
Draw the chromosomes, chromatids, and marker genes in the diagram below, attached
to the chromosome fibers, assuming that this particular meiosis is going to produce
four pollen grains with the indicated genotypes.
3. An organism that is heterozygous for one gene produces two different genotypes of
gametes; if heterozygous for two genes, four different genotypes can be produced.
How many different genotypes would you expect could be produced by an individual
heterozygous for three genes? Four genes? Is there a general formula for n genes?
4. Recall that in peas, Y and y determine yellow and green peas, respectively, and T and
t determine tall and short plants. A plant of genotype Y y T t is crossed to a short plant
that developed from green seeds.
(a) What is this kind of cross called?
(b) Out of 100 progeny seeds, how many do you expect to be yellow?
(c) Out of 100 progeny seeds, how many do you expect to be green and produce
short plants?
5. Write the genotypes of all of the genetically different pure lines that can be obtained
by inbreeding mice whose genotype is a a B b C c.
6. In guinea pigs, rough coat (R) is dominant over smooth coat (r). A rough coated
guinea pig is bred to a smooth coated one, producing 8 rough and 7 smooth progeny.
Write the genotypes of the parents, and the genotypes and ratios of the offspring:
Parents: X
Offspring:
7. Recall that two independently-segregating genes in maize determine plant height
(tall, T vs. short, t ) and leaf posture (relaxed, R vs. upright, r ). Two pure lines with
phenotypes tall relaxed and short upright are crossed.
(a) Write the genotypes of the parents: X
(b) Two F 1
individuals from this cross are themselves crossed to each other to produce
an F 2
generation. Use probability theory to calculate the proportion of the F 2
individuals that will be tall and upright, and can produce both tall and short offspring if
they are selfed.
