BioSc 231
General Genetics
Exam 4
Name __________________________________
Multiple Choice. (2 points each)
_____ Turner syndrome in humans is caused by which chromosomal conditions?
A. 47, XXY
B. 47, 21+
C. 45, X
D. 47, XYY
E. triploidy
_____ Clusters of highly repetitive DNA located near the centromeres and telomeres are called
A. Nucleosomes
B. Euchromatin
C. Chromatids
D. Heterochromatin
E. 30 nm chromatin
_____ Which histone protein is present as a monomer within the nucleosome and is not a part of the core
particle?
A. H1
B. H2A
C. H2B
D. H3
E. H4
_____ E. coli genomic DNA differs from a eukaryotic chromosome in that E. coli DNA
A. Has a single centromere
B. Has telomeres
C. Is circular
D. Does not undergo supercoiling
_____The genes coding for histones are repeated several times throughout the eukaryotic genome. These genes
would be described as
A. Highly repetitive DNA
B. Unique sequences
C. Heterochromatin
D. Transposons
E. Middle repetitive DNA
_____ A chromosome with its centromere in the middle is a
A. Submetacentric chromosome
B. Metacentric chromosome
C. Acrocentric chromosome
D. Telocentric chromosome
_____ Mosaicism is due to
A. X-inactivation
B. chromosome duplication
C. chromosome deletion
D. somatic mutations
E. gametic mutations
_____47,XXY is a condition known as
A. Trisomy-X syndrome
B. Klinefelter syndrome
C. Turner syndrome
D. Double-Y syndrome
E. Fragile-X syndrome
_____ A wild-type chromosome can be represented as ABC * DEFGH, and from this a chromosomal aberration
arises that can be represented AED * CBFGH. This is known as
(* = centromere)
A. Deletion
B. Pericentric inversion
C. Translocation
D. Paracentric inversion
E. Duplication
_____ A female Drosophila supposedly heterozygous for two recessive mutations cn and lz that are on the same
arm of the X chromosome (cn lz/+ +) surprisingly expresses both these genes. The male progeny of the female
will be
A. all wild type
B. all cn lz
C. 1/2 cn lz and 1/2 wild type
D. cn +
E. + lz
_____ When an organism gains or loses one or more chromosomes but not a complete haploid set, the
conditions is known as
A. polyploidy
B. euploidy
C. aneuploidy
D. triploidy
_____ It was once thought that the ____ karyotype was related to criminal disposition because it led to
aggressive behavior due to excessive "maleness".
A. XO
B. XY
C. XXY
D. XYY
_____ A set of Drosophila deletions in chromosome 2 was assembled as follows (the lines indicate the region
that has been deleted)
Regions
1
a
b
c
d
e
f
2
3
________
4
5
6
7
_________________
____________
_________
___________
__________
A geneticist clones a gene from chromosome2 and wants to use the deletions to identify where the gene is
located on chromosome 2. They use a radioactive DNA fragment containing their gene of interest and try to
hybridize the DNA fragment to the chromosomal DNA from each mutant. The radioactive DNA fragment only
bound to chromosomal DNA from mutants a and f. The gene must be in the region between
A. 1 and 2
B. 2 and 3
C. 3 and 4
D. 4 and 5
E. 5 and 6
_____ Pollen from one species germinates on the stigma of another related species and sexually fertilizes the
ovule. Most of the resulting plants are sterile but some of the resulting offspring undergo chromosome
duplication resulting in fertile plants. The fertile offspring are known as
A. hexaploid
B. autopolyploid
C. monoploid
D. diploid
E. allopolyploid
_____ In a mammal how many inactivated X chromosomes (Barr bodies) would be present in cells of
individuals who were XXX?
A. 0
B. 1
C. 2
D. 3
E. 4
_____ When an allotetraploid is backcrossed to one of its progenitor species, a sterile progeny is produced. The
genomic composition of this sterile individual can be best represented by (where n1 and n2 represent the haploid
genomes of each progenitor species)
A. n1 + n2
B. 2n1 + 2n2
C. 2n1
D. 2n2
E. 2n1 + n2
_____ Euploidy is
A. a chromosome number that is not an exact multiple of the haploid number
B. an example of aneuploidy
C. a chromosome number that is an exact multiple of the haploid number
D. the addition of an extra copy of a particular chromosome
E. the absence of a particular copy of a chromosome
_____ The basic diploid chromosome number in pumpkins is 16. A new species of pumpkin is found that has
four complete sets of the chromosomes found in the 16 chromosome species. This species is said to be
A. haploid
B. diploid
C. triploid
D. tetraploid
E. pentaploid
_____ Consider a species with a diploid (2n) number of 14 chromosomes. How many chromosomes would be
found in a trisomic body cell?
A. 13
B. 14
C. 15
D. 21
E. 28
_____ Consider a species with a diploid (2n) number of 40 chromosomes. How many chromosomes would be
found in a monoploid body cell?
A. 10
B. 20
C. 41
D. 39
E. 40
_____ How many different trisomics could be formed in a plant with a diploid number of 10?
A. 5
B. 10
C. 11
D. 9
E. 20
_____ When an organism gains or loses a complete monoploid set of chromosomes, the conditions is known as
A. polyploidy
B. euploidy
C. aneuploidy
D. triploidy
E. trisomy
Short Answer (2 points each)
What happens when monoploid plant cells are treated with colchicine?
What is the name of the process of staining the chromosomes from a metaphase cell and arranging the
chromosomes according to their length and centromere placement?
Why is polysomy more harmful than polyploidy?
How many Barr bodies would you expect to see in the cells of a person who has the condition 47, XXY?
Why are centromeres and telomeres required for chromosomes to be genetically stable?
Why is topoisomerase necessary during replication of the E. coli chromosome?
Explain why there is usually a single gene in the genome for a particular protein (i.e. an enzyme involved in a
biosynthetic pathway) whereas genes for ribosomal RNA (rRNA) and tRNA are repeated many times?
Recessive alleles a, b, c, d, e, f and g are closely linked but their order is unknown. A set of 7 deletions are used
to determine the gene order as revealed by the genes uncovered by each deletion. The genes uncovered by each
mutation are as follows:
1 – a and b
2 – a, b and e
3 – b and c
4–c
5 – d and f
6 – d, f and g
7 – e, f and g
What is the order of the genes?
Bonus (4 points) Describe the structure of eukaryotic chromatin from the basic building blocks to the compact
structure found in metaphase cells. Include all proteins involved in forming the structure and all intermediate
structures.
Please circle two topics that you would most like to cover over the last section of the course.
Bacterial Genetics
Gene Regulation
Gene Expression
Development
The Cell Cycle
Population Genetics and Evolution