Download Practice Exam III

Genetics 310
Practice exam III-1
1. What are the two types of molecules found in eukaryotic chromosomes?
DNA and protein
2. True or False?
__F_ Man has more DNA per genome than all other organisms.
__F_ The number of chromosomes is a direct reflection of the amount of DNA/genome
in a species.
__F_ All of the DNA in a eukaryote is unique sequence DNA, meaning that it codes for
enzymes or recognition signals such as promoters.
__F_ Each human chromosome is metacentric.
3. Write the standard karyotype of a normal human female. _____46; XX____
4. List 3 sex-linked single gene traits.
1; colorblindness
2;
hemophilia 3 Duchene muscular dystrophy etc.
]
5. A sex linked dominant gene would be: (true or false)
___F_ 1. passed from an affected man to all his sons
___T_ 2. Passed from an affected man to all his daughters
___F_ 3. passed from a normal female to half her sons (she doen't have it!)
___F_ 4. passed from a normal female to half her daughters
6. Fill in the chart below describing 4 different cases of abnormal numbers of sex
chromosomes in humans:
Sex Chromosme
Composition
Name of Syndrome
Phenotypic Sex
Fertile?
Klinefelter's
Male
No
47; XXX
TriploX
female
yes
45; XO
Turner's
Female
no
47; XYY
Jacob's
Male
yes
XXY
7. Why is the use of testosterone not beneficial to XY individuals with the tfm gene?
they have no testosterone receptors
8. What is a Barr body?
a condensed X chromosome
9. Give a legend that will explain the inheritance of pattern baldness.
Genotype
B'B'
B'B
BB
Male
bald
bald
hair
Phemale
bald (thin heai)
hair
hair
10. In Drosophila:
E_ = normal
ee = ebony
V_ = normal wing vein
vv = veinlet (missing vein)
In a cross of a normal , normal female to an ebony veinlet male, the following progeny
were obtained:
normal, normal
normal, veinlet
ebony, normal
ebony, veinlet
44
6
6
44
a) Are the genes linked? ___yes___ If so, at what distance? _____12 map units__
b) Give the genotype of the male ____e v/e v___ and the female_E 12 V/e v___
11. List 3 crucial technical advances that permitted the assignment of genes to human
chromosomes:
1; Isozyme separation (man and mouse version of an enzyme differ in charge)
2; chromosome banding; ability to identify every chromosome
3; formation of man-mouse stable hybrid cell lines that lose many human chromosomes
12. a) How are triploid plants produced? b) What is their practical value? c) Give an
example. 4N X 2N; seedless
13. Define the term "monosomy". having only one copy of a chromosome
14. a) What is the chromosomal composition of an individual with Down's syndrome?
47 (XX or XY)+ 21
b) What evidence can you site that shows Down's can pass through the egg? There is an
increase in frequency of trisomy 21 with age of mothers
c) How can the frequent recurrence of Down's in some families be explained? There are
cases where one parent has a translocation of 21 onto another chromosome so often pass
2 - 21's to a gamete
15. List two types of chromosomal aberrations that can cause semi-sterility in
heterozygotes.
translocations and insversions
16. Which chromosomal aberration has the apparent effect of suppressing crossing
over?
inversions
17. Which chromosomal aberration produces the following synaptic configuration?
translocation
18. What fraction of spontaneous abortions have chromosomal aberrations?
about 50% have a visible aberration
19. Give an example of a genetic defect that can be detected during amniocentesis based
on:
a) a missing enzyme
Tay Sachs disease
b) an extra chromosome
Downs syndrome
c) only with a DNA probe sickle cell anemia
20. What is the Lyon hypothesis? What does it explain?
Every X greater than one in cells of mammals is condensed and inactivated early
in embryology. This explains dosage compensation and mosaic patterns in
females such as calico cats