Revised 08
WORKSHEET
BIO 208 Unit 2
Also review list of objectives, notes, textbook, and homework assignments
1. Animals can teach us genetics! Match
Heterozygotes will exhibit two distinct proteins on
their red blood cells
A. Manx cat
Show a dominant and recessive relationship
B. Coat coloration in cats
An allelic series
C. Labrador retriever dogs
A dominant homozygote is lethal
D. Piebald spotting in beagles
Coat coloration is determined by 2 distinct genes
E. MN antigens
Shows variable expressivity
F. A and O blood alleles
A qualitative, or continuous, trait
G. Calico cat
Females mosaics for X-linked heterozygous color genes
H. Height of an individual
2. If Mendel only knew then what we know now.
EPISTASIS
CODOMINANCE
PENETRANCE
EXPRESSIVITY
INDEPENDENT ASSORTMENT
a.
b.
c.
d.
e.
f.
DOMINANCE
INCOMPLETE DOMINANCE
ALLELE
RANDOM SEGREGATION
The expression of both alleles of a heterozygous gene pair is called:
The degree to which a genotype is expressed in the phenotype:
The suppression of one gene by another non allelic gene :
The % of individuals of a genotype that show the expected phenotype:
Each gamete receives one allele of a gene :
When a single gene heterozygous genotype results in a phenotype
intermediate to the two alleles :
g. The alleles of one gene pair are inherited independently from those of
another gene pair :
h. An alternative form of a gene:
i. The expression of one allele to the exclusion of the other in a
heterozygote:
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PED'IGREE, n. from L. pes,pedis, foot. Lineage; line of ancestors from which a person or tribe
descends; genealogy.
3. Examine the pedigree below
Why is this NOT a Y linked trait?
Could this be an X – linked trait?
Is this inherited in an autosomal dominant or autosomal recessive manner?
How do you know for sure?
I
II
III
Which three modes of inheritance are possible for this trait. Show your reasoning by
indicating possible genotypes for each individual
I
II
4. It is probable that a probability question is in the future
From the cross AaBbccDdEeff X AABbCcDdeeFf what is the probability of
obtaining the genotype AabbCcDDEeff in the progeny?
5. Epistasis with two genes!
In horses, a dominant B will give the horse a black color, and a b will give the horse a
chestnut color. However, when a dominant W is present in the second gene pair, the
horse will be white no matter what. If the second gene pair is ww, then the horse will
be the color of whatever the first gene pair is made of. If a heterozygous white
(BbWw) mare is crossed with a heterozygous white (BbWw) stallion, what could the
offspring's phenotype and genotype be?
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6. Fill in the disorder
XY female
XX male
Patau syndrome
Phenylketonuria
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
Cri du Chat
Down syndrome
Anhydrotic ectodermal dysplasia
Hemophilia
Polydactyly
Achondroplasia
Alkaptonuria
Male, small testes, infertility
Female may not have ovaries or a uterus
Female heterozygotes have patches of skin that lack sweat glands
Inability to clot blood due to lack of a clotting factor
Dominant allele results in extra fingers and toes
Recessive allele prevents metabolism of phenylalanine
Dominant allele affects cartilage growth needed for bone lengthening
Retardation, higher risk of Alzheimer disease
Babies usually do not live beyond a year, deaf, blind
Microcephaly, abnormal larynx anatomy
Metabolic disease part of phe pathway, black urine
5 disorders that can be detected by karyotype
7. And let’s not forget human sex….. Arrange in the correct chronological order:
TDF, SRY, testosterone, male embryo, testes, Y chromosome
8. Fly sex…………
In Drosophila sex is determined by the ratio of the number of X chromosomes to the
number of sets of autosomes. Female ratio is 1 or greater, while males have a ratio of
0.5 or less. Identify the sex of the following flies
a. XY fly with 2 sets of autosomes ______________
b. XXY fly with 2 sets of autosomes ______________
c. XX fly with 3 sets of autosomes ______________
9. AND……………Bird sex…..
In birds, the male is the homogametic sex. Females are ZW. A dominant sex-linked
allele, ZS gives silver feather color. Zs gives gold. Mate a silver female with a gold
male. How can you identify male and female offspring by feather color alone?
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10. Who did it?
a. ___________ Random X-chromosome inactivation
Edwards
b. ___________ Characterized trisomy 21
Klinefelter
c. ____________Characterized trisomy 18
Barr
d. ___________ Discovered independent assortment
Mendel
e. ____________ Chromosomal theory of inheritance
Down
f. ____________Characterized XXY males
Sutton, Boveri
11. Do you know your numbers?
a.
b.
c.
d.
e.
f.
g.
h.
number of chromosomes in a human diploid cell __________
number of chromosomes in a human haploid cell _____________
number of chromosomes in a human Turner syndrome cell __________
number of chromosomes in a human trisomic cell __________
number of chromosomes in a human triploid cell __________
number of chromosomes in a human cell with a Robertsonian fusion __
number of chromosomes in a human fertilized egg _______
number of chromosomes in a normal human sperm _______
12. Ploidy, somy, and more Fill in:
RECIPROCAL TRANSLOCATION
MONOPLOID
LOCUS
MONOSOMY
TRIPLOID
TRISOMY
TETRAPLOID
BARR BODY
a. Position a gene occupies on a chromosome ___________
b. X chromosome in mammals seen as heterochromatin __________
c. An aberrant chromosome number in which a normally diploid cell has 3
copies of 1 chromosome _________________
d. An exchange of non-homologous chromosomes __________
e. An aberrant chromosomal condition in which a cell has 1 copy of a
chromosome and 2 copies of all others __________
f. An individual possessing 4 sets of chromosomes ____________
13. Deletion, Translocation, Inversion, Duplication, OR
Mosaicism?
a. __________ Involved in 46, 5pb. __________ May result in a position effect which affects gene expression
c. __________ May result in pseudodominance of an allele which is normally recessive
to a dominant allele
d. __________ Two genetically distinct populations of cells in a single individual
e. __________ Will result in abnormal gamete formation (more than one answer)
f. __________ Involved in familial Down syndrome
g. __________ Lethal if it occurs in the same region of two homologous chromosomes
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h. __________ No loss or gain of genetic material is involved (2 answers)
i. __________ Cell will have 45 chromosomes
j. __________ Increase of genetic material, may be tandem or reverse
k. __________ 46, XX/45, X (one individual)
14. Fill in the blanks on the pathway for phenylalanine metabolism. The arrows represent
a mutant enzyme (and corresponding gene) that does not function in the pathway.
a. Name of disease ________________
b. Why disease kills brain cells ____________
c. Name of pigment
______________
d. Black urine disorder name ________
15. MORE??
a. When true-breeding tall stem pea plants are crossed with true-breeding short stem
pea plants, all of the ______ plants, and 3/4 of the ______ plants had tall stems.
Therefore, tall stems are dominant
b. A genetic cross between two F1-hybrid pea plants having yellow seeds will yield
what percent green-seeded plants in the F2 generation? Yellow seeds are
dominant to green.
c. To identify genotype of yellow-seeded pea plants as either homozygous dominant
(YY) or heterozygous (Yy), you could do a test cross with plants of genotype ___.
d. What is the probability that a woman with cystic fibrosis (an autosomal recessive
disease) and normal male whose parents are homozygous dominant have a child
with cystic fibrosis?
e. Why is it not possible for a colorblind man (XcY) who mates with a normal
woman (XCXC) to have a colorblind son?
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f. Maple syrup disease is a rare genetic (inherited) disease. This disorder of
metabolism causes the baby’s urine to assume the odor of maple syrup. Two
individuals, heterozygous for the disease (phenotypically normal) have 10
children. How many children are expected to exhibit the disorder?
g. In Mendel's experiments, if gene for tall (T) plants was incompletely dominant
over gene for short (t) plants, what would be the result of crossing two Tt plants?
h. A genetic cross of inbred snapdragons with red flowers with inbred snapdragons
with white flowers resulted in F1-hybrid offspring that all had pink flowers. When
the F1 plants were self-pollinated, the resulting F2-generation plants had a
phenotypic ratio of 1 red: 2 pink: 1 white. The most likely explanation is:
i. A woman with type A blood and a man with type B blood could potentially have
offspring with which of the following blood types?
j. A pea plant is heterozygous for both seed shape and seed color. S is the allele for
the dominant, spherical shape characteristic; s is the allele for the recessive,
dented shape characteristic. Y is the allele for the dominant, yellow color
characteristic; y is the allele for the recessive, green color characteristic. What
will be the distribution of these two alleles in this plant's gametes?
k. Which of the following genetic crosses would be predicted to give a phenotypic
ratio of 9 :3:3: 1?
SSYY x ssyy
or
SsYy x SsYy or SSyy x ssYY or
ssYY x ssyy
l. In a dihybrid cross, AaBb x AaBb, what fraction of the offspring will be
homozygous for both recessive traits?
m. Following a SsYy x SsYy cross, what fraction of the offspring are predicted to
have a genotype that is heterozygous for both characteristics?
n. In a dihybrid cross, SsYy x SsYy, what fraction of the offspring will be
homozygous for both traits?
o. Hemophilia in humans is due to an X-chromosome mutation. What will be the
results of mating between a normal (non-carrier) female and a hemophiliac male?
p. A human female "carrier" who is heterozygous for the recessive, sex-linked trait
causing red-green color blindness has a child with a normal male. What
proportion of their male progeny will have red-green color blindness?
q. A human female "carrier" who is heterozygous for the recessive, sex-linked trait
red color blindness, marries a normal male. What proportion of their female
progeny will show the trait?
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r. A rooster with gray feathers is mated with a hen of the same phenotype. Among
their offspring, 15 chicks are gray, 6 are black, and 8 are white. What is the
simplest explanation for the inheritance of these colors in chickens? What
offspring would you predict from the mating of a gray rooster and a black hen?
s. A man has six fingers on each hand and six toes on each foot. His wife and their
daughter have the normal number of digits. Extra digits is a dominant trait. What
fraction of this couple's children would be expected to have extra digits?
t. A woman has the rare (hypothetical) disease called bent fingers. She has children
with a normal man, and all of their sons but none of their daughters have bent
fingers. What is the mode of inheritance of bent fingers? a. Autosomal recessive
b. Autosomal dominant c. X-linked recessive