Download Chapter 10 Genetics Guided Reading and Practice Problems

Chapter 10: The Basic Principles of Heredity Review
1. Define and discuss the following terms. Give examples and details where you can.
a. Heredity
b. Genetics
c. Hybrid
d. True-breeder
e. Phenotype
f. Dominant
g. Recessive
h. Alleles
i.
Locus (loci)
j.
Monohybrid cross
k. Homozygous
l.
Heterozygous
m. Punnett square
n. Genotype
o. Testcross
p. Dihybrid cross
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q. Linked genes
r. 2-point test cross
s. Recombination
t. Recombinant gametes
u. Parental gametes
v. Sex chromosomes
w. Homogametic
x. Heterogametic
y. Sex-influenced
2. Discuss the 2 rules of probability. Give examples.
3. Describe Mendel’s laws:
a. Principle of Segregation
b. Principle of Independent Assortment
4. Describe the relationship between crossing over and frequency.
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5. Describe the deal with sex chromosomes and X-linkage.
6. Describe and give examples of incomplete dominance.
7. Describe and give examples of codominance.
8. Describe and give examples of multiple alleles.
9. Describe and give an example of epistasis.
10. Describe and give an example of polygenic inheritance.
Genetics Problems:
Intermediate dominance:
1. In plants, the color red has genotype of RR and white has a genotype of rr. When these 2 plants are
crossed the genotype of Rr yields pink. If two pink plants are crossed what are the genotypic and
phenotypic results?
2. If a pink plant is backcrossed with each of its parents list the genotypic and phenotypic results.
Dihybrid:
In South America monkeys’ golden fur (G) is dominant over red fur (gg). A second trait controls
the presence or absence of a black stripe down the back. Those with the stripe have the genotype
BB or Bb. Those monkeys without the stripe have the genotype bb.
3. What are the phenotypic results of the following cross between a heterozygous golden,
heterozygous black striped monkey with a red no stripe monkey?
4. What are the results of a cross between 2 completely heterozygous monkeys?
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Dihybrid Intermediate inheritance:
In horses the gene for black coat is BB, reddish brown coat is Bb and tan coat is bb. Also the gene
for mane color is silver (SS), black (Ss) and red (ss).
5. List the possible phenotypes of horses if a brown coat, black mane horses is crosses with a brown
coat, silver mane horse.
6. List the phenotypes of the offspring in a mating between a black coat, silver mane horse with a
reddish brown, black mane horse.
Probability:
7. In a family of 8 children, what is the probability of getting the following:
a. all girls?
b. 6 boys and 2 girls in any order?
c. 4 boys and 4 girls in any order?
8. A breeder of hamsters has 2 golden teddy bear animals and breeds them. They are heterozygous
dominant. Recessive is brown. What is the probability of getting a litter of 5 hamsters – all golden?
All brown? 3 golden and 2 brown?
9. A gambler goes to Las Vegas to play dice games and discovers a new version of dice using 5 die.
What is the probability of getting – all 5’s? all the same number regardless of which number? Four
3’s and one 2?
10. A farmer has 2 heterozygous chickens which are blue. This is an intermediate dominant trait with
black BB and white bb as the homozygous conditions. What is the probability of the farmer getting
3 blue, 1 black and 2 white chickens from this set of parents?
11. A breeder has 2 heterozygous flowering African violets. In these plants purple (P) is dominant
over pink and plain or single flowers (S) is dominant over double or frilled flowers. What is the
probability of getting – 5 purple plain, 4 purple frilled, 3 pink plain and 1 pink frilled?
Sex Linked Problems:
12. In humans and other mammals the recessive gene for hemophilia, a clotting factor deficiency, is
located on the X chromosome. If a normal woman carries the gene and marries a normal man,
what are the genotypes and phenotypes possible for their children?
13. The genes for coat color in cats are sex-linked and intermediate. Use a BB for black and bb for
white. Calico is heterozygous. What are the phenotypes in a cross between a calico female and a
black male? Why is a calico male impossible under normal circumstances?
14. There are 2 genes for colorblindness which are both sex-linked. Deutan colorblindness is the
inability to see green and is recessive (d). Protan colorblindness is the inability to see red and is
recessive (p). A heterozygous normal woman (whose mother had deutan colorblindness and
whose father had protan colorblindness) marries a man with deutan colorblindness. List the
possible phenotypes of the children.
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15. The gene for hemolytic icterus is sex-linked and dominant (H). A second gene for albinism is
autosomal and recessive. A woman who is heterozygous normal for skin and doesn’t have the
icterus disease marries a man who has icterus and is heterozygous normal for skin. What are the
possible phenotypes for their children?
16. The gene for baldness is sex influenced. Baldness is dominant in males and recessive in females.
Therefore men with genotype BB and Bb are bald, and those with bb have hair. Women are the
opposite. Those with BB are bald and those with Bb and bb have hair. List the phenotypic results
from the following crosses:
a. Male HH x female hh
b. Both Hh
Gene Interaction, Epistasis and Polygenes
17. In humans skin color is determined by polygenes. The more dominant genes present the darker
the skin. Colors range from black (AABB), to dark (3 dominant), to mulatto (2 dominant), to light
(1 dominant) to white (aabb). List the skin colors of the following matings:
a. AaBb x AAbb
b. AABb x aaBb
18. Hair color follows gene interaction in terms of inheritance. There are 2 pigment genes. B is the
gene that produces brown pigment while R produces red. If both are present, B and R, the hair
color is auburn and if neither is present, bbrr, the color is blond. List the hair colors for the
following:
a. BbRr x BbRr
b. BbRr x bbrr
19. The gene for all white feather coloration is an epistatic dominant gene which covers other genes
for feather color. When this gene is recessive a second set of genes determines the feather color. In
the second gene pair brown is dominant over red. List the feather colors of the offspring in the
following cross.
a. WwBb x WwBb
20. In cats coat pattern is determined by a series of 3 genes. The gene for white patches is an
intermediate dominant trait with SS as extensive white, Ss as some white and ss as no white. A
second gene determines the intensity of the coat color and follows normal dominant /recessive
inheritance. DD or Dd is dark color and dd is dilute (light color). A third gene also follows normal
dominance in determining the presence of stripes. TT or Tt is stripes and tt is no stripes (solid).
List the possible phenotypes for kittens of the following parental cross:
a. SsDdTt x Ssddtt
21. Eye color in humans is inherited as trihybrid with epistatic and gene interaction. The first pair of
genes determines the presence or absence of pigment in the iris. BB or Bb codes for pigment and
bb as no pigment (blue). The blue no pigment condition is epistatic over the next 2 pairs of genes.
2 additional pairs of genes determine how much pigment is deposited must like those for skin
color. The more dominant genes the darker eye color. DDEE (4 dominant) is dark brown, 3
dominant is light brown, 2 dominant is hazel, 1 dominant is green and all recessive is blue.
a. A person with green eyes marries someone with dark brown eyes. They have a child with
blue eyes. What are the genotypes of the parents?
b. Cross the parents and list the phenotypes of other possible children.
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Multiple Alleles
22. In rabbits the gene for coat color has more than 2 allele choices. (C) full color, (L) chinchilla, (H)
Himalayan, (A) albino – listed in order from most to least dominant.
a. List the possible phenotypes of the offspring for CL x HA
b. What are the genotypes of the parents given the following offspring? Consider all
possibilities.
i. 2 full, 1 Himalayan, 1 albino
ii. 1 chinchilla, 1 albino
Blood Genetics
23. Consider just ABO genes and list the phenotypes of the offspring. Do all possible crosses:
a. Type A x Type B
b. Type AB x Type O
Linkage and Crossing Over – Calculate the percent crossing over for each cross and map the genes on a
chromosome.
24. Gray is dominant to black and straight is dominant to arc.
P = homozygous gray straight x black arc
F1 = heterozygous x black arc
F2 = gray straight – 1641
Gray arc – 1251
Black straight – 1180
Black arc – 1532
25. long is dominant over vestigial wings.
P = homozygous black long x gray vestigial
F1 = heterozygous x black vestigial
F2 = gray long – 283
Gray vestigial – 1294
Black long – 1409
Black vestigial – 250
26. P = homozygous long arc x vestigial straight
F1 = heterozygous x arc vestigial
F2 = long arc – 345
Long straight – 150
Vestigial arc – 137
Vestigial straight - 436
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