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Genetics (Chapter 9) Test Review Sheet
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1. The passing on of characteristics from parents to offspring is known as ____________. The study of
patterns of inheritance and variations in organisms is called ______________.
Heredity; Genetics
2. Gregor Mendel studied ________ plants.
pea
3. What is the difference between pollination and fertilization?
Pollination is the transfer of the male pollen grain to the pistil. Fertilization is when the male and
female gametes actually fuse together.
4. What are the three generations of a cross called? Describe what each includes.
P1 – The first generation in the cross
F1 – The second generation (the offspring of the P1 generation)
F2 – The third generation (the offspring of the F1 generation)
5. If a homozygous tall plant is crossed with a homozygous short plant, what percentage of the F2 generation
will be short if the F1 generation is self-fertilized? (Tall is dominant over short)
P1: TT x tt
F1: All Tt
F2: 75% Tall, 25%short
T
t
T
TT
Tt
t
Tt
tt
6. Why did Mendel call his cross a hybrid?
The plants were a cross between two parents that show different forms of a trait
7. Mendel concluded _______ factors controlled each trait. The difference forms of the genes are called
_____________.
Two, alleles
8. When Mendel crossed a tall pea plant with a short pea plant, why were all of the offspring tall?
The allele for tall was dominant over the allele for short
9. Describe the Law of Segregation
During meiosis, that factors that control each trait separate, and only one factor from each pair is
passed to the offspring
10. What is the difference between an organism’s genotype and its phenotype?
Genotype – what the genetic combination of the organism is
Phenotype – what the physical traits of the organism are
11. If an organism has the same two alleles for a trait, the organism is ____________. If an organism has two
different alleles for a trait, the organism is ____________.
Homozygous; heterozygous
12. What is the only way an organism can show a recessive trait?
If it is homozygous for the recessive trait
13. Define incomplete dominance. Give an example.
Incomplete dominance is a condition in which one allele is not completely dominant over another.
The phenotype expressed is somewhere between the two possible parent phenotypes.
An example is the flower color of snapdragons (RR – red, rr – white, Rr – pink)
14. What possible gametes could an organism give an offspring if they had the following genotypes:
a.
TT – T or T
b. Bb – B or b
c. AaBb – AB, Ab, aB, ab
d. PPGg – PG, Pg, PG, Pg
15. Describe the Law of Independent Assortment.
The inheritance of alleles for one trait is not affected by the inheritance of alleles for a different trait
if the genes are on different chromosomes.
16. The sex chromosomes for a female are ________. The sex chromosomes for a male are ________. A
mother can pass on an _____ or an _______. A father can pass on an ______ or a ________.
XX; XY, X or X; X or Y
17. What are the chances of a couple having a boy if they already have two daughters?
50%
18. Sex-linked traits are carried on the _____ or ______ chromosomes. Most sex-linked traits are carried on the
________ chromosome.
X or Y; X
19. Can a male be heterozygous for a sex-linked trait? Why or why not?
No; a male has only one of each sex chromosome so it can only carry one allele for any sex-linked
trait.
20. Human blood types demonstrate _______ alleles that demonstrate ___________ where heterozygous alleles
are expressed equally.
Multiple; codominance
21. What are the possible genotypes for each blood type (A, B, AB, and O)?
A – IAIA, IAi AA or AO
B – IBIB, IBi BB or BO
AB – IAIB
O – ii
AB
OO
22. If a man has type A blood and a woman has type B blood, could they be the parents of a baby with type O
blood?
Yes if they are IAi and IBi
23. If a man has type AB blood and a woman has type B blood, could they be the parents of a baby with type O
blood?
No, an IAIB parent would have no i to give an ii offspring
24. To make a Punnett square, the possible _______ from each parent are put on the top and sides of the square.
gametes
25. What are polygenic traits? Give an example.
Polygenic traits are traits that are controlled by two or more genes. These traits often show a great
variety of phenotypes, e.g. skin color.
26. What is a pedigree?
A pedigree is a chart to show an inheritance pattern (trait, disease, disorder) within a family through
multiple generations.
A pedigree can be used to track the genotype and phenotype of the family members and the genetic
characteristics (dominant/recessive, sex-linked) of the trait.
27. If a pedigree showed that more offspring had a trait than those who did not, what could that tell you about
that trait?
The trait is probably dominant
28. If a pedigree showed that more male offspring had a trait than female offspring, what could that tell you
about the trait?
The trait is probably sex-linked
29. Black fur (B) is dominant to white fur (b) in rabbits. For the following crosses, show a Punnett square and the
possible genotypes and phenotypes for their offspring.
a.
A homozygous black rabbit with a white rabbit
B
B
Genotype: 100% Bb
b
Bb
Bb
Phenotype: All Black
b
Bb
Bb
B
b
b. A heterozygous black rabbit with a white rabbit
Genotype: 50%Bb 50% bb
b
Bb
bb
Phenotype: 50% Black 50% white
b
Bb
bb
30. Black fur (B) is dominant to white fur (b) in rabbits. Long ears (L) are dominant over short ears (l). For the
following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring.
a.
Two rabbits heterozygous for both fur color and ear length
Genotype:
1BBLL: 2BBll; 1BBll: 2BbLL: 4BbLl;
2Bbll; 1bbLL; 2bbLl: 1bbll
Phenotype:
9 Black fur Long ears:
BL
Bl
bL
bl
BL
BBLL
BBLl
BbLL
BbLl
Bl
BBLl
BBll
BbLl
Bbll
bL
BbLL
BbLl
bbLL
bbLl
bl
BbLl
Bbll
bbLl
bbll
3 Black fur Short ears
3 White fur Long ears
1 White fur Short ears
b. A homozygous black fur, long eared rabbit with a white, short eared rabbit
Genotype:
All BbLl
Phenotype:
All Black fur Long ears:
BL
BL
BL
BL
bl
BbLl
BbLl
BbLl
BbLl
bl
BbLl
BbLl
BbLl
BbLl
bl
BbLl
BbLl
BbLl
BbLl
bl
BbLl
BbLl
BbLl
BbLl
31. Hemophilia is a sex-linked trait. The trait for hemophilia is reccesive (h) to the normal allele (H). For the
following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring.
a.
A father with hemophilia crossed with a normal mother who is a carrier for the disease
Xh
Y
Females: 50% Normal, 50% hemophilia
XH
XHXh
XHY
Males: 50% Normal, 50% hemophilia
Xh
XhXh
XhY
XH
Y
b. A hemophiliac mother and a normal father.
Females: 100% Normal
Xh
XHXh
XhY
Males: 100% hemophilia
Xh
XHXh
XhY
32. For the following crosses, show a Punnett square and the possible genotypes and phenotypes for their
offspring.
a.
A man with type O blood and a female with type AB
Phenotype: 50% Type A, 50% Type B
i
i
IA
IAi
IAi
IB
IBi
IBi
b. A man with type B blood (whose mother is type O) and a woman with type AB
IB
i
Phenotype:
IA
IA IB
IAi
25% Type A, 50% Type B, 25% Type AB
IB
IB IB
IBi