genetics test

Multiple Choice

Identify the choice that best completes the statement or answers the question.

____ 1. What is the probability that the offspring of a homozygous dominant individual and a homozygous recessive individual will exhibit the dominant phenotype?

a.	0.25	c.	0.66
b.	0.5	d.	1.0

____ 2. A genetic trait that appears in every generation of offspring is called

a.	dominant.	c.	recessive.
b.	phenotypic.	d.	superior.

____ 3. homozygous : heterozygous ::

a.	heterozygous : Bb	c.	BB : Bb
b.	probability : predicting chances	d.	homozygous : BB

____ 4. The phenotype of an organism

a.	represents its genetic composition.
b.	reflects all the traits that are actually expressed.
c.	occurs only in dominant pure organisms.
d.	cannot be seen.

____ 5. If an individual has two recessive alleles for the same trait, the individual is said to be

a.	homozygous for the trait.
b.	haploid for the trait.
c.	heterozygous for the trait.
d.	mutated.

____ 6. An individual heterozygous for a trait and an individual homozygous recessive for the trait are crossed and produce many offspring. These offspring are likely to be

a.	all the same genotype.
b.	of two different phenotypes.
c.	of three different phenotypes.
d.	all the same phenotype.

____ 7. Tallness (T) is dominant over shortness (t) in pea plants. Which of the following represents the genotype of a pea plant that is heterozygous for tallness?

a.	T	c.	Tt
b.	TT	d.	tt

In humans, having freckles (F) is dominant over not having freckles (f). The inheritance of these traits can be studied using a Punnett square similar to the one shown below.

____ 8. Refer to the illustration above. The genotype represented in box 1 in the Punnett square would

a.	be homozygous for freckles.
b.	have an extra freckles chromosome.
c.	be heterozygous for freckles.
d.	have freckles chromosomes.

____ 9. Refer to the illustration above. The genotype in box 3 of the Punnett square is

a.	FF.	c.	ff.
b.	Ff.	d.	None of the above

____ 10. How many different phenotypes can be produced by a pair of codominant alleles?

a.	1	c.	3
b.	2	d.	4

In rabbits, black fur (B) is dominant over brown fur (b). Consider the following cross between two rabbits.

____ 11. Refer to the illustration above. The device shown, which is used to determine the probable outcome of genetic crosses, is called a

a.	Mendelian box.	c.	genetic graph.
b.	Punnett square.	d.	phenotypic paradox.

____ 12. Refer to the illustration above. Both of the parents in the cross are

a.	black.
b.	brown.
c.	homozygous dominant.
d.	homozygous recessive.

____ 13. Refer to the illustration above. The phenotype of the offspring indicated by box 3 would be

a.	brown.
b.	black.
c.	a mixture of brown and black.
d.	The phenotype cannot be determined.

____ 14. Refer to the illustration above. The genotypic ratio of the F₁ generation would be

a.	1:1.	c.	1:3.
b.	3:1.	d.	1:2:1.

____ 15. What is the expected genotypic ratio resulting from a heterozygous ´ heterozygous monohybrid cross?

a.	1:2:1	c.	1:2
b.	1:3:1	d.	1:0

____ 16. codominance : both traits are displayed ::

a.	probability : crosses
b.	heterozygous : alleles are the same
c.	homozygous : alleles are the same
d.	Punnett square : chromosomes combine

____ 17. The X and Y chromosomes are called the

a.	extra chromosomes.
b.	phenotypes.
c.	sex chromosomes.
d.	All of the above

____ 18. Down syndrome : nondisjunction ::

a.	chromatids : centromere
b.	male : XY chromosomes
c.	haploid : mitosis
d.	meiosis : diploid

____ 19. female : XX ::

a.	female : gametes	c.	male : YY
b.	female : eggs	d.	male : XY

____ 20. Which of the following is the best explanation for the observation that females rarely get the disease hemophilia?

a.	Large quantities of male hormones are necessary in order for the allele carrying the disease to be expressed.
b.	Female fetuses that carry the allele for the disease die before birth.
c.	A female could get the disease only by having a mother who is a carrier and a father who has the disease. Since most males with the disease do not survive to reproductive age, this is an extremely unlikely event.
d.	A female could get the disease only by having parents who are both carriers of the disease. Because females cannot be carriers, this is an impossible event.

____ 21. A mutation caused by a piece of DNA breaking away from its chromosome and becoming attached to a nonhomologous chromosome is called

a.	deletion.	c.	inversion.
b.	duplication.	d.	translocation.

____ 22. A change in a gene due to damage or incorrect copying is called

a.	evolution.	c.	segregation.
b.	meiosis.	d.	a mutation.

____ 23. The effects of a mutation can be

a.	helpful.	c.	neutral.
b.	harmful.	d.	All of the above

____ 24. A diagram in which several generations of a family and the occurrence of certain genetic characteristics are shown is called a

a.	Punnett square.	c.	pedigree.
b.	monohybrid cross.	d.	family karyotype.

____ 25. Which of the following traits is controlled by multiple alleles in humans?

a.	sickle cell anemia	c.	Hemophilia
b.	blood type	d.	pattern baldness

____ 26. What would be the blood type of a person who inherited an A allele from one parent and an O allele from the other?

a.	type A	c.	type AB
b.	type B	d.	type O

____ 27. While studying several generations of a particular family, a geneticist observed that a certain disease was found equally in males and females and that all children who had the disease had parents who also had the disease. The gene coding for this disease is probably

a.	sex-linked recessive.
b.	sex-linked dominant.
c.	autosomal recessive.
d.	autosomal dominant.

____ 28. If both parents carry the recessive allele that causes cystic fibrosis, the chance that their child will develop the disease is

a.	one in two.	c.	two in five.
b.	one in four.	d.	100%.

____ 29. If a characteristic is sex-linked, it

a.	occurs most commonly in males.
b.	occurs only in females.
c.	can never occur in females.
d.	is always fatal.

____ 30. Since the allele for colorblindness is located on the X chromosome, colorblindness

a.	cannot be inherited.
b.	occurs only in adults.
c.	is sex-linked.
d.	None of the above

____ 31. The sex of an offspring is determined by

a.	the mother.	c.	both parents.
b.	the father.	d.	the offspring.

____ 32. If nondisjunction occurs,

a.	there will be too many gametes produced.
b.	no gametes will be produced.
c.	a gamete will receive too many or too few copies of a chromosome.
d.	mitosis cannot take place.

Completion

Complete each statement.

The partially completed pedigree below is for a family with a genetic disorder.

33. Refer to the illustration above. The father listed in the pedigree is most likely ____________________ for the trait.

34. Refer to the illustration above. Child 3 probably has a(n) _________________________ phenotype.