week 14- Human Genetics

Question 1

1. Characteristics of X-linked recessive disorders include which of the following?

A) All daughters of affected fathers are carriers.
B) Boys and girls are equally affected.
C) The son of a carrier mother has a 25% chance of being affected.
D) Affected fathers transmit the gene to all of their sons.

Answer 1

*A) All daughters of affected fathers are carriers.

Question 2

2. A foetus is most vulnerable to environmental teratogens during

A) birth.
B) conception.
C) the first trimester.
D) the last trimester.

Answer 2

*C) the first trimester.

Question 3

3. The normal human genome contains

A) 23 chromosomes.
B) 22 autosomal and 2 sex chromosomes.
C) 23 pairs of autosomal chromosomes.
D) 44 autosomal and 2 sex chromosomes.

Answer 3

*D) 44 autosomal and 2 sex chromosomes.

Question 4

4. Males are more likely than females to be affected by

A) X-linked disorders.
B) autosomal dominant disorders.
C) autosomal recessive disorders.
D) chromosomal nondisjunction disorders.

Answer 4

*A) X-linked disorders.

Question 5

5. Which of the following terms refers to the outwardly apparent physical and biochemical attributes of an individual?

A) Genotype
B) Phenotype
C) Chromatid
D) Chromosome

Answer 5

*B) Phenotype

Question 6

6. Genetic diseases that follow predictable patterns of inheritance usually affect

A) chromosomal structure.
B) chromosomal number.
C) single genes.
D) sex chromosomes.

Answer 6

*C) single genes.

Question 7

7. The various forms of any one gene are called

A) homologous.
B) homozygous.
C) heterozygous.
D) alleles.

Answer 7

*D) alleles.

Question 8

8. A factor associated with risk of Down’s syndrome is

A) family history of heritable diseases.
B) maternal age.
C) maternal alcohol intake.
D) paternal age.

Answer 8

*B) maternal age.

Question 9

9. Duchenne muscular dystrophy (DMD) is a classic example of

A) an autosomal dominant condition
B) an autosomal recessive condition.
C) an X-linked recessive condition.
D) a Y-linked dominant condition.

Answer 9

*C) an X-linked recessive condition.

Question 10

10. Which of the following chromosomal abnormalities has been linked with Down’s syndrome?

A) Translocation
B) Inversion
C) Deletion
D) Duplication

Answer 10

*A) Translocation

Question 11

11.  If a patient has a recessive trait, which of the following is the genotype of this patient?	
A)   aa      
B)  AA
C)  Aa
D)  aA

Answer 11

*A) aa

Question 12

12. Paired chromosomes are called
A) homologous.     
B) homozygous.
C) heterozygous.
D) autosomes.
E) alleles.

Answer 12

*A) homologous.

Question 13

13. Chromosomes that are not sex chromosomes are called
A) homologous.
B) homozygous.
C) heterozygous.
D) autosomes.     
E) alleles.

Answer 13

*D) autosomes.

Question 14

14. The various forms of any one gene are called
A) homologous.
B) homozygous.
C) heterozygous.
D) autosomes.
E) alleles.

Answer 14

*E) alleles.

Question 15

15. If an individual carries a pair of alleles that are the same, they are \_\_\_\_\_ for the trait.
A) homologous
B) homozygous     
C) heterozygous
D) autosomous
E) polygenic

Answer 15

*B) homozygous

Question 16

16. If an individual carries two different alleles for the same trait, they are
A) homologous.
B) homozygous.
C) heterozygous.     
D) autosomous.
E) polygenic.

Answer 16

*C) heterozygous

Question 17

17. In simple inheritance, phenotypic characters are determined, or controlled, by
    A) a single pair of alleles.
    B) multiple alleles.
    C) the action of a single gene.
    D) regulator genes on a chromosome other than the one that has the structural genes.
    E) the genes on the Y chromosome.

Answer 17

*A) a single pair of alleles.

Question 18

18. In polygenic inheritance, phenotypic characters are
    A) determined by a single pair of alleles.
    B) determined by multiple alleles.
    C) determined by the action of a single gene.
    D) always controlled by genes on the same chromosome.
    E) determined by the genes on the Y chromosome.

Answer 18

*B) determined by multiple alleles.

Question 19

19. If “A” stands for the dominant gene that prevents albinism and “a” stands for the recessive albinism trait, then an individual with the genotype of “aa” will express:
    A. albinism and will be a carrier.
    B. albinism and will not be a carrier.
    C. normal pigmentation and will be a carrier.
    D. normal pigmentation and will not be a carrier.

Answer 19

• A). albinism and will be a carrier.

Question 20

20.   An individual possessing the sex chromosome combination “XY” is genetically:
A.	a male.     
B.	a female.
C.	both.
D.	neither.

Answer 20

• A). a male.

Question 21

21. If an individual has only an X chromosome (“XO”), then that person is genetically:
    A. male.
    B. female.
    C. neither male nor female.
    D. The condition of “XO” can never occur.

Answer 21

*B). female

Question 22

22. The sickle cell/malaria relationship demonstrates the concept in medical genetics that “disease” genes:
    A. are always codominant.
    B. are never dominant.
    C. often provide some biological advantage for a human population in certain circumstances.
    D. never provide a biological advantage for human populations.

Answer 22

• C). often provide some biological advantage for a human population in certain circumstances.

Question 23

23.  Red-green color blindness shows X-linked recessive inheritance. Assume “X” is normal, “X1” is recessive for the trait, and “Y” is normal. Then, an individual with the genotype “XX1” will be a:
A.	normal female and a carrier.     
B.	color-blind male.
C.	normal female and not a carrier.
D.	normal male.

Answer 23

• A). normal female and a carrier.

Question 24

24. The condition called trisomy results from a(n):
    A. mistake in mitosis called nondisjunction.
    B. mistake in meiosis called nondisjunction.
    C. abnormality in a single gene.
    D. genetic predisposition.

Answer 24

*B). mistake in meiosis called nondisjunction.

Question 25

``` 25. A group of symptoms called Down syndrome results from: A. trisomy 15. B. trisomy 19. C. trisomy 21. D. trisomy 23. ```

Answer 25

* C). trisomy 21.

Question 26

``` 26. The syndrome that results from the genotype “XXY” is: A. Turner. B. Klinefelter. C. Down. D. Parkinson. ```

Answer 26

* B). Klinefelter.

Question 27

``` 27. A chart that illustrates genetic relationships in a family over several generations is called a: A. Punnett square. B. pedigree. C. genetic grid. D. karyotype. ```

Answer 27

*B). pedigree.

Question 28

``` 28. The genetic code is transmitted to offspring in discrete, independent units that are called: A. chromosomes. B. genes. C. gametes. D. nucleosomes. ```

Answer 28

*B). genes.

Question 29

``` 29. he entire collection of genetic material in each typical cell of the human body is called: A. diploid. B. haploid. C. nucleosomes. D. genome. ```

Answer 29

*D). genome.

Question 30

``` 30. If a karyotype found an X chromosome, a Y chromosome, and three 21st chromosomes, it would indicate a: A. female with Down syndrome. B. female with Turner syndrome. C. male with Klinefelter syndrome. D. male with Down syndrome. ```

Answer 30

* D). male with Down syndrome.