Fundamental tibbiyot kursi

Nazorat keyslar to’plami
Prefertilization Events
Directions: Each of the numbered items or incomplete statements in this section is followed by answers or by completions of the statement. Select the one lettered answer or completion that is best in each case.

1.Which of the following is a major characteristic of meiosis I?
(A) Splitting of the centromere
(B) Pairing of homologous chromosomes
(C) Reducing the amount of DNA to 1N
(D) Achieving the diploid number of chromosomes
(E) Producing primordial germ cells
2. A normal somatic cell contains a total of 46 chromosomes. What is the normal complement of chromosomes found in a sperm?
(A) 22 autosomes plus a sex chromosome
(B) 23 autosomes plus a sex chromosome
(C) 22 autosomes
(D) 23 autosomes
(E) 23 paired autosomes
3. Which of the following describes the number of chromosomes and amount of DNA in a gamete?
(A) 46 chromosomes, 1N
(B) 46 chromosomes, 2N
(C) 23 chromosomes, 1N
(D) 23 chromosomes, 2N
(E) 23 chromosomes, 4N
4. Which of the following chromosome compositions in a sperm normally results in the production of a genetic female if fertilization occurs?
(A) 23 homologous pairs of chromosomes
(B) 22 homologous pairs of chromosomes
(C) 23 autosomes plus an X chromosome
(D) 22 autosomes plus a Y chromosome
(E) 22 autosomes plus an X chromosome
5. In the process of meiosis, DNA replication of each chromosome occurs thereby forming a structure consisting of two sister chromatids attached to a single centromere. What is this structure?
(A) A duplicated chromosome
(B) Two chromosomes
(C) A synapsed chromosome
(D) A crossover chromosome
(E) A homologous pair
6. All primary oocytes are formed by
(A) week 4 of embryonic life
(B) month 5 of fetal life
(C) birth
(D) month 5 of infancy
(E) puberty
7. When does formation of primary spermatocytes begin?
(A) During week 4 of embryonic life
(B) During month 5 of fetal life
(C) At birth
(D) During month 5 of infancy
(E) At puberty
8. In the production of female gametes, which of the following cells can remain dormant for 12 to 40 years?
(A) Primordial germ cell
(B) Primary oocyte
(C) Secondary oocyte
(D) First polar body
(E) Second polar body
9. In the production of male gametes, which of the following cells remains dormant for 12 years?
(A) Primordial germ cell
(B) Primary spermatocyte
(C) Secondary spermatocyte
(D) Spermatid
(E) Sperm
10. Approximately how many sperm are ejaculated by a normal fertile male during sexual intercourse?
(A) 10 million
(B) 20 million
(C) 35 million
(D) 100 million
(E) 350 million
11. A young woman enters puberty with approximately 40,000 primary oocytes in her ovary. About how many of these primary oocytes will be ovulated over the entire reproductive life of the woman?
(A) 40,000
(B) 35,000
(C) 480
(D) 48
(E) 12
12. Fetal sex can be diagnosed by noting the presence or absence of the Barr body in cells obtained from the amniotic fluid. What is the etiology of the Barr body?
(A) Inactivation of both X chromosomes
(B) Inactivation of homologous chromosomes
(C) Inactivation of one Y chromosome
(D) Inactivation of one X chromosome
(E) Inactivation of one chromatid
13. How much DNA does a primary spermatocyte contain?
(A) 1N
(B) 2N
(C) 4N
(D) 6N
(E) 8N
14. During meiosis, pairing of homologous chromosomes occurs, which permits large segments of DNA to be exchanged. What is this process called?
(A) Synapsis
(B) Nondisjunction
(C) Alignment
(D) Crossing over
(E) Disjunction