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Case #7
Subject: Embryology
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
Medcloud™
Case #7
Subject: Embryology
The correct answer is E
At birth, a male has primordial germ cells in the testes that remain dormant until puberty, at
which time they differentiate into type A spermatogonia. At puberty, some type A spermatogonia
differentiate into type B spermatogonia and give rise to primary spermatocytes by undergoing
DNA replication.
Medcloud™
Case #11
Subject: Embryology
How much DNA does a primary spermatocyte contain?
A. 1N
B. 2N
C. 4N
D. 6N
E. 8N
Medcloud™
Case #11
Subject: Embryology
Medcloud™
Case #11
Subject: Embryology
The correct answer is C
Type B spermatogonia give rise to primary spermatocytes by undergoing DNA replication, thereby doubling the amount of DNA (2 x 2N = 4N) within the cell.
Medcloud™
Case #12
Subject: Embryology
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
Medcloud™
Case #12
Subject: Embryology
The correct answer is D
Synapsis (pairing of homologous chromosomes) is a unique event that occurs only during
meiosis I in the production of gametes. Synapsis is necessary so that crossing over, whereby
large segments of DNA are exchanged, can occur.
Medcloud™
Case #14
Subject: Embryology
Where do primordial germ cells initially develop?