Test Questions Flashcards
In mammals, cells of the early embryo are induced by signals of neighboring cells to become primordial germ cells. Which of the following provides a signal that initiates the specification of primordial germ cells in the laboratory mouse?
A. BMP
B. Sry
C. Hox
D. bicoid
E. Rspo1
A) BMP
Although many genes are involved, the SRY gene (for sex-determining region of the Y chromosome), is important for determining sex in humans. SRY is the key switch and individuals with SRY develop into males, while those without it develop into females. The SRY protein is detected in the bipotential gonad of XY individuals at about 42 days. It contains an HMG (high mobility group) box of 79 amino acids that binds to specific regions of DNA, causing the DNA molecule to bend. This bending is thought to make these regions more accessible to other transcription-regulating proteins which ultimately bring about the differentiation of the gonadal cells.
Which of the following is true with regard to sex determination and development?
A. Wnt4 expression is high during sex determination in the male
B. the Mullerian duct gives rise to male internal genitalia
C. In the mouse, PGCs are induced in the proximal epiblast by signals from the extra-embryonic ectoderm and once specified, migrate to the gonads.
D. P granules are initially clustered in the anterior portion of the Drosophilia egg
E. PGCs are quiescent (in a state or period of inactivity or dormancy) and do not divide on their migratory route through the gut and into the developing gonads.
C. In the mouse, PGCs are induced in the proximal epiblast by signals from the extra-embryonic ectoderm and once specified, migrate to the gonads.
- How much genetic material is present in a cell during anaphase I compared to a cell during metaphase?
A. twice as much
B. the same amount
C. one-half as much
D. four times as much
E. none of the above
B. the same amount
- Mendel’s law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene. Independent assortment is a feature of meiosis, but not mitosis.
Which of the following is true with regard to both mitosis and meiosis?
A. at the competition of both, there are two daughter cells
B. both have a stage where tetrads are present
C. at the completion of both, 4 cells are generated
D. the number of new chromosome combinations produced by both mitosis and meiosis is 2n
E. none of the above
E. none of the above
- During oogenesis, when does the completion of meiosis I and the onset meiosis II occur?
A. After the primary oocyte stage
B. Before the secondary oocyte is arrested at metaphase of meiosis II
C. When a sperm penetrates the secondary oocyte
D. Both A and B
E. A, B and C
D. Both A and B
- In humans, puberty is triggered by hormones from the hypothalamus and pituitary gland. Which of the following is (are) a false statement(s)?
A. LH and FSH can be detected in the blood
B. GnRH is produced by the anterior pituitary gland
C. An elevated estradiol level is required to trigger the LH surge that triggers ovulation
D. Both A and C are false
E. None are false. All are true.
B. GnRH is produced by the anterior pituitary gland
- During the secretory phase of the menstrual cycle ____
A. Progesterone and estradiol are secreted by the corpus luteum
B. The endometrium is thick
C. The levels of LH and FSH are relatively low
D. A woman is not usually menstruating
E. All of the above
E. All of the above
- As you know, the testes are composed largely of seminiferous tubules: coiled tubes, the walls of which contain cells that produce sperm. Seminiferous tubules may constitute up to 90 percent of the testis. The tubule walls consist of a multilayered germinal epithelium containing spermatogenic cells and Sertoli cells (nutritive support cells). During the process of spermatogenesis_____
A. Secondary spermatocytes undergo meiosis I to produce early spermatids
B. Primary spermatocytes are diploid
C. Spermatogonium reproduce by continuous meiotic divisions to yield haploid sperm
D. Both A and B
E. None of the above
B. Primary spermatocytes are diploid
Which of the following is not correctly matched?
A. Epididymis: structure where testicular spermatozoa mature
B. Leydig cell: has a receptor for LH
C. Acrosome: part of sperm head that has enzymes which facilitate egg penetration
D. Inhibin: secreted by Leydig cells; inhibits secretion of follicle stimulating hormone from the anterior pituitary.
E. Both A and B are not correctly matched
D. Inhibin: secreted by Leydig cells; inhibits secretion of follicle stimulating hormone from the anterior pituitary.
Ovulation during the menstrual cycle is triggered by the LH surge. What is the cause of this LH surge?
A. Increased levels of GnRH
B. Increased levels of estrogen
C. Increased levels of progesterone
D. Increased levels of FSH
E. Both Band C
B. Increased levels of estrogen
During the luteal/secretory phase of the menstrual cycle, the corpus luteum forms and secretes progesterone. What are the effects of this progesterone secretion?
A. Onset of menses with shedding of the endometrial lining and negative feedback of FSH/LH
B. Maintenance of the endometrial lining and positive feedback of FSH/LH
C. Onset of menses with shedding of the endometrial lining and positive feedback of FSH/LH
D. Maintenance of the endometrial lining and negative feedback of FSH/LH
E. None of the above
D. Maintenance of the endometrial lining and negative feedback of FSH/LH
The menstrual cycle is regulated by many hormones. What is the cause of the onset of menses?
A. Degeneration of the corpus luteum and subsequent drop in progesterone levels
B. Formation of the corpus luteum from the follicle and subsequent increase in progesterone and estrogen levels
C. LH surge that triggers ovulation
D. Negative feedback of progesterone on FSH and LH
E. Both B and D
A. Degeneration of the corpus luteum and subsequent drop in progesterone levels
Contraception aims to prevent pregnancy. Analogs of progesterone can be used as a form of contraception as either a pill or injection. What are the effects of progesterone that prevent pregnancy?
A. Suppression of FSH/LH secretion
B. Triggering the onset of menses
C. Thickening of the cervical mucus
D. A and C
E. None of the above
D. A and C
A patient has a rare condition in which they lack the 5-alpha reductase enzyme. The 5-alpha reductase enzyme is important for converting testosterone to DHT. Which of the following are the expected findings of this condition?
A. Ambiguous genitalia
B. Coronary artery disease
C. Low testosterone
D. Kidney failure
E. Diabetes
A. Ambiguous genitalia
The zona pellucida is important in the process of fertilization because it binds to sperm receptors, takes part in induction of the acrosome reaction, and becomes a block to polyspermy. The sea urchin also has blocks to polyspermy. Which of the following is involved with the slow block to polyspermy?
A. Intracellular calcium release
B. The release of resact
C. Transient membrane depolarization
D. The association of bindin with the vitelline membrane
E. None of the above
A. Intracellular calcium release
During gastrulation____
A. The blastocoel cavity is formed
B. The chick embryo has structures such as the epiblast, the hypoblast and the primitive streak
C. The human embryo is a hollow ball of cells
D. There is the formation of 4 primary cell layers (ectoderm, mesoderm, neuroderm and endoderm) is occurring
E. None of the above
B. The chick embryo has structures such as the epiblast, the hypoblast and the primitive streak
What is the purpose of mucopolysaccharides during the slow block to polyspermy?
A. facilitate the formation of an osmotic gradient which enables formation of the fertilization envelope
B. clip off sperm binding receptors to enable the formation of the fertilization envelope
C. mucopolysaccharides comprise the acrosomal process, which penetrates the jelly coat
D. to crosslink macromolecules of the vitelline membrane
E. to modify the extracellular matrix of the egg to help block sperm entry
A. facilitate the formation of an osmotic gradient which enables formation of the fertilization envelope
The yolk of the frog egg
A. prevents gastrulation
B. is concentrated at the animal pole
C. impedes the formation of the primitive streak
D. supports the high rate of cleavage at the animal pole compared to the vegetal pole
E. contains P granules that differentiate into gametes
D. supports the high rate of cleavage at the animal pole compared to the vegetal pole
Which of the following pairs is mismatched?
A. endoderm - bone
B. mesoderm - muscle
C. ectoderm - skin
D. neuroectoderm - nervous system
E. neural crest cells - peripheral nervous system, parts of teeth, skull
A. endoderm - bone
In a frog embryo, gastrulation
A. produces a blastocoel displaced into the animal hemisphere.
B. occurs along the primitive streak in the animal hemisphere.
C. is impossible because of the large amount of yolk in the ovum.
D. proceeds by involution as cells roll over the lip of the blastopore.
E. occurs within the inner cell mass that is embedded in the large amount of yolk.
D. proceeds by involution as cells roll over the lip of the blastopore.
In frogs, the archenteron eventually develops into the ___ and the blastopore becomes the ___
A. digestive tract; mouth
B. future ectoderm; anus
C. dorsal lip; primitive streak
D. neural tube; mouth
E. digestive tract; anus
E. digestive tract; anus
- At the time of implantation, the human embryo is called a
A. blastocyst.
B. gastrula.
C. fetus.
D. trophoblast
E. zygote.
A. blastocyst.
