High School Biology : Understanding Spermatogenesis

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #233 : Cell Biology

How many chromosomes and how many chromatids are contained in one spermatid?

Possible Answers:

46 chromosomes composed of 23 chromatids

46 chromosomes composed of 92 chromatids

46 chromosomes composed of 46 chromatids

23 chromosomes composed of 23 chromatids

23 chromosomes composed of 46 chromatids

Correct answer:

23 chromosomes composed of 23 chromatids

Explanation:

A spermatid is the final product of spermatogenesis. It is a haploid cell, meaning it has only one copy of each allele (one of each chromosome instead of two). Normal diploid cells have two copies of each chromosome, for a total of 46. Spermatids have half this number, for a total of 23 chromosomes. Each chromosome is composed of only a single chromatid following division, for a total of 23 chromatids.

When the zygote is formed during the fusion of the sperm and egg cells, the final cell is diploid, containing 46 chromosomes (23 from each gamete).

An outline of spermatogenesis is given here for further understanding.

Spermatogenesis Timeline:

1) Spermatogonium (46 chromosomes, 92 chromatids)

- Has a pair of each chromosome, and each individual chromosome has two chromatids.

- Undergoes mitosis (normal cell division) to produce a primary speratocyte.

2) Primary spermatocyte (46 chromosomes, 46 chromatids)

- Has a pair of each chromosome and each individual chromosome has one chromatid.

- Then replicates its DNA, resulting in 46 chromosomes with 92 chromatids.

- Then undergoes meiosis I (homologous chromosome pairs separate), producing two secondary spermatocytes.

3) Secondary spermatocytes (23 chromosomes, 46 chromatids)

- Has one of each chromosome, and each individual chromosome has two chromatids.

- Each secondart spermatocyte undergoes meiosis II (chromatids of each chromosome separate, similar to mitosis), producing a total of four spermatids.

4) Spermatids (23 chromosomes, 23 chromatids).

- Has one of each chromosome, and each individual chromosome has one chromatid

 

Example Question #234 : Cell Biology

Spermatogenesis is __________.

Possible Answers:

the formation of genetically identical spermatids via mitosis

the formation of genetically nonidentical spermatids via meiosis

a process that occurs in both human males and females

the formation of genetically nonidentical spermatids via mitosis

the formation of genetically identical spermatids via meiosis

Correct answer:

the formation of genetically nonidentical spermatids via meiosis

Explanation:

Spermatogenesis occurs only in human males (in the testes), not in females. It is the process by which spermatids are formed via meiosis. The process of meiosis contributes to genetic diversity. This is why siblings are not identical to each other or to their parents.

Example Question #235 : Cell Biology

Where does spermatogenesis occur?

Possible Answers:

Ampulla

Lumen

Seminal vesicle

Prostate gland

Seminiferous tubules

Correct answer:

Seminiferous tubules

Explanation:

Spermatogenesis is the process of producing the male gametes, spermatozoa (sperm). The spermatogonia in the seminiferous tubules of the testes mature into spermatocytes, which undergo meiosis to form spermatozoa. The spermatozoa complete their maturation process in the epididymas, then they are ready to enter the vas deferens before ejaculation. Lumen is a general term that means "an opening." Although spermatogenesis does occur in the lumen of the seminiferous tubules, the term lumen is too broad and is not the best answer. An ampulla is a general term that, in anatomy, means "the dilated end of a duct." There is an ampulla of the vas deferens before it enters the prostate gland, but spermatogenesis does not occur there. The prostate gland produces a milky, alkaline solution that comprises about 30% of semen. The seminal vesicles are glands that produce the majority of the solution that will become semen. Note the difference between semen (fluid) and sperm (cells).

Example Question #236 : Cell Biology

Often, in animals that sexually reproduce, hormones or chemicals that are present during normal gametogenesis are not strictly necessary, allowing for a chance of reproduction even under difficult environmental circumstances.

Which of the following hormones/proteins, while normally present, may not be strictly necessary for the process of spermatogenesis in the human male?

Possible Answers:

Inhibin

Testosterone

Androgen-binding protein

Estradiol

Follicle Stimulating Hormone

Correct answer:

Follicle Stimulating Hormone

Explanation:

Follicle-stimulating hormone may help to sequester testosterone in the testes (the Sertoli cells can perform the same function by releasing androgen-binding protein), but the only hormone needed to maintain spermatogenesis is testosterone itself. FSH is not needed for in-vitro maturation of spermatozoa, and thus cannot be said to be required inside the body for the process of spermatogenesis.

Example Question #1 : Understanding Spermatogenesis

What is the primary role of androgen-binding protein (ABP) in the process of spermatogenesis?

Possible Answers:

Maintains the blood-testis barrier to prevent the body's immune system from attacking and destroying the developing spermatocytes.

Regulates spermatid adhesion on the side of the blood-testis barrier towards the lumen.

Increases fertility in the reproductive tract by concentration of testosterone near the developing gametes.

Creates a pH-neutral environment for the rapid production of follicle stimulating hormone (FSH) in the testes.

Stimulates phagocytosis of leftover cytoplasm from spermiogenesis, cleaning the testicular fluid of dead cellular material.

Correct answer:

Increases fertility in the reproductive tract by concentration of testosterone near the developing gametes.

Explanation:

A very high level of testosterone (15-70 times greater than in the blood) is required for the initiation and maintenance of spermatogenesis, and androgen-binding protein's most direct role is ensuring this high concentration of testosterone by preventing absorption of testosterone back into the body across the blood-testis barrier.

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