Gametogenesis Questions in English

(B) The correct answer is $B$.
$Acrosome$ is a cap-like structure located at the anterior end of the sperm head.
It contains various hydrolytic enzymes,collectively known as sperm lysins.
During the process of fertilisation,these enzymes are released to dissolve the protective layers of the ovum (such as the $zona$ $pellucida$),which facilitates the entry of the sperm into the egg.
Failure of the acrosome reaction prevents the sperm from penetrating the egg,which is a common cause of male infertility.

(A) The correct sequence is: $spermatogonia \rightarrow spermatocyte \rightarrow spermatid \rightarrow sperms$.
Spermatogenesis is the process of formation of haploid spermatozoa (sperms) from diploid spermatogonia inside the testes of the male.
At sexual maturity, the undifferentiated primordial germ cells divide by mitosis to produce a large number of spermatogonia.
Each spermatogonium grows into a larger primary spermatocyte.
The primary spermatocyte undergoes the first meiotic division (reductional division) to form two haploid secondary spermatocytes.
Each secondary spermatocyte undergoes the second meiotic division to form two haploid spermatids.
Finally, the transformation of spermatids into mature spermatozoa is called spermiogenesis.

(D) The correct answer is $D$.
During spermatogenesis,the $spermatogonia$ $(2n)$ undergo mitosis to increase in number.
Some $spermatogonia$ grow and differentiate into $primary$ $spermatocytes$ $(2n)$.
These $primary$ $spermatocytes$ undergo the first meiotic division $(Meiosis-I)$,which is a reductional division,to form two haploid $(n)$ cells known as $secondary$ $spermatocytes$.
Following this,the $secondary$ $spermatocytes$ undergo the second meiotic division $(Meiosis-II)$ to produce $spermatids$ $(n)$,which eventually differentiate into $spermatozoa$.

(D) The correct answer is $D$. After ovulation,the ruptured Graafian follicle transforms into a temporary endocrine gland known as the corpus luteum.
During the menstrual cycle,the Graafian follicle protects the developing oocyte. Upon ovulation,the secondary oocyte is released,and the remaining follicular cells (zona granulosa and theca cells) undergo luteinization to form the corpus luteum.
The corpus luteum secretes large amounts of progesterone,which is essential for maintaining the endometrium during pregnancy,and also produces some estrogen.

(B) $(b) :$ Sertoli cells are located within the germinal epithelium of the seminiferous tubules.
These cells provide nourishment to the developing spermatozoa.
They facilitate the process of spermatogenesis by supporting the differentiation of spermatogonia into mature sperms.
These cells are primarily regulated by the Follicle Stimulating Hormone $(FSH)$,which is secreted by the anterior pituitary gland.

(B) Sexual reproduction involves the formation and fusion of gametes.
In humans,gametes (sperm and ovum) are produced through the process of meiosis.
Meiosis is a reductional division that reduces the chromosome number to half.
Therefore,human gametes are haploid $(n)$,containing $23$ chromosomes each.
Upon fertilization,the fusion of these two haploid gametes results in a diploid $(2n)$ zygote,which contains $46$ chromosomes.

(C) For normal fertility,it is essential that at least $60\%$ of all sperms must have normal shape and size.
Furthermore,at least $40\%$ of them must show vigorous motility to successfully reach the ovum for fertilization.
Therefore,the correct values are $60$ and $40$ respectively.

(B) The correct answer is $B$.
$1$. Seminal plasma along with sperms constitutes the semen. This is a true statement.
$2$. The nucleus in the sperm is haploid $(n)$,not diploid $(2n)$,because it is a gamete formed after meiosis. Thus,this statement is false.
$3$. During a single coitus,the human male ejaculates about $200$ to $300$ million sperms. This is a true statement.
$4$. The entire body of the sperm is enveloped by a plasma membrane. This is a true statement.

(C) The process of releasing the secondary oocyte (ovum) from the mature Graafian follicle into the fallopian tube is known as $Ovulation$.
$Menarche$ refers to the onset of the first menstrual cycle at puberty.
$Menopause$ refers to the permanent cessation of the menstrual cycle.
$Implantation$ is the process where the blastocyst attaches to the uterine wall.

(C) Spermiogenesis is the process of transformation of spermatids into mature spermatozoa. This process is primarily regulated by $FSH$ (Follicle Stimulating Hormone). $FSH$ acts on the Sertoli cells and stimulates the secretion of some factors which help in the process of spermiogenesis.

(A) The growth and maturation of the Graafian follicle in the ovary are primarily regulated by gonadotropins secreted by the anterior pituitary gland.
$FSH$ (Follicle Stimulating Hormone) stimulates the growth and development of ovarian follicles.
$LH$ (Luteinizing Hormone) is responsible for the final maturation of the Graafian follicle and triggers ovulation.
Therefore,the combined action of $FSH$ and $LH$ controls the growth and maturation of the Graafian follicle.

(B) The $Antrum$ is a fluid-filled cavity found within the $Graafian$ $follicle$ (the mature ovarian follicle). As the follicle matures,the follicular cells secrete fluid,which accumulates to form this central cavity,known as the $Antrum$.

(C) Spermatogenesis is the process of the formation of sperms from immature germ cells.
This process occurs within the testes, specifically inside the $Seminiferous$ $\text{tubules}$.
The germinal epithelium lining the $Seminiferous$ $\text{tubules}$ contains spermatogonia, which undergo meiosis to produce spermatozoa.
Therefore, the correct site where spermatogenesis begins is the $Seminiferous$ $\text{tubules}$.

(B) The process of oogenesis involves the formation of female gametes.
During the maturation of the primary oocyte,it undergoes the first meiotic division $(Meiosis-I)$.
This division is unequal,resulting in the formation of a large haploid cell called the secondary oocyte and a small haploid cell called the first polar body.
Therefore,the first polar body is produced during the formation of the secondary oocyte.

(B) In the process of spermatogenesis,the spermatogonia $(2n)$ undergo mitosis to increase their number. Some of these spermatogonia differentiate into primary spermatocytes $(2n)$. Both spermatogonia and primary spermatocytes are diploid $(2n)$. Secondary spermatocytes $(n)$,spermatids $(n)$,and sperm $(n)$ are haploid cells formed after meiotic divisions.

(B) The process of releasing the secondary oocyte (ovum) from the mature Graafian follicle into the fallopian tube is known as $Ovulation$.
$Menarche$ refers to the onset of the first menstrual cycle.
$Menopause$ refers to the cessation of the menstrual cycle.
$Parturition$ refers to the process of childbirth.

(B) In the structure of a human sperm,the middle piece contains numerous mitochondria.
These mitochondria are arranged in a spiral pattern,often referred to as the $Nebelkern$.
The primary function of these mitochondria is to produce $ATP$ (adenosine triphosphate) through aerobic respiration.
This $ATP$ provides the necessary energy for the motility of the sperm tail,which is essential for the sperm to swim through the female reproductive tract to reach the ovum.

(D) During a single ejaculation,a healthy human male releases approximately $200$ to $300$ million sperms.
For normal fertility,at least $60$ percent of sperms must have normal shape and size,and at least $40$ percent of them must show vigorous motility.

(B) The process of release of sperms from the seminiferous tubules is known as $Spermiation$.
$Spermiogenesis$ is the process of transformation of spermatids into spermatozoa.
$Oogenesis$ is the process of formation of a mature female gamete.
Therefore,the correct option is $B$.

(B) During spermatogenesis,the primary spermatocytes undergo the first meiotic division (meiosis-$I$) to form two haploid secondary spermatocytes.
These secondary spermatocytes then undergo the second meiotic division (meiosis-$II$),which is an equational division,to produce four equal,haploid spermatids.
Therefore,the correct answer is haploid spermatids.

(A) In human females,the primary oocyte undergoes meiosis-$I$ to form two unequal cells: a large haploid secondary oocyte and a small first polar body.
Although the primary oocyte is diploid $(2n = 46)$,the process of meiosis-$I$ is a reductional division.
Therefore,the secondary oocyte contains half the number of chromosomes compared to the primary oocyte.
Thus,the number of chromosomes in the secondary oocyte is $23$.

(C) Spermatogenesis is the process of formation of spermatozoa from immature germ cells.
$1$. The process begins with the multiplication phase where Spermatogonia $(a)$ undergo mitosis.
$2$. These cells then grow to become Primary spermatocytes $(c)$.
$3$. Primary spermatocytes undergo Meiosis-$I$ to form two haploid Secondary spermatocytes $(b)$.
$4$. Secondary spermatocytes undergo Meiosis-$II$ to form Spermatids $(d)$.
Therefore,the correct sequence is $a \rightarrow c \rightarrow b \rightarrow d$.

(B) $Spermiogenesis$ is the process of transformation of non-motile,spherical $spermatids$ into mature,motile $spermatozoa$ (sperm).
During this process,the $spermatid$ undergoes significant morphological changes,including the formation of the $acrosome$,condensation of the nucleus,and development of the flagellum.
Option $A$ is incorrect because the tail is formed,not disintegrated.
Option $C$ describes $spermiogenesis$ as the production of $spermatids$,which is actually the result of $spermiogenesis$ (the process is $spermiogenesis$,the result is $spermatozoa$).
Option $D$ refers to the process of $meiosis-II$.

(A) During oogenesis,the primary oocyte undergoes meiosis-$I$ to form two unequal cells: a large secondary oocyte and a small first polar body.
Since meiosis-$I$ is a reductional division,the chromosome number is halved.
Therefore,the primary oocyte $(2n)$ produces a secondary oocyte that is haploid $(n)$.

(C) The process of fertilization involves the penetration of the sperm into the ovum.
This process is facilitated by enzymes,such as hyaluronidase and acrosin,which are collectively known as sperm lysins.
These enzymes are stored in the acrosome,a cap-like structure present at the anterior end of the sperm head.
Therefore,the acrosome is essential for the sperm to penetrate the egg's protective layers (zona pellucida).

(A) Primary spermatocytes are formed from spermatogonia through the process of mitosis during the growth phase of spermatogenesis.
Since spermatogonia are diploid $(2n)$ cells,they contain $46$ chromosomes.
Primary spermatocytes are also diploid $(2n)$ cells because they have not yet undergone meiosis.
Therefore,primary spermatocytes contain $46$ chromosomes.

(C) Sertoli cells are specialized somatic cells found within the $seminiferous$ $\text{tubules}$ of the testes.
They play a crucial role in spermatogenesis by providing structural and nutritional support to the developing germ cells (spermatids/spermatozoa).
They also form the blood-testis barrier and secrete substances like androgen-binding protein $(ABP)$ and inhibin.

(A) Based on the structure of a human sperm:
$A$ points to the plasma membrane that envelops the entire body of the sperm.
$B$ points to the acrosome,which is a cap-like structure filled with enzymes that help in fertilization.
$C$ points to the nucleus,which contains the haploid chromosomal material.
$D$ points to the middle piece,which contains numerous mitochondria that provide energy for sperm motility.
$E$ points to the neck,which connects the head to the middle piece.
Therefore,the correct identification is $A$ - Plasma membrane,$B$ - Acrosome,$C$ - Nucleus containing chromosomal material,$D$ - Middle piece,$E$ - Neck.

(B) Spermatogenesis is the process of formation of spermatozoa from spermatogonia.
$1$. Spermatogonia $(2n)$ undergo repeated mitotic divisions to increase their number.
$2$. Some spermatogonia (primary spermatocytes) undergo meiosis ($I$ and $II$) to form haploid spermatids $(n)$.
$3$. These spermatids then undergo spermiogenesis (a process of differentiation) to transform into spermatozoa $(n)$.
Since the question asks for the process by which spermatogonia produce spermatozoa,meiosis is the critical reductional division involved in the formation of haploid gametes.

(A) $1$. During spermatogenesis,the primary spermatocyte undergoes meiosis-$I$ to form two haploid secondary spermatocytes.
$2$. Each secondary spermatocyte then undergoes meiosis-$II$ to form two spermatids. Thus,the statement $A$ is correct.
$3$. The transformation of non-motile spermatids into mature,motile spermatozoa is known as spermiogenesis. Thus,the statement $R$ is correct.
$4$. Since both statements are scientifically accurate,the correct option is $A$ and $R$ are correct.

(B) - The acrosome is a cap-like structure present in the anterior part of the sperm head,which contains enzymes necessary for fertilization. It does not contain mitochondria. Therefore,statement $A$ is incorrect.
$R$ - The middle piece of the sperm is packed with numerous mitochondria,which provide energy for the motility of the sperm. It does not contain enzymes. Therefore,statement $R$ is also incorrect.
Thus,both $A$ and $R$ are incorrect.

(D) $FSH$ (Follicle Stimulating Hormone) acts on the $Sertoli$ cells in the testes.
These cells provide nourishment to the developing germ cells and secrete factors that facilitate the process of spermiogenesis,which is the transformation of spermatids into spermatozoa.

(D) Oogenesis is the process of formation of a mature female gamete.
It begins with the multiplication phase where oogonia are formed.
These oogonia undergo differentiation to form primary oocytes.
The primary oocyte undergoes meiosis-$I$ to form a secondary oocyte and a first polar body.
The secondary oocyte then undergoes meiosis-$II$ to form an ovum and a second polar body.
Therefore,the correct sequence is: Oogonia $\rightarrow$ primary oocyte $\rightarrow$ secondary oocyte $\rightarrow$ ovum.

(B) The process of releasing sperm from the seminiferous tubules into the lumen is known as $Spermiation$.
$Spermatogenesis$ is the overall process of formation of sperm from spermatogonia.
$Spermiogenesis$ is the transformation of spermatids into mature spermatozoa.
$Oogenesis$ is the process of formation of female gametes (ova) in the ovaries.

(B) The corpus luteum is an endocrine structure in the ovary that secretes progesterone, which is a steroid hormone.
Steroid hormones are synthesized from cholesterol.
Cells that are specialized for the synthesis of steroid hormones require an extensive $Smooth \text{ } Endoplasmic \text{ } Reticulum$ $(SER)$ because the enzymes responsible for steroid biosynthesis are located within the $SER$ membrane.
Therefore, corpus luteum cells contain a high abundance of $SER$ to facilitate the production of progesterone.

(D) The pituitary gland secretes gonadotropins,which include $LH$ (Luteinizing Hormone) and $FSH$ (Follicle Stimulating Hormone).
$FSH$ acts on the Sertoli cells present in the testes.
It stimulates the secretion of some factors which help in the process of spermiogenesis.
Therefore,$FSH$ is the hormone responsible for the regulation of Sertoli cells.

(A) During oogenesis, the primary oocyte undergoes meiosis-$I$ to form a secondary oocyte and a first polar body. The secondary oocyte then begins meiosis-$II$ but gets arrested at the metaphase-$II$ stage. It is in this $Secondary$ oocyte stage that the ovum is released from the ovary during ovulation.

(C) During spermatogenesis,the primary spermatocyte undergoes meiosis-$I$ to form two haploid secondary spermatocytes.
Each secondary spermatocyte then undergoes meiosis-$II$ to produce two spermatids.
These spermatids eventually differentiate into spermatozoa.
Therefore,one secondary spermatocyte produces $2$ spermatozoa.

(C) In humans,the sex chromosome constitution of a female is $44 + XX$. During oogenesis,the primary oocyte undergoes meiosis to form a secondary oocyte and a polar body. The secondary oocyte is released during ovulation. Since the female has only $X$ chromosomes,the ovum produced after meiosis will always contain $22$ autosomes and one $X$ chromosome. Therefore,a freshly released human ovum contains one $X$ chromosome.

(A) The secondary oocyte remains arrested in the metaphase-$II$ stage of meiosis-$II$. The entry of the sperm into the secondary oocyte triggers the completion of meiosis-$II$. This process results in the formation of a large haploid ovum (ootid) and a small second polar body. Therefore,the extrusion of the second polar body occurs after the entry of the sperm but before the fusion of the male and female pronuclei (completion of fertilization).

(B) The acrosome is a cap-like structure present on the anterior portion of the sperm head.
It is derived from the Golgi apparatus and contains hydrolytic enzymes,collectively known as sperm lysins (e.g.,hyaluronidase and acrosin).
During fertilization,the acrosome undergoes the acrosome reaction,which involves the release of these lysins.
These enzymes help the sperm to penetrate the protective layers of the ovum (zona pellucida and corona radiata),thereby facilitating fertilization.

(A) The human egg (ovum) is classified as $Alecithal$ or $Microlecithal$ because it contains a very negligible or almost no amount of yolk. Since the human embryo receives nutrition from the mother through the placenta,the egg does not require a large amount of stored yolk.

(A) After the process of ovulation, the ruptured Graafian follicle undergoes a transformation process called luteinization.
Under the influence of Luteinizing Hormone $(LH)$, the remaining follicular cells (granulosa and theca cells) differentiate into a glandular structure known as the $Corpus$ luteum.
The $Corpus$ luteum acts as an endocrine gland and secretes large amounts of progesterone, which is essential for maintaining the endometrium during a potential pregnancy.

(B) The human sperm is composed of a head,neck,middle piece,and tail.
The middle piece contains numerous mitochondria,which are arranged in a spiral pattern (often called the $Nebelkern$).
These mitochondria provide the energy required for the movement of the tail,which facilitates sperm motility.
While the neck contains the proximal and distal centrioles,the middle piece is specifically characterized by the presence of mitochondria.

(A) The process of spermatogenesis involves several stages.
$1$. Spermatogonia $(2n)$ undergo mitosis to increase in number.
$2$. These cells then transform into primary spermatocytes $(2n)$.
$3$. The primary spermatocyte undergoes the first meiotic division (meiosis-$I$),which is a reductional division,resulting in the formation of two haploid $(n)$ cells known as secondary spermatocytes.
$4$. Therefore,after the first meiotic division,the primary spermatocyte differentiates into secondary spermatocytes.

(B) The human sperm consists of a head,neck,middle piece,and tail. The head contains a haploid nucleus and is covered by a cap-like structure called the acrosome.
The acrosome is derived from the Golgi apparatus and contains hydrolytic enzymes collectively known as sperm lysins (e.g.,hyaluronidase).
These enzymes are responsible for dissolving the protective layers of the ovum (corona radiata and zona pellucida),thereby facilitating the entry of the sperm into the egg during the process of fertilization.

(D) The viability of human sperm is typically $24$ to $48$ hours in the female reproductive tract. Sperm are highly sensitive to the $pH$ of the environment; they are immobilized in acidic conditions and show increased motility in alkaline environments. Sperm viability is indeed assessed by their motility,as non-motile sperm are generally considered non-viable. The statement that sperm must be concentrated in a thick suspension is incorrect,as sperm are typically transported in a fluid medium (semen) and do not require a 'thick suspension' to maintain viability; in fact,high concentration without proper fluid volume can be detrimental.