2n=16 is in a primary spermatocyte which is in metaphase of first meiotic division. What shall be the total number of chromatids in each of the secondary spermatocyte?
Secondary spermatocyte contains half the number of chromosomes i.e., 8. Each chromosome has 2 chromatids, therefore, 8 chromosomes will have 16 chromatids in all.
The second maturation division of the mammalian ovum occurs
During oogenesis, primary oocyte grows and completes- meiosis I (first maturation division) producing a large secondary oocyte and a small polar body. The secondary oocyte proceeds with meiosis II (second maturation division) but the division gets arrested at metaphase stage. It is in this stage of oocyte that the ovum is shed during ovulation. It passes into oviduct, where the cell cycle resumes only after the entry of sperm.
In humans, at the end end of the first meoitic division, the male germ cells differentiate into the
During embryonic development the primordial germ cells migrate to the testis where they become spermatogonia. At puberty the spermatogonia proliferate rapidly by mitosis. Some undergo growth phase to become primary spermatocytes that further undergo through meiotic division I to become secondary spermatocytes. After completion of meiotic division II the secondary spermatocytes produce spermatids which differentiate to form spermatozoa.
Which of the following options is correct?
The secondary oocyte is formed by the meiotic division of primary oocyte (2n), therefore, it is haploid. Primary spermatocyte is formed by the mitotic division of spermatogonium (2n), therefore it is diploid.
Consider the following statements each with two blanks.
(A) Seminiferous tubules produce (i) while Leydig's cells produce (ii).
(B) In females, urethra is small and conducts (iii) while in males it conducts urine and (iv).
(C) The process of formation of spermatozoa from spermatogonia is called (v) and the process of maturation of spermatids into spermatozoa is called (vi).
Which one of the following options, gives the correct fill ups for the respective blank numbers from (i) to (vi) in the statements?
Given below is an incomplete flow chart showing influence of hormones on gametogenesis in human females. Study it carefully and identify A, B, C and D.
Hypothalamus releases Gonadotropin releasing hormone (GnRH) that stimulates anterior pituitary to release FSH (follicle stimulating hormone) and LH (leuteinsing hormone). These hormones induce ovary to release estrogen and progesterone.
The principal tail piece of human sperm shows the microtubular arrangement of
The axial filament in the tail of human sperm has 9+2 microtubular arrangement like that of flagella and cilia.
The sperms undergo physiological maturation, acquiring increased motility and fertilizing capacity in
In the head of the epididymis, the sperms undergo physiological maturation, acquiring increased motility and fertilizing capacity.
Which one is released from the ovary?
Female gamete is released from the ovary in the secondary oocyte stage by rupturing the wall of the ovary.
At what stage of life is oogenesis initiated in a humanfemale?
Oogenesis is the process of formation of functional haploid ova from the diploid germinal cells in the ovary. Oogenesis begins during embryonic development but is completed only at puberty of the secondary oocyte with the sperm.
The given table shows differences between spermato genesis and spermiogenesis. Select the incorrect option.
Spermatogenesis involves conversion of a diploid structure (spermatogonia) into haploid structures (spermatozoa). Spermiogenesis changes a haploid structure (spermatid) into another haploid structure (spermatozoon).
The correct sequence of spermatogenetic stages leading to the formation of sperms in a mature human testis is
In human males, the primordial germ cells divide mitotically and produce spermatogonia. Some of the spermatogonia grow into large primary spermatocytes. Each primary spermatocyte undergoes first maturation division which is a reductional (meiotic) one. Thus, the primary spermatocyte divides into two haploid daughter cells called secondary spermatocytes. Each secondary spermatocyte now undergoes second maturation division which is a mitotic one. Thus, each secondary spermatocyte gives rise to two spermatids that undergo transformation to form two sperms. Overall, two secondary spermatocytes give rise to four sperms.
During oogenesis, each diploid , primary oocyte produces
In human females, certain cells in the germinal epithelium divide by mitosis to produce a large number of oogonia (diploid). The oogonia multiply by mitotic divisions to form primary oocytes (diploid). Each primary oocyte undergoes two maturation divisions. In the first meiotic division the primary oocyte divides into two very unequal haploid daughter cells- a large secondary oocyte and a small first polar body. In the second maturation division (mitotic), the first polar body may divide to form two second polar bodies and the secondary oocyte divides to form two unequal daughter cells, a large ootid and a small polar body. The ootid grows into a haploid ovum. Thus, from one oogonium, one ovum and three polar bodies are formed.
So, the correct answer is 'One functional egg and three polar bodies'.
The middle piece of the sperm contains
The middle piece of sperm contains mitochondria coiled around the axial filament. They provide energy for the movement of the sperm.
Immediately after ovulation, the mammalian egg is covered by a membrane known as
Immediately after ovulation, the layer that forms around the ovum is called corona radiata. It is formed by the granulosa cells of cumulus oophorus. Corona radiata probably increases the likelihood that the ovum will be picked up in the uterine tube.
A cross section at the midpoint of the middle piece of a human sperm will show
The middle piece is the tubular structure in which mitochondria are spirally arranged and it also has the beginning part of the flagellum. The sperm tail or the flagellum is based upon unique 9+2 arrangement
Spermatogenesis is induced by
FSH acts on the Sertoli cells and stimulate secretion of some factors which help in the process of spermatogenesis.
How many sperms are formed from 4 primary spermatocytes?
One primary spermatocyte produces four spermatozoa, therefore, four primary spermatocytes will produce 16
Which of the following contains the actual genetic part of a sperm?
Head of the sperm is anterior, broad, flattened and oval structure. It consists of two parts, posterior large nucleus and anterior small cap-like acrosome. The nucleus consists of condensed DNA and basic proteins.
Acrosome is a type of
Acrosome, a cap like structure present at the tip of the sperm, is a lysosome like organelle derived from Golgi apparatus. It contains a variety of digestive enzymes that break the egg membrane during penetration of the sperm into the egg.