Given below are two statements. [2023]
One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Endometrium is necessary for implantation of blastocyst.
Reason (R): In the absence of fertilization, the corpus luteum degenerates that causes disintegration of endometrium.
In the light of the above statements, choose the correct answer from the options given below:
(A) is true but (R) is false.
A is false but (R) is true.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is not the correct explanation of (A).
(4)
The corpus luteum secretes large amount of progesterone which is essential for maintenance of the endometrium. This endometrium is necessary for implantation of the fertilised ovum (blastocyst). In the absence of fertilisation the corpus luteum degenerates. This causes disintegration of the endometrium leading to menstruation, marking a new cycle.
Receptors for sperm binding in mammals are present on [2021]
zona pellucida
corona radiata
vitelline membrane
perivitelline space
Extrusion of second polar body from egg occurs [2019, 1993]
simultaneously with first cleavage
after entry of sperm but before fertilisation
after fertilisation
before entry of sperm into ovum
(2)
Entry of sperm into the secondary oocyte induces the completion of the meiotic division of the secondary oocyte. The second meiotic division is unequal and results in the formation of a second polar body and a haploid ovum (ootid). Soon the haploid nucleus of the sperm and that of the ovum fuse together to form a diploid zygote.
Capacitation occurs in [2017]
epididymis
vas deferens
female reproductive tract
rete testis
(3)
The sperms in the female’s genital tract are made capable of fertilising the egg by secretions of the female genital tract. These secretions remove coating substances deposited on the surface of the sperms particularly those on the acrosome. Thus, the receptor sites on the acrosome are exposed and sperm becomes active to penetrate the egg. This phenomenon of sperm activation in mammals is known as capacitation.
Fertilisation in humans is practically feasible only if [2016]
the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the cervix
the sperms are transported into cervix within 48 hrs of release of ovum in uterus
the sperms are transported into vagina just after the release of ovum in fallopian tube
the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the fallopian tube.
(4)
The fusion of a haploid male gamete (sperm) and a haploid female gamete (ovum) to form a diploid zygote is called fertilisation. In human beings, it takes place in the ampullary-isthmic junction of the oviduct (fallopian tube).
In human females, meiosis-II is not completed until [2015]
uterine implantation
birth
puberty
fertilisation
(4)
In human beings, ovum is released from the ovary in the secondary oocyte stage. The maturation of secondary oocyte is completed in the mother’s oviduct (fallopian tube) usually after the sperm has entered the secondary oocyte for fertilisation. Entry of the sperm restarts the cell cycle breaking down MPF (M-phase promoting factor) and turning on APC (Anaphase promoting complex). Completion of meiosis II converts the secondary oocyte into a fertilised ovum (egg) or zygote (and also a second polar body).
Capacitation refers to changes in the [2015]
ovum after fertilisation
sperm after fertilisation
sperm before fertilisation
ovum before fertilisation
(3)
The sperms in the female’s genital tract are made capable of fertilising the egg by secretions of the female genital tract. These secretions remove coating substances deposited on the surface of the sperms particularly those on the acrosome. Thus, the receptor sites on the acrosome are exposed and sperm becomes active to penetrate the egg. This phenomenon of sperm activation in mammals is known as capacitation.
