Fertilisation and implantation — NEET & JEE Questions

Question 1 · difficulty L1 · recall

Where does fertilisation normally occur in the human female reproductive tract?

• A. Uterine fundus
• B. Cervix
• C. Ampullary-isthmic region of the oviduct
• D. Vagina

Question 2 · difficulty L2 · understanding

Twins are born to a family that lives next door to you. The twins are a boy and a girl. Which of the following must be true?

• A. They were conceived through in vitro fertilization.
• B. They have $75 \%$ identical genetic content.
• C. They are monozygotic twins.
• D. They are fraternal twins.

Question 3 · difficulty L2 · understanding

What is the immediate result of fusion between the male and female gametes?

• A. Release of hCG from the pituitary
• B. Formation of a haploid morula
• C. Implantation of the blastocyst
• D. Formation of a diploid zygote

Question 4 · difficulty L2 · understanding

In humans, fertilisation of the ovum by the sperm normally takes place in the

• A. uterus
• B. ampullary-isthmic junction of the fallopian tube
• C. cervix
• D. vagina

Question 5 · difficulty L3 · understanding

Receptors for sperm binding in mammals are present on :

• A. Zona pellucida
• B. Corona radiata
• C. Vitelline membrane
• D. Perivitelline space

Question 6 · difficulty L3 · application

Which stage normally implants into the uterine endometrium?

• A. Blastocyst
• B. Primary oocyte
• C. Morula immediately after fertilisation
• D. Spermatozoon

Question 7 · difficulty L3 · application

A sperm binds to the zona pellucida of an ovum and induces changes in the membrane that block the entry of additional sperms. What is the immediate next event within the ovum?

• A. The zygote undergoes cleavage
• B. The blastocyst forms
• C. The secondary oocyte completes the second meiotic division, forming the ootid and a second polar body
• D. The primary oocyte begins meiosis I

Question 8 · difficulty L3 · application

The mitotic divisions of the zygote as it moves through the isthmus of the oviduct produce 2, 4, 8 and 16 blastomeres. What is the 8-16 celled embryo called, and what does it become on further division?

• A. Blastocyst; it becomes a morula
• B. Gastrula; it becomes a blastocyst
• C. Ootid; it becomes a zygote
• D. Morula; it becomes a blastocyst with trophoblast and inner cell mass

Question 9 · difficulty L4 · analysis

A fertilised human egg undergoes normal cleavage but the trophoblast cannot attach to the endometrium. Which process fails most directly?

• A. Spermatogenesis
• B. Implantation
• C. Ovulation
• D. Formation of the male pronucleus

Question 10 · difficulty L4 · application

In a blastocyst, one group of cells attaches to the endometrium and another group gives rise to the embryo. Which option identifies them correctly and states what implantation involves?

• A. Trophoblast attaches to the endometrium and the inner cell mass differentiates into the embryo; the uterine cells divide rapidly and cover the blastocyst, which becomes embedded in the endometrium
• B. Inner cell mass attaches to the endometrium and the trophoblast forms the embryo; implantation is the attachment alone
• C. Both layers form the embryo; the endometrium is not involved
• D. The zona pellucida attaches to the endometrium; the trophoblast forms the placenta only