General Embryology

Question 1

OMI means

Answer 1

Oocyte Maturation Inhibitor

Question 2

Trisomy 21 is also known as

Answer 2

Down Syndrome

Question 3

The only monosomy compatible with life is

Answer 3

Turner Syndrome which is a monosomy of the X chromosome

Question 4

Angelman’s syndrome occurs due to

Answer 4

Microdeletion on maternal chromosome 15 (15q11-15q13)

Question 5

Prader Willi’s syndrome occurs due to

Answer 5

Microdeletion on paternal chromosome 15 (15q11-15q13)

Question 6

Oogenesis is

Answer 6

The differentiation of oogonium to mature oocyte

Question 7

Spermatogenesis can be divided into three phases, namely

Answer 7

Spermatocytosis
Spermatidogenesis
Spermiogenesis

Question 8

When do the Primordial Germ cells reach the gonads in a developing embryo

Answer 8

By the end of the fifth week

Question 9

Chromosomal abnormalities such as Trisomy occurs mostly in which chromosomes

Answer 9

Chromosomes 8, 9 ,13, 18 and 21, but mostly in chromosome 21

Question 10

When does Oogenesis and Spermatogenesis begin

Answer 10

Oogenesis begins before birth while Spermatogenesis begins at puberty

Question 11

The four major groups or families of Paracrine signaling factors or growth and differentiation factors (GDFs) are

Answer 11

1. Fibroblast Growth Factors (FGF)
2. Wingless and Int-1 (WNT)
3. Hedgehog
4. Transforming growth factor-B (TGFBeta)

Question 12

What are the the three phases of fertilization?

Answer 12

1. Penetration of Corona Radiata
2. Penetration of Zona Pellucida
3. Fusion of oocyte and sperm cell membranes

Question 13

What is the main cause of infertility in men

Answer 13

Low sperm count

Question 14

What is the main cause of infertility in women

Answer 14

Occlusion of uterine (fallopian) tube which can be caused by Pelvic Inflammatory diseases such as gonorrhea

Question 15

Corpus luteum originated from

Answer 15

Theca interna (ovarian stromal cells) and Granulosa cells.

Question 16

When does the corpus luteum degenerate during pregnancy

Answer 16

Approximately by the beginning of the fourth month when the placenta has fully developed

Question 17

What are the results of fertilization

Answer 17

1. Restoration of diploid number of chromosomes
2. Determination of chromosomal sex
3. Initiation of cleavage

Question 18

The three stages the uterine endometrium passes through during the menstrual cycle

Answer 18

1. Follicular or Proliferative phase
2. Secretory or Progestational phase
3. Menstrual phase (Gravid phase during pregnancy)

Question 19

Approximately what day is the morula formed

Answer 19

By the third day

Question 20

When does implantation begin

Answer 20

By the 6th day

Question 21

When does ovulation occur during the menstrual cycle

Answer 21

Approximately at the 14th day (mid cycle) in a 28 day cycle

Question 22

Why is the second week of development known as the week of 2’s

Answer 22

1. The trophoblast differentiates into two: Syncytiotrophoblast and Cytotrophoblast
2. The embryoblast differentiates into two layers: Epiblast and Hypoblast (Bilaminar germ disc)
3. The extraembryonic mesoderm splits into two: extraembryonic splanchnic (visceral) mesoderm and extraembryonic somatic (parietal) mesoderm
4. Formation of two cavities: Amniotic cavity and yolk sac

Question 23

Why is the conceptus not rejected by immunological response of the mother’s body upon it is a foreign body

Answer 23

This is not fully understood but recent evidences show it is due to
1. Secretion of Immunosuppressive molecules such as cytokines and proteins
2. The expression of unrecognizable antigens of major histocompatibility complex
which protect the foetus from rejection

Question 24

What condition cause one to have high plasma human chorionic gonadotropin (hCG) and placental tissue but absence of an embryo

Answer 24

Hydatidiform mole which can eventually cause invasive mole or choriocarcinoma

Question 25

A pregnant woman who has missed two menstrual periods but complains of intense abdominal pain likely has

Answer 25

Ectopic pregnancy in the uterine (fallopian) tube

Question 26

The frequency of ectopic pregnancy and Down syndrome increases with maternal age over

Answer 26

35 years

Question 27

What week of gestation is most prone to Teratogenic insult

Answer 27

Week 3 which is the week of gastrulation

Question 28

What day does gastrulation occur

Answer 28

On the 15th - 16th day

Question 29

What genes are responsible for sidedness

Answer 29

Nodal and PITX2 ( which is a transcription factor and master gene for left-sidedness)

Question 30

What gene is probably responsible for establishing the right side

Answer 30

Snail

Question 31

What condition occurs due to insufficient mesoderm in caudal regions and abnormal gastrulation

Answer 31

Caudal dysgenesis or Sirenomelia

Question 32

What birth defect can be caused due to alcohol intake on or around the third week of development

Answer 32

Fetal Alcohol syndrome which results in intellectual disability and abnormal facies

Question 33

The presence of a mass around the sacral region of a foetus indicates

Answer 33

A sacrococcygeal teratoma which occurs mostly due to remnants of the primitive streak and occurs three times more in female foetuses

Question 34

The study of embryological origins and causes of defects is

Answer 34

Teratology

Question 35

The period from the third to eighth week is known as

Answer 35

Embryonic period or Period of organogenesis

Question 36

SHH means

Answer 36

Sonic Hedgehog which is one of the familes of Paracrine signaling factors

Question 37

The period from the end of the embryonic period to birth is

Answer 37

Fetal period

Question 38

The absence of one or more limbs is called

Answer 38

Amelia which was caused by the drug Thalidomide in 1961

Question 39

ZPA means

Answer 39

Zone of Polarizing Activity

Question 40

The absence of long bones is called

Answer 40

Phocomelia