Lecture 3

Question 1

List the process of fertilization

Answer 1

motile sperm passes through corona radiate of the oocyte, penetration of zona pellucid by sperm cell and entry of sperm nuclei into oocyte, nucleus of sperm swells and forms male pronucleus within the cytoplasm, second oocyte completes its division and becomes mature oocyte and second polar body

Question 2

In what phase is the secondary oocyte arrested in during fertilization?

Answer 2

meiosis II metaphase II

Question 3

when the nucleus of the oocyte swells, what does it become?

Answer 3

female pronucleus

Question 4

when is the end of the fertilization process?

Answer 4

when membranes of male and female pronuclei disappear and their replicated chromosomes are arranged in center for mitotic division

Question 5

when is the egg known as a zygote?

Answer 5

at the end of the fertilization process

Question 6

what happens before the female pronucleus forms?

Answer 6

the ovum completes its second meiotic division and second polar body extruded in to extra vitaline space

Question 7

What are the results of fertilization?

Answer 7

restoration of 46 chromosomes, mingling of paternal and maternal genetic material (variation in species), determination of sex of embryo

Question 8

What are the three things occurring during week one - post conception

Answer 8

-zygote divides repeatedly by mitotic division moving down the fallopian tube towards the uterus, mass of cells known as morula are formed, fluid seeps into the solid mass forming a cavity at which point the morula is known as a blastocyst

Question 9

By what day does the morula reach the uterine cavity?

Answer 9

4th day

Question 10

For how many days does the blastocyst float into uterine cavity

Answer 10

three days

Question 11

By what day does the blastocyst get implanted in the uterine wall and start to grow?

Answer 11

10th day

Question 12

What does the inner cell mass divide into?

Answer 12

epiblast and hypoblast

Question 13

Name the two fluid filled sacs

Answer 13

amniotic sac- from epiblast

yolk sac- from hypoblast

Question 14

What is the bilaminar embryonic disc?

Answer 14

area of contact, gives rise to the whole body

Question 15

When is the fetal period?

Answer 15

Week 9-38 after conception (or until birth)

Question 16

What are the major fetal events?

Answer 16

organs grow in size and complexity

Question 17

Homeobox genes (Hox genes)

Answer 17

involved in regulation of patterns of anatomical development- they specify the anterior-posterior axis and segment identify organisms during early embryonic development

Question 18

define dysjunction

Answer 18

the separation of chromatids in second step of meiosis

Question 19

define non dysjunction

Answer 19

non separation of any one pair of chromosomes- may result in one gamete containing 24 and another containing 22 chromosomes

Question 20

WHat will be the result of fertilization taking place in non dysjunction gametes?

Answer 20

the offspring will have one extra chromosome (47 total) or one less chromosome (45 total)

Question 21

where is non dysjunction fertilization seen on the karyotype?

Answer 21

pair 22 or sex pair (23)

Question 22

WHat is the disease called when non dysjunction occurs on 23rd pair producing XXY?

Answer 22

trisomy 23 or Klinefelter’s Syndrome

Question 23

If dysjunction produces only an X on the 23rd chromosome, what is the disease called?

Answer 23

Monosomy 23 or Turner’s Syndrome

Question 24

What is another name for Trisomy 21?

Answer 24

Down Syndrome- non dysjunction occurring on the 21st pair

Question 25

Characteristics of someone with Klinefelter’s syndrome?

Answer 25

individual will be male, long legs, slightly enlarged breasts, small testes, sterility and chronic pulmonary disease

Question 26

Characteristics of someone with Turner’s Syndrome

Answer 26

immaturity of sex organs causing sterility, webbed neck, short stature, cardiovascular and learning defects

Question 27

How can Turner’s Syndrome be treated?

Answer 27

Hormone therapy using estrogen and growth hormones

Question 28

What is the most common genetic disorder?

Answer 28

Down syndrome- 1 in 600 births

Question 29

What are the characteristics of someone with Down Syndrome?

Answer 29

learning difficulties, multiple bone structural abnormalities, thick tongue, single transverse palmar crease and cardiac abnormalities

Question 30

What is hydratidiform mole (vesicular mole)?

Answer 30

when the embryonic mass do not differentiate in to different organ systems and tropoblastic cells proliferate in to a disorganized mass of cells– cells are known as this

Question 31

In which two ways can twin pregnancy occur?

Answer 31

When two ova released and fertilized by two sperms result in twin pregnancy (dizygotic)
THe embryoblast divides into two masses and develops into two embryos (monozygotic)

Question 32

Which type of twin is more common?

Answer 32

dizygotic- can be same sex or different sexes

Question 33

What is another name for dizygotic twins?

Answer 33

fraternal twins/non identical twins

Question 34

In what ethnicity are twins most common?

Answer 34

certain African populations (1 in 20)

Question 35

What is it called when the inner cell mass divides in to cell masses and develop into two embryos with one placenta?

Answer 35

embryonic premordia

Question 36

What twin birth is hereditary and which is random?

Answer 36

dizygotic is hereditary and monozygotic is random