Week 1 Development

Question 0

How does the sperm find the oocyte?

Answer 0

chemotaxis toward oocyte attractants help guide sperm to the secondary oocyte

Question 1

Where does fertilization usually occur?

Answer 1

occurs in the ampulla of the oviduct

Question 2

What is the length of the window of opportunity for fertilization?

Answer 2

up to 24hrs

Question 3

Penetration of corona radiata is facilitated by what enzyme?

Answer 3

Hyaluronidase released from acrosome

-capacitated sperm readily move through corona radiata cells

Question 4

Penetration of zona pellucida is facilitated by what enzyme?

Answer 4

Acrosin causes lysis of thee zona pellucida to create a path

Question 5

What is the zona reaction?

- What is the outcome

Answer 5

Zona reaction are the changes in the zona pellucida after the first sperm penetrates
- makes zona pellucida impenetrable by additional sperm

Question 6

What of sperm enters oocyte during the fusion of sperm and secondary oocyte plasma membranes?

Answer 6

sperm contents

Question 7

What happens when secondary oocyte completes meiosis II?

Answer 7

• mature ovum and secondary polar body form

- ovum nuclear material decondenses somewhat to become the female pronucleus

Question 8

How does the male pronucleus form?

Answer 8

forms as the sperm nucleus enlarges somewhat

Question 9

How is the male pronucleus distinguishable from the female pronucleus?

Answer 9

They are morphologically indistinguishable

Question 10

After the formation of the male pronucleus, what happens to thee rest of the sperm?

Answer 10

the other sperm contents degenerate

Question 11

What is an Ootid?

Answer 11

An Ootid is the cell at the point containing the 2 pronuclei

Question 12

What happens to the DNA in both pronuclei?

Answer 12

It is duplicated to form double-strand chromosomes

Question 13

What happens when the male and female pronuclei fuse?

Answer 13

creation of a zygote

Question 14

what is the ploidy number of the zygote?

Answer 14

4N

Question 15

What is the chromosomal content of the zygote?

Answer 15

Genotypical sex is established as 46 XX, or 46XY

Question 16

How are the follicles stimulated to grow in In Vitro fertilization?

Answer 16

development of multiple mature ovarian follicles is stimulated chemically

Question 17

How are the oocytes harvested in in vitro fert.?

Answer 17

Mature secondary oocytes are harvested laparoscopically just prior to ovulation
- Or by ultrasound guided needle aspiration via the vaginal canal

Question 18

Mature secondary oocytes are mixed with what after being harvested?

Answer 18

They are mixed with capacitated sperm in a Petri dish

Question 19

How long does the development progress in vitro?

Answer 19

fertilization and early zygote cleavage are monitored microscopically for 3-5 days

Question 20

How many embryos are typically transferred?

Answer 20

1-2 embryos are transferred by catheter into uterine lumen

Question 21

In what position is the patient told to remain in to allow for implantation?

Answer 21

Supine for several hours

Question 22

What happens to the rest of the embryos in in vitro fert.?

Answer 22

remaining viable embryos are cryopreserved in liquid nitrogen for later use

Question 23

Gamete intrafallopian transfer involves what?

Answer 23

Placing harvested oocytes and capacitated sperm in the ampulla of the oviduct

Question 24

What is done in surrogacy?

Answer 24

Placing in vitro fertilized oocytes of one woman into uterus of a different woman

Question 25

What occurs in intracytoplasmic sperm injection?

Answer 25

single sperm injected directly into cytoplasm of mature oocyte - used if male sperm count is low

Question 26

When does the first division of the zygote occur?

Answer 26

30hrs after fertilization

Question 27

Where is the zygote during the repeated mitotic divisions?

Answer 27

occurs as zygote is moving through oviduct towards uterus | - still surrounded by thick zona pellucida

Question 28

What are blastomeres?

Answer 28

embryonic cells formed by zygote cleavage | - get progressively smaller with each mitotic division

Question 29

How does the zygote change in size?

Answer 29

Gets progressively smaller with each mitotic division (forming blastomeres)

Question 30

What is the process of compaction?

Answer 30

- occurs after the 8-cell stage | - Increases cell contact and is mediated by cell surface adhesion glycoproteins

Question 31

Why is compaction a necessary step?

Answer 31

its a necessary step prior to forming certain cells that will become embyro

Question 32

What is the composition and appearance of a morula?

Answer 32

many mitotically divided cells (12-32 blastomeres) in the inside and zona pellucida on the outside

Question 33

When does a morula form?

Answer 33

Forms ~3 days after fertilization

Question 34

Which blastomeres of the morula will form the: 1) embryo 2) embryonic part of the placenta

Answer 34

1) internal cells will become the embryo | 2) outer cells will become the embryonic part of the placenta

Question 35

What is the chromosomal condition referred to as mosaic?

Answer 35

results from nondisjunction in early mitotic cleavage of zygote

Question 36

What are the results of mosaic?

Answer 36

results in 2+ cell lines with different chromosomal complements

Question 37

Is Mosaic a permanent condition?

Answer 37

These may be a lost or persist as development continues

Question 38

Where is the morula on day 4?

Answer 38

enters the uterine cavity

Question 39

How does the blastocyst differ from the morula?

Answer 39

Blastocyst is the next stage of development in which the morula has developed a fluid-filled cavity

Question 40

What is the blastocoele?

Answer 40

The fluid filled cavity of the blastocyst

Question 41

Where does the fluid in the blastocyst come from?

Answer 41

Fluid diffuses through the zona pellucida into the blastocoele from the uterine cavity

Question 42

What is the trophoblast?

Answer 42

thin outershell of blastomeres

Question 43

What are the 2 groups that the blastomeres are separated into?

Answer 43

1) Trophoblast | 2) Embryoblast

Question 44

What will the Trophoblast develop into?

Answer 44

Develops into the embryonic portion of placenta

Question 45

What is the embryoblast? Embryonic pole?

Answer 45

- Embryoblast is a cluster of cells located on inner surface in one region of trophoblast (will develop into embryo) - The region of blastocyst containing the embryoblast is the embryonic pole

Question 46

When does the zona pellucida disappear?

Answer 46

Day 5

Question 47

What happens to the zygote after Day 5

Answer 47

The blastocyst will finally start increasing in size

Question 48

Will the blastocyst implant immediately?

Answer 48

The blastocyst will float freely in the uterine cavity for up to 2 days

Question 49

How do monozygotic twins develop?

Answer 49

from one zygote

Question 50

how common are monozygotic twins?

Answer 50

~25% of all twins

Question 51

When does twinning like monozygotic occur?

Answer 51

twinning usually occurs in week 1 with division of the embryoblast in blastocyst

Question 52

What is the genotype and phenotype of the monozygotic twins?

Answer 52

same sex, genetically identical, very similar physical appearance

Question 53

How many physical differences in monozygotic twins occur?

Answer 53

Physical differences may result from varied placental blood supply

Question 54

How do dizygotic twins develop?

Answer 54

Develop from 2 ova fertilized by 2 sperm in the same cycle

Question 55

How common do dizygotic twins occur?

Answer 55

~75% of all twins

Question 56

When does twinning like dizygotic occur?

Answer 56

hereditary tendency - recurrence in families is approx 3x the general population

Question 57

What is the phenotype and genotype of dizygotic twins?

Answer 57

may be same sex or different sex (fraternal twins) | - no more genetically similar than other brothers/sisters

Question 58

How do Conjoined monozygotic twins develop?

Answer 58

due to incomplete separation of the embryonic disk

Question 59

What is craniopagus?

Answer 59

joined at the head

Question 60

What is thoracopagus?

Answer 60

joined at the anterior thorax

Question 61

How are the unions structured in conjoined monozygotic twins?

Answer 61

Unions may be skin only or involve other tissues as well

Question 62

How are embryonic stem cells harvested?

Answer 62

Derived from embryoblast cells

Question 63

What are embryonic stem cells potential?

Answer 63

pluripotent - can form virtually any cell or tissue type

Question 64

What are the ethical considerations for stem cells?

Answer 64

obtained from embryos produced by in vitro fertilization | - limit the availability of cells from these sources

Question 65

What are adult stem cells?

Answer 65

multipotent - restricted in their availability to form only certain cells or tissue types

Question 66

What are the disadvantages to working with adult stem cells?

Answer 66

difficult to isolate and they have a low mitotic index

Question 67

Therapeutic cloning is also known as?

Answer 67

somatic cell nuclear transfer

Question 68

How does therapeutic cloning work?

Answer 68

- insert nucleus of adult skin cell into an enucleated oocyte - oocyte is stimulated to differentiate into a blastocyst to provide embryonic stem cells

Question 69

What are the advantages of therapeutic cloning?

Answer 69

stem cells are genetically identical to recipient and no fertilization is involved