Embryology 1

Question 1

Name the 2 types of chromosomes.

Answer 1

44 Autosomes and 2 Sex chromosomes

Question 2

Define a chromosome.

Answer 2

A long, threadlike structure composed DNA carry genetic material

Question 3

What is a chromatid?

Answer 3

Each of the 2 threadlike structures divide into which chromosome divide during cell division

Question 4

What is the centromere?

Answer 4

Region chromosomes where microtubules attach via kinetochore

Question 5

Heterozygous vs Homozygous allele?

Answer 5

Homo - 2 alles for both blue

Hetero - 1 allele for blue and 1 allele for brown

Question 6

What are the 2 types of mutations and their differences?

Answer 6

Structural and Chromosomal Numerical mutations
-Structural - caused by radiation or chemical mutagens
- deletions, insertions, translocations, duplications of NUCLEOTIDE BASES
-Chromosomal numerical - due to non-disjunction during meiosis (usually 1st meiotic
division)
- e.g trisomy 21

Question 7

Briefly discuss spermatogenesis.

Answer 7

1. 1 Spermatogonium undergo mitosis to form a primary spermatocyte diploid (2n)
2. Meiosis 1: 2 secondary spermatocytes haploid (n)
3. Meiosis 2: 4 spermatids formed (immobile)

Question 8

Briefly discuss oogenesis

Answer 8

1. Women before born have developed all primary oocyte
2. Stay in prophase 1 till puberty
3. Primary oocytes continue first meiotic division each month
4. As primary oocyte divides: 1 daughter cell receives most cytoplasm and half chromosomes - secondary oocyte and the other becomes - polar body (degenerates and dies)
5. Secondary oocyte undergoes 2nd meiotic division to form ovum (STEP 4 repeated)

Question 9

Why do oocytes form polar bodies

Answer 9

Conserve as much cytoplasm as possible while reducing genome.

Question 10

What is the chance of fertilization?

Answer 10

• 300 million sperm ejaculation
  -survive 5 days
  -1 oocyte per cycle
  -24-48 hrs survival
  25% chnace 48hrs before ovulation
  -5% rest cycle
  1 in 20 for healthy couple

Question 11

What is an acrosomal reaction?

Answer 11

Enable penetration sperm head into zona pellucida

Question 12

What is capacitation?

Answer 12

AKA maturation sperm
Membrane sperm hyperpolarized to increase metabolic activity
happens before acrosomal reaction

Question 13

What occurs in the early period of human embryo development?

Answer 13

WEEK 1-2

a) Fertilisation = Zygote
b) Cleavage of zygote = Blastula

Question 14

What occurs during the embryological period?

Answer 14

WEEK 3-8

a) Gastrulation = gastrula
b) Notogenesis = notochord
c) Organogenesis = adult body form
d) Neurulation - neural tube

Question 14

What occurs during the embryological period?

Answer 14

WEEK 3-8

a) Gastrulation = gastrula
b) Notogenesis = notochord
c) Organogenesis = adult body form
d) Neurulation - neural tube

Question 15

What is the last stage of human embryo development?

Answer 15

WEEK 9-38

a) Fetal period

Question 16

What of the spermatocyte and oocyte fuse during fertilisation to form a zygote?

Answer 16

Plasmalemma

Question 17

What results in blastomeres?

Answer 17

Repeated mitiotic divisions of zygote

Question 18

Difference between cleavage and mitotic cell division?

Answer 18

CLEAVAGE:

• aka cytokinesis
• division of cytoplasms of daughter cells
• occur animal cells only
• cells smaller each cleavage

MITOTIC CELL DIVISION

• division parent cell into daughter nuclei
• animal and plant cells
• nr cells increase (no enlargement mass size zygote)

Question 19

What is the inner cell mass?

Answer 19

Embryoblast

Question 20

What is the ring outer cell mass?

Answer 20

Trophoblast

Question 21

16 cell stage is called?

Answer 21

Morula

Question 22

When does implanataion occur?

Answer 22

6-8 days after fertilisation

Question 23

What happens at the same time as implanataion?

Answer 23

Cleavage of zygote

Question 24

What happens to the trophoblast during implantation?

Answer 24

1. It start to proliferate
2. Differentitates into cytotrophoblast (cellular)and syncytiotrophoblast (multinucealted mass no cell boundaries - produces enzymes erode waste material)