Topic 12 - Cell growth

Question 1

What is a zygote?

Answer 1

A zygote is formed when a sperm nucleus fuses with an egg nucleus forming a diploid cell with its genome comprised of half the genetic info of each gamete.

Question 2

What is an embryo?

Answer 2

Entity produced by first mitotic division of zygote after fertilisation completion until 8th week of development.

Question 3

What is a foetus?

Answer 3

The foetus is 9 weeks after fertilisation, characterised by presence of all major body organs though not full developed.

Question 4

What is gastrulation?

Answer 4

Complex cell migration that reorganises inner cell mass of embryo blastocyst into three layers (germ layers) comprised of stem cells that can differentiate or give rise to the various cell types forming mature organism.

Question 5

What is a blastocyst?

Answer 5

A blastocyst is a hollow fluid filled structure with an inner cell mass and outer layer of cells.
Occurs after 5 days of development.
Inner = germ layers that later form cells of mature organism.
Outer = embryonic placenta contribution.

Question 6

What are stem cells?

Answer 6

Cells that have the capacity to reproduce themselves and then differentiate into either one or different types of cells. For example in the bone marrow, a type of cell that reproduces and differentiates into different kinds of blood cells.

Question 7

What are the two broad categories of stem cells in mammals?

Answer 7

Embryonic stem cells - isolated from blastocyst inner cell mass.
Adult stem cells - found in various tissues.

Question 8

What is the potency of a totipotent stem cell?

Answer 8

They have ability to give rise to all cell types

EXAMPLES: fertilised egg

Question 9

Describe the potency of pluripotent stem cells.

Answer 9

Form primary germ cell layers, can differentiate into many cell types but not all.

EXAMPLE: inner cell mass of blastocyst

Question 10

Describe the potency of multipotent stem cells.

Answer 10

Can differentiate into closely related family cells.

EXAMPLE: blood stem cells –> RBC, WBC, platelets

Question 11

What is therapeutic cloning?

Answer 11

Cloning carried out to create an embryo from which stem cells can be harvested for use in treatment. Used for treating patient who has degenerative disease.

Question 12

What is cell based therapy?

Answer 12

The use of stem cells to replace lost or damaged cells with the scope of treating or preventing a disease or condition.

Question 13

What are congenital abnormalities arising during antenatal development referred to as?

Answer 13

Genetic factors - single gene defects and chromosomal abnormalities

Environmental factors - teratogens (mutagens)

Question 14

What is cancer?

Answer 14

Disease in which cells divide at uncontrolled manner forming abnormal mass of cells. Disease results from loss of control of cell cycle.

Question 15

What cells do the those from the ectoderm germ layer differentiate into?

Answer 15

Skin, brain, spinal cord, pituitary gland. Pluripotent

Question 16

What cells do those form the mesoderm differentiate into?

Answer 16

Heart and blood vessels, smooth skeletal cells and cardiac muscle

Question 17

What cells do those from the endoderm differentiate into?

Answer 17

Larynx, trachea, lungs, liver, pancreas.

Question 18

Why is it important to regulate the cell cycle?

Answer 18

In case genetic info is not passed on accurately resulting in subsequent cell divisions inheriting the defect
Uncontrolled cell division results in cancer.

Question 19

What are proto-oncogenes?

Answer 19

Genes that code for proteins stimulating cell to grow and divide.

Question 20

What are tumour suppressor genes?

Answer 20

Genes that code for proteins to slow down cell division and repair DNA

Question 21

Explain how mutations in proto-oncogenes and tumour suppressor genes could lead to cancer.

Answer 21

Proto-oncogenes code for proteins that stimulate cell to grow and divide, mutations could lead to increased and uncontrollable cell division forming cancers.

Mutations in tumour suppressor genes result in less suppression of cell division thus more uncontrolled cell division.

Question 22

What are cyclins?

Answer 22

Proteins that ensure chromosomes are attached to correct spindle fibre.

Question 23

What are germ line cells?

Answer 23

Cells found in the gonads of an organism which undergo Meiosis to produce gametes.