Unit 1 KA1 Division & Differentiation in Human Cells

Question 1

What is a somatic cell?

Answer 1

A body cell, uninvolved in the reproduction system

eg, not a germline cell or gamete

Question 2

What is mitosis?

Answer 2

The process of cell division, when a single mother cell becomes two daughter cells

Each cell would be diploid (46 chromosomes)

Question 3

How many chromosomes are in a somatic cell?

Answer 3

46

23 pairs of 2 homologous partner chromosomes

Question 4

What is the sequence of events that takes place in a cell during mitosis?

Answer 4

1. Chromosomes replicate and pair up with each’s homologous partner
2. Nuclear membrane breaks down
3. Chromosomes line up along the equator of the cell
4. Spindle fibers pull chromosomes apart (into chromotids) towards the poles
5. Nuclear membranes reform
6. Cytoplasm divides
7. Two daughter cells

Question 5

What is a germline cell?

Answer 5

A cell that can produce gametes through meiosis

Gametes = sex cells. Meiosis produces haploid cells from diploid cells

Question 6

Where are germline cells found?

Answer 6

Reproductive organs, overies in females, testes in males

Germline cells are found in the seminiferous tubules in the testes

Question 6

How do germline cells divide?

Answer 6

• Through mitosis, they produce two daugherd diploid germline cells
• through meiosis, they produce haploid gametes

Haploid = 1 set of chromosomes, Diploid = 2 sets of chromosomes

Question 7

How many chromosomes are in a germline cell?

Answer 7

46

As they are diploid, they have two sets of chromosomes

Question 8

How many chromosomes are found in a gamete?

Answer 8

23

Gametes are haploid, so only have one set of chromosomes

Question 9

What does “Haploid” mean?

Answer 9

A cell with one set of chromosomes

One human chromosome set contains 23 chromosomes

Question 10

What does “Diploid” mean?

Answer 10

A cell with two sets of chromosomes

Two sets of chromosomes in humans is 23 chromosomes

Question 11

What is Differentiation?

Answer 11

When an unspecialised cell becomes specialised to carry out a specific function

Question 12

How does a cell differentiate?

Answer 12

By expressing certain genes that would produce proteins characteristic for that type of cell

Question 13

What are Stem cells?

Answer 13

Unspecialised cells that can differentiate ibto specialised cells

Question 14

What are the roles of stem cells?

Answer 14

• Self-renew (Divide to make more of themselves)
• Diffentiate (Turn into other types of cells)

Question 15

What are the two types of stem cells?

Answer 15

1. Tissue Stem cells (Multipotent)
2. Embryonic Stem cells (Pluripotent)

Question 16

Define Multipotent

Answer 16

A stem cell that can differentiate into several types of speialised cells

Question 17

Define Pluripotent

Answer 17

A stem cell that can differentiate into any type of cell

Question 18

Where are tissue stem cells found?

Answer 18

In every tissue of a human

Question 19

Where are embryonic stem cells found?

Answer 19

In a blastocyst, a very early stage of pregnancy, a ball of about 100 cells

Question 20

Why can embryonic stem cells differentiate into all types of cells (Pluripotent) while tissue stem cells can only differentiate into a few types of cells (multipotent)?

Answer 20

Because in an embryonic stem cell, all genes can be expressed while in a tissue stem cells a lot of the genes have already been switched off so cannot be expressed.

Question 21

Tissue stem cells can only differentiate into a few cell types

What types can they differentiate into?

Answer 21

The types of cells found in that particular tissue

Question 22

What therapeutic uses of stem cells are there?

Answer 22

1. Corneal Repair
2. Regeneration of damaged skin

Question 23

What research uses for stem cells are there?

Answer 23

• Cell growth
• Differation
• Gene regulation
• Model cells for development of diseases or drug testing

Question 24

What is the ethical arguments for the use of embryonic stem cells?

Answer 24

• A fertislised egg is not a person
• At less then 14 days, the embryo has no nervous system and thus no feelings
• Abortion is allowed until 20 weeks, so 2 weeks should be fine
• Research into embryonic stem cells could help many people with medical conditions
• Most stem cells are leftovers from IVF and would be destroyed anyway

Question 25

What are cancer cells?

Answer 25

Cells that divide excessively because they do not respond to regulatory signals

Question 25

What are the ethical arguments against the use of embryonic stem cells?

Answer 25

• Human life begins with fertisation so the embryo should not be killed
• A fertilised egg has a soul
• Stem cell research is unnatural

These are quite weak arguments im afraid, just out of my textbook :(

Question 26

What is a tumor?

Answer 26

A mass of abnormal cells

Question 27

How are secondary tumors formed?

Answer 27

When cells in a tumor fail to attach to each other, they can break apart and be carried through the blood to other tissues and organs when they can settle and form a secondary tumor