Unit 1: Human Cells - Key Area 1 - Division and differentiation in human cells

Question 1

What are somatic cells?

Answer 1

A somatic cell is any cell in the body other than cells involved in reproduction.

Question 2

Why do somatic cells divide?

Answer 2

Somatic cells divide during growth and repair to increase and maintain total cell numbers.

Question 3

How many pairs of homologous chromosomes do diploid cells have?

Answer 3

Diploid cells have 23 pairs of homologous chromosomes.

Question 4

Why is the maintenance of the chromosome complement important?

Answer 4

The maintenance of the chromosome complement is important to ensure that no genetic information is lost or duplicated and that each daughter cell contains all of the characteristics of its species.

Question 5

What are stem cells?

Answer 5

Stem cells are undifferentiated and have a unique property in that they can not only make new copies of themselves(self renew), but can also differentiate to become a range of specific cell types.

Question 6

What is Cellular Differentiation?

Answer 6

Cellular Differentiation is a process in which an unspecialised cell becomes one of the many specialised cells that make up the tissues within a multicellular organism due to it having required genes for its function switched on and others which are not required for its function switched off.
or
Cellular differentiation is the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell. This allows a cell to carry out specialised functions.

Question 7

What do differentiated cells only have a few of and what does this mean for the cell?

Answer 7

Differentiated cells only have a few genes switched on and those that are not required for that specific cells function are switched off, meaning only the proteins that the cell requires to function are produced.

Question 8

Where are adult tissue stem cells found?

Answer 8

Adult tissue stem cells are found in the tissue of adults and children, including the brain skin and bone marrow.

Question 9

Are adult tissue stem cells capable of dividing into a wide range of differentiated cells?

Answer 9

No they are only capable of dividing into a LIMITED range of differentiated cells.

Question 10

Can adult tissue stem cells be used successfully in bone marrow transplants?

Answer 10

Yes

Question 11

Where are embryonic stem cells found?

Answer 11

In the inner cell mass of early embryos around 4-5 days.

Question 12

Are embryonic stem cells capable of dividing into a wide range of differentiated cells?

Answer 12

Yes

Question 13

What is the meaning of multipotent?

Answer 13

Cells that have the ability/are capable giving rise to a limited number of cell types/fates.

Question 14

What is the meaning of pluripotent?

Answer 14

Cells that have the ability/are capable of developing into ALL types of cells.

Question 15

What is an example of a multipotent cell?

Answer 15

Adult tissue stem cells

Question 16

What is an example of a pluripotent cell?

Answer 16

Embryonic stem cells

Question 17

Why are embryonic stem cells capable of differentiating into any specialised cell type?

Answer 17

They are pluripotent.

Question 18

Why do adult tissue need stem cells?

Answer 18

To maintain cell numbers, by repairing/replacing damaged cells within tissues or organs where they are found.

Question 19

Where is the location of the tissue stem cells which develop into blood cells?

Answer 19

Bone marrow

Question 20

What are germline cells?

Answer 20

A lineage of cells that divide to form/produce gametes?

Question 21

Are germline cells diploid or haploid?

Answer 21

Diploid

Question 22

How many pairs of chromosome do germline cells have?

Answer 22

23 pairs of homologous chromosomes.

Question 23

How do germline cells divide to produce more germline cells?

Answer 23

By mitosis

Question 24

What is the process of division called that germline cells undergo to produce haploid gametes?

Answer 24

Meiosis

Question 25

After mitosis are the daughter cells genetically different?

Answer 25

No the are identical

Question 26

After meiosis are the daughter cells genetically different?

Answer 26

Yes

Question 27

What is the main difference between Meiosis and Mitosis?

Answer 27

During Meiosis the daughter cells undergo 2 rounds of genetic separation and cellular division to produce 4 genetically different haploid daughter cells. Whereas during Mitosis the daughter cell only undergo 1 round of genetic separation and cellular division to produce 2 genetically identical diploid cells.

Question 28

What is the very centre of the chromosome called?

Answer 28

The centrome

Question 29

What is each of the 4 parts of the ‘ X ‘ shape of the chromosome called?

Answer 29

The chromatids

Question 30

What are examples of somatic cells?

Answer 30

All body cells of an organism – apart from the sperm and egg cells, like red blood cells, muscle cells and hair cells etc.

Question 31

What are examples of gametes?

Answer 31

Sperm and egg.

Question 32

How do somatic cells divide and why is this important?

Answer 32

Somatic cells divide by mitosis so the daughter cells obtain all of the genetic info they need to function and no genetic info is lost/to maintain the diploid chromosome number..

Question 33

How many chromosomes do haploid cells have?

Answer 33

23

Question 34

How many chromosomes do diploid cells have?

Answer 34

46

Question 35

How does a germline cell divide to produce more germline cells?

Answer 35

By Mitosis

Question 36

How does a germline cell divide to produce gamete cells?

Answer 36

By Meiosis

Question 37

describe how division by meiosis produces haploid gametes?

Answer 37

The nucleus of a germline stem cell can divide by
meiosis. It undergoes two divisions, firstly separating
homologous chromosomes and secondly separating
chromatids. Haploid gametes contain 23 single
chromosomes.

Question 38

Why can embryonic stem cells differentiate into any type of cell?

Answer 38

All the genes in embryonic stem cells can be switched

on so these cells can differentiate into any type of cell.

Question 39

Why are cells in the very early embryo pluripotent?

Answer 39

Cells in the very early embryo can differentiate

into all the cell types that make up the individual and so are pluripotent.

Question 40

Why are adult tissue stem cells multipotent?

Answer 40

Adult tissue stem cells are multipotent as they can
differentiate into all of the types of cell found in a
particular tissue type. For example, blood stem cells
located in bone marrow can give rise to red blood cells,
platelets, phagocytes and lymphocytes.

Question 41

What are adult tissue stem cells involved in and why is this?

Answer 41

Adult tissue stem cells are involved in the growth, repair and renewal of the cells found in that tissue. As They are multipotent.

Question 42

What do the therapeutic uses of stem cells include?

Answer 42

Therapeutic uses involve the repair of damaged or diseased organs or tissues. For example Bone marrow transplants and skin grafts.

Question 43

Describe 2 ways how stem cells are used therapeutically in bone marrow transplants?

Answer 43

Bone marrow transplants are most common in leukaemia and can be done in 2 ways.

1) A stem cell transplant - This involves using healthy stem cells from the blood or bone marrow of one person – ideally a close family member with the same or similar tissue type – and transferring them to another person. Which is called an allogeneic transplant. It’s also possible to remove stem cells from your own body and transplant them later, after any damaged or diseased cells have been removed. This is called an autologous transplant.
2) Cord Blood - This involves taking blood from the umbilical cord and placenta which is rich in stem cells and are donated form people after the birth of their new born baby. The blood after testing can then be transplanted into leukaemia sufferers etc.

Question 44

Describe 2 ways how stem cells are used therapeutically in skin grafts?

Answer 44

1) Using embryonic stem cells which are manipulated to differentiate into skin cells.
2) Taking sections of healthy skin from other places of the body and placing them on the required area.

Question 45

What can stem cell research be used for?

Answer 45

• Providing info on how cell processes work.
• Drug testing
• Researching how diseases work

Question 46

What do stem cell researchers use to research the stem cells?

Answer 46

A stem cell line

Question 47

What is a stem cell line?

Answer 47

A collection of cells that are derived (come from) from a parent group of cells. They are grown in culture dishes; they constantly divide and are undifferentiated for many years.

Question 48

What is the cut off time by which embryos are either used or destroyed?

Answer 48

14 days

Question 49

Why are embryos that are passed 14 days old not used for research?

Answer 49

After 14 days, the nervous system starts to develop.

Question 50

Why are people against embryonic stem cell research and what is the opposing argument?

Answer 50

Against
People believe that it is wrong to create a human life simply for the purpose of scientific research.

For
The fact that embryonic stem cells have the potential to discover cures for diseases or which there are currently none.

Question 51

Describe how cancer can develop and spread through the body?

Answer 51

Cancer cells divide excessively because they do not respond to regulatory signals. This results in a mass of abnormal cells called a tumour. Cells within the tumour may fail to attach to each other, spreading through the
body where they may form secondary tumours or could say undergo metastasis.

Question 52

In a developing embryo, how are tissues such as muscle and nerve produced?

Answer 52

By stomatic cells dividing by mitosis