B2(2.1-2.4) Cell Division

Question 1

What are the roles of chromosomes and where are they found?

Answer 1

-they are found in the nucleus
-they carry the genes that contain the information needed for making new cells

Question 2

What is a gene?

Answer 2

A gene is a small packet of information that controls a characteristic

Question 3

How many chromosomes do humans have?

Answer 3

• 46 chromosomes (23 pairs)

Question 4

Define multicellular.

Answer 4

-An organism that consists of more than one cell

Question 5

Why do all multicellular eukaryotic organisms require new cells?

Answer 5

-Growth
-Development
-Repair

Question 6

Define a stem cell.

Answer 6

-Undifferentiated cell that can develop into one or more types of specialised cell

Question 7

What are two types of stem cell in mammals?

Answer 7

-Adult stem cells
-embryonic stem cells

Question 8

What are adult stem cells?

Answer 8

-stem cells from adults that can only differentiate into certain specialised cells

Question 9

Where are adult stem cells found?

Answer 9

Bone marrow

Question 10

What are embryonic stem cells?

Answer 10

-Stem cells from embryos that can differentiate into any specialised cell.

Question 11

Where are embryonic stem cells found?

Answer 11

-in early human embryos (usually spare from fertility clinics)

Question 12

What is therapeutic cloning?

Answer 12

-When patient’s cells are used to create an early embryo clone of themselves - stem cells from that embryo can then be used to treat the patients medical conditions

Question 13

State one advantage of therapeutic cloning.

Answer 13

-Stem cells from the embryo are not rejected when transplanted because they have the same genes as the patient

Question 14

State two advantages of using embryonic stem cells.

Answer 14

-Can differentiate into any specialised cell, so can be
used to treat many diseases
-Easier to obtain as they are found in spare embryos
from fertility clinics

Question 15

State two disadvantages of using embryonic stem cells.

Answer 15

-Ethical issues surrounding their use, as every embryo
is a potential life
-potential risks involved with treatments, such as
transfer of viral infections

Question 16

State one advantage of using adult stem cells.

Answer 16

-Fewer ethical issues as obtained from adults who can
consent to their use

Question 17

State two disadvantages of using adult stem cells.

Answer 17

-Can take a long time for a suitable donor to be found
-Can only differentiate into some specialised cell types,
so treat fewer diseases

Question 18

What are plant meristems?

Answer 18

-An area where rapid cell division occurs in the tips of roots and shoots

Question 19

State two advantages of using plant meristems to clone
plants.

Answer 19

-Rare species can be cloned to protect them from
extinction
-Plants with special features (e.g., disease resistance)
can be cloned to produce many copies

Question 20

State one disadvantage of using plant meristems to
clone plants.

Answer 20

-No genetic variation, so, for example, an entire cloned
crop could be destroyed by a disease

Question 21

What is cell division by mitosis?

Answer 21

-Body cells divide to form two identical daughter cells

Question 22

What is the purpose of mitosis?

Answer 22

-Growth and repair of cells, asexual reproduction

Question 23

What happens during the first stage of the cell cycle?

Answer 23

-Cell grows bigger, chromosomes duplicate, number
of subcellular structures (e.g., ribosomes and
mitochondria) increases

Question 24

What happens during mitosis?

Answer 24

-One set of chromosomes is pulled to each end of the cell and the nucleus divides

Question 25

What is the second stage of the cell cycle?

Answer 25

-Mitosis

Question 26

What happens during the third stage of the cell cycle?

Answer 26

-The cytoplasm and cell membrane divide, forming two
identical daughter cells

Question 27

What is the term for cell division in bacteria?

Answer 27

-Binary fission