T1 cell division

Question 1

what are chromosomes made up of

Answer 1

DNA molecules combined with proteins.

contain genes which provide instructions for protein synthesis.

Question 2

what is a gene

Answer 2

section of DNA which codes for a protein

Question 3

number of chromosomes found in the nucleus of gametes

Answer 3

23

Question 4

three main stages of cell cycle

Answer 4

1. replication of DNA and synthesis of organelles
2. mitosis
3. division of cell

Question 5

why is mitosis important

Answer 5

produces identical cells which all have same genetic information

produces additional cells for growth and repair

Question 6

describe the first stage of the cell cycle

Answer 6

longest stage - cells grow and increase in mass, replicate DNA and synthesise more organelles

Question 7

describe the second stage of the cell cycle

Answer 7

each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.

Question 8

describe the third stage of the cell cycle

Answer 8

cytoplasm and cell membrane divide - two identical daughter cells are produced.

Question 9

what is a stem cell

Answer 9

unspecialised cell which is capable of differentiating into other cell types and of self-renewal

Question 10

function of stem cells in embryos

Answer 10

embryonic stem cells can replicate themselves and differentiate into many other types of cells

may be able to treat conditions such as paralysis by dividing to replace damaged cells

Question 11

function of stem cells in adult bone marrow

Answer 11

can differentiate into several cell types to replace dead or damaged tissues

Question 12

function of stem cells in plant meristems

Answer 12

meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifecycle - can differentiate into any cell which is required by the plant

Question 13

what is therapeutic cloning

Answer 13

cloning method where an embryo is produced with the same genetic makeup as the patient.

stem cells which originate from the embryo will not be rejected by patient’s immune system, so can be used to treat certain medical conditions.

Question 14

advantages of cloning plants using meristem stem cells

Answer 14

can prevent rare plants from becoming extinct.

can produce large numbers of plants with a favourable characteristic

can produce identical plants for research

Question 15

what are the issues associated with the use of embryonic stem cells

Answer 15

many are sourced from aborted embryos - ethical or religious objections

development is slow, expensive and difficult.

adult stem cells infected with viruses could transfer infections to patients.

if donor stem cells don’t have similar genetic makeup to patient, immune response could be triggered.