cell division

Question 1

what are chromosomes made up of?

Answer 1

DNA molecules combined with proteins. They contain genes which provide the instructions for protein-synthesis,

Question 2

what is a gene

Answer 2

a section of DNA which codes for a protein

Question 3

how many chromosomes are found in the nucleus of human body cells

Answer 3

46

Question 4

how many chromosomes are found in the nucleus of gametes?

Answer 4

23

Question 5

how are chromosomes arranged in the nucleus of a body cell?

Answer 5

arranged in pairs - 46 chromosomes from 23 pairs

Question 6

what are the three main stages of the cell cycle

Answer 6

replication of DNA and synthesis of organelles, mitosis, division of cell.

Question 7

give 2 reasons why mitosis is important?

Answer 7

for growth and repair in the cells,
produces identical cells which all have the same genetic information

Question 8

describe the first stage of the cell cycle

Answer 8

longest stage. cells grow and increase in mass, replicate DNA and synthesise more organelles (eg mitochondria and ribosomes)

Question 9

describe the second stage of the cell cycle

Answer 9

mitosis - each chromosome is pulled to opposite poles of the cell, then the nucleus divides

Question 10

describe the third stage of the cell cycle

Answer 10

the cytoplasm and cell membrane divide to produce two identical daughter cells.

Question 11

what is a stem cell

Answer 11

a unspecialised cell that can differentiate into other cell types and can self-renew.

Question 12

what is the function of stem cells in embryos

Answer 12

embryonic stem cells can replicate themselves and differentiate into many other types of cells.
embryonic stem cells are able to treat conditions such as paralysis sand diabetes by dividing to replicate damaged cells.

Question 13

what is the function of stem cells in adult bone marrow

Answer 13

adult stem cells can differentiate into several cell types to replace dead or damaged tissues. for example, bone marrow stem cells can form many different types of blood cell.

Question 14

what is the function of stem cells in plant meristems

Answer 14

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

Question 15

what is therapeutic cloning

Answer 15

a cloning method where an embryo is produced with the same genetic makeup as the patient. the stem cells which originate from the embryo will not be rejected from the patient’s immune system, so can be used to treat certain medical conditions

Question 16

what are the advantages of cloning plants using meristem stem cells

Answer 16

can prevent rare plants from becoming extinct;
can produce large amounts of plants with a favourable characteristic;
can produce identical plants for research

Question 17

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

Answer 17

Many embryonic stem cells are sourced from aborted embryos, some people have ethical/religious objection;
Development of stem cell therapies is slow, expensive and difficult;
Adult stem cells infected with viruses could transfer infections to patients;
If donor stem cells do not have similar genetic makeup to the patient, an immune response could be triggered.