cell division and stem cells

Question 1

what is a chromosome and what does it contain

Answer 1

a chromosome is a linear DNA molecule tightly coiled around proteins

it contains genes

Question 2

how many chromosomes are in the human body

Answer 2

46 chromosomes (23 pairs)

Question 3

how many chromosomes are in the human body

Answer 3

46 chromosomes (23 pairs)

Question 4

what are sex chromosomes

what are the male and female sex chromosomes

Answer 4

a pair of chromosomes that determine sex
male = XY
female = XX

Question 5

what is mitosis

Answer 5

a form of cell division that produces two ‘daughter cells’

both are genetically identical to the parent cell with the same number of chromosomes (46 chromosomes)

it involves 1 division

Question 6

why is mitosis important in organisms

Answer 6

growth
repair of damaged cells
cell replacement
asexual reproduction

Question 7

wat is meiosis

Answer 7

a form of cell division involved in the formation of gametes

it involves two devision, producing four gametes

chromosome number is halved (23 chromosomes)

Question 8

what are gametes

Answer 8

sex cells (e.g sperm cells egg cells)
they contain half the chromosome number

Question 9

why is meiosis important for sexual reproduction

Answer 9

it increases genetic variation

ensures that the resultant zygote has a full set of chromosomes

Question 10

compare mitosis and meiosis

Answer 10

MITOSIS

occurs in non reproductive cells

produces two daughter cells

daughter cells are genetically identical

daughter cells have 46 chromosomes

it occurs for the growth, repair and replacement of damaged cells

            MEIOSIS

occurs only in reproductive cells

produces four daughter cells

daughter cells are genetically different

daughter cells have 23 chromosomes

occurs for the formation of gametes during sexual reproduction

Question 11

how is cancer caused by uncontrolled mitiosis

Answer 11

the rate at which cells divide by mitosis is controlled by genes
if there is a change in one of the genes that controls cell division, a cell may start dividing uncontrollably. this can result in a mass of abnormal cells called a tumour.
if the tumour invades and destroys surrounding tissues it is called cancer

Question 12

what are stem cells

Answer 12

stem cells are unspecialised cells that can differentiate into a range of different cell types

Question 13

what is meant by differentiation

Answer 13

the process by which a stem cell becomes specialised (have a specific function)

some genes switch on or off determining the cell type

Question 14

why is cell differentiation important

Answer 14

enables the formation of specialised tissues with specific functions
e.g muscle tissues

Question 15

what are embryonic stem cells

Answer 15

stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type

Question 16

what is the function of embryonic stem cells

Answer 16

enable the growth and development of tissues in human embryos

Question 17

where can embryonic stem cells be collected from

Answer 17

donor stem cells removed from embryos grown in vitro

patients own stem cells removed from the umbilical blood before birth

Question 18

what are adult stem cells

Answer 18

stem cells that can differentiate into a limited range of cell types e.g bone marrow stem cells

Question 19

what are adult stem cells

Answer 19

stem cells that can differentiate into a limited range of cell types e.g bone marrow stem cells

Question 20

what is the primary function of adult stem cells

Answer 20

replacement of dead cells

Question 21

describe the potential use of stem cells in medicine

Answer 21

treat disease

used to repair damaged tissue

used in scientific research

growing organs for transplants

Question 22

what are the ethical issues related to the use of stem cells in medicine

Answer 22

the embryos used to provide stem cells are destroyed and a waste of a potential human life
could lead to the ‘farming’ of embryos for stem cells

may lead to the reproductive cloning of humans

Question 23

fill in the blanks
the cells in mature _____ have generally lost the ability to _____; some cells, in both _____ and _____, do not lose this ability and these are called ____ ____

Answer 23

the cells in mature tissues have generally lost the ability to differentiate; some cells, in both plants and animals, do not lose this ability and these are called stem cells

Question 24

What are both adult and embryonic stem cells used for

Answer 24

To replace damaged tissue