Cell biology - Cell division

Question 1

what are chromosomes

Answer 1

• they are coiled up lengths of DNA molecules
• carry large number of genes

Question 2

what are genes

Answer 2

parts of chromosomes that control the development of different characteristics such as hair colour

Question 3

how many pairs of chromosomes are in a single cell

Answer 3

23, there are 46 all together

Question 4

why is the cell cycle beneficial

Answer 4

• allows for the growth, repair and asexual reproduction of cells

Question 5

what is the stage of the cell cycle where the cell divides

Answer 5

mitosis

Question 6

what do multicellular organisms use mitosis for

Answer 6

to grow or replace damaged cells

Question 7

what does the end of the cell cycle result inn

Answer 7

• two new cells which are identical to the original cell, with the same number of chromosomes

Question 8

describe the initial growth stage

Answer 8

• the cell grows and increases the amount of subcellular structures such as mitochondria and ribosomes
• chromosomes double and line up in the middle of the cel; both “arms” of the chromosome are identical

Question 9

summarise mitosis

Answer 9

• Cell grows and increases number of subcellular structures such as mitochondria and ribosomes
• cell duplicates it’s DNA. The DNA is copied and forms X shaped chromosomes
  3. The chromosomes line up at the centre and get pulled apart by cell fibres, Each arm of the chromosome go to opposite ends of the cell
  5. Cytoplasm and cell membrane divide
  6. Cell had now produced two new identical daughter cells

Question 10

what is mitosis

Answer 10

a type of cell division which produces daughter cells identical to the parent

Question 11

Length of time in phase

Answer 11

observed number of cells at the stage / total number of cells observed x total length of time cycle

Question 12

what is binary fission

Answer 12

how prokaryotic cells divide into two / replicate

Question 13

describe the steps of binary fission

Answer 13

1- the circular DNA and plasmids replicate
2 - the cell gets bigger and the DNA strands move to opposite ends of the cell
3- cytoplasm begins to divide, new cell walls begin to form
4- cytoplasm divides and two daughter cells are produced, each having one copy of the circular DNA, but having a variable number of copies of the plasmids

Question 14

what are stem cells

Answer 14

undifferentiated cells which can divide and differentiate into different kinds of cells, depending on what instruction they are given

Question 15

where are stem cells found ( humans )

Answer 15

• in early human embryos, have potential to turn into any kind of cell at all
• also in adults, only certain places though like bone marrow,and unlike embryonic cells, cannot turn into any type of cell, only certain ones like blood cells

Question 16

stem cell uses

Answer 16

• therapeutic cloning, where embryo could be made to have the same genetic info as the patient
• curing things such as diabetes, spinal injuries,

Question 17

where are stem cells found in plants

Answer 17

in the meristems ( where growth occurs )

Question 18

whats the difference between adult human stem cells and adult plant stem cells

Answer 18

unlike a human adult stem cell, throughout a plants entire life, cells in the meristem can differentiate into any type of plant cell, not restricted

Question 19

risks of stem cell

Answer 19

• difficult to find suitable stem cell donors
• stem cells grown in a lab could be contaminated with a virus which could passed on to patient and make them sick
• the donor has to be compatible with the patients or else WBC produced by the donated bone marrow could attack the patients body
• no guarantee how successful these therapies will be

Question 20

ethical issues with stem cell

Answer 20

• human embryos being used for experiments goes against many religious beliefs ( sanctity of life )
• does the embryo have rights?
• For therapeutic cloning is it right to create embryos for therapy, and destroy them in the process?

Question 21

social issues with stem cell

Answer 21

educating the public about what stem cells can, and can’t do, is important

• talk about whether the benefits outweigh the risks

Question 22

advantages of stem cells

Answer 22

• embryonic stem cells can be used to replace faulty cells in sick people, e.g you could make insulin producing cells for people with diabetes
• therepeutic cloning, an embryo is made with the same genetic info as patient, meaning the body won’t reject it

Question 23

what is the importance of mitosis in unicellular organisms

Answer 23

for asexual reproduction

Question 24

how can stem cells be used for bone marrow transplants

Answer 24

• leukaemia is a cancer if the bone marrow
• to treat it, the patients existing bone marrow is destroyed using radiation
• patient then receives a transplant of bone marrow from a donor
• the stem cells in the bone marrow now divide and form new bone marrow. they also differentiate and form blood cells

Question 25

why might we clone a plant?

Answer 25

• to stop it going extinct
• to increase yield for farmers
• cheap