7.3 Stem Cells

Question 1

define totipotent

Answer 1

has the potential to form all 216 different cell types needed for a human

Question 2

is a zygote totipotent, pluripotent or multipotent

Answer 2

totipotent

Question 3

is a blastocyst totipotent, pluripotent or multipotent

Answer 3

pluripotent

Question 4

how many days after fertilisation is a blastocyst formed

Answer 4

4 days

Question 5

define pluripotent

Answer 5

some of the genes are switched off but lots are still switched on so can form all cell types needed in future

Question 6

what are the 3 types of natural stem cells

Answer 6

totipotent
multipotent
pluripotent

Question 7

define multipotent

Answer 7

can differentiate when needed to form some specialised cells but not all

Question 8

what is another name for adult stem cells

Answer 8

somatic stem cells

Question 9

what kind of cells can adult bone marrow stem cells differentiate

Answer 9

blood cells

Question 10

where are umbilical cord stem cells found

Answer 10

in blood that drains from the placenta and umbilical cord is rich in pluripotent stem cells

Question 11

what kind of animals were tested on to test hypothesis for cell determination

Answer 11

frogs and fruit flies

Question 12

what did the early embryo in the cell determination experiment consist of

Answer 12

cells that are determined to produce skin cells as well as cells that are determined to produce brain cells

Question 13

what was the hypothesis of the cell determination experiment

Answer 13

cell determination occurs irreversibly early after fertilisation

Question 14

describe experiment one of the cell determination experiment

Answer 14

in the early embryo, the potential skin cells are taken and mixed with potential brain cells
the donor skin cells turned into brain cells

Question 15

describe experiment two of the cell determination experiment

Answer 15

in an older embryo, the potential skin cells are taken and mixed with potential brain cells
this time, the donor skin cells remain as skin cells

Question 16

do the experiments conducted in the cell determination experiment approve or disprove the hypothesis

Answer 16

the experiments disprove the hypothesis

Question 17

what do cell determination and specialisation occur due to

Answer 17

the control of gene expression e.g transcription factors, epigenetics

Question 18

as development of organism progresses, what happened to the genes

Answer 18

more genes are silenced

Question 19

what is the structure of human haemoglobin

Answer 19

contains 2 alpha and 2 beta polypeptide chains

Question 20

what is the structure of human fetal haemoglobin

Answer 20

contains 2 alpha and 2 gamma polypeptide chains so it has a higher affinity to oxygen

Question 21

describe how a globin gene is turned into a globin polypeptide

Answer 21

globin gene is transcribed into mRNA and then translated into a globin polypeptide

Question 22

what does epigenetics do

Answer 22

they change the proteins that the cell makes

Question 23

what are the three methods of using stem cells

Answer 23

stemm cell therapy
therapeutic cloning
induced pluripotent stem cells

Question 24

what can we use stem cells to do

Answer 24

produce cells

replace damaged or non-functional cells

Question 25

describe the process of stem cell therapy

Answer 25

bone marrow cells from donor are given to a recipient with blood cancer
the stem cells then differentiate to produce normal blood cells

Question 26

give some disadvantages of stem cell therapy

Answer 26

• difficult to control differentiation
• can cure patient but may develop cancer
• ethical issues
• risk of rejection

Question 27

give some advantages of stem cell therapy

Answer 27

• used to make new body parts
• no rejection as cells come from own body
• research about replacing damaged heart cells after heart attack

Question 28

what is therapeutic cloning

Answer 28

using stem cells to produce a large quantity of a specific tissue

Question 29

describe the process of therapeutic cloning

Answer 29

1. take out nucleus from cell of a male person with illness and fuse with egg from healthy female
2. this produces pre-embryonic cell containing ill person’s DNA that will divide to give multiple cells
3. the stem cells are removed and made to differentiate into required tissue type
   4 in a person with type 1 diabetes, stem cells develop into beta cells of islet of Langerhans of pancreas, which produce insulin

Question 30

what hormone converts glucose to glycogen

Answer 30

insulin

Question 31

what hormone converts glycogen to glucose

Answer 31

glucagon

Question 32

what happens in pancreas when blood concentration is too low

Answer 32

the alpha cells secrete glucagon

Question 33

what happens in pancreas when blood concentration is too high

Answer 33

beta cells secrete insulin

Question 34

what is damaged in type 1 diabetes

Answer 34

beta cells are damaged so they secrete little to no insulin

Question 35

what are iPS cells

Answer 35

induced pluripotent stem cells

Question 36

summarise how pluripotent stem cells can be formed

Answer 36

adult differentiated cell, eg skin cells, can genetically engineered into pluripotent cells using viruses

Question 37

describe fully how pluripotent stem cells can be formed

Answer 37

1. virus infects adult differentiated cell
2. virus carries genes that code for transcription factors e.g Oct 3, Oct 4, Socks family
3. genes are transcribed and translated to produce transcription factors
4. transcription factors activate or inactivate genes in cell making it pluripotent

Question 38

give an advantage of iPS cells

Answer 38

removes ethical issues

Question 39

give disadvantages of iPS cells

Answer 39

• difficult to carry out
• leads to cancer development
• not identical to human embryonic stem cells