Gene Expression

Question 1

Define ‘mutation’

Answer 1

Any change to the base sequence of DNA

Question 2

What are the 6 types of genetic mutation?

Answer 2

Addition, deletion, inversion, translocation, duplication, substitution

Question 3

What are the 3 main types of genetic mutation (effect on phenotypes)?

Answer 3

Silent, termination/nonsense, frameshift

Question 4

What is an ‘addition’ mutation?

Answer 4

One or more bases are added to the DNA sequence.

Question 5

What is a ‘substitution’ mutation?

Answer 5

One or more bases are swapped with another.

Question 6

What is an ‘inversion’ mutation?

Answer 6

A sequence of bases is reversed.

Question 7

What is a ‘deletion’ mutation?

Answer 7

One or more bases are removed from the DNA sequence.

Question 8

What is a ‘duplication’ mutation?

Answer 8

One or more bases are repeated.

Question 9

What is a ‘translocation’ mutation?

Answer 9

A sequence of bases is removed from one location in the genome and inserted into another location, on the same chromosome or a different chromosome.

Question 10

What is meant by a ‘silent’ mutation?

Answer 10

Has no effect on AAs coded for/protein produced/phenotype.

Question 11

What is meant by a ‘Termination/Nonsense’ mutation?

Answer 11

A stop codon is coded for and protein made shorter.

Question 12

What is meant by a ‘Frameshift’ mutation?

Answer 12

Changes the number of amino acids coded by the DNA sequence.

Question 13

4x Mutagenic Agents?

Answer 13

UV radiation; ionising radiation; chemicals; viruses.

Question 14

Chemicals can act as ____ ____, which cause mutations how?

Answer 14

Can act as base analogs: they substitute for a base in DNA replication.

Question 15

How do alkylating agents cause mutation with guanine?

Answer 15

Chemicals can delete or alter bases, e.g. alkylating agents that add an alkyl group to guanine, so its new structure pairs with thymine.

Question 16

How does UV radiation cause mutation with thymine?

Answer 16

Causes adjacent thymine bases to pair up together.

Question 17

What is a zygote?

Answer 17

A cell as soon as sperm fuses with egg

Question 18

What is a blastocyst? How many cells?

Answer 18

A hollow ball of cells in very early embryonic development with cells differentiated into either placenta cells or embryo cells. Around 128 cells.

Question 19

What is the structure and function of the umbilical cord?

Answer 19

Vessel that connect embryo to placenta, in order to provide oxygen, nutrients and remove waste material from the embryo

Question 20

What is a stem cell?

Answer 20

An undifferentiated cell lineage with the ability to divide indefinitely (and form more stem cells).

Question 21

What is differentiation (of cells)?

Answer 21

To become a specialised cell lineage (type)

Question 22

What is a totipotent stem cell?

Answer 22

A stem cell lineage that can become any type of differentiated cell

Question 23

• What is a pluripotent stem cell?

Answer 23

• A stem cell that can differentiate into most cell types, e.g. a stem cell lineage in the blastocyst phase of development (embryonic cell or placenta cell).

Question 24

What is a multipotent stem cell? Example?

Answer 24

A stem cell lineage that can become a few types of differentiated cell. E.g. bone marrow stem cells can differentiate into red blood cells (erythrocytes), lymphocytes and platelets

Question 25

What is a unipotent stem cell?

Answer 25

A tem cell lineage that can become one type of differentiated cell

Question 26

Benefits of stem cells in regenerative medicine? (x4)

Answer 26

Scientists can gain access to adult human cells without taking tissue from patient; and use these to grow new tissues; which will not be attacked by the patient’s immune system, (as they display the same antigens as the patient themselves); patient will also not be required to take long courses of immunosuppressants, which can be harmful.

Question 27

What impacts the growth and development of plant tissues? What impacts their effect?

Answer 27

Plant growth factors affect the differentiation of plant stem cells. These are chemicals involved in the growth and development of plant tissues - they have wide effects on plant growth and these effects depend on concentration of the growth factors.

Question 28

Where are pluripotent stem cells usually taken from? When?

Answer 28

The inner cell mass of the blastocyst. These are taken from excess embryos from IVF

Question 29

When are pluripotent stem cells available naturally?

Answer 29

Usually, these pluripotent stem cells are only present in very early development post-fertilisation: once the blastocyst stage of development has commenced (approx. 4 days post-fertilisation), where the inner cell mass totipotent stem cells differ as they cannot differentiate to form a placenta.

Question 30

What are iPS cells?

Answer 30

Induced pluripotent stem cells

Question 31

How do you get iPS cells?

Answer 31

• Adult cells are made to express a series of specific transcription factors, which are usually associated with embryonic pluripotent stem cells.
• These factors cause adult body cells to express genes associated with pluripotency.
• Via infection of the adult cells with a modified virus, which passes on its genes to the adult cell’s DNA, allowing the adult cell to produce the required transcription factors and undifferentiate!

OR, via the transfer of and then growth of adult stem cells in an altered growth medium containing certain transcription factors.

Question 32

Two main advantages of iPS cells?

Answer 32

• Avoid the need of embryos! Can derive pluripotent SCs from adult tissues.
• Could make iPS cells from a patient’s own cells - genetically identical and avoid tissue rejection by the immune system.