The control of gene expression B8

Question 1

What is a mutation? (20.1)

Answer 1

Any changes to the quantity or the structure of the DNA of an organism.

Question 2

What is gene mutation? (20.1)

Answer 2

Any change to one or more nucleotide bases or any rearrangement of the bases in DNA

Question 3

What is substitution of bases? (20.1)

Answer 3

When a nucleotide in a section of a DNA molecule is replaced by another nucleotide.

Question 4

What are the possible consequences of substitution of bases? (20.1)

Answer 4

The formation of one of the three stop codons that mark the end of a polypeptide chain resulting in a protein stopped early than wanted and a non-functional protein
The formation of a codon for a different amino acid meaning that the structure and shape of the protein would change
The formation of a different codon that produces the same amino acid as before. This is because the code is degenerate

Question 5

What is deletion of bases? (20.1)

Answer 5

The loss of a nucleotide base from a DNA sequence

Question 6

What is the outcome of deletion of bases? (20.1)

Answer 6

The whole DNA sequence is read in triplets so a frame shift happens and the bases code for different triplets.

Question 7

What is addition of bases? (20.1)

Answer 7

When an extra base becomes inserted in the sequence

Question 8

What is duplication of bases? (20.1)

Answer 8

When one or more bases are repeated.

Question 9

What is inversion of bases? (20.1)

Answer 9

When a group of bases become separated from the DNA sequence and rejoin in the same position but in the reverse order (back to front)

Question 10

What is translocation of bases? (20.1)

Answer 10

When a group of bases become separated from the DNA sequence on one chromosome and become inserted into a DNA sequence in another chromosome.

Question 11

Name the types of gene mutation (6)? (20.1)

Answer 11

Translocation of bases
Inversion of bases
Duplication of bases
Addition of bases
Deletion of bases
Substitution of bases

Question 12

The basic mutation rate can be increased by outside factors known as what? (20.1)

Answer 12

Mutagenic agents or Mutagens

Question 13

Name some mutagenic agents? (20.1)

Answer 13

High energy ionising radiation eg alpha and beta particles or short wavelength radiation
Chemicals eg nitrogen dioxide

Question 14

Are mutations good or bad? (20.1)

Answer 14

+ The produce genetic diversity for natural selection and speciation

• Can produce a less adapted organism
• Disrupt normally cellular activities eg cell division causing cancer

Question 15

What is cell differentiation? (20.2)

Answer 15

The process by which each cell develops into a specialised structure suited to the role that it will carry out .

Question 16

Why is it that cells from the small intestine produce maltase instead of insulin and the pancreas produce insulin rather than maltase? (20.2)

Answer 16

Although the cells contain all the same genes only some are switched on at any one time.

Some genes are permanently switched on and some turn on and off when needed.

Question 17

Differentiated cells differ from each other, often visibly so. Why? (20.2)

Answer 17

this is mainly because they each produce different proteins. Codded for by the genes turned on.

Only part of the DNA of the cell is translated into a protein

Question 18

How are genes prevented from expressing themselves? (20.2)

Answer 18

Preventing transcription and so preventing the production of mRNA
Preventing translation

Question 19

What is totipotent cells? (20.2)

Answer 19

Cells such as fertilised eggs which can mature into any body cell
Are found in the early embryo and can differentiate into any type if cells.
Since all body cells are formed from a zygote, zygotes are totipotent. Its cells develop into slightly more specialised cells called pluripotent stem cells

Question 20

What are induced pluripotent stem cells-iPS? (20.2)

Answer 20

They are a type of pluripotent cell that is produced from unipotent stem cells. The unipotent cells can be almost any body cell.
These cells can be genetically altered to achieve the characteristics of embryonic stem cells. The two are not identical. They are self renewal and have the potential to replace embryonic stem cells in medical research overcoming the ethical issues associated with embryos.

Question 21

Can specialised cells turn into another cell after they have already matured? (20.2)

Answer 21

No but stem cells can(undifferentiated)

Question 22

What are stem cells? (20.2)

Answer 22

They are undifferentiated diving cells that occur in adult animals tissues and need to be constantly replaced. they therefore have the ability to divide to form an identical copy of themselves in a process called self renewal.

Question 23

Name the sources of stem cells(4)? (20.2)

Answer 23

Embryonic stem cells
Umbilical cord blood stem cells
Placental stem cells
Adult stem cells

Question 24

What are the different types of stem cells(4)? (20.2)

Answer 24

Totipotent stem cells
Pluripotent stem cells
Multipotent stem cells
Unipotent stem cells

Question 25

What are pluripotent stem cells? (20.2)

Answer 25

They are found in embryos and can differentiate into almost any type of cell. Examples include embryonic stem cells and fetal stem cells

Question 26

What are multipotent stem cells? (20.2)

Answer 26

They are found in adults and can differentiate into a limited number of specialised cells. they usually develop into cells of a particular type for example stem cells in the bone marrow can produce any type of blood cell. Examples of multipotent stem cells are adult stem cells and umbilical cord blood stem cells

Question 27

What are unipotent stem cells? (20.2)

Answer 27

They can only differentiate into a single type of cell. They are derived from multipotent stem cells and are made in adult tissue.