Topic 8: mutations and stem cells

Question 1

During which stage of the cell cycle are gene mutations most likely to occur?

Answer 1

DNA replication / S phase/ interphase

Question 2

If a gene mutation only affects 1 triplet code, why might the mutation not result in a change to the encoded amino acid?

Answer 2

The genetic code is degenerate, so the new triplet code may still code for the same amino acid.

Question 3

What is meant by a frame shift?

Answer 3

When every bases shifts position, changing all of the triplet codes downstream of the mutation.

Question 4

What is meant by a mutagenic agent?

Answer 4

A factor that increases the mutation rate

Question 5

Describe the translocation of bases mutation

Answer 5

When a section of bases on one chromosome detaches and attaches onto a different chromosome.

Question 6

What is a stem cell?

Answer 6

Undifferentiated cells that can continually divide and become specialised.

Question 7

Name the 4 different types of stem cells and where they are located.

Answer 7

1) Totipotent - early mammalian embryo
2) Pluripotent - embryos
3) Multipotent - Mature mammals e.g. bone marrow
4) Unipotent - Mature mammals

Question 8

Which type of stem cells are used to create new cardiomyocytes?

Answer 8

Unipotent

Question 9

During development, what happens to totipotent stem cells for them to become specialised cells?

Answer 9

Totipotent cells translate only part of their DNA

Question 10

5 types of mutation?

Answer 10

deletion
addition
substitution
inversion
duplication

Question 10

Explain induced pluripotent stem cells (iPS cells

Answer 10

Induced pluripotent stem cells (iPS cells) can be produced from adult somatic cells using appropriate protein transcription factors to overcome some of the ethical issues with using embryonic stem cells.
iPS cells are created from adult unipotent cells. These cells, which can be from almost any body cell, are altered in the lab to return them to a state of pluripotency. To do this, the genes that were switched off to make the cell specialised must be switched back on.
This is done using transcription factors. iPS cells are very similar to embryonic pluripotent stem cells but do not cause the destruction of an embryo and the adult can give permission.
The iPS have shown a self-renewal property, in that they can divide indefinitely to give limitless supplies. For these reasons, they could be used in medical treatment instead of embryonic stem cells.