Gene expression Flashcards
What is a gene mutation?
A random change in the DNA base sequence
When do gene mutations occur?
During DNA replication, in the interphase (S phase) part of the cell cycle.
What is a mutagenic agent?
Factors that damage DNA and increase the rate of mutation.
Why are deletion mutations more likely to produce a non-functional protein?
Because the removal of one base pair changes every triplet code after the point of deletion, causing a frameshift so a completely different protein is made.
Why are substitution mutations less likely to produce a non-functional protein?
Because the genetic code is degenerate, so the new triplet may code for the same amino acid, resulting in the same protein being produced.
What is a substitution mutation?
When one or more bases are swapped for another.
What is an addition mutation?
When one or more bases are added.
What is a deletion mutation?
When one or more bases are removed.
What is an inversion mutation?
When one or more bases are reversed.
What is a duplication mutation?
When one or more bases is repeated.
What is a translocation mutation?
When a sequence of bases is moved from one location to another (either on same chromosome or onto another).
What are the 3 mutations that produce a non-functional protein?
-Deletion
-Addition
-Duplication
What are stem cells?
Undifferentiated cells that divide by mitosis to produce more stem cells that mature to become adapted for a specific function.
What changes does cell differentiation involve?
Changes to the cell shape, cell contents, or numbers of organelles. These are permanent changes.
How do stem cells replace themselves?
They divide by mitosis.
What happens to genes during cell differentiation?
Some genes are switched on and expressed , whereas others are switched off and not expressed. The expressed genes are transcribed in mRNA, which is then translated into proteins. These proteins modify the cell so that it becomes specialised for specific functions.
What are totipotent stem cells?
Embryonic stem cells that can produce any type of body cell and only occur for a limited amount of time (in the first few divisions). After this, it becomes pluripotent.
What are pluripotent stem cells?
Embryonic cells present after the first few divisions that can produce any type of body cell EXCEPT cells that make up the placenta.
What are multi-potent stem cells?
Stem cells found in mature mammals which produce a limited number of different cell types. Their role is to replace cells that have been damaged or died.
What are unipotent stem cells?
Stem cells found in mature mammals which produce only one type of cell.
What does stem cell therapy involve?
It involves injecting stem cells into a patient, which then divide and differentiate to replace damaged tissue by illness or injury.