Control Of Gene Expression Flashcards
Every cell contains the same gene. So how do cells work in different ways?
Although they all contain the genes, only certain genes are expressed in any cell at one time
Why do differentiated cells differ from each other?
They produce different proteins coded by the genes that are expressed in that cell
What is a totipotent cell?
Cells that can mature into any body cell
Such as fertilised eggs
During the process of cell specialisation only some genes are expressed so only some of the DNA is translated into proteins. Therefore only making proteins required to carry out specific jobs
How are genes prevented from expressing themselves?
Transcription is prevented, preventing the production of mRNA
Break down mRNA before it is translated
What are stem cells?
Undifferentiated dividing cells found in adult tissue and need to be constantly replaced
Found in the small intestines, skin and bone marrow
What are transcriptional factors?
Specific molecules that move from the cytoplasm into the nucleus
How do transcriptional factors regulate transcription?
The factor binds to a specific region of DNA stimulating it to begin the process of transcription
mRNA is produced and the genetic code is translated into a polypeptide
When a gene isn’t expressed the site on the factor is blocked by an inhibitor preventing transcription
Why is oestrogen a good molecule for switching on a gene?
It’s lipid soluble and so easily diffuses through the phospholipid bilayer
Combines to a site on a receptor as complimentary
Oestrogen changes the shape and so releases the inhibitor so DNA can bind to the transcriptional factor
Transcriptional factor moves into nucleus
The effect of siRNA
Prevents gene expression by breaking down mRNA before it is translated
How is siRNA used?
An enzyme cuts double stranded RNA into siRNA
Some of the siRNA combines with an enzyme
The siRNA guides the enzyme to a mRNA by pairing it’s bases with complementary sections of the mRNA
Enzyme cuts the mRNA into smaller sections
mRNA can no longer translate it
What are some possible uses for siRNA
Used to identify the role of genes in a biological pathway. siRNA that blocks a particular gene can be added to a cell and determine from the effects what role the blocked gene is
Use siRNA to block genes causing diseases
