Topic 8 Flashcards
(18 cards)
Stem cells
.Undifferentiated cells which can continually divide and become specialised cells
Different types of stem cells (4)
Totipotent - Can differentiate into any type of body cell, occur in early stages of mammalian embryos, only translate 1 part of DNA to become specialised
Pluripotent - Can differentiate into most cells (not placenta cells) - in embryo
Multi-potent - Can differentiate to form a limited number of cells - found in bone marrow
Unipotent - Only differentiate to form one type of cell
Problem with using stem cells
.As they continually divide, they can form tumours
.Therapeutic cloning (unlike reproductive cloning, we don’t clone to make a living individual, we clone to make stem cells)
.Destroying the embryo (debate on of it is destroying a life)
What are IPS
Induced pluripotent cells, made from using transcription factors to switch on genes on unipotent cells , making pluripotent stem cells
Epigenetics and what causes it
.Heritable changes in gene function without changing DNA base sequence
.Factors such as diet, stress and toxins can add chemical tags to DNA/Histones (CHANGES THEIR EPIGENOME)
Difference between heterochromatin and chromatin
Heterochromotin is tightly coiled (gene will not be transcribed) whereas chromotin is loosely coiled ( Gene will be transcribed)
What are transcription factors
These are protein found in the cytoplasm which move into the nucleus and bind to a complimentary base sequence (promotor region) to turn on/turn off genes (it allows RNA polymerase to bind DNA )
Without binding of transcription factors, the gene is INACTIVE (turned off)
Describe Methylation
When methyl groups attach to cytosine base on DNA, Increased methylation results in heterochromatin (due to positive charge) so inhibits transcription by preventing transcriptional factors from binding
Describe acetylation
Bind to the histones, and due to negative charge they repel DNA (causing it to be loosely packed) allowing for transcription factors to bind.
What are tumour suppressor genes and what are oncogenes
.Genes which produce proteins that slow down (regulate) cell division and cause cell death if copying errors are detected
.Oncogenes creates a protein which triggers mitosis to occur.
Why is breast cancer more likely after menopause
Fat cells in breast tissue start to produce oestrogen, which can bind to transcription factor which turns on a proto-oncogene, if this is permanently switched in cell division occurs uncontrollably.
.This is an example of positive feedback as more breast tissue is made and this increases concentration of oestrogen even more.
Whats the role of Oestrogen
This is a steroid hormone (meaning it’s lipid soluble and can simply diffuse from the blood into the cell) which binds to the receptor site on the transcriptional factor , cause DNA binding site to change shape slightly, making it complementary to DNA and able to bind
What is the role of RNAi
The prevent translation by destroying mRNA
How is siRNA (small interfering RNA) made
dsRNA (double stranded RNA) is cut into small sections by an enzyme, making siRNA
How does siRNA prevent translation
One strand of siRNA combines with an enzyme to form an siRNA-enzyme complex which will bind to complementary base sequence in mRNA , and the mRNA is cut up so it CAN NOT BE TRANSLATED)
differences between Benign tumour and malignant tumours (5)
. Benign tumour grow at a slow rate whereas malignant grow rapidly ( due to them being able to grow projections into the blood supply as they have no capsule and so they obtain oxygen and glucose)
. Benign tumour produce adhesive molecules, sticking them together to a particular tissue whereas malignant don’t produce adhesive molecules so break off and spread to other parts of the body
. Benign tumour are surrounded by a capsule so they remain compact whereas malignant are contained in a capsule
. Benign tumour can be removed from surgery and rarely return whereas malignant recurrence is much more likely
. Benign tumours impact is localised whereas malignant effect is systematic
How tumours can develop
.Increased oestrogen concentration
.Gene mutation in tumour suppressor gene
.Gene mutation on oncogene
.Abnormal methylation of tumour suppressor genes (increased methylation) or oncogene (decreased methylation)
What are proto-oncogene gene and oncogenes
.Oncogenes are mutated proto-oncogenes (cells divide continually as its permanently activated)
.Proto-oncogenes is a protein which initiates DNA replication
