What are totipotent cells?
Cells which can mature into any body cell
How do totipotent cells differentiate?
Translate only part of their DNA
What are pluripotent stem cells?
Stem cells which can differentiate an unlimited number of times into a limited number of specialised cells
-e.g bone marrow stem cells
What are unipotent stem cells?
Stem cells which can only differentiate into a single type of cell
-e.g cardiomyocte
How are induced pluripotent stem cells produced?
Unipotent stem cells and the appropriate protein transcription factors
What do transcription factors do?
Control the transcription of genes
How do transcription factors function?
- Move from cytoplasm to nucleus
- Bind to specific DNA site (promoter region) of the target gene (upstream)
- Activator or repressor for RNA polymerase activity
How does oestrogen affect transcription?
- Binds to oestrogen receptor ( transcription factor) outside of the nucleus
- Forms oestrogen - oestrogen receptor complex which moves into nucleus
- Binds to promoter region
- Activator / repressor
What are epigenetic changes?
Inheritable chemical changes to DNA that alter DNA’s interaction with other proteins without altering the base sequence
Effect of increased methylation?
- More methyl groups attach to DNA
- Prevents transcriptional machinery to interact with the gene
Effect of increased acetylation?
- Acetyl groups bond to histone proteins
- More acetyl groups = chromatin less condensed around histones ∴ less coiling
- Allows transcriptional machinery to access
Why can epigenetic changes cause disease?
Increased/ decreased transcription of genes e.g. t.s.g or oncogenes
What is RNAi
RNA interference is when small, double stranded RNA molecules can prevent the translation of mRNA
What are the molecules involved with RNAi
siRNA - small interfering
miRNA - micro
Associated proteins/enzymes
Processing bodies
Describe the action of siRNA
1) Double stranded siRNA associate with proteins and winds
2) Single strand binds to complementary target mRNA
3) Proteins cut mRNA into fragments
4) Fragments move to a processing body to be degraded
Describe the action of miRNA
1) Single stranded miRNA associate with proteins and binds mRNA
2) Complex blocks translation
3) Complex moved to processing body to either store or degrade
Differences between siRNA and miRNA
- miRNA isn’t fully complementary ∴ can target multiple mRNA molecules
- miRNA binds with proteins and mRNA together
Tumour definition
Abnormal mass of tissue formed of excess cells
Malignant tumour definition
- Tumours which grow quick and invade and destroy surrounding tissue
What contains benign tumours?
Fibrous tissue which prevents cell invasion
Tumour suppressor gene function
Produce proteins which control cell division and apoptosis to control cell life cycle
Proto-oncogene function
Produce proteins which stimulate cell division
Are oncogenes more active than proto-oncogenes?
Yes hence cancer
What can contribute to breast cancer?
Increased oestrogen exposure
-
2.1 Cell Structure27
-
2.1.2 Studying cells12
-
2.2 Cells arising15
-
2.3 Transport across cells15
-
3.2 Gas exchange14
-
3.4 Mass transport12
-
4.1 DNA9
-
4.2 Protein Synthesis9
-
4.3 Meiosis10
-
4.4 Diversity6
-
4.5 + 6 + 7 Taxonomy Biodiversity8
-
5.1 Photosynthesis13
-
5.2 Respiration15
-
5.3 Energy and Ecosystems13
-
5.4 Nutrient Cycles20
-
6.1 Stimuli23
-
6.2 Nerves18
-
6.4 Homeostasis26
-
8.2 Gene Expression24
-
8.4 Recombinant DNA13
