Stem Cells & Control of gene expression Flashcards
Explain what is meant by the terms of totipotent and pluripotent
- totipotent cells can give rise to a complete human/all cell types e.g zygote & early embryo
- pluripotent can only give some cell types e.g embryonic and fatal stem cells
Explain what is meant by the terms of multipotent and unipotent
- multipotent have the ability to differentiate into a limited number of different cell types e.g adult stem cells
- unipotent are capable of giving rise to only one cell type e.g cardiomyocytes
Explain how oestrogen enables RNA polymerase to transcribe its target gene
- oestrogen diffuses through phospholipid cell membrane because its lipid soluble
- diffuses through nuclear envelope and binds to the oestrogen receptor
- changes tertiary structure and releases the transcription factor
- transcription factor binds to the promoter region
- stimulates RNA polymerase to transcribe gene
Describe the control of translation
- single strand of siRNA and miRNA binds to protein in the cytoplasm to form a complex (RNA-induced silencing complex)
- the miRNA/siRNA has a complementary base sequence to part of a specific mRNA molecule
- complex inhibits gene expression by binding to complementary mRNA which causes either:
- mRNA being hydrolysed by an enzyme
- prevents ribosome from attaching to the mRNA
- TRANSLATION DOES NOT TAKE PLACE
Define epigenetics
- inheritable changes in gene expression without changes to the DNA base sequence
Describe the mechanism by which a signal protein causes the synthesis of mRNA
- signal protein binds to receptor on surface membrane
- messenger molecule moves from cytoplasm and enters nucleus
- transcription factor binds to promoter region
- RNA polymerase transcribes target gene
Compare the structure of dsRNA and DNA
Similarities:
- have pentose sugar
- double stranded & hydrogen bonds
Differences:
- dsRNA contains ribose whereas DNA contains deoxyribose
- dsRNA is shorter whereas DNA is longer
Explain how methylation of tumour suppressor genes can lead to cancer
- methylation prevents transcription of gene
- protein not produced that prevents cell division leading to uncontrolled division
- no control of mitosis
Describe how alterations to tumour suppressor genes can lead to the development of tumours
- increased methylation of tumour suppressor genes
- mutation in tumour suppressor genes
- tumour suppressor genes are not transcribed
- results in uncontrollable cell division
Describe malignant and benign tumours
- Malignant tumours grow rapidly whereas benign tumour grow very slowly
- Malignant are more likely to life threatening whereas benign are less likely to be life threatening
- malignant tumours metastasise whereas benign tumours do not metastasise
Describe how altered DNA may lead to cancer
- DNA altered by mutation
- which changes base sequence of gene controlling cell growth of tumour suppressor gene
- changes protein structure
- tumour suppressor genes produce proteins that inhibit cell division
- mitosis
- leads uncontrollable cell division
Describe what happens if there are changes to a tumour suppressor gene
- increased methylation: rate of cell division increases
- increased acetylation: rate of cell division decreases
Describe what happens if there are changes to an onco gene
- decreased methylation: rate of cell division increases
- decreased acetylation: rate of cell division decreases
What is acetylation?
- acetylation of histone molecules result in them becoming loosely packed
- the promoter region is exposed and transcription factors are able to bind
- this then allows RNA polymerase to bind and target gene can be transcribed
