T20 Flashcards
What are induced pluripotent stem cells and what are their advantages?
Induced pluripotent stem cells (iPS cells) are produced from adult unipotent stem cells that are genetically altered to acquire characteristics of embryonic stem cells.
This involves switching on certain genes within the cells to induce the expression of genes and transcription factors.
Advantages of iPS cells:
They can self-renew indefinitely.
They can differentiate into various cell types.
They avoid ethical issues associated with using embryonic stem cells.
They could provide an unlimited source of stem cells for research and medical treatments.
What are transcription factors?
Transcription factors are proteins that bind to specific DNA sequences to initiate the transcription of genes into mRNA.
mRNA is that is produced during transcription then carries the genetic code from DNA to ribosomes, allowing the production of proteins. Transcription factors therefore have a crucial role in gene expression regulation.
When a gene is ‘switched off’, transcription factors cannot bind to DNA. This prevents the transcription process and so the synthesis of polypeptides.
How does oestrogen (steroid hormones) regulate transcription?
Steroid hormones diffuse through the cell-surface membrane into the cell.
Inside the cell, these hormones bind to receptors on transcription factors.
This binding changes the shape of the transcription factor, activating it.
The activated transcription factor then enters the nucleus and binds to specific DNA sequences.
This binding stimulates the transcription of the gene located at these sequences.
What is the effect of increased DNA methylation?
Addition of methyl groups to DNA
Increases hydrophobic interactions, tightening DNA coiling
Condenses chromatin
Silences genes by preventing binding of proteins for transcription
What is the effect of decreased histone acetylation (deacetylation)?
Enzymatic removal of acetyl groups from histones
Increases histones’ positive charge
Condenses chromatin
Silences genes by preventing binding of proteins for transcription
How do mutations effect tumour suppressor genes?
Tumour suppressor genes regulate cell division, repair DNA, and initiate apoptosis to prevent tumour formation.
Mutations can deactivate these genes.
This prevents them from producing proteins that normally regulate cell division, DNA repair, and apoptosis, leading to uncontrolled cell growth and cancer.
How do mutations effect proto-oncogenes?
Proto-oncogenes stimulate cell division when growth factors bind to the cell’s receptors, activating DNA replication.
Mutations or excessive growth factor production can amplify the function of proto-oncogenes.
This causes them to promote excessive DNA replication and cell division.
Once mutated, proto-oncogenes are known as oncogenes.
What is DNA barcoding and its advantages?
DNA barcoding involves comparing the DNA sequence of an unidentified organism to a database of standard ‘barcode’ sequences for known species. This means researchers can find similarities between new DNA sequences and those already in databases. This indicates common ancestry and allows scientists to build evolutionary trees with greater accuracy.
DNA barcoding offers advantages such as:
Fast and affordable sequencing.
The classification of new species.
Updating of classifications.
Estimating evolutionary divergence times based on predictable DNA mutation rates to construct evolutionary trees.
