B20- Gene Expression Flashcards
What is a point mutation?
Single nucleotide replacement that changes the triplet code
What is a nonsense mutation
Cause a premature stop in a polypeptide chain
What is a missense mutation
Result in a different amino acid affecting proteins folding
Silent mutation
No change in amino acid due to genetic code redundancy
What is a frame shift mutation?
Base deletion affecting triplet reading frame (includes addition, duplication, inversion, translocation)
What are the causes?
- Spontaneous mutations: Occur naturally with predictable frequencies
- Ionizing radiation: X-rays create free radicals affecting bases; UV radiation causes thymine binding issues
- Chemical agents:
- Nitrogen dioxide: Removes NH2 from cytosine, converting it to uracil
- Benzopyrene: Disrupts base pairing by adding groups to guanine
What are stem cells?
unspecialised cells
What is the order of versatility?
- Totipotent: Can develop into any cell type, including eggs
- Pluripotent: Found in embryos, can become almost any cell type
- Multipotent: Can become a limited number of cell types
- Unipotent: Can only become one cell type
What is the promoter region
Part of gene that is not transcribed
How does the transcription factor work?
Transcriptional factor (TF) molecules activate genes for transcription that bind to specific DNA sequence. Once bound, transcription begins, leading to mRNA production and protein synthesis. When genes are not being expressed, the TF binding site remains inactive.
How does oestrogen work?
- Oestrogen enters cells through diffusion (lipid-soluble)
- Inside the cell, oestrogen binds to a binding site on the transcriptional factor.
- TF changes shape and enters nucleus via nuclear pore
- TF binds to DNA on a specific sequence, transcription is stimulated
How does small interfering RNA work
- Enzyme cuts large dsRNA into smaller sections, called siRNA
- One of the strands combine with another enzyme
- siRNA guides enzyme to the mRNA, complementary bases allow pairing between siRNA and mRNA
- Enzymes cut mRNA into sections and so it can not be translated into a polypeptide.
- Gene expression is blocked
Acetylation of Histone-
An acetyl group from acetyl coenzyme A is transferred to the histone protein this causes the lysine group in histone to lose its positive charge, weakening the attraction between DNA and histone as a result, transcription of the gene becomes possible.
DNA methylation
is a key epigenetic mechanism where methyl groups (-CH3) are added to cytosine bases. This process has two main effects:
- It prevents transcription factors from binding
- It attracts proteins that further condense the DNA-histone complex
This mechanism plays a vital role in gene regulation, particularly during embryonic development and cell differentiation.
What is a proto-oncogene
code for growth factors which control cell division. If mutated, they stimulate cells to divide too quickly (oncogene)
What is a Tumour Suppressor Genes
slow cell division, repair DNA and promote apoptosis (programmed cell death), mutations can inactivate these genes resulting in uncontrolled cell division.
What are the effects of hyper methylation
increased methylation of the promoter region of the tumour suppressor genes inactivates the gene → cancer.
How does whole-genome shotgun sequencing
- Cut DNA into small chunks that can be easily sequenced
- Sequence them
- Use a computer to align overlapping fragment and assemble the whole genome.
What is SNP?
Single Nucleotide polymorphism is a single base variation within genes associated with diseases. Medical intervention and treatment as well as establishing evolutionary relationships.
Why do we study prokaryotes genome?
Understanding prokaryotic genomes helps in developing treatments, creating vaccines, and using organisms for pollution cleanup
