gene expression Flashcards
what is a mutation?
a change to the base sequence of DNA that results in an altered polypeptide
A mutation can lead to various effects on protein function, depending on the type and nature of the change.
what is substitution
when one base is replaced by another
This can potentially lead to the development of new functions of polypeptides.
what are the types of substitution
silent: same amino acid coded for due to degenerate nature of code
missense: different amino acid -> dysfunctional polypeptide
nonsense: stop codon
This can manifest in different forms, such as silent, misense, or nonsense mutations.
what happens when a gene is duplicated
two copies of the same gene on the same chromosome -> development of new function of polypeptide
These mutations do not affect the amino acid sequence of the resulting protein.
what is an insertion or deletion mutation?
one or more bases added/removed → frameshift
This alters the reading frame of the genetic code, potentially leading to significant changes in the protein.
what is an inversion mutation?
sequence of bases reversed
This can disrupt the normal function of genes in the affected region.
what happens when bases are translocated
bases separate from DNA sequence and are inserted onto different gene
This can lead to new gene combinations and potentially new functions or diseases.
what are mutagenic agents?
increase the risk of mutation development
ie radiation (changes DNA structure)
chemicals (alter bases / incorporate into code)
viruses (inject genetic information into host DNA)
what are the effect of mutations
beneficial → provides genetic variation for natural selection (antibiotic resistance in bacteria)
neutral → degenerate nature of code
harmful → genetic disorders (cystic fibrosis) or cancer
What are stem cells?
Undifferentiated cells that can divide indefinitely and specialise into any cell
Stem cells have the unique ability to develop into different types of cells in the body.
what does totipotent mean
stem cells that can specialise into any body cell, including placental cells
what does pluripotent mean?
stem cells that can specialise into any body cell, except placental cells
Pluripotent stem cells are derived from the inner cell mass of the blastocyst.
what does multipotent mean?
stem cells that specialise into a limited range of body cells (e.g., bone marrow cells → blood cells)
what does unipotent mean?
stem cells that can divide into one body cell type (e.g., heart muscle cells / cardiomyocytes)
Unipotent stem cells have the least differentiation potential.
what are induced pluripotent stem cells?
unipotent adult cells that have been genetically reprogrammed to behave like pluripotent embryonic stem cells using specific transcriptional factors
what are the pros and cons of using iPSCs
✅ avoid ethical concerns linked to embryo destruction
✅ no risk of rejection if the patient’s own cells are used
✅ can be generated from a variety of adult cell types
❌ risk of mutations leading to cancer
❌ still in early stages of development and research
what are uses of stem cells
regenerative medicine and transplants
research and drug development
what are ethical concerns behind stem cells
destruction of embryos → potential human life
could lead to reproductive cloning
religious and moral views
consent issues
what are transcription factors
proteins that control gene expression by influencing RNA polymerase activity
what is an activator transcription factor
bind to promoter region → allow RNA polymerase binding to DNA → stimulates transcription → more mRNA → more protein production
what is a repressor transcription factor
bind to operator region → prevent RNA polymerase attachment to DNA → decrease or inhibit transcription → less or no protein production
what is oestrogen and how does it function
a lipid soluble steroid hormone that diffuses from the bloodstream into the cell
binds to an oestrogen receptor (transcription factor) → changes its shape → forms oestrogen receptor complex
inhibitor molecule released → transcription factor binding site exposed
binds to promoter region → allows RNA polymerase attachment → initiates transcription
what is RNA interference?
post-transcriptional gene regulation mechanism that prevents specific gene expression before translation
RNA interference involves mechanisms like small interfering RNA (siRNA) and micro RNA (miRNA) to control gene expression.
what does small interfering RNA (siRNA) do?
silences specific genes by breaking down mRNA before translation
siRNA is double-stranded and targets specific mRNA to prevent protein production.
