1-5 Gene expression Flashcards
What is a Genotype?
the particular set of genes an organism has for a trait
What is a Phenotype:
the physical result of the genotype (observable characteristics)
What is Phenotypic expression of a gene
refers to the physical, biochemical, or physiological characteristics that it produces.
Characteristics are determined by a combination of genetics and environmental conditions.
what factors influence gene expression
gender, chemicals, temperature, and products of other genes.
when can the expression of genes be regulated
regulated at either the transcription OR translation stage of protein synthesis.
what are transcription factors
are regulatory proteins that control gene expression.
Some switch genes ‘on’ by binding to DNA
Some switch genes ‘off’ by blocking the attachment of RNA polymerase
traits of Micro RNA
Small non-coding RNA
Approx 22 nucleotides
Help regulate gene expression after transcription
Bind in a complementary fashion to a specific mRNA molecule
Small section of the mRNA is now double stranded
Prevents the ribosome from accessing the mRNA code
Gene is not expressed
traits of small interfering RNA
Silencing RNA or small interfering RNA
Act on mRNA preventing translation
Usually consist of 21 nucleotides.
Bind to a specific mRNA molecule
Promotes the destruction of the mRNA molecule.
Therefore the mRNA strand is not translated
Gene expression is stopped.
traits of long non-coding RNA
Silencing RNA or small interfering RNA
Act on mRNA preventing translation
Usually consist of 21 nucleotides.
Bind to a specific mRNA molecule
Promotes the destruction of the mRNA molecule.
Therefore the mRNA strand is not translated
Gene expression is stopped.
Environmental factors affect transcription and translation.
ENVIRONMENTAL FACTOR causes on
PHENOTYPIC EXPRESSION
Lack of oxygen-Increased RBC production
Increased UV exposure-Change in skin colour – due to increased melanin
Lack of iodine-Goitre in humans – enlargement of the thyroid
what is Differentiation
the process whereby cells become specialised in both form and function.
examples of differentiated cells
the process whereby cells become specialised in both form and function.
HOW IS DIFFERENTIATION ACHIEVED?
All of the cells in an organism have the same genome (and hence the same genes)
Certain genes of certain cells are activated to produce specific proteins, thus giving rise to cells with different cell function.
For example, genes that code for certain proteins required in nerve cells but not required in liver cells, are activated in the nerve cells but ‘switched off’ in the liver cells.
This is how differentiation is achieved.
What is Methylation
Where heritable changes are made to the DNA outside traditional mutations (base sequence).
Methyl groups attach to cytosine nucleotides.
Methyl groups cause the DNA to coil more tightly
what happens when the gene is switched on
active (open) chromatin, unmethylated cytosines, acetylated histone, transcription possible.
what happens when the gene is switched off
silent (condensed) chromatin, methylated cytosines, deacetylated histones, transcription not possible.
how are identical siblings Epigenetically indistinguishable during the early years of life but differences increase as they age?
different environmental conditions e.g. diet, exercise, chemicals.
Changes in the epigenome could result in genes not being expressed that then lead to disease. A change in the rate of production of insulin for example.
May also result in genes being expressed that then lead to disease.
Cancer, which is uncontrolled cell division is one example that is being closely studied.
What are Clones and name examples?
Clones are organisms that are genetically identical
Identical Twins are examples of natural clones
Plants grown from cuttings or any asexual method are clones
what are oncogenes
the mutated form of the normal genes called proto-oncogenes.
what are proto-oncogenes
genes that code for proteins that regulate normal cell growth and division
what are tumour-suppressor genes
genes that inhibit cell division. When these genes are mutated, cell division is no longer inhibited – cell then divides rapidly and uncontrollably.
