1.3 Control of Gene expression Flashcards
What forms the genetic code?
the base sequence of DNA
Where is the genetic code found?
in all forms of life suggesting all life originated from a common ancestor
What are genes?
Genes are the units of genetic code that make up the genotype of an organism
Genes are expressed to produce proteins
These proteins form the structure and control the functions of the organism
What is the phenotype?
the phenotype of an individual is determined by the proteins produced by the expression of its genes
Only a fraction of the genes in a cell are expressed depending on the proteins required by the cell
TOPTIP
order of DNA bases | (genotype) order of mRNA bases | (phenotype) order of amino acids in proteins
What is the basic structure of a protein?
protein contains the element carbon, hydrogen, oxygen and nitrogen
Protein molecules are polypeptide chains
Polypeptide is a chain of amino acids held together by peptide bonds
What is the 3D protein structure?
polypeptide chains fold into the final protein shape
the shape is held by hydrogen and ionic bonds and links between sulphur atoms
Describe the different levels of protein structure?
primary - a single polypeptide chain (sequence of amino acids joined by peptide bonds
secondary - folding of polypeptide chain held by hydrogen bonds (alpha helices and beta sheets)
tertiary - Interaction between amino acids forming a complex protein molecule. hydrogen, ionic and sulphur bonds hold the proteins shape
Quaternary - interaction between polypeptide chains
The final protein structure can be fibrous or globular. Explain these terms?
Fibrous form from parallel polypeptides into cable shapes for structural roles.
example: keratin in hair, nails and hooves and collagen
Globular proteins are folded into a specific spherical shape that allows it to carry out a functional role
Example: enzymes, hormones, antibodies
TOPTIP
the shape of a protein allows it to perform its specific function
Name the four protein groups?
structural
enzymes
hormones
antibodies
Function of structural proteins and an example?
building blocks of cell structure e.g. actin and myosin from contractile fibres in muscle cells
Function of enzymes and example?
speed up the rate of chemical reactions e.g. pepsin speed up the breakdown of proteins in the stomach during digestion
Function of hormones and example?
chemical messengers involved in regulations e.g. Insulin is involved in the regulation of sugar levels in blood
Function of antibodies and example?
Defensive substances that give immunity against specific diseases e.g. measles immunoglobulin specifically recognises measles antigens and renders them in active
What is chromatography?
A technique used to separate a mixture which differ in the components solubility in a solvent
As the solvent passes up through absorbent paper it carries the components of the mixture different distances
The more soluble the component the further it travels along the paper
How to calculate RF values?
distance travelled by component
divided by
distance travelled by solvent front
What is gene expression?
Genes are transcribed and translated during gene expression
Gene expression is controlled by the regulation of transcription and translation
Gene expression can be influenced by intracellular and extracellular environmental factors
What are the stages of gene expression?
DNA (sequence of bases) –> mRNA (sequence of bases) –> Protein (sequence of amino acids)
What is RNA?
a second type of nucleic acid involved in gene expression
Types of RNA?
Messenger (mRNA)
Transfer (tRNA)
Ribosomal (rRNA)
What is mRNA?
formed in the nucleus during transcription
transports a copy of the base sequence of gene to the cytoplasm where it attaches to a ribosome
Compare DNA and mRNA?
DNA sugar - deoxyribose bases - Adenine, thymine, cytosine, guanine number of strands - two location - nucleus
mRNA sugar - ribose bases - adenine, uracil, cytosine, guanine number of strands - one location - nucleus and cytoplasm
What is transfer (tRNA)?
tRNA are molecules in the cytoplasm which carry specific amino acids to mRNA at the ribosome, placing them in the order determined by the base sequence on the mRNA to form a polypeptide chain.
this is called translation