Eukaryotic DNA
- Linear
- Kept in a membrane-bound nucleus in the cell
- Forms a double helix
- Mitochondria and chloroplasts contain their own DNA, which is referred to as non-nuclear DNA
- Wrapped around histone proteins
Prokayotic DNA
- Circular and not in a double helix shape, but two circles of DNA twisted around each other
- Not contained in the membrane, so it floats around the cytoplasm
Why are Polypeptides Important?
- variation
- proteins
- complexity
Important for the increasing complexity of organisms, the more proteins, the more complex the organisms
At each stage of polypeptide synthesis, there are opportunities for variation, which is crucial for the continual development and adaptation of the species.
Production of proteins:
- Proteins can be: enzymes, hormones, etc
- Enzymes: build and repair
- Hormones: our genes help us to build the right proteins at the right time
What do proteins do?
Enzymes:
- speed up reactions in the body
- build and repair
Hormones
- Body’s chemical messenger
Sequence of Polypeptide Synthesis:
D A P F
DNA code –> amino acids –> polypeptide chain –> folds into a protein
Importance of mRNA
Allows for genetic code in DNA to be translated into proteins.
DNA is held in the nucleus of a eukaryotic cell and is too large to penetrate the nuclear membrane.
The single-stranded mRNA is able to pass through and thus translate the genetic instruction to the protein
Importance of tRNA
- Important molecule in transcription that attaches to mRNA to give a specific sequence of amino acids that synthesis into a protein.
- Important for the attachment of amino acids to form a growing polypeptide chain.
- Maintains the sequential synthesis of the protein
Function and importance of polypeptide synthesis
-transcription and translation are carried out in the cells for the creation of proteins –> Proteins are essential biological molecules that cells and tissues require for their specific function
- genetic information being translated via RNA contains full and accurate instructions for the correct functioning of a cell.
- If there are any errors in the creation of mRNA or the pairing of the nucleotides, the end-products may change, thus compromising the survival of the organism.
- Gene expression is regulated by proteins, important that polypeptide synthesis is carried out accurately phenotype for an organism
Environment on phenotype
The environment does not chemically modify the sequence of bases, but influences the phenotype via chemical markers or tags being added to DNA
Temperature can cause organisms to express the phenotype of mutant alleles through colour of fur, etc
E.g. hydrangeas → the pH of soil influences the phenotype and causes a change in the colour of the flower
Chemical Structure of Proteins
Chain of amino acids bonded together by polypeptides folded into a protein. The fold of the protein determines its function
