1 DNA, RNA And Protein Synthesis Flashcards
Describe DNA in prokaryotic cells.
DNA molecules are short, circular and not associated with proteins.
Describe DNA in eukaryotic cells.
DNA molecules linear, very long and associated with proteins, called histones. Together a DNA molecule and its associated proteins form a chromosome.
Describe the mitochondria and chloroplasts of eukaryotic cells DNA.
Mitochondria and chloroplasts of eukaryotic cells also contain DNA which, is short, circular and not associated with protein.
What is a gene?
A base sequence of DNA that codes for either the amino acid sequence of a polypeptide or a functional RNA. It occupies a fixed position called a locus, on a particular DNA molecule.
What is a triplet?
A sequence of 3 DNA bases that code for a specific amino acid. The genetic code is universal, non-overlapping and degenerate.
Explain why most DNA in eukaryotic cells doesn’t code for polypeptides.
- some genes don’t code for polypeptides at all, thy code for functional RNA.
- in eukaryotic DNA, genes coding for polypeptides contain sections that don’t code for amino acids, called introns.
- all bits of gene that do code for amino acids called exons.
- introns removed during protein synthesis,so don’t affect amino acid order.
- eukaryotic DNA also contain regions of multiple repeats outside of genes, these are DNA sequences that repeat over and over, these areas don’t code for amino acids either so called non-coding repeats.
Describe the structure of mRNA.
- made during transcription.
- carries genetic code from DNA to ribosomes, where it’s used to make protein during translation.
- it’s a single polynucleotide strand.
- in mRNA groups of 3 adjacent bases are usually called codons.
Describe the structure of tRNA.
- involved in translation.
- carries amino acids that are used to make proteins to the ribosomes.
- it’s a single polynucleotide strand that’s folded into a clover shape.
- hydrogen bonds between specific base pairs hold molecule in this shape.
- every tRNA molecule has a specific sequence of 3 bases at one end called an anticodon. Also have an amino acid binding site at other end.
Describe the first stage of protein synthesis- transcription.
- DNA helicase separates DNA strand.
- breaking hydrogen bonds.
- free RNA nucleotides attach to template strand.
- complementary base pairing
- RNA polymerase joins nucleotides together
- hydrogen bonds reform.
Describe the products of transcription in prokaryotes.
Results directly in production of mRNA and DNA. No splicing.
Describe the products of transcription in eukaryotes.
Results in production of pre-mRNA which is spliced to form mRNA.
Describe the second stage of protein synthesis- translation.
- ribosome binds on to mRNA at a start codon.
- codon is matched to an anticodon by complementary base pairing.
- ribosome holds tRNA in place.
- amino acids joined together with a peptide bond.
- used tRNA goes back to cytoplasm to attach a new amino acid(same each time)attaching amino acid requires ATP.
What is the concept of the genome and of the proteome?
- concept of genome is the complete set of genes in a cell
- concept of proteome is full range of different proteins that a cell is able to produce.
