DNA, genes and protein synthesis Flashcards
What is produced by translation
Proteins
What is produced by transcription
mRNA
What is the genetic code
-Order of bases on DNA. Consists of codons (triplets of bases that code for a particular amino acid)
Process of translation
-The anti-codon of tRNA attaches to the complementary bases on the mRNA
-Amino acids bonded to tRNA form peptide bonds, continuing to form a polypeptide chain until a stop codon is reached
-Process requires ATP
Process of transcription
-DNA uncoils into two strands with exposed bases. One is used as a template
-Free nucelotides line up next to their complementary bases and are joined together by RNA polymerase
Where does translation take place
In the cytoplasm (on ribosomes)
How is DNA in eukaryotic cells different from in prokaryotic cells
-Eukaryotic
-Found in nucleus, long and linear
-Associated with histone proteins to form chromosomes
-Mitochondria and chloroplasts contain prokaryotic linr DNA
Prokaryotic
-Short and circular. not associated with proteins
Structure of tRNA
-A single strand of about 80 nucleotides that is folded over into a 4 leaf clover shape.
-On one end is an anti-codon, on the opposite end is an amino acid binding site
Gene
A sequence of bases on a DNA molecule that codes for a specefic sequence of amino acids to make a polypetide. Can also code for functional RNA
What is produced by translation
Proteins
Locus
-Fixed position on a DNA molecule occupied by a gene
what happens to mRNA after transcription
-In eukaroyotic cells, pre-mRNA must be spliced to remove introns, leaving only the coding regions. It then moves out of the nucleus and attactchs to a ribosome
Genome
Complete set of genetic information contained in the cells of an organism
Advantages of using mRNA rather than DNA for translation
-Shorter and contains more uracil= breaks down quickly so no excess polypeptide forms
-Single stranded and linear= ribosome moves along strand and tRNA binds to exposed bases
-Contains no introns
Outline the process of transcription
-DNA uncoils into two strands with exposed bases, one is used as a template
-Free nucleotides line up next to their complementary bases and are joined together by RNA polymerase
Structure of mRNA
-Long single strand
-Base sequence is complementary to the DNA it was transcribed from
What happens to mRNA after transcription
In eukaryotic cells, pre-mRNA must be spliced to removed introns, so only coding regions remain.
It then moves out the nucleus and attatchs to a ribosome
Exons
Regions of DNA that code for amino acid sequences. Seperated by one or more introns
Where does transcription take place
The nucleus
Features of the genetic code
-Non-overlapping= each triplet is only read once
-Degenerate= more than one triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
-Universal= same bases and sequences ised by all species
Preteome
Complete set of proteins that can be produced by a cell
Introns
Regions of DNA that do not code for anything
Role of RNA
Transfers genetic information to ribosomes for protein sytnthesis
