Transcription And Translation Flashcards
What is a polypeptide?
A polymer consisting of a chain of amino acids joined by peptide bonds.
What is a gene?
A length of DNA that codes for one or more polypeptides.
What is a genome?
The entire DNA sequence of an organism.
What are the characteristics of the DNA code?
It is a triplet code, 3 bases per amino acid, all amino acids except methionine have more than one code, there are stop and start codes, it is a widespread code but not a universal one
Describe the process of transcription
The gent to be transcribed unwinds and unzips. To do this the length of DNA that makes up the gene dips into the nucleus, the hydrogen bonds break. RNA nucleotides bind to their complimentary bases on the template strand. 2 extra phosphates are released. The mRNA produced is complimentary to the nucleotide base sequence on the template strand and therefore a copy of the coding strand. The mRNA is released and passes through a pore, out of the nucleus.
What is translation?
The assembly of polypeptides at ribosomes
What is tRNA?
Transfer RNA are made up of lengths of RNA that fold into hairpin shapes and have 3 exposed bases at one end where a particular amino acid can bind. At the other end are 3 unpaired nucleotide bases, known as an anticodon, which can bind temporarily with its complimentary codon
How is a polypeptide assembled?
mRNA binds to a ribosome, 2 codons are attached to the small subunit of the ribosome and exposed to the large subunit. The first exposed codon is always AUG. tRNA with methionine and the anticodon UAC forms h bonds with this codon. A second tRNA with a different amino acid binds to the second exposed codon. A peptide bond forms between the 2 adjacent amino acids. The ribosome moves along the mRNA and a third tRNA molecule brings another amino acid and it forms a peptide bond with the dipeptide, forming a chain. The first tRNA leaves to collect another amino acid. The chain grows until a stop codon is reached.
