Protien synthesis. Flashcards
what is a gene
a length of DNA that codes for a polypeptide/ protien.
what is a genome
the complete set of genes present in a cell.
what is the proteome
the full range of protiens that a cell is able to produce.
genome vs proteome explain
proteome is larger - large amount of post translational modification of protiens often in golgi.
how can a geme produce multiple different protiens?
alternative splicing.
what does a phosphodiester bond link? Think primes
the 5’ of one pentose sugar to the 3’ of the next nucleotide.
mRNA structure
single stranded molecule
made up of a sugar-phosphate backbone and exposed unpaired bases.
Uracil bases present instead of thymine bases.
tRNA structure
single stranded molecule.
sugar phosphate backbone
folded shape - there are hydrogen bonds between some of the complementry bases.
amino acids bind to a specific region of the molecule
the specific anticodon found on the tRNA molecule is complementary to a specific codon on an mRNA molecule.
what is transcription and translation, simple.
transciption - DNA is transcribed and an mRNA molecule is produced.
translation - mRNA is translated and an amino acid sequence is produced.
Transcription process.
In nucleus
Part of a DNA molecule unwinds, the hydrogen bonds between COMPLIMENTRY BASE PAIRS break
this exposes the gene to be transcribed.
A complimentry copy of the code is made by building a single-stranded nucleic acid called mRNA.
free activated RNA nucleotides pair up via hydrogen bonds with their complementry bases.
the sugar-phosphate groups on the RNA nucleotides are then bonded together by RNA polymerase
the hydrogen bonds between the mRNA and DNA strands break and the double stranded DNA molecule reforms.
after transcripiton:
pre-mRNA is formed which is then spliced to make mRNA
mRNA molecule then leaves via the nuclear envelope
What is the difference between transcription in prokaryotes and eukaryotes?
prokaryotes - directly leads to mRNA
eukaryotes - leads to pre-mRNA which is spliced to form mRNA.
alternative splicing, what is it and why?
splicing in different ways to produce different mature mRNA molecules.
this means that a single gene in a eukaryote can code for more than one polypeptide chain.
this is part of the reasoin the proteome is much bigyger than the genome.
translation process.
occurs in the cytoplasm
mRNA moecule attaches to a ribosome
there are free molecules of tRNA in the cytoplasm.
these tRNA molecules have a triplet of unpaired bases at the end ANTICODON
at the other end, they have a region where a specific amino acid can attach.
tRNA molecules bind with their specific amino acids (also in the cytoplasm)
and it brings them to the mRNA molecule on the ribosome.
Two tRNA molecules fit onto the ribosome at any one time. bringing the amino acid they are carrying side by side.
a peptide bond forms between the 2 amino acids.
the formation of a peptide bond requires energy - ATP
provided by mitocondria.
continues until stop codon is reached.
polypeptide is produced.
what is a triplet?
a sequence of 3 DNA bases which codes for a specific amino acid.
what is a codon?
a sequence of 3 mRNA bases that codes for a specific amino acid.
transcribed from the triplet.
