Protein Synthesis:
Translation and Transcription
EQ: What is the Central Dogma
and what processes does it
involve?
Describe processes
Central Dogma
O Transcription converts a gene into a single-
stranded RNA molecule
O RNA carries DNA’s instructions out of the nucleus
O The central Dogma states that information flows in
one direction from:
DNA
RNA
Protein
Central Dogma
O The central dogma
includes three
processes:
O Replication
O Transcription
O Translation
O RNA is a link between
DNA and proteins
RNA
O RNA differs from DNA in
three major ways.
O RNA has a ribose
sugar while DNA has
Deoxyribose
O RNA has uracil
instead of thymine
found in DNA
O RNA is single
stranded while DNA is
double stranded
Transcription
O Transcription copies DNA to make a strand
of RNA
RNA being transcribed
Transcription
O Transcription makes three types of RNA
O Messanger RNA (mRNA) carries the message that will
be translated to form a protein
O Ribosomal RNA (rRNA) forms part of ribosomes where
proteins are made
O Transfer RNA (tRNA) brings amino acids from the
cytoplasm to a ribosome.
Translation
O Translation coverts an mRNA message into a protein
Translation
O Amino acids are coded by mRNA base sequences
O Translation converts mRNA messages into proteins
O A codon is a sequence of 3 nucleotides that code for an
amino acid
Translation
O Amino acids are linked
to become a protein
O An anticodon is a set
of three nucleotides
that is complementary
to an mRNA codon.
O An anticodon is
carried by a tRNA
Translation
O Translation occurs at the ribosome
O For translation to begin, tRNA must bind to a
corresponding codon. Ex. tRNA anticodon – UAC
binds with mRNA codon AUG
O Then attaches amino-acid to form a protein
Mutation
O Mutations are changes in DNA that may or
may not affect an organisms traits and
expression of genes
Mutations
O Some mutations affect a single gene, while others
affect an entire chromosome
O A mutation is a change in an organism’s DNA
O Many kinds of mutations can occur, especially during
replication
O A point mutation substitutes on nucleotide for another
Mutations
O Chromosomal mutations affect many genes
O Chromosomal mutations may occur during meiosis
Mutations
O Mutations may or may not affect expression of genes
O Chromosomal mutations tend to have a big effect
O Some gene mutations change gene expression
O A mutation may change protein shape
O Some gene mutations do not affect gene expression
Mutations
O Mutations can be caused by several factors
O Replication errors can cause mutations
O UV rays and chemicals can cause mutations
O Some cancer drugs use these properties to kill cancer
cells.
O e.g. radiation treatment or chemotherapy