Protein Synthesis:Translation and Transcription

EQ: What is the Central Dogma and what processes does it

involve? Describe processes

Central DogmaO Transcription converts a gene into a

single-stranded RNA moleculeO RNA carries DNA’s instructions out of the

nucleusO The central Dogma states that information

flows in one direction from: DNA RNA Protein

Central DogmaOThe central dogma includes three processes:OReplicationOTranscriptionOTranslation

ORNA is a link between DNA and proteins

RNAORNA differs from DNA

in three major ways.ORNA has a ribose

sugar while DNA has Deoxyribose

ORNA has uracil instead of thymine found in DNA

ORNA is single stranded while DNA is double stranded

TranscriptionO Transcription copies DNA to make a

strand of RNA

RNA being transcribed

TranscriptionO 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.

TranslationO Translation coverts an mRNA message into

a protein

TranslationO Amino acids are coded by mRNA base

sequencesO Translation converts mRNA messages into

proteinsO A codon is a sequence of 3 nucleotides that

code for an amino acid

TranslationOAmino acids are

linked to become a proteinOAn anticodon is a

set of three nucleotides that is complementary to an mRNA codon.

OAn anticodon is carried by a tRNA

TranslationO 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

MutationO Mutations are changes in DNA that

may or may not affect an organisms traits and expression of genes

MutationsO Some mutations affect a single gene, while

others affect an entire chromosomeO A mutation is a change in an organism’s DNAO Many kinds of mutations can occur, especially

during replicationO A point mutation substitutes on nucleotide for

another

Mutations

O Chromosomal mutations affect many genesO Chromosomal mutations may occur during

meiosis

MutationsO Mutations may or may not affect expression

of genesO Chromosomal mutations tend to have a big

effectO Some gene mutations change gene expression

O A mutation may change protein shapeO Some gene mutations do not affect gene

expression

MutationsO Mutations can be caused by several factors

O Replication errors can cause mutationsO UV rays and chemicals can cause mutationsO Some cancer drugs use these properties to kill

cancer cells. O e.g. radiation treatment or chemotherapy