LEQ: How does RNA help to make a protein?

10.6 to 10.9

The Central Dogma of Biology

The Central Dogma of Biology Transcription – DNA

making RNA

Translation – RNA making Protein; (aka protein synthesis)

The Central Dogma of Biology Archibald Garrod (1909) –

determined that genes dictate phenotype through enzymes

His ideas stem from his observations of an inherited disease – Alkaptonuria where affected individuals have a defective enzyme that does not break down two amino acids as aresult the produce Alkapton which makes their urine to turn black

The Central Dogma of Biology George Beadle and

Edward Tatum (1940’s) – American geneticists working with bread mold (Neuraspora crassa)

Strains of nutritional mutants helped them prove that specific enzymes were need to at specific steps in metabolic pathways

“One Gene/One Enzyme”

Transcription DNA making RNA Takes place in the

nucleus One main enzyme –

RNA Polymerase RNA is transcribed

in a 5’ to 3’ direction

Only ONE strand of DNA is transcribed at a time

DNA language is rewritten in the process of Transcription

Nucleic acid language is converted to the language of proteins in the process

of Translation

TRANSCRIPTION Initiation – DNA separates and ONE strand serves as a template for the RNA; RNA polymerase binds to the promotor region of DNA

TRANSCRIPTION

Elongation -RNA elongates as complementary RNA nucleotides match up with DNA

nucleotides are added in a 5’ to 3’ direction; U is substituted for T

As RNA polymerase moves forward, RNA releases from DNA; and DNA rewinds

TRANSCRIPTION Termination – RNA polymerase reaches the terminator sequence & releases the DNA and RNA; DNA rewinds; RNA is ready for the next step

Transcription Promoter – specific nucleotide sequence in

DNA, located @ the start of a gene; binding site for RNA polymerase; where transcription begins

Transcription region – segment of DNA that is made into RNA; the gene

Terminator – sequence of nucleotides in DNA that marks the end of a gene. It signals

Sense Strand – the strand of DNA that is transcribed into DNA

Nonsense Strand – the strand of DNA this in not transcribed

The Rosetta Stone of Life

Genetic Code Universal – shared by all organisms;

the set of rules giving the correspondence between nucleotide triplets (codons) and amino acids in proteins

Codes for Amino acids –› Building blocks of a proteins› 20 different amino acids› Coded for by groups of three nucleotide

bases - codons

Codons

Codons – groups of three consecutive nucletides in mRNA that specifies a particular amino acid or a polypeptide termination signal› AUG – start codon; indicates the starting point for

translation; also codes for methionine› Stop codons – don’t code for an amino acid

instead it signals the end of translation