Bio Protein Synthesis: Transcription and Translation

Protein Synthesis

the process in which the cell makes proteins

2 stages of protein synthesis

• Transcription

• Translation

What does the nucleus do for protein synthesis?

• where transcription takes place

• holds the DNA

What does cytoplasm do in protein synthesis?

• where translation takes place

• where amino acids and ribosomes are located

DNA

genetic material located in the nucleus

RNA

ribonucleic acid that carries a “copy” of genetic information

Ribosomes

• create proteins

• made up of rRNA and proteins

Amino acids

• monomers of protein

• 20 different kinds of amino acids

• the order in which they are bonded makes different proteins

• bond between amino acids is called a peptide bond

Peptide bond

bond between amino acids

DNA sugar

deoxyribose

RNA sugar

ribose

Can DNA exit the nucleus?

no, but RNA can

What does RNA use instead of thymine?

uracil

What are the differences between DNA and RNA?

• DNA sugar = deoxyribose

• RNA sugar = ribose

• DNA is double stranded

• RNA is single stranded

• DNA can’t exit the nucleus, but RNA can

• RNA uses uracil instead of thymine

mRNA

messenger RNA

tRNA

transfer RNA

rRNA

ribosomal RNA

What are the different kinds of RNA? (3)

• mRNA = messenger RNA

• tRNA = transfer RNA

• rRNA = ribosomal RNA

Transcription

the process by which a cell makes an RNA copy of a piece of DNA

In transcription, how is the DNA copied?

gene for gene

What is the first step in protein synthesis?

transcription

Promoter

• the gene for transcription

• signals the beginning of transcription

What does the TATA box on the DNA do? (Transcription)

helps the RNA polymerase figure out where exactly it needs to bind to the DNA

What does RNA polymerase do when it binds to the DNA?

starts transcription by unwinding and unzipping DNA

Why does the RNA polymerase read the DNA? (Transcription)

so RNA nucleotides can be added to a growing strand starting at the promoter

• Remember that RNA does not have T, but instead U

When will the RNA polymerase stop? (Transcription)

when a termination signal on the DNA is reached

What happens when a termination signal on the DNA is reached? (Transcription)

The mRNA is released and modified. The parts that are kept are called exons and the “junk” that gets cut out are introns

Once modified, where does is the mRNA able to move?

out of the nucleus

Translation

the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis

In translation, what does the mRNA strand get fed to?

a ribosome

What is the first nucleotide sequence on mRNA?

AUG, which is the start codon

Start codon

signals beginning of translation, universal start codon is AUG

How will the ribosome read the mRNA strand? (Translation)

3 letters at a time, where each set is called a codon

How does the amino acid code work?

Three nucleotides code for 1 amino acid (ex: ACG = Threonine)

What does the ribosome and then tRNA do in translation?

Ribosome finds matching “pieces of puzzle,” and a tRNA will bring the correct amino acid

What does the next codon get matched with?

the next tRNA

What does each amino acid get connected with? What does this start?

each amino acid gets connected onto the previous amino acid, starting a polypeptide chain, which is the beginning of a protein

What are the end/stop codons?

• UAA

• UAG

• UGA

What happens once an end/stop codon is reached?

translation stops and the polypeptide chain is released from the ribosome

What happens when translation stops and the polypeptide chain is released from the ribosome?

The protein then folds itself and contorts very precisely until the end product comes together

What happens due to the complexity of protein synthesis?

errors called mutations occur

Types of mutations

• Some mutations do not change the end product = no harm done

• Other mutations = detrimental to life