From DNA to Protein

Section 11.2

Pg. 294-301

There are 3 types of RNA:

1. messenger RNA (mRNA) – The RNA that brings information from the DNA in the nucleus to the cytoplasm.

2. transfer RNA (tRNA) –Transports amino acids to the ribosome to be assembled into a protein.

3. Ribsomal RNA (rRNA)- Ribosomes, made of rRNA clamp onto the mRNA and use its information to assemble the amino acids

TRANSCRIPTION

Transcription is the process where the DNA code is copied onto a strand of messenger RNA (mRNA). This occurs in the nucleus.

Steps of Transcription:

1st Step

– Enzymes “unzip” DNA

Steps of Transcription:

2nd Step– RNA nucleotides

pair with complementary DNA nucleotides on one of the DNA strands.

Steps of Transcription:

3rd Step – When base pairing

is completed mRNA is formed and the DNA strands rejoin.

– Each set of 3 nitrogen bases on mRNA is a codon. Each codon codes for an amino acid.

Steps of Transcription:

4th step– Once mRNA is

made it leaves the nucleus and it attaches to a ribosome (made of rRNA) in the cytoplasm.

Translation:

Translation - process of converting the info in a sequence of nitrogen bases in mRNA into a sequence of amino acids.

Occurs in the ribosomes (made of rRNA) in the cytoplasm.

More Information on tRNA

Role of tRNA is to bring amino acids to the ribosomes, so proteins can be built.

How do they do this?– tRNA has the anticodon,

which is a nucleotide triplet which binds to the complimentary codon on the mRNA

– tRNA only carries amino acids that the anticodon speifies.

Steps of translation include:

1. tRNA with its amino acid attaches to a ribsome (made of rRNA).

2. tRNA (carrying specific amino acid) has an anticodon that bonds with the first mRNA codon.

3. When a signal is given ribosome (made of rRNA) slides along the mRNA to the next codon

Steps of translation include:

4. New tRNA molecule carries an amino acid pairs with the second mRNA codon

5. Enzyme joins the amino acids by forming a peptide bond

6. The process continues until the protein has been completely made.

Steps of translation include: