RNA AND PROTEIN SYNTHESIS

RNA3 types: mRNA – used in

transcription tRNA – used in translation rRNA – makes up

ribosomesComposed of nucleotides 5 carbon sugar = ribose phosphate group nitrogen bases (no

Thymine…uses Uracil) A,U,C,G

RNA has a Single strand

PROTEIN SYNTHESIS–

STEP 1: TRANSCRIPTION

The information that tells a cell which proteins to make is encoded in the DNA by the arrangement of nucleotides.

DNA is in the nucleus.

Proteins are made in the cytoplasm on ribosomes.

Problem: The message on DNA has to be carried to the ribosomes.

Solution: The message from DNA is carried to the ribosomes using RNA.

The process of copying the DNA message in the nucleus onto RNA to be carried to the ribosomes is called TRANSCRIPTION.

TRANSCRIPTIONCopying the

information on DNA to a strand of messenger RNA (mRNA)

WHAT HAPPENS IN TRANSCRIPTIONStarts in the

nucleus

DNA opens

One side of DNA is a template

Makes a section of mRNA

STEPS OF TRANSCRIPTION1) RNA polymerase

unzips DNA double strand.

2) New RNA nucleotides are attached to one side of DNA.

3) mRNA is removed, DNA reforms, mRNA leaves the nucleus.

INFO ON TRANSCRIPTIONBase pair rule is still used but there is

never any thymine in RNA so: (A-U & C-G).

DNA can never leave the nucleus, so mRNA serves as the messenger to the ribosome

RNA has one strand while DNA has 2.

mRNA leaves the nucleus and travels to the ribosome to start Translation.

PROTEIN SYNTHESIS– PART 2: TRANSLATION

A FEW THINGS TO REMEMBER ABOUT PROTEINS1) Made of amino acids2) There are only 20 amino acids

to make up 100s of proteins3) Proteins are a major

component of cells4) Proteins are made on

ribosomes

FROM GENE TO PROTEIN Amino acids are added to a protein

based on 3-nucleotide sequences called codons.

Codons are “read” on the ribosome and the appropriate amino acid is added to the protein chain by tRNA.

Each tRNA molecule has an “anticodon” that matches with the nucleotide sequence on the mRNA strand.

TRANSLATION…process of

making protein from information carried by mRNA.

…occurs on the ribosome

A RIBOSOME

STEPS OF TRANSLATION1) mRNA travels to the

ribosome. 3 bases on mRNA

make a codon.

2) tRNA has anticodons. Each anticodon attaches to a complementary codon.

STEPS OF TRANSLATION CONTINUED3) A tRNA gets its

amino acid in position then releases it.

4)The next codon is “read” in order and another tRNA brings the next amino acids.

5) A chain of amino acids forms.

TRANSLATION•A start codon begins the process. •Once the amino acids are delivered the tRNA leaves and gathers more. •A stop codon ends the process and the amino acid chain makes a protein.

THE GENETIC CODE…is based on the sequence of bases in

DNA (sequence of triplets)

…is universal.

…some amino acids have more than one codon

…there are stop & start codons

GENETIC CODE