RNA Ribonucleic Acid

YOUR TURN ! Describe what a nucleotide is. What molecules do you need to build one?

Structure of RNA: RNA consists of a long chain of nucleotides There are 3 main differences between RNA and DNA: The sugar in RNA is ribose instead of deoxyribose RNA is usually single-stranded RNA contains the nitrogen base uracil in place of thymine

Structure of RNA: Why have RNA? DNA is such a large molecule that it cannot fit through nuclear membrane RNA serves as a disposable copy of a segment of DNA (a working copy of a SINGLE gene)

Types of RNA: Type One = messenger RNA (mRNA) Responsible for carrying copies of the instructions needed to assemble amino acids into proteins

Types of RNA: Type Two = ribosomal RNA (rRNA) Along with different proteins, it forms the ribosomes where proteins are assembled

Types of RNA: Type Three = transfer RNA (tRNA) Responsible for transferring amino acids to the ribosome to be assembled into a protein

YOUR TURN ! Describe the differences that you see between the structure of DNA and RNA.

Protein Synthesis Transcription

Protein Synthesis?

Transcription Process in which RNA molecules are produced by copying part of the DNA nucleotide sequence into a complimentary sequence in RNA Requires the enzyme RNA polymerase

YOUR TURN ! What does a store do to let you know that they are having a big sale?

How does RNA polymerase “know” where to start and stop? RNA polymerase can only bind to PROMOTERS A promoter region is a specific base sequence that can code for “starting” transcription or “stopping” transcription

Steps to Transcription: RNA polymerase binds to DNA promoter region and separates the DNA strands. RNA polymerase uses one strand of DNA as a template to assemble a strand of RNA.

STEP ONE: TRANSCRIPTION G T A C G G C A T T A C G

RNA nucleotide T A A A U T C G G T A A C G G G C C A U T T A A C G G

YOUR TURN ! Describe the main purpose of transcription. Explain why a promoter region is important to a cell.

Reading the Genetic Code Protein Synthesis Reading the Genetic Code

Reading the Genetic Code: The genetic code is read in a series of THREE mRNA nucleotides Combination of 3 mRNA nucleotides is called a CODON. Each codon codes for a specific amino acid (any one of twenty amino acids)

Practice Reading Codons: CODON: AUG “Read your codon AROUND the chart.”

The first letter, A, refers to the letters on the LEFT side of the chart.

The second letter, U, refers to the letters on the TOP of the chart.

The third letter, G, refers to the letters on the RIGHT side of the chart.

Follow the three letters to where they intersect…

YOUR TURN ! What does the codon CAU code for?

Codons to Remember: START Codon = AUG (codes for the amino acid methionine) STOP Codon = UAA, UAG, UGA

Protein Synthesis Translation

Translation The decoding of a mRNA message into a chain of amino acids (a.k.a. into a protein) Remember… Transcription in nucleus Translation in cytoplasm at ribosome

STEP TWO: TRANSLATION Ribosome A U G A tRNA G C U mRNA U A A C G

U A A U C G A G C U A G

U A A U C G A G C U U C A G G

U A A U C G U A C G G C U A G

A U G U A C G G C A U U A C G

A U G U A C G G C A U U A C G

A U G A G C A U U A C G

A U G A G C A U U A C G Protein

Steps to Translation: mRNA molecule attaches to the ribosome tRNA molecule brings an amino acid and binds to the mRNA codon Anticodon = 3 bases on tRNA that are complementary to the codon on mRNA ribosome has a second binding site for another tRNA molecule

Translation Lysine Phenylalanine tRNA Methionine Ribosome mRNA Start codon

YOUR TURN ! Identify the parts of the tRNA molecule. Summarize the job of the tRNA molecule.

Steps to Translation: The ribosome forms a peptide bond between the 1st and 2nd amino acid First tRNA molecule is released Ribosome moves on to the third codon… The process continues until the ribosome reaches a stop codon Polypeptide (protein) is released mRNA is released

Translation

Translation

YOUR TURN ! Describe the main purpose of translation in your own words.

Genes and Proteins: An Overview… The sequence of bases in DNA is used as a template for mRNA. The codons of mRNA specify the sequence of amino acids in a protein. Proteins play a key role in producing an organism’s traits.

Review Question… The role of a master plan in a building is similar to the role of which molecule? messenger RNA DNA transfer RNA ribosomal RNA

Review Question… A base that is present in RNA but NOT in DNA is thymine. uracil. cytosine. adenine.

Review Question… The nucleic acid responsible for bringing individual amino acids to the ribosome is transfer RNA. DNA. messenger RNA. ribosomal RNA.

Review Question… A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the intron. exon. promoter. codon.

Review Question… A codon typically carries sufficient information to specify a(an) single base pair in RNA. single amino acid. entire protein. single base pair in DNA.