RNA AND PROTEIN SYNTHESIS

The Plan… How does DNA control cell activities if it

can’t leave the nucleus? It sends a messenger! - messenger RNA

(mRNA for short) Remember, DNA contains the code for

making proteins. DNA can’t leave the nucleus, so RNA has

to help out and actually make the proteins on the ribosomes.

Ribonucleic Acid

Ribonucleic acid (RNA) - molecule that controls the production of proteins for cells.

A strand of RNA is made of repeating units (monomers) called nucleotides (like DNA)

What makes up a nucleotide?

RNA vs. DNA

Three differences between RNA and DNA: Single-stranded Ribose instead of

Deoxyribose Uracil instead of

Thymine

Checkpoint: RNA vs. DNA

Double strand Deoxyribose Contains

Thymine Stays in nucleus

Single Strand Ribose Contains Uracil Leaves nucleus

DNA RNA

Types of RNA

Messenger RNA (mRNA) single, uncoiled strand serves as pattern for assembly of

amino acids Transfer RNA (tRNA)

carries amino acids to the ribosome

single stranded Ribosomal RNA (rRNA)

globular form makes up the structure of the ribosome

Transcription

Process of making mRNA from a single–strand of DNA.

The nitrogen bases in RNA always bond to their complement on the DNA strand ADENINE binds to URACIL GUANINE binds to

CYTOSINE

Steps in Transcription

1. The enzyme RNA polymerase “unzips” the complementary strands of DNA into two single strands.

2. RNA nucleotides bond to a single strand of DNA

3. The finished mRNA is released and the two DNA strands “re-zip”

Steps in Transcription

RNADNA

RNApolymerase

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

Transcription animation

mRNA Processing

Enzymes remove (cut out) introns because they interrupt the coding sequence

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

• INTRONS INTERRUPT … INTRONS OUT !!!• Exons are left behind to be “expressed” (translated)

as needed proteins

Again...unit of transcription in a DNA strand

exon intron

mature mRNA transcript

snipped out

snipped out

exon exonintron

transcription into pre-mRNA

Checkpoint!

Transcribe the DNA strand into RNA:

TAC TCG TCC ATA GGC ATCAUG AGC UGG UAU CCG UAG

Protein Synthesis

Bases in mRNA code for the amino acids which will make a functioning protein.

A group of three sequential bases on an mRNA strand is a CODON.

Lab – Part 1

Read the introduction and highlight 5 important facts

Transcribe the two DNA sequences.

Complete the Codon activity

The Genetic Code

There are a possible 64 CODONS that code for 20 AMINO ACIDS and a START/STOP SIGNAL.

The genetic code is universal among all organisms.

The Genetic Code

mRNA strand – G C A A C G U U G C U A C U G

Amino Acids – Alanine -Threonine - Leucine -Leucine - Leucine -

Steps in Translation

Process of using RNA to assemble amino acids into proteins.

1. mRNA moves out of the nucleus and attaches to ribosome.

2. tRNA transports amino acids to the ribosome.

Steps in Translation

Steps in Translation

3. The anticodon on tRNA bonds to the complementary codon on mRNA.

4. Amino acids form peptide bonds and form a strand – a polypeptide.

5. The stop codon on mRNA ends the process and the new protein is released.

Steps in Translation

Translation animation

Your Turn!Be A Ribosome …

Translate your codonsinto amino acids:

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

Met His Ser Leu

Protein Synthesis Video

Lab – Part 2

Now it’s your turn to be RNA!

Concept Mapping for RNA

Translation --------------------------Anti-codon

Peptide bond ----------------------Amino

Acids

Uracil --------------------------------RNA

Challenge: mRNA -----tRNA ------rRNA