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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