Nucleic Acids and Protein Synthesis. What are nucleic acids?
Nucleic Acids and protein synthesis Higher Human Biology.
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Transcript of Nucleic Acids and protein synthesis Higher Human Biology.
Nucleic Acids and protein synthesis
Higher Human Biology
Lesson Aims
• To examine the structure of DNA• To compare the structure of DNA and
RNA• To discuss the differences and
similarities between mRNA and tRNA• To examine the role of the nucleus
and nucleolus during RNA synthesis• To study the synthesis of proteins
• It was Francis Crick and James Watson who unraveled the DNA molecule.
DNA Molecule
• In 1966 the Genetic code was discovered.
• Scientists are now able to predict characteristics by studying DNA. This leads to genetic engineering, genetic counseling.
An international team of scientists began the project to map the human genome.
1990Gene therapy was used on patients for
the first time.
1994The FDA approved the first genetically engineered food -- FlavrSavr tomatoes
engineered for better flavour and shelf life.
1997Dolly the Sheep - the first adult animal clone.
Dolly the sheep, pictured here with her first lamb Bonnie
2000J. Craig Ventor, along with Francis Collins,
jointly announce the sequencing of the entire human genome.
The Central Dogma
• DNA codes for the production of DNA (replication) and of RNA (transcription).
• RNA codes for the production of protein (translation).
The Central Dogma
• Genetic information is stored in a linear message on nucleic acids. We use a shorthand notation to write a DNA sequence: – 5'-AGTCAATGCAAGTTCCATGCAT....
• A gene determine the sequence of amino acids in proteins. We use a shorthand notation to write a protein sequence:
NH2-Met-Gln-Cys-Lys-Phe-Met-His.... (or a one letter code: M Q C K F M H)
DNA Structure - Nucleotide
DNA Structure – Double Helix
Comparison of DNA and RNA
DNA RNA
Found in nucleus
Found in nucleus and cytoplasm
Double strands
Single strand
Bases – A, T, G, C
Bases – A, U, G, C
Deoxyribose sugar
Ribose sugar
Transcription
• First stage of protein synthesis• Occurs in the nucleus• Double helix uncoils• Double strands split• DNA strand acts as template for formation of
mRNA (messenger RNA)
Part of chain B sequence. Uncoiled DNA double helix which has split exposing bases
Transcription
• Free RNA nucleotides in the nucleus base pair with DNA nucleotides A-T, T-U, G-C, C-G
• Strong bonds form between phosphate group and ribose sugar of neighbouring RNA nucleotides
• Catalysed by enzyme RNA polymerase• mRNA moves out of nucleus through nuclear pore
Single strand of DNA coding for Chain B
Strand of mRNA copied from DNA
Role of Rough Endoplasmic Reticulum
• Network of membranes
• Found in cytoplasm• Has ribosomes on
surface• Proteins produced
during translation pass into ER
Translation
• Second stage of protein synthesis• Occurs on ribosomes in cytoplasm• Code on mRNA is used to make protein chain
Translation
Comparison of mRNA and tRNA
mRNA• Messenger RNA• Made in nucleus
during transcription
• Moves to cytoplasm
• Codes for protein• Base triplets -
codons
tRNA• Transfer RNA• Found in cytoplasm• Involved in
translation• Assembles amino
acids into correct order for proteins
• Anti-codons present
Overview
Overview
Role of Golgi Apparatus
• Found in cytoplasm• Flattened sacs
which are continually formed
• Involved in processing and packaging proteins
• Vesicles bud off with processed protein
Secretion
• Also called exocytosis• Vesicle which has pinched off Golgi apparatus
moves towards cell membrane• Membrane of vesicle fuses with cell membrane • Insulin secreted from cell
The Facts You Need To Know
• page 1-2• from “chromosomes which remain in
….”• to “the sequence of bases in the
DNA…”