Nucleic Acids and protein synthesis Higher Human Biology.

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Nucleic Acids and protein synthesis Higher Human Biology

Transcript of Nucleic Acids and protein synthesis Higher Human Biology.

Page 1: Nucleic Acids and protein synthesis Higher Human Biology.

Nucleic Acids and protein synthesis

Higher Human Biology

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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

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• It was Francis Crick and James Watson who unraveled the DNA molecule.

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DNA Molecule

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• In 1966 the Genetic code was discovered.

• Scientists are now able to predict characteristics by studying DNA. This leads to genetic engineering, genetic counseling.

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An international team of scientists began the project to map the human genome.

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1990Gene therapy was used on patients for

the first time.

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1994The FDA approved the first genetically engineered food -- FlavrSavr tomatoes

engineered for better flavour and shelf life.

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1997Dolly the Sheep - the first adult animal clone.

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Dolly the sheep, pictured here with her first lamb Bonnie

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2000J. Craig Ventor, along with Francis Collins,

jointly announce the sequencing of the entire human genome.

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The Central Dogma

• DNA codes for the production of DNA (replication) and of RNA (transcription).

• RNA codes for the production of protein (translation).

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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)

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DNA Structure - Nucleotide

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DNA Structure – Double Helix

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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

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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

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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

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Role of Rough Endoplasmic Reticulum

• Network of membranes

• Found in cytoplasm• Has ribosomes on

surface• Proteins produced

during translation pass into ER

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Translation

• Second stage of protein synthesis• Occurs on ribosomes in cytoplasm• Code on mRNA is used to make protein chain

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Translation

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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

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Overview

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Overview

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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

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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

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The Facts You Need To Know

• page 1-2• from “chromosomes which remain in

….”• to “the sequence of bases in the

DNA…”