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Cells Lecture IV. DNA and Protein Synthesis. Biology Standards Covered. 1d ~ students know the central dogma of molecular biology outlines the flow of information from transcription of ribonucleic acid (RNA) in the nucleus to translation of proteins on ribosomes in the cytoplasm.

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cells lecture iv

Cells Lecture IV

DNA and Protein Synthesis

biology standards covered
Biology Standards Covered
  • 1d ~ students know the central dogma of molecular biology outlines the flow of information from transcription of ribonucleic acid (RNA) in the nucleus to translation of proteins on ribosomesin the cytoplasm
the structure of dna
The Structure of DNA
  • DNA is a long molecule made up of nucleotides
  • Each nucleotide is made up of three parts:
    • 5-carbon sugar called deoxyribose
    • Phosphate group
    • Nitrogen Base
the nucleotides
The Nucleotides

Nitrogen Bases

A- adenine

G- guanine

C- cytosine

T- thymine

Adenine

Guanine

Cytosine

Thymine

(Deoxyribose)

5-Carbon Sugar

Phosphate group

chargaff s rules
Chargaff’s Rules
  • According to Erwin Chargaff:
    • Adeninealways pairs with Thymine
    • Cytosinealways pairs with Guanine
the double helix
The Double Helix

Nucleotide

  • base pairing-hydrogen bonds forming only between certain “base pairs”

Hydrogen bonds

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine(C)

Guanine (G)

central dogma
Central Dogma
  • The term central dogma is used in science to describe the “making of proteins” from instructions coded in the DNA
  • An equation to remember for Central Dogma would be:

DNA mRNA Amino Acid Chain

Transcription

Translation

transcription inside the nucleus
Transcription inside the Nucleus

Adenine (DNA and RNA)

Cystosine (DNA and RNA)

Guanine(DNA and RNA)

Thymine (DNA only)

Uracil (RNA only)

RNApolymerase

DNA

RNA

transcription
Transcription
  • Promoters – specific sites where the enzyme-protein RNA Polymerase binds to the strand of DNA to begin transcription
central dogma1
Central Dogma
  • Proteins are assembled into polypeptides
    • These are long chains of amino acids
    • There are 20 different types of amino acids
    • The properties of proteins are determined by which order these amino acids are joined
central dogma2
Central Dogma
  • Each of these amino acids that mRNA “codes” for recognizes the three base pair sequence
  • A codon consists of “three nucleotides in a row” that code for a single amino acid
    • AUG codes for the amino acid Methionine
the 20 amino acids
The (20) Amino Acids

Methionine is the universal “start codon” for all proteins

central dogma3
Central Dogma
  • Along with the twenty amino acids there are “special” base pair sequences that “code for” startand stopcodons
  • Stop codons are like the “period at the end of a sentence”.
    • They signify the end of a polypeptide (amino acid chain)
translation
Translation
  • The term central dogma is used in science to describe the “making of proteins” from instructions coded in the DNA
  • An equation to remember for Central Dogma would be:

DNA mRNA Amino Acid Chain

Transcription

Translation

translation1
 Translation

Nucleus

mRNA

Lysine

tRNA

Phenylalanine

Methionine

Transfer RNA

Ribosome

Start codon

mRNA

translation2
Translation
  • Each strand of mRNA is separated into three base pairs called codons
  • AUG —- UUC --- AAA (mRNA)
  • This is where transfer RNAcomes in (tRNA)
translation3
Translation
  • tRNA is responsible for getting the right anticodon with each of the mRNA codons
  • An amino acidis attached to each anticodon

Lysine (Amino Acid)

tRNA

Ribosome

mRNA

translation4
Translation

The Polypeptide “Assembly Line”The ribosome joins the two amino acids & breaks the bond between the tRNA & it’s amino acid

Growing polypeptide chain

Ribosome

tRNA

Lysine

tRNA

mRNA

Completing the Polypeptide

The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.

mRNA

Ribosome

Translation direction

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