Protein synthesis
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PROTEIN SYNTHESIS - PowerPoint PPT Presentation

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PROTEIN SYNTHESIS. DNA vs. RNA. I. DNA vs. RNA. A . Differences 1. # of Strands: DNA = 2 RNA = 1 2. Sugars: Deoxyribose in DNA, ribose in RNA 3 . Bases: DNA (A, C, T, G), RNA (A, C, U , G). RNA replaces thymine with uracil. B. Similarities 1. Both are Nucleic Acids

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I dna vs rna
I. DNA vs. RNA

A. Differences

1. # of Strands: DNA = 2 RNA = 1

2. Sugars: Deoxyribose in DNA,

ribosein RNA

3. Bases: DNA (A, C, T, G), RNA (A, C, U, G). RNA replaces thymine with uracil

B. Similarities

1. Both are Nucleic Acids

2. Both are made of units called nucleotides

The Central Dogma of Biochemistry


DNA RNA Protein

Occurs in the nucleus Occurs in the cytoplasm


Ii transcription occurs in the nucleus
II. Transcription – occurs in thenucleus

  • Definition- The process of transferring information from DNA to mRNA (or tRNA or rRNA).

B. The Process:

1. DNA “puffs” in the region of the needed gene

2. 1 DNA strand serves as the template, directing the sequence of mRNA nucleotides

3. RNApolymerase matches RNA bases with their complementary bases on the DNA

4. The mRNA strand leaves the nucleus and attaches to a ribosome in the cytoplasm to be translated

Example : DNA= A T C G A

RNA= ___________

C the details rna splicing
C. The details: RNA Splicing

1. Long non-coding stretches of nucleotides called intronsare cut out of the pre-mRNA and the remaining nucleotides called exonsare glued back together. Exons"exit" the nucleus.

D the details rna processing
D. The details: RNA Processing

1. A polyAtail is attached to one end of the mRNA strand to help it leave the nucleus through a pore and to determine it's lifetime in the cytoplasm.

2. An mcapprotects the RNA from wandering enzymes and help the mRNA attach to a ribosome.

Iii translation occurs on ribosomes
III. Translation (Occurs on ribosomes)

A. Definition- The process of translating mRNA to proteins

B. Proteins are made of chains of amino acids. (Chains = polymers)

C the process
C. The Process:

1. tRNAbrings amino acids to mRNA at ribosomes

a. On one side of a tRNA are 3 bases known as an anticodon

b. On the other side of a tRNA is a specific amino acid

c. Anticodons line up across from complementary mRNA codons

2. Amino acids bond together to form a protein

3. tRNAreleases amino acid and returns to the cytoplasm

D. The details

1. tRNA

a. Enzymes match individual tRNA molecules with a specific amino acid.

2. The code may be redundantbut it is never ambiguous.

E ribosomes
E. Ribosomes

1. A, P, and E sites exist on ribosomes

a. A site - where new tRNAattach

b. P site - where the two amino acids next to each other form peptide bonds

c. E site - where the tRNAexitfrom the ribosome

2. polyribosomes- more than one ribosome can work on the same mRNA strand at a time.

Iv mutations
IV. Mutations

A. Base-Pair substitutionUsually not a big deal.

1. missense--> one altered codon --> one different amino acid

2. nonsense --> one altered codon changes amino acid to "STOP"

3. Disease example: ________________

B. Base-Pair Insertions and Deletions...some are disasterous

1. Alters reading frame = __________ mutations (all codons and resulting amino acids will be different after the insertion or deletion.

2. Disease example: ____________________