DNA and Protein Synthesis

Bethany, Kayla, and Alanna

Key Vocabulary

RNA (ribonucleic acid)- carries out protein synthesis

mRNA (messenger)- brings instructions from DNA in the nucleus to the ribosomes in the cytoplasm

rRNA (ribosomal)- binds to mRNA to help assemble amino acids in the correct order

tRNA (transfer)- carries amino acids to the ribosomes

gene- a segment of DNA that specifies the sequence of amino acids in a polypeptide of a protein


(deoxyribonucleic acid)- determines the traits of an organism by controlling the production of proteins

Why do we need DNA?

DNA controls what a organism looks like by controlling the production of proteins.

What to know about DNA

  • DNA is in the form of Double Helix- Scientist Crick and Watson were credited for discovering this.
  • The Monomer of DNA is nucleotide which is made up of a sugar, phosphate, and a nitrogen base.
  • There are 4 types of nitrogen bases, A-Adenine, G-Guanine, T-Thymine, C-Cytosine.
  • Adenine and Thymine bond together and Guanine and Cytosine bond together.
  • The double helix consists of sides and rungs.
  • The rungs are made up of nitrogen bases.
  • Adenine and Guanine are purines, which has double rings
  • Thymine and Cytosine have single rings, which means they are pyrimidines
  • The sides are made up of sugar and phosphate.
  • The DNA can only exist in the nucleus.
  • Hershey and Chase

DNA Replication

This process starts with one double strand of DNA. The nitrogen bases break their hydrogen bond and the double helix separates. Then free floating nitrogen bases come in and pair with the separated nitrogen bases. This process makes two identical strands of DNA that are also identical to the original DNA strand.

What is Semiconservative Replication?

It is when each new double helix has one strand from the original double helix and one new strand.
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(Ribonucleic Acid) - Carries out protein synthesis.

Types of RNA

  • mRNA (messenger) - Brings the instructions from the DNA that is located in the nucleus to the ribosomes in the cytoplasm.
  • rRNA (ribosomal)- Binds to mRNA to help assemble amino acids in the correct order
  • tRNA (transfer) - Carries amino acids to the ribosome.
  • mRNA transcript leaves the nucleus and goes to the ribosome with all the needed information.
  • mRNA has introns and exons- exons are expressed, introns are not expressed.
  • Before mRNA goes to the ribosome it must first get rid of any introns.


The RNA polymerase come and attach to the DNA promoter. It creates a bubble and opens the DNA up. Once it is open like a bubble, the polymerase starts to copy the DNA into mRNA. Then the polymerase reaches a code called to terminated, this code tells the polymerase to stop coding. The polymerase falls off the DNA strand and the rest of the DNA closes up. Whats left is a mRNA strand and the original DNA strand.


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A small ribosomal subunit attaches to the mRNA strand. Then tRNA comes while carrying a amino acid. Then the large ribosomal subunit comes and sandwiches the tRNA and the mRNA. Then another tRNA comes next to the last one. The ribosome moves along the mRNA. As this is happening the amino acids begin to attach and form a chain. The tRNA will continue and connect with the mRNA, and old tRNA will fly off.

RNA nitrogen bases.

  • A-Adenine
  • G-Guanine
  • C-Cytosine
  • U-Uracil
  • A pairs with U
  • C pairs with G

What is a codon?

A codon is a set of three mRNA bases that code for a amino acid. They are attached to the mRNA.

  • An anticodon is the complementary pair to the codon
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