DNA, RNA, and Protein Synthesis

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DNA, RNA, and Protein Synthesis
Questions How do we become who we are? Is
this predetermined in part by a genetic
code? How does this genetic code work?
Can we alter this code to our benefit? Do
we want to?
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We have Learned

• DNA is holds the GENETIC CODE
• DNA (Deoxyribose) is the molecule of heredity.
• This fact was discovered by an amazing variety of
  experiments, performed by scientists including
  Watson and Crick, Griffiths, and Avery.

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We have Learned

• PROTEINS ARE IMPORTANT
• Proteins are precise combinations of amino acids,
  which dont form on their own.
• Proteins play both a major structural role
  (muscles, etc) and a major regulatory role in our
  bodies (enzymes, hormones)
• DNA codes for heredity, so it must code for our
  proteins.

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We have Learned

• DNA STRUCTURE is important to its function
• Double helix, with a sugar-phosphate backbone,
  and base-pair rungs.
• Genetic information is stored in the base pairs.
• The strands in a DNA molecule are complimentary.
• This characteristic allows for DNA replication.

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A little more information about DNA and
replication

• Each strand of DNA
• Has a 3 end and a 5 end
• (phosphorous group at 5)
• The 2 strands in a molecule are
• Complimentary
• Anti-parallel

One molecule
One strand
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Why are 3 and 5 important

• Anti-parallel is like a two lane road
• the lanes are along side one another, but flow
  in different directions.
• When DNA is built, it is built from 5 to 3
• Always.

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DNA replication Review (a.k.a. DNA synthesis)

• Starts by the DNA strand unzipping
• Replication continues by matching base pairs to
  the original strand
• Each unzipped strand produces its complimentary
  strand
• This completes each double-helix molecule
• Produces two Identical strands of DNA
• DNA replication is semi-conservative, which means
  each DNA molecule is half old, and half new.

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MORE DNA replication (a.k.a. DNA synthesis)
DNA replication is incredibly complex and is a
multi step process. DNA replication, like most
everything in your body, does not happen
spontaneously. Instead, multiple enzymes act to
carry out the steps of the process. Here is a
good animation of the process http//www.bioteach
.ubc.ca/TeachingResources/MolecularBiology/DNARepl
ication.swf Remember, replication of each strand
is from 5 to 3 !
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DNA cant be the whole story

• How does the cell figure out the DNA blueprint?
  Read it?
• DNA is found in the Nucleus.
• So how does the rest of the cell know what to do?
• Proteins are constructed in the ribosomes,
  located in the cytoplasm, which we will learn
  more about later. How do they know what to do?

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The Answer RNA, Ribonucleic Acid

• RNA is the messenger between the DNA in the
  nucleus and the ribosomes (protein factories) in
  the cytoplasm.
• This flow of information from DNA to the
  protein, through RNA is known as the Central
  Dogma.

As shown, the way DNA produces RNA is called
transcription, and the way RNA produces protein
is call Translation (or protein synthesis).
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What is RNAs Structure?

• Like DNA, RNA is a nucleic acid formed of a
  repeating chain of nucleotides.

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What is RNAs Structure?
Like DNA, the sides of RNA are made up of
alternating sugar and phosphate groups.
But the sugar is Ribose, not Deoxyribose
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What is RNAs Structure?

• RNA also has nitrogenous bases.

C
G
A
T
U
Uracil is almost identical to Thymine. Uracil
even bonds and pairs with Adenine. So our base
pairs in RNA are CG, and AU
Look,
But wait.
RNA has Uracil instead of Thymine
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Other Differences
RNA is a single stranded helix, not double
RNA, while still a very long molecule, comes in
shorter lengths than DNA, coding for specific
portions of the DNA.
There are actually three types of RNA. The type
that acts as a messanger from the DNA to the
ribosomes gets its name from its job Messenger
RNA, written as mRNA
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DNA vs. RNA

• Sugar Phosphate backbone
• Nitrogenous base pairs
• Chain of nucleotides
• Found in the nucleus
• Sugar Deoxyribose
• Double Helix (two strands)
• Base Pairs are ATCG
• extremely long!
• One type, DNA is DNA

• Sugar Phosphate backbone
• Nitrogenous base pairs
• Chain of nucleotides
• Made in the nucleus, but lives in the cytoplasm
• Sugar Ribose
• Single Strand
• Uracil, instead of Thymine
• Long, but only codes for a small section of a DNA
  strand
• Three types of RNA mRNA, tRNA, rRNA

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RNA synthesis Transcription

• Steps
• Unzipping a portion of DNA
• RNA polimerase makes complimentary strand of RNA
• DNA zips back up

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RNA transcription
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Code of Life

• We know DNA holds the genetic code
• This code holds directions on how to build and
  maintain a specific organism.
• We now know how the code is transported from the
  nucleus to the ribosomes.
• But how is the code deciphered? What does the
  code mean???

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Coding Activity

• Using the letters ABCD and no spaces, make a code
  that can represent all letters and words.
• What kind of codes work, what kinds of codes
  dont?