DNA: The Genetic Material

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DNA The Genetic Material

• The Structure of DNA
• The Replication of DNA
• Protein Synthesis

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The Structure of DNA

• DNA stands for deoxyribonucleic acid
• DNA is a molecule that makes up genes
• Determines the traits of all living things
• All living organisms have DNA in their cells
• Humans, plants, bacteria, protozoans, etc
• DNA has a shape like a ladder
• The shape of DNA was first described by James
  Watson and Francis Crick (1950s)

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The Structure of DNA

• The DNA ladder is made up of repeating
  nucleotides
• Nucleotides are made up of a sugar, a phosphate
  and a nitrogen-containing base
• There are 4 types of nitrogen-containing bases
• Adenine (A)
• Thymine (T)
• Guanine (G)
• Cytosine (C)

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The Structure of DNA

• Six features of the DNA model
• DNA has 2 main sides - the sides are like the
  sides of a ladder
• The sides of DNA are made up of a sugar and a
  phosphate
• The rungs of the ladder are made up of the 4
  different types of nitrogen bases
• The 4 different bases (of DNA) are A, T, G and C
• A will only fit with T, and C will only fit with
  G
• The ladder has a twisting shape called a helix

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DNA Base pairings
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The Structure of DNA
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The Structure of DNA

• DNA is in every cell in your body
• The DNA is found in the nucleus
• DNA makes up the chromosomes
• Small segments of DNA are called genes
• A gene is a short segment of DNA
• It contains a certain number of bases
• Genes determine traits

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The Structure of DNA
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The Structure of DNA

• Scientists used bacteria to prove that DNA
  controls traits
• They injected bacteria into mice
• Living, non-harmful bacteria did not kill the
  mice
• Living, harmful bacteria killed the mice
• Dead, harmful bacteria did not kill the mice
• Living, non-harmful and dead, harmful bacteria
  did not kill the mice WHY?

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The Replication of DNA

• The process of making a copy of DNA is called DNA
  replication
• DNA replication takes place during the S phase of
  interphase of the cell cycle
• There are 3 main steps involved in DNA replication

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The Replication of DNA

• Step 1
• The double helix unwinds
• Enzymes help this to happen
• The bonds between the complementary nitrogen
  bases are broken
• The unwound ends of the DNA are called the
  replication forks

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The Replication of DNA

• Step 2
• Enzymes known as DNA polymerases move along the
  DNA strands
• They add new complementary nucleotides to each
  strand of unwound DNA
• Two new double helixes are being formed

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The Replication of DNA

• Step 3
• A signal will be sent when the DNA has finished
  copying itself
• The DNA polymerase will detach
• 2 new DNA molecules are formed
• The nucleotide sequences in each of the new DNA
  molecules are identical

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The Replication of DNA

• Checking for errors
• DNA polymerases can proof-read the new strands
  of DNA
• If there is a mismatched nucleotide, the DNA
  polymerase can replace it with the correct
  nucleotide
• Only about 1 in a billion errors will occur
• Errors, or changes in the nucleotide sequence,
  are called mutations

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On Youtube

• DNA replication by CoolScience Videos 747 min
• Protein Synthesis by Shadowlabsdotorg 428 min

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Protein Synthesis

• Proteins are made using DNA and RNA (ribonucleic
  acid)
• RNA differs from DNA in 3 ways
• RNA is a single strand of nucleotides
• RNA is a ribose sugar (it has one more oxygen
  than DNA sugar)
• RNA contains the base uracil (U) instead of
  thymine (T)

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Protein Synthesis

• Protein synthesis occurs after DNA replication
• There are 2 main steps
• Transcription DNA is transcribed into RNA
• Translation RNA is translated into a protein

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Protein Synthesis

• The directions for making a protein are found in
  the genes on the chromosomes
• Sequence of nucleotides code for specific
  proteins
• The instructions for proteins are transferred
  from the gene to an RNA molecule during the
  process known as transcription
• Later, amino acids string together to make
  proteins

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Protein Synthesis

• Transcription transfers information from DNA to
  RNA
• There are 3 steps of transcription
• RNA in the nucleus binds to DNA
• RNA causes the DNA to unwind
• RNA reads the DNA and makes a copy
• Uracil is substituted for thymine
• A pairs with U, C pairs with G

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Transcription
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Protein Synthesis

• There are several types of RNA
• Messenger RNA (mRNA)
• Carries the information from the DNA and takes it
  to the ribosome to make a protein
• The mRNA leaves the nucleus and moves to a
  ribosome
• mRNA instructions are written as a series of 3
  nucleotides called codons
• Each codon gives the information for one amino
  acid

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Protein Synthesis

• Translation takes place in the cytoplasm on the
  ribosome
• Transfer RNA (tRNA) are single strands of RNA
  that carry an amino acid on one end
• These are called anti-codons
• These are series of 3 nucleotides that match up
  with the mRNA codon
• The amino acids are strung together to make a
  protein

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Protein Synthesis

• Ribosomal RNA (rRNA)
• Molecules of RNA that are make the ribosome
• rRNA temporarily hold the mRNA and tRNA so
  translation and transcription can take place
• Transcription from DNA to RNA
• translation- - from RNA to protein

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Protein Synthesis
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Protein Synthesis