Chapter 12 DNA

1
Chapter 12DNA RNA

• Section 12-3RNA Protein Synthesis

2
Types of RNA

• RNA Used For Protein Synthesis
• Three Types of RNA
• Messenger RNA, mRNA
• Ribosomal RNA, rRNA
• Transfer RNA, tRNA

3
Types of RNA

• mRNA
• Template to construct protein. It brings the
  message from the DNA to the ribosome.
• rRNA
• Part of ribosome structure
• tRNA
• Transports amino acids from cytoplasm to the
  ribosomes

4
Transcription

• The process of copying part of the DNA nucleotide
  sequence into a complementary sequence of RNA

5
Transcription

• Requires the enzyme RNA Polymerase
• Step 1. RNA polymerase binds to DNA and
  separates the DNA strands.
• Step 2. RNA Polymerase uses one strand of DNA as
  a template to polymerize nucleotides into RNA

6
RNA Editing

• After Making mRNA Introns
• Are Snipped Out
• Exons Remain,
• (active segments of nucleotides)

7
The Genetic Code

• Proteins are long chains of amino acids.
• There are 20 different amino acids
• The order of amino acids in the protein determine
  its shape and function

8
The Genetic Code

• There are 20 amino acids but only
• 4 bases in RNA
• Adenine A
• Cytosine C
• Guanine G
• Uracil U

9
The Genetic Code

• The genetic code consists of words three bases
  long
• Each word is called a Codon
• three consecutive nucleotides that specifies a
  single amino acid

10
The Genetic Code

• For Example
• UCGCACGGU RNA Sequence
• UCG-CAC-GGU Codons
• UCG codes for Serine
• CAC codes for Histidine
• GGU codes for Glycine

11
Code Wheel
12
The Genetic Code

• 4 Bases
• Codons Defined with 3 Bases
• There Are 64 Possible
• 3-base codons
• Since there are only 20 amino acids, some amino
  acids are represented by multiple codons

13
Translation

• Translation is the process of of decoding the
  mRNA into a polypeptide chain
• Ribosomes
• Read mRNA and construct the proteins

14
Translation Step 1

• mRNA leaves the Nucleus

15
Translation Step 2

• mRNA binds to the ribosome. tRNA attaches
• Anticodons on the tRNA line up with codons on
  mRNA The other end of the tRNA is an amino acid

16
Translation Step 3

• Ribosome connects the amino acids together as
  they come into the ribosome

17
Translation

• Step 4
• A polypeptide (Chain of Amino Acids) is formed.
• Polypeptide chain grows until the mRNA STOP
  Codon is reached

18
The Roles of RNA DNA

• DNA
• Master Plan
• RNA
• Blueprints of the Master Plan

19
Proteins

• At the end of translation a protein is formed.
• Proteins are enzymes that catalyze and regulate
  chemical reactions
• Proteins can also be structural.