Download DNA Replication

DNA
Deoxyribonucleic acid
DNA carries genetic information
• _______determines an organism’s traits
• How does DNA achieve its control?
• By producing ________(enzymes)
• Enzymes are important because they control the chemical
reactions needed for life
Structure of DNA
• Very long molecule
• Made of repeating subunits called nucleotides:
Composition of Nucleotide
• Simple sugar- ___________________
• Phosphate group – PO4
• Nitrogen base- A carbon ring structure that contains one or more
Nitrogen’s
• guanine(G) Adenine(A) Cytosine(C) Thymine(T)
– 4 possible DNA nucleotides depending on nitrogen bases
Nucleotides Cont
• Nucleotides join together to form long chains
• The phosphate group of one nucleotide bonding to the deoxyribose
sugar of an adjacent nucleotide. This form the backbone of DNA
• The nitrogen bases stick out
DNA Nitrogen Bases
• In DNA, the amount of adenine is always equal to the amount of
thymine
• The amount of guanine is always equal to the amount of cytosine
Base Pair Rules
•
•
•
•
Adenine always pairs with thymine
Guanine always bonds with Cytosine
A-G-T-C-C opposite strand would be
T-C-A-G-G
James Watson and Francis Crick
• __________helix is like a long zipper that is twisted
How can organisms be so different from each other if their
genetic material is made of the same four nucleotides
DNA Replication
• DNA is copied _____________ cell division
• Without replication, new cells would only have half of DNA from
their parents
• When a DNA molecule replicates, 2 molecules are formed
• Each molecule has 1 original strand and one new strand
Steps of DNA Replication
• 1) Two nucleotide strands separate at their base pairs. Hydrogen
bonds between are broken
• 2) Free nucleotides base pair with exposed nucleotides
• 3) The sugar and phosphate parts of adjacent nucleotide strands
bond together to form backbone of new strand
• 4) The process of replication produces 2 molecules of DNA. Each
new molecule has been newly synthesized from free nucleotides in
the cell
DNA Transcription
• DNA encodes the instructions for making ____________thereby
controlling the cells
RNA
• Ribonucleic acid
• Different from DNA in 3 ways
– 1. RNA is single stranded
– 2. Ribose-sugar
– 3. Uracil takes the place of thymine
RNA’s JOB
• RNA ________instructions from the DNA on how a protein should
be assembled
• After this, they then assemble the protein, amino acid by amino
acid until the protein is made.
Three types of RNA
• mRNA- messenger RNA
• Brings information from the DNA in the nucleus to the cell’s
cytoplasm
• rRNA- ribosomal RNA- Ribosome's made of ribosomal RNA clamp
onto the mRNA and use its information to assemble the amino
acids in the correct order
• tRNA- transfer RNA- transports amino acids to the ribosome to be
assembled into a protein
Transcription- takes place in Nucleus
• 1) The process of transcription begins as enzymes unzip the
molecule of DNA, just as they do during DNA replication
• 2) As DNA unzips, free RNA nucleotides pair with complementary
DNA nucleotides on one of the DNA strands
• When the process of base pairing is completed, the mRNA
molecule breaks away as the DNA rejoins.
• The mRNA leaves the nucleus and enters cytoplasm
The Genetic Code
What is the genetic code?
• A code is needed to convert the language of mRNA into the
language of proteins
•
•
•
•
•
Amino Acids
Building blocks of proteins
20 amino acids
For every 1 amino acid there are 3 nucleotides
Each set of 3 nucleotides makes a codon
There are 64 codons in the genetic code
Genetic Code Continued
• Some codons do not code for amino acids, they provide
instructions for assembling proteins
• UAG is a start codon UAA is a stop codon
• Genetic code is universal
Translation: From mRNA to Protein
• The process of converting the information in a sequence of
nitrogen bases in mRNA into a sequence of amino acids that make
up protein
Translation
•
•
•
•
Takes place in _____________in the cytoplasm
mRNA- made in nucleus, ribosomes attach to them
tRNA- bring the amino acids to the ribosomes
Correct translation-depends on the joining of each mRNA codon
with the correct tRNA molecule
Codon and Anticodon
•
•
•
•
Group of three amino acids-CODON
Anti-codon- opposite code
A-C-A codon
anticodon is U-G-U
Steps of Translation
• 1) the starting end of the mRNA strand attaches to the ribosome
• 2)tRNA which are carrying a specific amino acid , approach the
ribosome
• 3) The tRNA anticodon pairs with the first mRNA codon and
temporarily join
Steps of Translation
• 4) The first code from mRNA is AUG, this signals the start of
protein synthesis
• 5) The ribosome slides along the mRNA to the next codon
• 6) A new tRNA molecule carrying amino acid pairs with the 2nd
mRNA codon
• 7) When the first and 2nd amino acids are in place, an enzyme joins
them by forming a peptide bond between them
Steps of the Translation
• 8) As the process continues, a chain of amino acids is formed until
the ribosome reaches a stop codon on the mRNA strand
Types of Mutations
• Any change in the DNA sequence that also changes the protein it
codes for