Chapter 10
DNA, RNA, and Protein Synthesis
The first experiments
• Fredrick Griffth
• Studied bacterium Streptococcus pneumoniae and was trying
to develop a vaccine for the bacteria
• Discovered transformation
• The transfer of genetic material from one cell to another
cell, or from organism to organism.
Hey girl, I like your
dna
• DNA is a nucleic acid made of two long chains of
repeating subunits called nucleotides
• DNA is responsible for storing an organism’s genetic
information and controlling the production of proteins
• Also called the biochemistry of an organism
• Nucleotides consist of three parts:
• A five-carbon sugar
• A phosphate group
• A nitrogenous base
• The five carbon sugar in DNA is called dioxyribose
• The nitrogenous base contains nitrogen atoms, carbon
atoms and is a base (that means it accepts hydrogen)
Science can be sexy
The nitrogenous bases
• You have 4 nitrogenous bases in your DNA
• Form hydrogen bonds in the double helix
• Can be purines ( double ringed) or pyrimidines (single ringed)
Compliments are nice
• Base pairing rules determine
that the bases will pair with only
one compliment.
• These compliments are called
complementary base pairs
• Adenine with Thymine
• Guanine with Cytosine
• The order of these repeating
base pairs in DNA is called base
sequence
DNA Replication
• DNA replication is the process by which DNA is
copied in a cell before a cell divides by mitosis,
meiosis, or binary fission
• The two strands separate and each acts as a template
of synthesis of a complementary strand
Making dna 101
• Steps of replication
1.
Enzyme helicase separates the DNA strands
1.
This creates a replication fork
2.
Enzymes called DNA polymerases add complimentary
nucleotides
3.
DNA polymerases finish adding bases
4.
DNA ligase acts like a glue to close any gaps and seal the new
strand together
What about the prokaryotes
or the Eukaryotes?
• Prokaryotes
What about the prokaryotes
or the Eukaryotes?
• Eukaryotes
• Because eukaryotic chromosomes are long and not
circular, a fast method had to arise
Dna errors
• DNA replication usually occurs with great accuracy
• 1 error for every billion paired nucleotide added
• When a mistake does happen this causes a mutation
• A change in the nucleotide sequence of a DNA molecule
• Some errors can escape repair by the body, or can be
the result of chemicals and UV light
Protein is good
• Know that a gene is a segment of DNA that is located
on a chromosome and that codes for a hereditaty
character
• Hair color, eye color,
• These genes code for nucleic acids called RNA, or
ribonucleic acid
How do we make it?
• Transcription- the DNA acts as a template for the
synthesis of RNA
• Translation RNA directs the assembly of proteins
• Protein synthesis the forming of proteins based on
information in DNA
• DNARNAProtein
RNA structure
• Much like DNA but different
in 4 ways
• RNA contains the sugar
ribose, not dioxyribose
• RNA contains the
nitrogenous base Uracile, not
thymine
• RNA is single stranded, not
double stranded
• RNA is much shorter in
length, usually only
containing one gene, while
DNA contains thousands of
genes
The types of rna
• Did you know there are 3 types or RNA?
• Messenger RNA a single stranded RNA molecule that
carries the instructions from a single gene to make a
protein
• Ribosomal RNA part of the structure of ribosomes
• Transfer RNA which transfers amino acids to the
ribosome to make protein
Structure yo
Transcription
• 3 step process occurring in the nucleus
1. RNA polymerase
• An enzyme that binds to a promoter, or a specific
nucleotide sequence of DNA that initiates transcription
2. RNA polymerase adds free RNA nucleotides that are
complementary to the nucleotides on the DNA
strands
3. RNA polymerase reaches a termination signal, a
specific sequence of nucleotides that marks the end of
a gene
Transcription
The genetic code
• Genetic code-term for
the rules that relate how
a sequence of
nitrogenous bases in
nucleotides corresponds
to a particular amino
acid
• Codon is the name for
the 3 nucleotide
sequence in mRNA that
encodes for a particular
amino acid
Translation
• Translation-the making of a protein
• Proteins are made of one or more polypeptides
• Chains of amino acids linked by peptide bonds
• There are 20 different amino acids
• Can make up chains of hundreds or thousands
• Amino acid sequence will determine the structure of
the polypeptide
• Protein shape is critical to function!!!!!!!!
Steps of translation
• There are 5 main steps to translate genetic information
to form a polypeptide
This all occurs in the cytoplasm of the cell!!!
1. 2 ribosomal subunits tRNA and mRNA join together
1. tRNA contains anitcodon-the 3 nucleotides that are
complementary to the codon sequence on the mRNA
2. The polypeptide chain is put together and grows in
length
3. No joke, the third step is that it just keeps growing
Steps of translation
4. A polypeptide chain continues to grow until a stop
codon is reached. This causes the newly formed
polypeptide to detach
5. The components of translation disassemble
4. The components can either start coding a new
mRNA or translate the same strand.
Translation
The Human genome
• The entire gene sequence of the human genome, the
complete genetic content, is know
• Scientists know the order of the 3.2 billion base pairs
in the 23 human chromosomes
• Bioinformatics is when scientists use computers to help
interpret different DNA sequences