DNA and RNA are 2 types of nucleic acid
Nucleotides are the building blocks of DNA and
RNA
The bases create 4 different nucleotides
A strand of DNA
is held together by covalent
Two strands are linked by (relatively weak)
hydrogen bonds between pairs of nucleotides
The 4 different nucleotides can only pair in
certain ways
Because of the
specific
pairings of the two strands: A-T and G-C, DNA
Point out an
Tightly packaged DNA
Nearly all of your cells have 46
chromosomes (somatic cells)
23 from your mom and 23 from your
dad
Chromosome After Replication Chromosome
During S phase of cell division, the cell
duplicates its DNA. This copying process is called replication.
Why does our DNA need to be copied?
DNA strands are held
together by weak hydrogen bonds between base pairs
If you know the sequence of
one strand, you can figure out the sequence of the other
Use your model and a white
board to simulate replication
ATACGCAT
Main enzyme of replication. It adds
• DNA Polymerase has
proofreading and repair abilities.
– Can find mistakes
– Back up
– Remove the improper
nucleotide
1. Find a phosphate.
2. Find a deoxyribose sugar.
3. What do the blue beads represent?
1. In DNA, Adenine pairs with ____.
2. Nitrogenous bases are held together by _____ bonds.
3. If 30% of the DNA is G, what % is A?
4. Which two parts of the nucleotide make up the backbone (legs of the
DNA ladder)?
5. The process of copying DNA is called ____________.
6. This process occurs during what part of the cell cycle?
7. The main enzyme of replication that joins nucleotides together is
called _______ _________.
8. Write the complimentary DNA strand:
AATGCGCT
9. Nearly all of the DNA in eukaryotic cells is found in the _____________.
Identify the three main parts of a nucleotide.
13.
DNA is
• Transcribed into
RNA which is
• Translated into
Another type of nucleic acid, but is
usually a single strand (not double helix).
DNA cannot leave the nucleus, so a
“copy” is made in the form of RNA.
RNA can leave the nucleus and is
Transcription is the process that makes an
RNA copy of the DNA ‘template’ in the nucleus
This temporary copy, which carries
instructions for making proteins, is called
messengerRNA or mRNA.
Only one gene is transcribed at a time
RNA has U instead of T
The sugar in RNA is called
A small piece of a
chromosome
A sequence of DNA
that gets transcribed into RNA
• Many times the RNA is
made into a protein
• Human chromosomes
The promoter DNA sequence tells RNA
Polymerase where to attach
The promoter determines when, where and
how much RNA is made
RNA Polymerase makes an RNA “transcript”
or copy of a gene
Amino acids are the
building blocks of proteins.
The order of amino acids
Uses mRNA sequence to create an amino acid sequence called a protein
Occurs within the ribosomes. (Where are they?)
The ribosome is mostly made of rRNA and small proteins
Translation requires: tRNA, rRNA, mRNA
• plus amino acids and
The mRNA made by transcription carries
the ‘genetic code’ for a protein
Every three nucleotides is called a
codon and this is specific for a particular amino acid
– The first codon in every gene
is always AUG (Methionine)
– The last is UAA, UGA, or UAG.
The rules that govern translation are
called the genetic code
The genetic code is (almost) universal
tRNAs are transcribed but
never made into protein
tRNAs bring amino acids
to the ribosome
They have two business
ends
• Anticodon which is
complementary to the codon on mRNA
rRNA makes up the ribosome
The ribosome decodes mRNA to make a
protein
Ribosomes are the protein-making
Mass
production of proteins
~40 amino acids per second
Many
ribosomes per mRNA
Heritable changes in the genetic
material (DNA)
Mutations are caused in one of
two ways:
• Errors in DNA replication
Mispairing of bases by DNA polymerase
• Mutagens
Agents that damage DNA
Two main types of mutation:
• Point mutations
• Chromosomal
A change in one or a few nucleotides of DNA
Single base substitutions can result in 3 types of
Insertions and
deletions of
nucleotides can
completely change how the DNA is read
Frameshift mutations
change every amino acid after the in/del.
This can have
Involve changes in the number or structure
Mutations are the mode of evolution.
All life began as a single cell. Mutations
and selection have created all the diversity you see.
Other examples:
• Lactose tolerance
Cystic Fibrosis is caused
by a deletion of 3 nucleotides
Huntington’s Disease is
caused by amplification of 3 nucleotides
Sickle Cell Anemia is
caused by a single nucleotide change
• To understand the effects of these mutations, we have to understand transcription and translation…
Nucleotide
DNA Replication
DNA Polymerase
Transcription
mRNA
Translation
tRNA
rRNA
Codon
Amino acid
Mutation
