Replication & Expression
carries genetic information
a polymer . . .
. . . made of ______________________________
What is a polymer?
The Basic structure of a nucleotide:
involved in translating genetic code
a polymer . . .
. . . made of 4 different nucleotides
What are two differences between RNA and DNA nucleotides?
DNA forms a double helix
Who discovered this?
sketch the basic structure
Involves the Precise pairing of nucleotides
- what are the two pairings?
- strands are held together by ________________
“It has not escaped our notice that the specific pairing we have postulated
immediately suggests a possible copying mechanism for the genetic material.”
– Watson & Crick
1. Strands separate
2. Each strand serves as template for a new strand
A pairs with ___
G pairs with ___
Replication occurs at many sites simultaneously & involves 3 enzymes
Sketch the process & describe the function of each enzyme
What does it mean to say that replication is semiconservative?
What is a gene?
How many genes are in the human genome?
How do we know?
What determines an individual’s phenotype?
The Genetic Code
Problem: polymer made up of 4 nucleotides (DNA) must be translated into a
polymer made up of 20 amino acids (protein)
• specify one amino acid
“DNA codon” amino acid
What do we mean by saying that the Genetic Code is arbitrary . . .
. . . and universal
What are the evolutionary implications of this?
Why would it be impossible for humans to mate with aliens?
Where, the sequence of nucleotides in a gene … TCTACCATG
specify a sequence of amino acids …
Overview of Gene Expression:
Transcription in detail
What is the promoter region?
What is its function?
Why is the enzyme called RNA polymerase?
Where does transcription take place? Why?
Judging from the photograph, how many mRNA’s can be made from one
gene at a time?
Translation: mRNA protein
Three things needed to make a protein:
Transfer RNA (tRNA)
Why does Dr. Gendron liken tRNA to the Rosetta Stone?
Where is the synthesis of proteins carried out?
What is a mutation?
1. Chromosomal Mutations
The 2 types of chromosomal mutation and examples of each:
2. Point Mutations: Changes in the DNA sequence
When are these most likely to occur?
Tyrosine – Alanine - Leucine
b. Deletions & Insertions are examples of _________________________
why are they called that?
THE FAT CAT ATE THE SAD RAT
What causes mutations?
2. mutagenic factors
Consequences of Mutation
which is more likely to be harmful – a simple substitution or a frame-
How can a mutation be neutral (i.e. be neither harmful or beneficial)?
How can the accumulation of neutral mutations be used as an
Why are mutations necessary for evolution to occur?
What determines if a mutation will be passed on to your offspring?
Living or not? WHY?
• Viruses parasitize a host cell
• Genetic Material of Viruses
• Basic Structure of Viruses
Virus Life Cycle
The current avian flu virus (H5N1) is the most virulent form ever recorded
Cases Death Mortality
Dec 03 – Mar 04 35 24 69%
Apr 04 – Oct 04 9 8 89%
Dec 04 – Nov 05 78 30 38%
How the Avian Flu virus could become more dangerous:
In February 2004, avian influenza virus was detected in pigs in Vietnam,
increasing fears of the emergence of new variant strains. In May 2005, the
occurrence of Avian influenza in pigs in Indonesia was reported ("swine flu").
Along with the continuing pattern of virus circulation in poultry, the occurrence
in swine raises the level of concern about the possible evolution of the virus
into a strain capable of causing a global human influenza pandemic. Health
experts say pigs can carry human influenza viruses, which can combine (i.e.
exchange homologous genome sub-units by genetic reassortment.) with the
avian virus, swap genes and mutate into a form which can pass easily among
What is Differentiation?
How do cells become different?
What is evidence for differential expression of genes during differentiation?
Gene regulation in prokaryotes
A generalized metabolic pathway:
G1 G2 G3
There are two possible control mechanisms
1. genes are normally “off” - turned “on” by ________________
2. genes are normally “on” - turned “off” by ________________
Lactose metabolism in E. coli
G1 G2 G3
To summarize, the lac genes
- normally turned off by repressor molecule (in absence of lactose)
- repressor inactivated by lactose (the substrate of the metabolic pathway above)
Gene Regulation in Humans (& other eukaryotes)
There are different levels of control in eukaryotes
1. Regulatory proteins
2. Gene packing can be used to disable genes
What is it?
- packed genes are not accessible to RNA polymerase
In females one X chromosome is permanently disabled by packing
3. Introns may play a role in gene expression
Introns – “nonsense” code
Exons – usable code
How does the cell deal with these non-coding regions
Cell metabolism is also be regulated at the level of the protein
Genetics in the 21st Century
Scientific knowledge tends to grow exponentially and Genetics is one of the
most active fields
The Human Genome Project
• ~______________________ genes
• Function unknown for 50% of genes
• ______% identical in all people
• ______% "Junk DNA"
Genetic engineering, in a sense, has been around for a long time
Today genetic engineering often involves recombinant DNA
what is it?
recombinant DNA occurs naturally
How are genetically modified organisms (GMO’s) most often used in
How is genetic engineering used in medicine? What are its potential uses?
Forensic use of Biotechnology
What is the primary use of biotechnology in forensics?
cloning of genes vs. cloning of individuals
reproductive cloning vs. therapeutic cloning