Genetics
• The Study of
1. Heredity
2. What Genes Are
3. How Genes Function
4. How Genes Carry Information
5. How Genetic Information is Expressed
6. How Genes are Replicated and Passed
Genome and DNA
• Genome is the genetic
information of the cell.
• Genome is composed of
chromosomes containing
genes.
Genes
1. Short Sections of
DNA
2. Code for
Proteins
3. 1000’s of Bases
4. 41000 Possibilities
• Gene expression: When a gene
is expressed two process occur:
• 1) transcription – DNA transcribed to
produce RNA
• 2) translation – RNA then translated
to produce proteins
Genotype and Phenotype
• Genotype
1. Genetic Composition of an Organism
2. Represents the Potential Properties
• Phenotype
1. The Expression of the Genes:
proteins
2. What You See: products of genes
DNA
replication
RNA
transcription
(Occurs in nucleus)
Proteins
translation
(Occurs in cytoplasm)
• DNA
– Nucleotides, Double helix, Genes
• RNA
– Single strand
– mRNA, tRNA, rRNA
– Contains URACIL instead of THYMINE
• Proteins
– Amino acids
RNA Functions
DNA
replication
RNA
transcription
Proteins
translation
Three major RNAs
mRNA (messenger RNA): DNA transcript
tRNA(transfer RNA): transfer amino acid
during protein synthesis
rRNA(ribosomal RNA): make up ribosomes
Replication
• The duplication of DNA which occurs
during the S phase of Interphase.
• 1 Strand  2 Complementary Strands
• DNA Polymerase
http://www.stolaf.edu/people/gia
nnini/flashanimat/molgenetics/dn
a-rna2.swf
Transcription
• The process by which a molecule of DNA is
copied into a complementary strand of
RNA.
• RNA Polymerase
http://stolaf.edu/people/
giannini/flashanimat/mo
lgenetics/transcription.s
wf
Label the diagram
Step 1: Hydrogen bonds
between complimentary
bases break
DNA “unzips”
Step 2: DNA strands
pull apart from each other
Step 3:
RNA nucleotides in RNA nucleotide
the nucleus match up
with only one side of
the
“unzipped” DNA,
the sense strand
-each “unzipped’
strands forms a
template for a mRNA
strand
Step 4:
RNA nucleotides
continue to match
up with
“unzipped” DNA
until the message
is completely
transcribed
mRNA strand
One side of DNA strand
mRNA strand
Step 4:
mRNA strand
breaks off
from the DNA
strand
One side of DNA strand
Step 5:
mRNA strand
leaves the
nucleus for
the ribosome
Step 6: Once the mRNA
leaves, the DNA “zips”
back together
Translation: at ribosomes
• The process in which the information in the
nucleotide base sequence of mRNA is used to
dictate the amino acid sequence of a protein.
• 1 Strand RNA  Amino Acid Chain  Protein
RNA and Protein Synthesis
• RNA is a Single Stranded Nucleic Acid
• RNA Acts as a Messenger between DNA
and Ribosomes
• Process Takes Amino Acids and Forms
Proteins
• http://www.stolaf.edu/people/giannini/flash
animat/molgenetics/translation.swf
DNA
Transcribed
Onto
mRNA
1 CODON
(mRNA)
1 ANTICODON
(tRNA)
1 amino acid
Why Is It Necessary?
• DNA / Nucleus
• Ribosomes / Cytoplasm
• Need a Messenger
Composition
• Nitrogenous Bases
a. Guanine
b. Cytosine
c. Adenine
d. Urasil
• Ribose Sugar
• Phosphate
Definitions
• Codon
1. Three-base segment of mRNA that
specifies amino acids.
• Anticodon
1. Three-base segment of tRNA that
docks with a codon.
2. Docking results in deposition of amino acid.
How does a particular sequence of
mRNA specify a particular
sequence of amino acids?
Answer:
BY tRNA’s!!!!
Transfer RNA molecules, code
specifically for 1 of 20 amino
acids and a corresponding codon
in the mRNA.
The code on the tRNA is
called the anticodon
tRNA enable codons in
mRNA to be translated into a
sequence of amino acids
making up a protein.
Protein Synthesis
• Proteins are coded directly from the mRNA
with 3 bases (one codon) for each amino
acid. What’s up with that?
(tRNA)
DNA sense template = CGATGCCTCGAAGCCTCGATC
mRNA = GCUACGGAGCUUCGGAGCUAG
7 Anticodons of tRNA = CGAUGCCUCGAAGCCUCGAUC
Amino Acid
=Alanine+Threonine+Glutamine+Leucine+Argnine+Serine+STOP
http://www.johnkyrk.com/DNAreplication.html
http://learn.genetics.utah.edu/content/begin/dn
a/transcribe/
Induction and Repression
• Induction
The process that initiating transcription
with an inducer.
• Repression
The repressing of transcription with a
repressor.
Mutation
• A change in the nitrogenous base sequence
of DNA; that change causes a change in the
product coded for by the mutated gene.
• Neutral
• Hazardous
• Beneficial
Mutations
What happens when you get insertions or deletions of bases in
the DNA sequence?
Usually you end up with a mess.
THE BIG FAT CAT ATE THE RAT AND GOT ILL
Deletion of one base
THE IGF ATC ATA TET HER ATA NDG OTI LL
And its all pops and buzzes!!
• Base Substitution
- One base pair in DNA is replaced with a
different base pair
• Deletion
- A piece of DNA breaks off and is lost
• Duplication and Translocation
- A piece of DNA breaks off and is
incorporated into another strand of DNA
• Frameshift
- Deletion or Addition results in a shift in
the DNA frame
Types of Mutations
• Single Base Substitution
- Also called Point Mutation
- Two Kinds
1. Transition
Purine Replaced by a Purine
Pyrimidine Replaced by Pyrimidine
2. Transversion
Purine Replaced by a Pyrimidine
or Vice Versa
• Purines
1. Adenine
2. Guanine
• Pyrimidines
1. Thymine
2. Cytosine
Types of Mutations
• Missence Mutation
- Codon is Altered Producing Altered Amino Acid
- Example: Sickle Cell Disease
GAG  GTG
• Nonsense Mutation (Example Thalidomide)
- Sense Codon is Altered to Stop Codon
- TGG  TAA
- TGG  TAG
- TCA  TGA
Sickle-Cell
Anemia
Types of Mutations
• Silent Mutation
- Codon Changed but Still Codes for Same
- Serine is TCT and TCG and TCA and TCC
• Deletion (Results in Frameshift)
- GAGCCGCAACTTC Deletion Occurs
- GAGCCGCATTC Altered State Results
• Insertion (Results in Frameshift)
- GAGCCGCAACTTC Insertion Occurs
- ACGAGCCGCAACTTC Altered State Results
Types of Mutations
• Frameshift
GAG CCG CAA CTT C…
ACGAGCCGCAACTTC
GAG CCG CAA CTT C…
ACG AGC CGC AAC TTC
Mutagens
•
•
•
•
•
•
•
Tobacco products
Nitrous Acid
Mold Toxins
X-rays
Gamma Rays
UV Radiation
Some Artificial Sweeteners
UV Light
• Skin cancer is the
most commonly
occurring cancer in the
United States.
Tobacco Products
• All forms of tobacco
products have been
shown to cause cancer.
Frequency of Mutations
•
•
•
•
•
•
Rare
Somatic / Germline
Occurs During S Phase
Cell Error Checks
97% Junk DNA
Males Contribute to More Mutations