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Main Idea #4
Gene Expression is regulated by the cell, and
mutations can affect this expression
Controlling Gene Expression
• Transcription Factors
• proteins that ensure that a gene is
used at the right time and that
proteins are made in the right
amounts
• Structure of DNA
• the structure of DNA provides some
inhibition
Mutations
• Mutation - a permanent change in a
cell’s DNA; changes in the genetic
material of a cell
Types of Mutations
• Point mutations
• chemical changes in just one base
pair of a gene
• Can be enough to cause a genetic
disorder
Point Mutation
Point Mutations
Point mutations within a gene can be divided into two
general categories:
Base-pair substitutions
Base-pair insertions or deletions
Point Mutations
1. Substitutions
point mutation in which one base pair is exchanged for
another
Missense mutations - most substitutions are missense.The
DNA code is altered so that it codes for the wrong amino
acid
Nonsense mutations - a substitution type that changes the
codon for an amino acid to a stop codon.
•Cause translation to terminate early.
•Most always leads to proteins that cannot function
normally
Missense Mutation
Nonsense Mutations
2. Insertions and Deletions
Insertions and deletions involves the gain or
loss of a nucleotide in the DNA sequence
Insertion - additions of nucleotides to the DNA
sequence
Deletion - loss of a nucleotide
2. Insertions and Deletions
These mutations have a disastrous effect on the
resulting protein more often than substitutions
do
Insertion or deletion of nucleotides may alter the
multiples of three from the point of insertion or
deletion, producing a frameshift mutation
because they change the “frame” of the amino
acid sequence
Insertion
Deletion
Chromosome Mutations
Large portions of DNA also can be involved in a mutation.
A piece of an individual chromosome containing one or more genes can be
deleted or moved to a different location on the chromosome, or even to a
different chromosome.
Such rearrangements of the chromosome often have drastic effects on the
expression of these genes.
Chromosome Mutations
Deletion (1)- results in the loss of a piece of chromosome due to the
breakage of that chromosome; genetic information will be lost
Duplication (2)- results in the copying of a segment of the chromosome
Inversion (3)- a segment of a chromosome breaks off and reattaches itself
to the chromosome in a reversed order
Chromosome Mutations
Insertion (1) - a segment of
a chromosome breaks off
and reattaches itself to
another homologous
chromosome
Translocation (2) segments of chromosomes
break off and exchange
places on different
chromosomes
Causes of Mutation
3. Mutagens
Spontaneous mutations can occur during DNA
replication, recombination, or repair
Mutagens are substances (physical or chemical
agents) that can cause mutations
Biotechnology
13
The Big Idea
Genetic technology improves
human health and quality of life
Main Idea #2
Researchers use genetic engineering to manipulate
DNA
DNA Technology
• An organism’s genome is the total DNA
in the nucleus of each cell
• DNA tools can be used to manipulate
DNA and to isolate genes from the rest
of the genome
DNA Technology
Some bacteria contain powerful defenses again
viruses.
These cells contain proteins called Restriction
enzymes.
Restriction enzymes recognize and bind to specific
DNA sequences and cleave the DNA within the
sequence
Scientists use restriction enzymes as powerful tools
for isolating specific genes or regions of the genome.
DNA Technology
EcoRI specifically cuts DNA
containing the sequence
GAATTC.
The ends of the DNA
fragments, called sticky ends,
contain single-stranded DNA
that is complementary.
DNA Technology
The type of biotechnology in which an electric current is
used to separate DNA fragments according to the size of
the fragments is a process called gel electrophoresis
When an electric current is applied, the DNA fragments
move toward the positive end of the gel.
The smaller fragments move farther faster than the larger
ones.
DNA Technology
The unique pattern created based on the size of the
DNA fragment can be compared to known DNA
fragments for identification
DNA Fingerprinting
Protein-coding regions of DNA are almost identical
among individuals.
The long stretches of noncoding regions of DNA are
unique to each individual.
When regions of DNA are cut by restriction
enzymes, the set of DNA fragments produced is
unique to every individual.
DNA fingerprinting involves separating these DNA
fragments to observe the distinct banding patterns
that are unique to every individual