Main Idea #4Gene 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 substitutionsBase-pair insertions or deletions

Point Mutations

1. Substitutionspoint 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 DeletionsInsertions 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 MutationsDeletion (1)- results in the loss of a piece of chromosome due to the breakage of that chromosome; genetic information will be lostDuplication (2)- results in the copying of a segment of the chromosomeInversion (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 chromosomeTranslocation (2) - segments of chromosomes break off and exchange places on different chromosomes

Causes of Mutation

3. MutagensSpontaneous mutations can occur during DNA replication, recombination, or repairMutagens are substances (physical or chemical agents) that can cause mutations

Biotechnology13

The Big Idea

Genetic technology improves human health and quality of

life

Main Idea #2Researchers 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 TechnologyThe unique pattern created based on the size of the DNA fragment can be compared to known DNA fragments for identification

DNA FingerprintingProtein-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