Mutations

A mutation is a mistake made when the cell is copying DNA

If a gene in one cell is altered it is passed on to every cell that develops.

2 types Gene mutations-produce a change in a singe

gene Chromosomal mutations-produce changes in a

whole chromosome

Gene Mutations

Point Mutations Involve changes in one or a few nucleotides Occur at a single point in the DNA sequence Occur during replication 3 types

Substitution Insertion deletion

Substitutions

One base is changed to a different baseAffect one amino acidSometimes have no affect at all

Insertions and Deletions

A base is inserted or removed from the DNA sequence

Bases are still read in groups of 3 but now those groupings shift in every codon that follows the mutation

Insertions and Deletions

Also called “framshift mutations” because they shift the reading frame of the genetic mutation

Changes every amino acid after the point of mutuation

Can change a protein so much it alters its function

Chromosomal Mutations

Involves changes in the number or structure of chromosome.

These mutations can change the location of genes on chromosomes and can even change the number of copies of some genes.

4 types: deletion, duplication, inversion, translocation

Deletion

Loss of all or part of a chromosome

Duplication

Produces an extra copy of all or part of a chromosome

Inversion

Reverses the direction of parts of a chromosome

Translocation

Part of one chromosome breaks off and attaches to another

Effects of Mutations

Genetic material can be altered by natural events or by artificial means.

The resulting mutations may or may not affect an organism.

Some mutations that affect individual organisms can also affect a species or even an entire ecosystem.

Mutagens

Some mutations arise from mutagens, chemical or physical agents in the environment.

Chemical Mutagens Examples: pesticides, tobacco, smoke,environmental pollutants

Physical:x-rays, ultraviolet light,electromagnetic radiation

If the mutagen interacts with DNA they can produce mutations at high rates.

Harmful and Helpful

Whether a mutation is negative or beneficial depends on how its DNA changes relative to the organism’s situation.

Harmful Helpful

Some cancers genetic disorders. Sickle cell disease

Point mutation

new or altered functions

polyploidy. An extra set of

chromosomes Larger and stronger

than diploid plants

Prokaryotic Gene Regulation

Prokaryotes produce only those genes needed to function by doing this prokaryotes can respond to changes in their environment

DNA-binding proteins in prokaryotes regulate genes by controlling transcription.

Prokaryotic Gene Regulation

DNA-binding proteins in prokaryotes regulate genes by controlling transcription.

The genes in bacteria are organized into operons.

An operon is a group of genes that are regulated together.

Lac Operon

Lactose is made of Glucose and Galactose

A cell must bring lactose across its membrane then break the bond Performed by a protein called the lac operon

If lactose is the only food source it must make proteins to break these bonds

If on another food source it has no need for these proteins

Promoters and Operators

The operon has 3 genesOn one side of these genes there are 2

regulatory genes Promoter- RNA polymerase binds here to begin

transcription Operator-DNA lac opressor (blocker) can bind

here to stop production

Turning Off

When lactose is not present the lac repressor binds to the O region blocking transciption

This switches the operon “off”

Turning OnLac repressor has a place for lactose to

bindWhen lactose is present it bonds to this

site and makes the repressor fall offRNA polymerase can now bind to the

promoter and begin transcriptionIf lactose is present it is automatically

turned “on”

Eukaryotic Gene Regulation

TATA Box Found just before a gene Marks the point just before a gene begins to

help guide RNA polymerase into the right position

Transcription Factors

Transcription factors regulate gene expression at the transcription level

Can control the expression of genes Examples:

enhance transcription by opening up tightly packed chromatin

attract RNA polymerase block access to certain genes

Multiple factors must bind before RNA polymerase can attach to the promoter

Cell Specialization & RNA Interference

Complex gene regulation in eukaryotes is what makes specialization possible.

Small RNA molecules that do not belong to any major group ( mRNA,tRNA,rRNA) are found in the cell.

These RNA molecules interfere with mRNA and control gene expression

RNA Interference

Blocking gene expression by means of an miRNA silencing complex is known as RNA interference the small interfering RNA molecules fold into

double-stranded hairpin loops the “Dicer” enzyme cuts loops into microRNA miRNA pieces attaches to a cluster of proteins

called the silencing complex This destroys any mRNA containing a

sequence that is complementary to the miRNA

RNA Interference in pictures

Genetic Development

different sets of genes are regulated by transcription factors and repressors.

Gene regulation helps cells undergo differentiation, becoming specialized in structure and function.

Homeotic genes, regulates organs that develop in specific parts of the body. Lewis grew a fly with a leg in place of an

antennae!

Homeobox

Homeobox genes code for transcription factors that activate other genes that are important in cell development and differenetiation Code for legs and wings in fruit flies

Hox Genes Homeobox genes known as Hox genes determine the body plan of

an embryo They are arranged in the order in which they are expressed

Anterior to posterior A mutation in these genes can change the order of the body or

what parts develop

Environmental Influences

Temperature,salinity,and nutrient availibility can influence gene expression Lac operon in e.coli Alligator Eggs Metamorphosis

Genome

Full set of genetic information that an organism carries in its DNA.

Shows us what makes us uniquely human

Karyotype

Shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size.

Karyotype

Biologists photograph the cells during mitosis so the chromosomes are condensed and easy to view

Scientists then

cut out the

chromosomes and

arrange them

Chromosomes

Humans have 46 chromosomes grouped together in 23 pairs

44 of the chromosomes are autosomal chromosomes (autosomes)

2 of the 46 chromosomes are sex chromosomes Females have 2 x chromosomes Males have 2 y chromosomes

Interesting…..

The human Y chromosome is much smaller than the X chromosome and contains only about 140 genes, most of which are associated with male sex determination and sperm development More than 1200 genes are

found on the X chromosome, some of which are shown.

Chromosomes

A sex linked gene is a gene located on a sex chromosome Genes on the y chromosome are found only in

males and are passed directly from father to son

Genes on the x chromosome are found in both sexes but tend to occur more often in males

Color Blindness

Humans have 3 genes for colorblindness all on the x chromosome

A defective allele for any of these genes results in color blindness for males about 1 in 12 males

In order for this to be expressed in females they need an effective allele on both of their x chromosomes about 1 in 200

If one X chromosome is enough, how do females cope with having 2?

Most of the genes in 1 x chromosome are turned off This forms a dense area in the nucleus called a

Barr Body

X inactivation happens in other mammals as well

Spotted Cats!

In cats a gene that codes for the color of spot is located on the X chromosome. One x may have an allele for

orange spots, and one x may have an allele for black spots

In cells in some parts of the body, one X chromosome is switched off. In other parts of the body, the other X chromosome is switched off. As a result, the cat’s fur has a mixture of orange and black spots.

Pedigree

Analyzes the pattern of inheritance followed by a particular trait

Shows the relationship within a familyBased on a pedigree, you can often

determine if an allele for a trait is dominant or recessive, autosomal or sex-linked.

This pedigree shows the inheritence of the white forelock trait which is dominant

Grandfather has the trait 2 of his 3 children have the trait 3 of the 5 grandchildren have the trait Since every child does not have the trait

Grandfather must be heterozygous The children and grandchildren without the

trait are homozygous recessive

Genetic Disorders

The molecules present affect the traits we display/have

The genotype correlates to the phenotypeGenetic Disorders are molecular

DNA is altered, changing the sequence of amino acids, this changes the proteins produced, and directly affects the phenotype

Sickle Cell Anemia

Defective allele for beta globin

This forces cells into a distinct, rigid, sickle shape

The cells get stuck in capillaries and can damage tissues and organs

Cystic Fibrosis

Results from the deletion of just 3 basesPhenylalanine is missing from proteins, Phen. Normally lets Cl pass through

membranesWithout Cl the body’s tissues malfunctionProduces digestive problems,thick heavy

mucus, labored breathing

Cystic FibrosisRecessive Trait

Meaning you need to be homozygous recessive to have CF

Huntington’s Disease

Caused by a dominant allele for a protein found in brain cells Causes a long string of the codon CAG

Symptoms Mental deterioration uncontrollable movements Does not present until middle age

The longer the string of CAG the earlier it appears