MutationsA 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 base Affect one amino acid Sometimes have no affect at all
Insertions and DeletionsA 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 Partof 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 new or altered genetic disorders. functions Sickle cell disease polyploidy. Point mutation 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 genes On 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 On Lac repressor has a place for lactose to bind When lactose is present it bonds to this site and makes the repressor fall off RNA polymerase can now bind to the promoter and begin transcription If 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 differentsets 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 Fullset 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.
ChromosomesA 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 dofemales cope with having 2? Mostof the genes in 1 x chromosome are turned off This forms a dense area in the nucleus called a Barr BodyX 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 family Based 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 phenotype Genetic 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 bases Phenylalanine is missing from proteins, Phen. Normally lets Cl pass through membranes Without Cl the body’s tissues malfunction Produces digestive problems,thick heavy mucus, labored breathing
Cystic Fibrosis Recessive 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