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13 and 14 powerpoint 13 and 14 powerpoint Presentation Transcript

  • 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 base Affect one amino acid Sometimes 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 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.
  • 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 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 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 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