Mutations and Chromosomal Disorders

Mutation or birth defect?

Mutations Random Accidents/Generally Insignificant or Beneficial or Bad Accidents- Replications/Transcriptions Mitosis Meiosis Gene Mutation: More Common

Do all mutations affect the organisms? No! Mutations may occur in a gene that is turned off in a cell (ex. Kidney cell vs. Heart Cell) When this occurs, there is no affect on the organism! Example: Concert Sound Board

Mutagen Factors in the environment that cause mutations Can you think of a few? X-Rays, UV waves, various chemicals

Mutations Gene Mutation Chromosome Mutation Substitution Deletion Point mutation Deletion Frame-shift mutation Addition Chromosome Mutation Nondisjunction Fragmentation translocation Inversion Addition Deletion Polyploidy

Translocation

A mutation can only be passed on to offspring IF THE MUTATION IS PRESENT IN THE GAMETES / SEX CELLS

Gene Mutations Substitution (point mutation)- changes one codon Deletion (frameshift mutation)- everything changes after the removal of that nucleotide Same effect in an addition *more detrimental than substitutions

Chromosomal Mutation Affects the whole chromosome and all genes on chromosomes Will be more detrimental! Mutations passed on if occur in sex cells

DNA template strand T A C T T C A A A C C G A T T A T G A A G T T T G G C T A A mRNA A U G A A G U U U G G C U A A Protein Met Lys Phe Gly Stop Amino end Carboxyl end Nucleotide-pair substitution: missense T instead of C T A C T T C A A A T C G A T T A T G A A G T T T A G C T A A A instead of G A U G A A G U U U A G C U A A Met Lys Phe Ser Stop

DNA template strand T A C T T C A A A C C G A T T A T G A A G T T T G mRNA A U G A A G U U U G G C U A A Protein Met Lys Phe Gly Stop Amino end Carboxyl end Nucleotide-pair deletion: frameshift causing extensive missense A missing T A C T T C A A C C G A T T A T G A A G T T G G C T A A U missing A U G A A G U U G G C U A A Met Lys Leu Ala

Nondisjunction Chromosomes that normally separate during Meiosis stay together and can cause several genetic disorders in humans Examples: Down Syndrome, Turner’s, Klinefelter’s

Down’s Syndrome -extra copy of chromosome # 21 Turner’s Syndrome -underdeveloped sexual characteristics -webbed neck

Klinefelter’s Syndrome -two X chromosomes and a Y -male with underdeveloped sex organs

Polyploidy Cells have some multiple of the normal chromosome number Example: Plants with Polyploidy are usually larger with larger fruit

Polygenetics Polygenic Trait- traits controlled by many genes (examples  height, skin color, eye color)

Genetic Screening When a person’s genetic make-up is analyzed to determine the possibility of genetic disorders for themselves and that could be passed on to future offspring

Common Genetic Disorders

Sex-linked Disorders Hemophilia Color-Blindness Male Pattern Baldness

Autosomal Disorders Sickle Cell- sickle shaped blood cells Tay –Sachs-death by the age of 4 Cannot breakdown lipids in the brain PKU-Caused by mutation and cannot break down phenylalanine Cystic Fibrosis-(refer to video on Active Transport) Missing gene to control formation of mucus Huntington’s Disease-fatal but do not appear until 30 years old-due to breakdown of the brain cells Pompe Disease- caused by mutation in the GAA gene (leads to excessive build up of glycogen in muscle cells)

Detecting Genetic Disorders Karyotyping Amniocentesis Chorionic villus sampling Ultrasound

Karyotype: Normal

Karyotype: Edward’s Syndrome

Edward’s Syndrome

Amniocentesis (Ultrasound)

Amniocentesis

Amniocentesis

Ultrasound

Genetic Engineering

Definition The process of producing altered DNA, usually by breaking a DNA molecule and inserting new genes

Recombinant DNA (Gene Splicing) DNA from two different species is joined together Provides a way of producing large amounts of sometimes rare substances Example: Insulin and clotting factors that treat Hemophilia What is used to cut DNA? (Hint: Electrophoresis) Restriction Enzymes

Gene Therapy The process of correcting genetic defects by transferring normal genes to cells that have defective genes Sometimes normal genes are introduced to the cell by means of virus or bacteria Used in both Plants and Animals