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11/6/2014 12-4 Mutations 1 Mutation How - change in genetic material do they occur? Spontaneous mutations - mutations occurring during replication (mitosis/meiosis) Mutagen - chemical or physical agent that causes a mutation Gene mutation - changes in a single gene Chromosomal mutation - changes in whole chromosomes (affects many genes) 2 1 11/6/2014 Gene Mutations Point Mutations - Changes in one or a few nucleotides Include: substitutions, insertions, and deletions 3 Types of Point Mutations Substitutions - one base is changed to another Usually affects a single amino acid Insertions - one base is inserted Deletions - one base is deleted More dramatic changes Cause frameshift mutations 4 2 11/6/2014 Frameshift Mutations that shifts the “reading” frame of the genetic message by inserting or deleting a nucleotide Mutation May change every amino acid after that point Frameshift mutations can alter a protein so much that it is unable to perform its normal functions. 5 6 3 11/6/2014 Chromosomal Mutations Changes in # or structure of chromosomes May even change # of copies of some genes 5 Types: Insertions - addition of part of a chromosome Deletions - loss of all or part of a chromosome Duplications - extra copies of parts of a chromosomes Inversions - reverse direction of parts of a chromosomes Translocations - part of one chromosome breaks 7 off and attaches to another Chromosomal Mutations 8 4 11/6/2014 9 Significance of Mutations Most have little effect Most mutations occur in portions of the DNA that is not currently being used. Dramatic changes = usually harmful Producing defective proteins that don’t do their job Mutations = source of genetic variability! Can be very good! Useful! 10 5 11/6/2014 Polydactyly 6 11/6/2014 Chromosomal Mutations & their effects Karyotype A picture of the chromosomes of an individual (or a species), including number, form, and size of the chromosomes. Often used to diagnosis chromosomal abnormalities 7 11/6/2014 Chromosomes Humans have 23 pairs 22 pairs are autosomes 1 pair are sex chromosomes • (women = XX, men = XY) Chromosomes have a centromere that holds the chromatids (two parts of the chromosome) together. The top ½ of the chromosome is called the “p” arm and the bottom ½ is “q” Nondisjunction Disorder Nondisjunction - failure of chromosome pairs to separate during meiosis (making of gametes – sex cells) Can cause some gametes to gain an extra chromosome and others to lose one Monosomy - A chromosome having no homologue (matching chromosome) Trisomy - Having 3 copies of a given chromosome in each somatic (body) cell (normal number: 2 copies) 8 11/6/2014 9 11/6/2014 Normal Male Karyotype Normal Female Karyotype 20 10 11/6/2014 21 Turners Syndrome 1 in 5,000 births 45 chromosomes (X only) #23 Monosomy Nondisjunction 11 11/6/2014 Turners Syndrome 96-98% do not survive to birth No menstruation No breast development Broad shoulders and neck No hips Cri-Du-Chat Syndrome 1 in 216,000 births 46 chromosomes XY or XX #5 Deletion of upper arm of chromosome 12 11/6/2014 Cri-Du-Chat Syndrome Moon-shaped face Heart disease Mentally retarded Malformed larynx Normal lifespan Aniridia-Wilms Tumor Syndrome 1 in 500,000 births 46 chromosomes XY or XX #11 Deletion of upper arm 13 11/6/2014 Aniridia-Wilms Tumor Syndrome Mental retardation Growth retarded Blindness Tumors on kidneys Short lifespan Thirteen Q Deletion Syndrome 1 in 500,000 births 46 chromosomes XY or XX #13 Deletion of lower arm 14 11/6/2014 Thirteen Q Deletion Syndrome Mentally retarded Deformed face No thumbs Heart disease Short lifespan Prader-Willi Syndrome 1 in 15,000 to 1 in 25,000 46 chromosomes XY= 97% XX= 3% #15 Deletion of lower arm on paternal chromosome (Angelman’s syndrome = 15 q deletion of maternal chromosome) 15 11/6/2014 Prader-Willi Syndrome Small hands and feet Slow mental development Respiratory problems Obesity Short lifespan Very flexible Poor muscle tone Short stature Eighteen Q Deletion Syndrome 1 in 40,000 births 46 chromosomes XY or XX #18 Deletion of lower arm 16 11/6/2014 Eighteen Q Deletion Syndrome Mentally retarded Heart disease Abnormal hands and feet Large eyes Large ears Normal lifespan Cat-Eye Syndrome 1 in 1,000,000 births 46 chromosomes XY or XX #22 Deletion of bottom arm 17 11/6/2014 Cat-Eye Syndrome Fused fingers and toes Mentally retarded Small jaw Heart problems Normal lifespan Four-Ring Syndrome 1 in 10,000,000 births 46 chromosomes XY or XX #4 Inversion 18 11/6/2014 Four-Ring Syndrome Cleft palate Club feet Testes don’t descend Short lifespan Down Syndrome Down Syndrome Trisomy 1 in 31,000 births 1 in 1,250 births 46 chromosomes XY=97% XX=3% 47 chromosomes - XY or XX #14/21 Translocation #21 Trisomy Nondisjunction 19 11/6/2014 Down Syndrome Short, broad hands Stubby fingers Rough skin Impotency in males Mentally retarded Small round face Protruding tongue Short lifespan Edward’s Trisomy Syndrome 1 in 4,400 births 47 chromosomes XX=80% XY=20% #18 Trisomy Nondisjunction 20 11/6/2014 Edward’s Trisomy Syndrome Small head Mentally retarded Internal organ abnormalities 90% die before 5 months of age Jacob’s Syndrome 1 in 1,800 births 47 chromosomes XYY #23 Trisomy Nondisjunction 21 11/6/2014 Jacob’s Syndrome Normal physically Normal mentally Increase in testosterone ? Acne Normal lifespan Klinefelter Syndrome 1 in 1,100 births 47 chromosomes XXY only #23 Trisomy Nondisjunction (sometimes seen as Kleinfelter) 22 11/6/2014 Klinefelter Syndrome Scarce beard Longer fingers and arms Sterile Delicate skin Low mental ability Normal lifespan Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only #23 Trisomy Nondisjunction 23 11/6/2014 Triple X Syndrome Normally physically Normal mentally Tall Fertile normal lifespan This is a cell after it has been broken open. A photo is taken of this and then manipulated on a computer. Each chromosome is cut out of the h t 24