Mutations

2  Mutation = change in genetic material  Gene mutation = changes in a single gene  Chromosomal mutation = changes in whole chromosomes (affects many genes)

3 Gene Mutations  Point Mutations = Changes in one or a few nucleotides  Include: substitutions, insertions, and deletions

4 Types of Point Mutations  Substitutions = one base is changed to another Usually affects a single amino acid Usually affects a single amino acid  Insertions = one base is inserted  Deletions = one base is deleted More dramatic changes More dramatic changes Cause frameshift mutations Cause frameshift mutations Changes all amino acids after theChanges all amino acids after the point of change point of change

Frameshift Mutations  mutation that shifts the “reading” frame of the genetic message by inserting or deleting a nucleotide  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

7 Chromosomal Mutations  Changes in the number or structure of chromosomes  May even change the number of copies of some genes

8 5 Types of Chromosomal Mutations  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 off and attaches to another

9 Chromosomal Mutations

10

11 Significance of Mutations  Most have little effect Most mutations occur in portions of the DNA that is not currently being used. 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 Producing defective proteins that don’t do their job  Mutations = source of genetic variability! Can be very good! Useful! Can be very good! Useful!

Polydactyly

12-5 Gene Regulation 14  A typical gene includes start and stop signals, with the nucleotides to be translated in between.  Regulatory Sites = determine if gene is on or off.

Lac Repressor in E. coli  Prokaryotic cells  Cells turn genes on and off as needed 15

Eukaryotic Gene Regulation  Similar but more complex than prokaryotes  Many eukaryotic genes include a sequence called the TATA box that may help position RNA polymerase. 16

 Enhancer sequences in DNA: Protein binding area that can enhance transcription by opening up tightly packed chromatin enhance transcription by opening up tightly packed chromatin attract RNA polymerase attract RNA polymerase block access to genes block access to genes  More complex because of cell specialization Not all proteins are needed in every cell Not all proteins are needed in every cell 17

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.

Chromosomes  Humans have 23 pairs 22 pairs are autosomes 22 pairs are autosomes 1 pair are sex chromosomes 1 pair are sex chromosomes (women = XX, men = XY)(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 is the failure of chromosome pairs to separate during meiosis (making of gametes – sex cells)  it can cause some gametes to gain an extra chromosome and others to lose one  Monosomy = A chromosome having no homologue (matching chromosome)  Trisomy =The condition of having three copies of a given chromosome in each somatic (body) cell rather than the normal number of two.

Normal Male Karyotype Normal Female Karyotype

Turners Syndrome 1 in 5,000 births 45 chromosomes X only #23 Monosomy Nondisjunction

Turners Syndrome 96-98% do not survive to birth No menstruation No breast development No hips Broad shoulders and neck

Cri-Du-Chat Syndrome 1 in 216,000 births 46 chromosomes XY or XX #5 Deletion of upper arm of chromosome

Cri-Du-Chat Syndrome Moon-shaped face Heart disease Mentally retarded Malformed larynx Normal lifespan

Aniridia-Wilms Tumor Syndrome 1 in 50,000,000 births 46 chromosomes XY or XX #11 Deletion of upper arm

Aniridia-Wilms Tumor Syndrome Mentally retarded 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

Thirteen Q Deletion Syndrome Mentally retarded Deformed face No thumbsHeart disease Short lifespan

Prader-Willi Syndrome 1 in 5,000,000 births* (new info = 1 in 25,000) 46 chromosomes XY= 97% XX= 3% #15 Deletion of lower arm paternal chromosome (Angelman’s syndrome = 15 q deletion of maternal chromosome)

Prader-Willi Syndrome Small bird-like headvery flexible Mentally retardedlow muscle tone Respiratory problems Obesity Short lifespan

Eighteen Q Deletion Syndrome 1 in 10,000,000 births 46 chromosomes XY or XX #18 Deletion of lower arm

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

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

Four-Ring Syndrome Cleft palate Club feet Testes don’t descend Short lifespan

Down Syndrome 1 in 31,000 births 46 chromosomes XY=97% XX=3% #14/21 Translocation 1 in 1,250 births 47 chromosomes - XY or XX #21 Trisomy Nondisjunction Down Syndrome Trisomy

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

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

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)

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

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 photo.