1. Germ Cell vs. Somatic Cell
Mutations
Germ Cell vs. Somatic Cell

2. Point Mutations
Gene Mutation: affects either one nucleotide or one codon
Substitution: one nucleotide is replaced with a different nucleotide resulting in a new codon
If the new codon codes for same amino acid – no effect is show. (Silent Mutation)
If the new codon codes for a different amino acid or stop codon. (causing mis-sense or non-sense mutations)
Ex: Sickle Cell Anemia
Substitution: Adenine replaced by Thymine in a single codon; results in a defective form of hemoglobin

3. Point mutations are small (but significant) changes
Point mutations are small (but significant) changes.often in a single nucleotide base.

4. Point Mutations cont.
Frame-shift Mutation: caused by additions and deletions of one nucleotide; all codons after mutation are grouped incorrectly
Mutation at beginning of gene is worse than near the end of gene
Frame shift mutations result from either addition or deletion of one or two nucleotide bases. When this occurs the "reading frame" is changed so that all the codons read after the mutation are incorrect, even though the bases themselves may be still present.

6. Point Mutations

7. Chromosomal Mutations
Germ-Cell: occurs in gametes; only affect offspring
Somatic Cell: affects body cells; only affects organism
Lethal: causes death; often before birth (miscarriages)
Chromosome: changes to part or the whole chromosome; cannot be repaired by enzymes
Deletion: loss of a piece or whole chromosome
Inversion: segment of chromosome breaks off and reattaches in the reverse order on same chromosome
Translocation: piece of chromosome breaks off and reattaches to a nonhomologous chromosome
Down’s Syndrome: Trisomy 21; 3rd 21 can translocate to chromosome 13 (young mothers)
Duplication: part of chromosome attaches to homologous chromosome giving two copies of gene on that chromosome
Nondisjunction: failure of a chromosome to separate from its homologous chromosome during anaphase of meiosis; one gamete receives extra copy of chromosome other gamete does not receive one

8. Karyotype
Karyotype: chromosomes are stained and photographed under the microscope, cut from photo and arranged by size and shape; can detect chromosomal abnormalities
Monosomy: a zygote with only 45 chromosomes; one copy of a chromosome
Trisomy: three copies of a chromosome; 47 chromosomes total
Both result from nondisjunction

9. Down's Syndrome Trisomy 21 Mild to severe mental retardation
Distinct Facial Features
Heart Defects
Fingerprints – Sworl
Most Common Birth Defect – 1/700 births
Mother’s Age over 40 – 1/80
Problems during Oogenesis

10. Klinefelter's Syndrome
Trisomy of sex chromosomes; XXy male
Feminine Characteristics, Infertile
George Washington?
No Children – Sterile?
Dental Problems
Height – Very tall for generation
Still Inconclusive

11. Turner's Syndrome Monosomy of Sex Chromosomes; XO female Infertile
Dwarfism
Overweight
Some mental retardation
Webbed Neck

12. Edward's Syndrome Trisomy 18 Elfin Appearance Low set ears
Malformation of many organs – specifically heart/lungs
“Blue Babies” due to lack of oxygen
90% die within first 6 months

13. Edward's Syndrome

14. Patau's Syndrome Trisomy 13 Cleft Lip and Palate
Polydactyl – more than ten fingers/toes
1/6000 births
Most die within first year

15. Cri-du-chat “Cat’s Cry” Syndrome Deletion of a portion of Chromosome 5
Mental Retardation

16. Causes of Mutations
Spontaneous Mutations – Occur naturally within a cell, although at a normally low rate.
Induced Mutations – caused by a mutagen introduced into the cell.
Include:
Physical - agents that forcibly break nucleotide sequences and cause changes to one or both strands of a DNA molecule.
Chemical – molecules that enter a cell and induce permanent changes in the DNA.