1. DNA and Mutations

3. How Do Mutations Occur?
A section of DNA on a chromosome where instructions for making specific proteins are found is called a gene
Differences in genes can affect genetic traits as well as the sequencing in making proteins
Given the huge number of base pairs in DNA, there is always room for error when DNA is copied
Errors that occur during DNA replication can be affected by the environment, such as ultraviolet, radiation, or x-rays; can also be affected by natural and human made toxins

4. A change in the nucleotide sequence of a gene is a mutation
There are several types of mutations that change the sequence of nitrogen base pairs causing a mutated gene to code for a different protein than a normal gene
The overall effects of the mutation depends on where in the DNA sequence the mutation occurs and the type of mutation

5. Types of Mutations

6. Chromosome Mutations May Involve:
Changing the structure of a chromosome
The loss or gain of part of a chromosome

7. Chromosome Mutations Five types exist: Deletion Inversion
Translocation
Nondisjunction
Duplication

8. Deletion
Due to breakage
A piece of a chromosome is lost

9. Inversion Chromosome segment breaks off Segment flips around backwards
Segment reattaches

10. Duplication
Occurs when a gene sequence is repeated

11. Translocation Involves two chromosomes that aren’t homologous
Part of one chromosome is transferred to another chromosome

12. Nondisjunction Failure of chromosomes to separate during meiosis
Causes gamete to have too many or too few chromosomes
Disorders:
Down Syndrome – three 21st chromosomes
Turner Syndrome – single X chromosome
Klinefelter’s Syndrome – XXY chromosomes

13. Chromosome Mutation Animation

14. Down Syndrome
Trisomy 21…extra chromosome on the 21st pair (nondisjunction)
Most common genetic disorder; 1 in 691 are born with Down’s

15. Klinefelter’s
Occurs in males who have an extra X chromosome (XXY); affects different stages of physical, language, and social development and most common symptom is infertility (nondisjunction)

16. Turner’s
Occurs in females who have a single X chromosome (X); very rare disease causing short stature, infertility, delayed puberty, hearing loss (nondisjunction)

17. Gene Mutations Change in the nucleotide sequence of a gene
May only involve a single nucleotide
May be due to copying errors, chemicals, viruses, etc.

18. Types of Gene Mutations
Include:
Point Mutations
Frameshift

19. Point Mutation Change of a single nucleotide
Includes the deletion, insertion, or substitution of ONE nucleotide in a gene

20. Sickle Cell Anemia
Not enough healthy red blood cells to carry oxygen to the rest of the body
In order for the offspring to have sickle cell anemia, both parents must be a carrier; point mutation

21. Hemophilia
Is carried on the X chromosome (female); occurs more frequently in males than females
“Free bleeder” because the blood doesn’t clot for lack of the clotting agent
Sometimes referred to as the “royal disease”
According to the Mayo Clinic, there are 3 types of hemophilia; A, B, and C
Each of these 3 types are determined by the lack of a certain clotting factor