1. Genome Human Genome = the sequence of DNA nitrogenous bases found on the 23 sets of chromosomes in humans Human Genome Project (HGP) = a collaborative worldwide project to sequence the nitrogenous bases in human DNA – Launched in 1990 – Goal = determine the complete 3 billion nitrogenous base sequence of human DNA – 2000+ scientists collaborated

2. DNA Review Nucleotide = the repeating unit of DNA; it comprises of: – a deoxyribose sugar – a phosphate group – and one of the 4 nitrogenous bases

3. Nitrogenous Bases

5. DNA Structure

6. Mutations

7. Mutation = change in the genetic code Caused by environmental agents such as: – damaging radiation – certain chemicals – or errors in cell division Effect of the mutation may be: – Positive – Negative – or neutral

8. Point Mutations Point Mutation = a small scale change in the nitrogenous base sequence of a DNA 1)Base-pair substitution 2)Insertion 3)Deletion 1 2 3

9. Mutations Most mutations occur in parts of DNA that do not code for genes Many mutations that do occur are immediately corrected during the copying process As organisms age, mistakes during mitosis occur more frequently which can lead to cancer Mutations that occur in somatic (body) cells are not passed on to offspring Mutations in gamete (sex) cells can be passed on to offspring

10. Inheriting Mutations DNA that mutates in an egg or the sperm that fertilizes it becomes part of the DNA of the zygote This means that the new individual will have a copy of the mutation in EVERY cell of its body and will be able to pass on the mutation to future generations – Dominant Mutation = will be expressed phenotypically in the first generation – Recessive Mutation = likely will not be expressed for many generations until, by chance, two individuals with the same mutation produce a homozygous recessive offspring

12. Sickle-Cell Anemia (SCA) an autosomal recessive genetic blood disorder with incomplete dominance Mutation  a gene in which a single adenine base was substituted by a thymine (point mutation = base-pair substitution) Healthy red blood cells = round SCA red blood cells when oxygen levels are low = C- shaped, doesn’t allow them to move through blood vessels properly = impaired blood flow, cells must be removed and destroyed Shortened life expectancy Can be both beneficial and harmful

14. Harmful vs. Beneficial Harmful = pain, increased risk of infection Beneficial = in tropical climates where Malaria is a serious parasitic disease If a SCA individual gets infected with Malaria the cells become sickle shaped, the infected red blood cell is then removed from the body and destroyed, killing the parasite in the process 1/3 of all indigenous inhabitants of Sub-Saharan Africa carry the gene Where malaria is common there is a “fitness” benefit in carrying the mutated gene

15. Malaria Risk

16. Sickle-Cell Anemia