A karyotype is a “picture” of a persons chromosomes. A normal human female has 22 pairs of homologous autosomes and 1 set of sex chromosomes (XX). A normal human male has 22 pairs of homologous autosomes and 1 set of sex chromosomes (XY). **Normal humans have 46 chromosomes!**

Nondisjunction Sometimes during meiosis, the homologous pair OR the sister chromatids may fail to separate – this is called “nondisjunction” and it leads to an abnormal number of chromosomes.

Down Syndrome: 47, +21 Trisomy 21 = Down Syndrome Fig Cummings, Human Heredity, 6th ed.

Fig Singer, Human Genetics, 2nd edition The incidence of Down syndrome increases from 1 in 1000 births to over 10 in 1000 births for women over 40 years of age No such correlation exists with the age of the father. Thus, it is believed that most cases of Down syndrome are the result of mistakes made during egg formation.

Patau Syndrome: 47, in 15,000 live births cleft lip and palate eye defects, polydactyly malformation of internal organs (brain, nervous system, heart) survival rarely past 1 year Edwards Syndrome: 47, in 11,000 births small at birth, growth retarded malformed hands and feet heart malformations death within first year usually caused by heart failure or pneumonia Figs , Human Heredity, Michael R. Cummings, 4 th edition

Down Patau Edwards Turner, Klinefelter No other extra chromosome karyotypes are found - not because they aren’t formed, but because their effects are too severe to survive development. An estimated 20-50% of all human conceptions end in spontaneous abortion - 50% of those are due to abnormal chromosome numbers GENE DOSAGE IS IMPORANT

DNA TECHNOLOGY How can we use DNA? – Solve crimes, diagnose genetic disorders, solve paternity cases, compare species, study and cure disease, modify foods, etc. Where do we get DNA samples? – Blood, skin, hair, semen, etc. Human DNA – 99.9% the same; 0.1% different

Human Genome Project Completed in 2003 Map and sequence human genome Find where all genes are located and sequence DNA Uses: diagnose genetic disorders Gene therapy – Insert normal genes into cells to correct genetic disorders

DNA Extraction Open cells to isolate DNA from other cell parts

Polymerase Chain Reaction (PCR) Used to amplify regions of DNA (make many copies of a small amount of DNA)

Restriction Enzymes “cutting DNA” Large DNA molecules are cut into smaller fragments Restriction enzymes recognize and cut DNA at specific sequences

Gel Electrophoresis A way to separate DNA based on size Put sample in a gel and add electricity DNA fragments move – DNA has negative charge (moves to + end) – Smaller fragments travel farthest

Using Gel Electrophoresis Solving a Crime – Compare the DNA bands – Must be an exact match Paternity Test – Compare DNA bands – Child’s DNA must come from mother or father

Genetic Engineering = Recombinant DNA Technology = Genetic Recombination Cutting (cleaving) DNA from one organism into small fragments and inserting the fragments into a host organism of the same or different species The host then uses the foreign DNA as its own

Recombinant DNA = DNA fragments that have been connected (recombined) from different species Transgenic Organsims = organisms that contain functional recombinant DNA (foreign DNA)

Uses of Recombinant Bacteria Industry – To break down pollutants – Clean up oil spills Medicine – Make insulin, etc. – Transgenic organisms to study disease Agriculture – Remove bacterial gene that causes frost in strawberries – Transgenic plants to resist herbicides or increase protein production

Cloning Making genetically identical offspring through nuclear transplant.