Human Genetics

Biology

Human Chromosomes• Karyotype

– Picture of chromosomes arranged in pairs

• Autosomes – 44 chromosomes that everyone has no matter what sex they are

• Sex chromosomes – 2 chromosomes that determine sex

• Females = XX, Males = XY

How is sex determined?

• Eggs = 22 autosomes, 1 sex chromosome (X)• Sperm = 22 autosomes, 1 sex chromosome (X or Y)

Human genetic

disorders can exist within the

autosomes (chromosome pairs 1-22) or

the sex chromosomes (chromosome

pair 23) Meiotic division

Human Genetic Disorders

Changes in autosomal chromosomes

Ways genetic disorders happen:

-substitution: one nucleotide base is substituted for another

-insertion: an extra base pair not normally present is added to the code.

-deletion: a base pair is subtracted from the normal code

http://www.cancer.gov/cancertopics/understandingcancer/cancergenomics/AllPages

Changes can happen in a DNA sequence within an individual chromosome

Example: Sickle Cell Anemia• Recessive gene on

chromosome 11• Results in mutated hemoglobin

(protein that allows red blood cells to carry oxygen)

• Red blood cells are misshapen (like sickles)

• Common in African Americans

Changes can happen to a whole chromosome

• multiple/missing chromosomes: caused by possession of too many or not enough chromosomes – nondisjunction: failure

of chromosome pairs to separate properly during cell division

• translocation: small parts of chromosomes break and rejoin other chromosomes

• http://

www.knowledgene.com/public/view.php3?db=gene_school&uid=62

Example: Trisomy 18

• Edward’s Syndrome– Most die before birth; those born die within 2

months– Heart abnormalities– Difficulty breathing– Small in size

• 99 Balloons:

• http://www.youtube.com/watch?v=th6Njr-qkq0&safety_mode=true&persist_safety_mode=1

Human Genetic Disorders

Changes in sex chromosomes

Sex Chromosome Abnormalities

• X-linked (previously covered in class)

• Chromosomal abnormalities on the 23rd pair of chromosomes

Jacob’s Syndrome

Male Sex Chromosome Abnormalities

• Klinefelter Syndrome

• Males with 2 X chromosomes (XXY)– Tend to be overweight, tall– Some feminine traits (breasts,

higher pitched voice)– Sperm count is low– Hormone injections can help

The Human Genome Project

• Sequence all the DNA in a human cell• Find out what protein that DNA codes for• Better understand human genetics and how our

DNA works• Cure diseases?

Gene Therapy• With Human Genome Project, we understand

what our genes do• With gene therapy, we can try to fix them• Cure genetic diseases• Replace faulty genes with the correct one• Cells begin to produce the proper protein and

disease is cured!