Transcript Types of Chromosomes and Human Genetic Disorders

Types of Chromosomes
and
Human Genetic Disorders
Types of Chromosomes
Karyotyping
Specific disorders
Karyotyping
• Taking a photograph of chromosomes (usually
from the blood) during mitosis and pairing
them (homologous chromosomes paired) to
see chromosome abnormalities.
Sex Chromosomes
• X: bigger chromosome than Y
– 1200 + genes
– Colorblindness, muscular dystrophy, hemophilia
• Y: much smaller
– 140 genes
Autosomes
• 22 pairs (44 total)
• Mutations of these chromosomes have a
greater affect on a person’s health
Disorders Caused by
Individual Genes
• Sickle Cell Anemia: caused by a defective
allele for a polypeptide in
hemoglobin (protein which carries
O2)
– Makes hemoglobin stick together b/c
it’s less soluble and becomes sickle
shaped
– Clogs capillaries to damage cells, tissue, or organs
Disorders Caused by
Individual Genes
• Cystic Fibrosis: usually caused by a deletion of
3 bases (removal of phenylalanine
from a protein) which causes the
protein to be destroyed (recessive)
– Leads to tissue malfunctions in
digestive system and causes thick,
heavy mucus to clog lungs and breathing
passageways
Disorders Caused by
Individual Genes
• Huntington’s Disease: caused by a repeat of
CAG (glutamine) more than 40
times
– Symptoms include mental deterioration
and uncontrollable movements
– The greater the # of repeats the earlier
the disease appears and it will be more severe
Disorders Caused by
Individual Genes
• Advantages:
– Those heterozygous for sickle cell anemia are
highly resistant to malaria and will not get either
disease
– Proteins produced by CF block the entry of a
bacteria that causes typhoid fever—those
heterozygous for CF will have an advantage if they
live in a city w/ poor sanitation and polluted water
and won’t get either ailment
Chromosomal Disorders
• Nondisjunction: chromosomes don’t separate
during meiosis get abnormal # of
chromosomes
– Trisomy: 2 copies of autosomes fail to separate so
you get 3 copies of a chromosome
– Chromosome 21 = Down’s syndrome
– XXX = sterile
• X chromosome nondisjunction can also cause
XO = sterile(Turner’s Syndrome), or XXY =
sterile (Klinefelter’s Syndrome)