The Human Genome

 Karyotype: When chromosomes are photographed, then paired to observe size and number.

 Human Body Cell: Has 46 chromosomes, 2 of the 46 chromosomes are sex chromosomes and the remaining 44 are autosomal

chromosomes 23rd pair of a Female is XX 23 rd pair of a Male is XY

Normal Human Karyotype

Normal Karyotype

Nondisjunction

 Failure of homologous pairs of chromosomes to separate properly during meiosis.  This results in cells with an uneven number of chromosomes

Down Syndrome  Down syndrome is caused by a person having three copies of chromosome 21 instead of two copies.

Down Syndrome

 Patient has 47 chromosomes  Some characteristics are: short, broad hands; short height; broad head; round face; large tongue; slanting eyes and mental retardation

Down syndrome

Patau Syndrome  Caused by an extra copy of chromosome 13.  Severe mental deficiency, polydactylism, cleft lip/palate, heart problems  low survival rate after 3 months.

Patau Syndrome Facial Clefting shown to the right

Patau Syndrome

Klinefelter’s syndrome  Patient has 47 or 47+ chromosomes. (One to several extra X or Y)  Male  Characteristics: small testes, female-like breasts, female-like voice and retardation

Klinefelter’s Syndrome

Extra Y Chromosome  Patient has 47 chromosomes (one extra Y chromosome.

 male  1 in 1000 males have 47-XYY  Slightly taller, but rather normal development

Turner’s Syndrome  Patient has 45 chromosomes  Missing one X.

 Female, sterile  dwarfism