Karyogram and karyotype • Diagram of arrangement of chromosomes • Chromosomes are paired according to size • Arrangement is called karyogram • Set of chromosomes is called a karyotype • Human karyogram shows the 23 pairs of chromosomes • Chromosome set 23 indicate the sex of the individual
Karyogram Normal Male Normal Female
Down syndrome • Down's syndrome is caused by the presence of three copies of the 21st chromosome. • This chromosomal defect is known as Trisomy-21. • Down's syndrome almost always results in mental retardation, though the severity of the retardation varies.
Epicanthic fold Small, oblique eyes Flattened, nasal bridge Open mouth Protruding tongue Broad neck Small underdeveloped ears set low on head Characteristics of Down syndrome
Wide gap between first and second toe Incurved finger Single palmar (“simian”) crease Short broad hands
Assessment • Identify on the karyogram if the individual is female or male? • Does this individual has an abnormal number of chromosomes? • Name the genetic disease that the individual suffer from.
Assessment (LO1) Use the table below and draw a graph to show the relation of maternal age to Down syndrome
Hutchinson-Gilford progeria syndrome This isa rare condition of premature ageing that begins in childhood or early adult life and leads to death within a few years
Albinism A person or animal whose melanocytes in the skin do not contain any melanin (pigment) is called an albino. This results in a characteristic appearance with snow-white hair, pink or blue eyes, and pinkish-white skin that is very sensitive to sunlight
Albinism is inherited ♂Carrier A a ♀Carrier A a ½ a ½ A ½ a ½ A ¼ aa ¼ aA ¼ AA ¼ Aa carriers ½ albino normal phenotype ¾