2009
3(c ) Diagram 2.2
shows the formation of a type of genetic disorder.
i)State three
characteristic of this genetic disorder.
- Broad face
- Slant eyes
- Protruding tongue
- Flat nose
(ii) Explain how a
fault in the formation of cell R can cause this genetic disorder.
Chromosome mutation
- When homologous chromosome no. 21 fail
to separate during meiosis, there will be an extra chromosome (24 ) in the
ovum or less one (22) in the ovum.
- When a normal sperm (23 chromosome)
fertilizes an abnormal ovum (24 chromosomes), a zygote with 47 chromosomes
is formed.
- This zygote has an extra copy of
chromosome n0 21 (47 chromosome). The genetic disorder is Down syndrome.
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