1. List and discuss different types of genetic disorders.
- down syndrome: down syndrome is caused by having three copies of chromosome 21. It is also referred to
as trisomy 21. Individuals that have down syndrome have abnormal facial features, short stature, heart
defects, susceptibility to respiratory infection, mental retardation, and an increased risk of developing
leukemia orAlzheimer's disease.
- Patau syndrome: Patau syndrome is a result of trisomy 13.Affected individuals have eye, brain, and
circulatory defects. They also have a very short life span, rarely surviving more than one year.
- Edward's syndrome: Edward's syndrome is caused by trisomy 18. This disease affects almost all of the
bodies organs, and results in a very short life span (about 10 weeks).
- Cri du chat: cri du chat is a genetic disorder that results from the deletion of chromosome 5. Individuals with
this disorder are mentally retarded, have small heads with unusual facial features, and have a cry that sounds
like a cat meowing. This syndrome is fatal.
2. Explain what are carries in terms of recessive genetic disorders.
Recessively inherited disorders show up only in homozygous individuals who inherit a recessive allele
from each parent. Carriers are individuals with heterozygous genotypes, who lack the obvious phenotype
effects of a recessively inherited genetic disorder, but still carry the recessive allele in there
chromosomes. They have a possibility of transmitting the recessive allele to their offspring.
3.Why is mating between close relatives discouraged?
If a recessive allele is rare, it is highly unlikely that the two carriers will meet and mate. However, matings
between close relatives increases the risk of two carriers mating and passing on the recessive allele to the
offspring. In general populations, it is unlikely that two carriers of the same disorder will meet and have
children. However, within close relatives, there is an increased chance that both brother and sister