Give a comprehensive account of chromosomal abnormalities during prenatal stage of development.

Ans:

Synopsis:

• Chromosomal abnormalities
o Phenylketonuria (PKU)
o Downs syndrome
o Sickle cell anaemia
o Klinefelter’s syndrome
o Turner’s syndrome
o XYZ syndrome

• Causes Of Chromosomal Abnormalities

• Tests To determine chromosomal abnormalities
o Ultrasound sonography
o Amniocentesis
o Chorionic Villus test
o Maternal blood test

Introduction:

When the reproductive cell divides in the course of meiosis, the actual distribution of its Fouthy-six chromosomes into sperm and ovum may also be uneven. In other words, one of the resulting reproductive cell may have a lot of bodies even though the others have got handful of. Most these types of chromosomal abnormalities caused by uneven distribution regarding chromosomes are lethal. However, some chromosomal abnormalities are not lethal as one child in two-fifty is born with chromosomal abnormality..

Chromosomal Abnormalities:

1. Phenylketonuria (PKU):

• It is a genetic disorder in which the individual cannot properly metabolise an amino acid. It involves a recessive gene and takes place about once in every 10,000 to 20,000 live births. Phenylketonuria is currently very quickly detected but when not treated, retardation and also hyperactivity may possibly outcome. Whenever recognized, the problem is actually taken care of by diet plan to stop a great excessive accumulation associated with phenylalanine, an protein. PKU accounts for about one per cent of institutionalised mentally retarded individuals and occurs primarily in whites.

2. Down Syndrome:

• It is a common genetically transmitted form of mental retardation, caused by the presence of an extra (47th) chromosome. An individual with Down syndrome has
o a round face,
o a flattened skull,
o an extra fold of skin over the eyelids,
o protruding tongue,
o short limbs and
o retardation of motor and mental abilities.


• It is not known why the extra chromosome is present, but the health of the male sperm or female ovum may be involved. Women between the ages of eighteen and thirty eight are less likely to give birth to a Down syndrome affected child than younger or older women. Down syndrome appears approximately once in every hundred live births.

3. Sickle-cell Anaemia:

• Sickle-cell anemia is a genetic abnormality affecting the red blood cells. Any red blood cell is generally disk shaped, but in sickle-cell anaemia there is a change in its shape to a hook-shaped “Sickle”. These cells die rapidly, leading to anemia and early death of the individuals because of their failure to carry oxygen to the body’s cells.

4. Klinefelter’s Syndrome:

• Klinefelter’s syndrome is really a genetic disorder where males have an extra chromosome, making them XXY as opposed to XY. Males with thiscondition possess undeveloped testes and they normally have enlarged breasts and grow to be taller. Klinefelter’s syndrome occurs approximately one in every 80 live male births.

5. Turner’s Syndrome:

• Turner’s Syndrome is genetic disorder in which females are missing an X chromosome, making them XO instead of XX. These females are short in stature and have a webbed neck. They may be mentally retarded and sexually undeveloped. Turner’s syndrome occurs approximately one in every 3000 live female births.

6. XYY Syndrome:

• XYY syndrome is a genetic disorder in which the male has an extra Y chromosome. Early interest in this syndrome involved the belief that the Y chromosome, found in males, contributed to male aggression and violence. It was then reasoned that if a male had an extra Y chromosome, he would likely to be extremely aggressive and possibly develop a violent personality. However, subsequent researchers found that XYY males were no more likely to commit crimes than were XY males.