Bài 21+22: Genetics and its Applications

Content:

1. Genetic Counseling:

• Disease Diagnosis Methods:

• Pedigree analysis: Constructing a family tree to track the transmission of traits, allowing prediction of the risk of disease in future generations. Note: This method is often used to identify carriers of recessive genes.

• Prenatal diagnosis:

• Amniocentesis: Taking a sample of amniotic fluid to analyze fetal cells, checking for genetic abnormalities in the fetus. Note: This procedure is typically performed between the 16th and 18th weeks of pregnancy.

• Chorionic villus sampling (CVS): Taking a sample of placental tissue to analyze fetal cells, checking for genetic abnormalities in the fetus. Note: This procedure is typically performed between the 11th and 14th weeks of pregnancy.

• Consequences of Consanguineous Marriage: Increased risk of expressing harmful recessive genes, leading to reduced viability in offspring. Note: Consanguineous marriage is discouraged.

• Gene Therapy: Replacing a mutated gene causing disease with a healthy gene, offering potential treatment for genetic diseases in humans. Note: Gene therapy is currently in the experimental phase and not widely applied.

2. Genetic Diseases and Syndromes:

• Diseases and Syndromes Caused by Structural Chromosomal Mutations:

• Leukemia (Blood cancer): Can be caused by structural chromosomal mutations, such as chromosomal translocations. Note: Leukemia is a cancer that affects blood cells.

• Syndromes Caused by Aneuploidy:

• Down syndrome (Trisomy 21): Caused by an extra copy of chromosome 21. Note: Down syndrome is the most common genetic disorder, causing physical and intellectual disabilities.

• Color blindness: Caused by a recessive allele on the non-homologous region of the X sex chromosome. Note: Color blindness is more common in males than females.

• Muscular dystrophy: Caused by a recessive gene mutation on the X sex chromosome, with no corresponding allele on the Y chromosome. Note: Muscular dystrophy is more common in males than females.

• Other genetic diseases, disorders, and syndromes:

• Phenylketonuria (PKU): Caused by a recessive gene mutation on an autosome, leading to a disorder in phenylalanine metabolism. Note: PKU can be managed with a special diet.

• Hemophilia: Caused by a recessive gene mutation on the X sex chromosome, leading to a blood clotting disorder. Note: Hemophilia can be treated with clotting factors.

3. Sex-linked inheritance:

• Color blindness:

• Origin of the disease-causing gene: The child inherits the gene causing color blindness from their mother. Note: A father with color blindness will pass on the gene to his daughters, but the daughters will not be affected because they carry the dominant allele.

• Parental genotypes: X^MX^m x X^MY. Note: X^M: dominant allele for normal color vision, X^m: recessive allele for color blindness.

• Probability of albinism: 25% when both parents are heterozygous. Note: Albinism is caused by a recessive gene on an autosome.

• Conclusion: If a woman with red-green color blindness marries a man with hemophilia, their son will definitely have color blindness. Note: Hemophilia is caused by a recessive gene on the X sex chromosome.

General Notes:

• The information provided in this article is for reference only.

• For accurate and personalized advice, consult a genetics professional.