meiosis and patterns of disease inheritance

• What are the three sex chromosome systems mentioned?

  XX-XO, XX-XY, ZZ-ZW
• What does morphologically heterogenous sex chromosomes indicate?

  They are a more evolved condition
• What is believed to have caused the degeneration of the Y chromosome?

  Degeneration started about 320 million years ago
• How many genes are found in both the X and Y chromosomes?

  19 genes
• What does 'n' represent in the context of chromosomes?

  One set of chromosomes (haploid)
• What does '2n' represent in the context of chromosomes?

  Two sets of chromosomes (diploid)
• What is the role of the synaptonemal complex in meiosis?

  It mediates synapsis and homologous recombination
• In which phase of meiosis does the synaptonemal complex form?

  Prophase I
• What does independent assortment in meiosis lead to?

  Genetic variation in gametes
• How many possible gametes can be produced from 23 chromosomes?

  $8.4 \times 10^6$ possible gametes
• What is non-disjunction?

  Failure of chromosomes to separate properly
• What syndrome is caused by non-disjunction of chromosome 21?

  Down syndrome
• What are the symptoms of Down syndrome?

  Short stature, mental retardation, heart defects
• What syndrome is caused by non-disjunction of chromosome 18?

  Edwards syndrome
• What are the symptoms of Edwards syndrome?

  CNS abnormalities and facial malformations
• How is non-disjunction associated with maternal age?

  Increased risk of chromosomal abnormalities
• What are the main patterns of inheritance in genetics?

  • Non-Paternity
  • Pedigrees
  • Mendelian Diseases:
  • Autosomal Dominant
  • Autosomal Recessive
  • X-linked
  • Abnormal Inheritance Patterns
  • Importance of environment
• What are the major categories of genetic disorders?

  Single Gene Defects, Chromosomal Disorders, Multifactorial Disorders
• What is the prevalence of autosomal dominant disorders per 1000 people?

  2-10
• What is the prevalence of autosomal recessive disorders per 1000 people?


  2
• What is the prevalence of X-linked recessive disorders per 1000 people?

  1-2
• What is the prevalence of chromosomal abnormalities per 1000 people?

  6-7
• What is the prevalence of multifactorial disorders per 1000 people?

  30
• What is the total prevalence of genetic disorders per 1000 people?

  38-51
• What is the vision for the future in genetics?

  • Identify genes for common genetic defects
  • Risk identification and predictive testing
  • Screening programs and preventive treatments
  • Cure genetic disorders
  • Advances in prenatal screening
• Who coined the term 'gene'?

  Wilhelm Johannsen
• What did Thomas Hunt Morgan demonstrate using fruit flies?

  Genes are units of heredity on chromosomes
• What hypothesis did Beadle and Tatum affirm through their experiments?

  The one gene, one enzyme hypothesis
• What are the symbols used in pedigrees?

  • Unaffected female
  • Unaffected male
  • Carrier male
  • Affected male
  • Affected female
  • Pregnancy, miscarriage, termination symbols
• What are the characteristics of single gene defects?

  • Presence of a single mutated gene
  • Passed down through generations
  • Occur spontaneously in germ or somatic cells
  • High risks within families
• What are the patterns of single gene defects inheritance?

  • Autosomal Dominant
  • Autosomal Recessive
  • X-linked Inheritance
• What is the pattern of inheritance for autosomal dominant disorders?

  Vertical aspect in family trees
• What is the most common form of human genetic dwarfism?

  Achondroplasia
• What is the role of FGFR3 in achondroplasia?

  Regulates chondrocyte differentiation and bone growth
• What is incomplete penetrance?

  Inherited mutated allele without developing disorder
• What is the pattern of inheritance for autosomal recessive disorders?

  Horizontal aspect in family trees
• How are X-linked recessive disorders expressed in males?

  Males are affected due to single X-chromosome
• What happens in heterozygous females with X-linked recessive disorders?

  Mutant alleles can be expressed if X-inactivation occurs
• What is Duchenne Muscular Dystrophy (DMD)?

  X-linked recessive condition causing muscle weakness
• What is the typical age of onset for Duchenne Muscular Dystrophy?

  Early childhood