Genetics

• What can be predicted using Punnett squares?

  Probable frequencies of genotype and phenotype of offspring
• What factors must be considered when predicting offspring genotypes and phenotypes?

  Patterns of inheritance, including dominance, co-dominance, autosomal or sex-linked alleles, and multiple alleles

  
• Which genetic disorders show different inheritance patterns?

  Huntington's disease, PKU, ABO blood groups, red-green colour blindness, and haemophilia
• What can Punnett squares predict in monohybrid crosses?

  • Genotype ratios
  • Phenotype ratios
• How do autosomal and sex-linked conditions impact offspring probabilities?

  They affect the probabilities of genotypes and phenotypes of offspring
• How can the probability of genotypes and phenotypes from monohybrid crosses be determined?

  From known parents or by test crosses
• What does the offspring of multiple allele inheritance depend on?

  The alleles present in the parents
• What is the purpose of pedigree charts?

  • Constructed for families with a genetic disorder
  • Reveal patterns of inheritance
  • Assist in determining the probability of inheriting the condition in future generations

  
• How can pedigree charts be interpreted?

  To identify genotypes and phenotypes of individuals
• What can be deduced from pedigree charts and family trees?

  The mode of inheritance
• What symbols do pedigree charts use?

  Internationally recognised symbols
• What are examples of genetic disorders influenced by genetic and environmental factors?

  • Duchenne muscular dystrophy
  • Haemophilia
  • Osteogenesis imperfecta
  • Club foot
  • Pyloric stenosis
  • Dislocation of hip
  • Peptic ulcer
  • Diabetes
  • Tuberculosis
  • Phenylketonuria
  • Galactosaemia
  • Spina bifida
  • Ischaemic heart disease
  • Ankylosing spondylitis
  • Scurvy

  
• What are the characteristics of rare and common genetic disorders?

  Rare:

  • Simple genetics
  • Unifactorial
  • High recurrence rate

  
  

  Common:

  • Complex genetics
  • Multifactorial
  • Low recurrence rate
• Who is known as the father of modern genetics?

  Gregor Mendel
• Where did modern genetics begin?

  In an abbey garden where Gregor Mendel documented inheritance
• What advantages did Mendel have when studying pea plants?

  • Strict control over plant mating
  • Each plant has male and female organs
  • Ability to cross-pollinate plants
• What traits did Mendel study in pea plants?

  1. Stem length (long or short)
  2. Flower color (purple or white)
  3. Seed color (yellow or green)
  4. Flower position (axil or terminal)
  5. Pod shape (inflated or constricted)
  6. Pod color (yellow or green)
  7. Seed shape (round or wrinkled)

  
• What does Mendel's first hypothesis state about genes?

  Alternative versions of genes (different alleles) account for variations in inherited characters
• What does Mendel's second hypothesis state about allele inheritance?

  For each character, an organism inherits two alleles, one from each parent
• What is the significance of dominant and recessive alleles according to Mendel's third hypothesis?

  The dominant allele is fully expressed, while the recessive allele has no noticeable effect

  
• What does Mendel's law of segregation state?

  The two alleles for each character segregate during gamete production
• What happens if an organism has identical alleles for a character?

  That allele exists as a single copy in all gametes
• How is the separation of alleles summarized?

  As Mendel’s law of segregation
• What are the definitions of monogenic dominant and recessive traits?

  • Dominant alleles cover the effect of an alternative allele.
  • Recessive alleles are expressed only when two are present.
• How are dominant alleles represented?

  With a capital letter
• How are recessive alleles represented?

  With a lowercase letter
• What does homozygous mean?

  Having the same alleles for a particular allele pair
• What does heterozygous mean?

  Having different alleles for a particular allele pair
• What is the definition of genotype?


  The genes an individual has
• What is the definition of phenotype?


  The physical expression of the allele or the observed characteristic
• How can the phenotype of flower color in peas be the same for different genotypes?

  Both PP and Pp plants have the same phenotype (purple) but different genotypes
• What is required to produce a white phenotype in pea plants?

  Being homozygous recessive (pp) for the flower-color gene
• What does a Punnett square help predict?

  • The result of a genetic cross
  • The genotypes of offspring
• What does a Punnett square display?

  The predicted genotypes of offspring
• What do genetic crosses show regarding offspring genotypes?

  They show the statistical probability of an offspring having a particular genotype
• What are some Mendelian traits in humans?

  • Ability to taste PTC
  • Albinism
  • Blood type
  • Brachydactyly
  • Cheek dimples
  • Cleft chin
  • Free or attached earlobes
  • Wet or dry earwax
  • Face freckles
  • Hitch hiker’s thumb
  • Polydactyly
  • Widow’s peak
  • Tongue rolling
• What is the inheritance pattern and cause of Phenylketonuria (PKU)?

  • Inheritance: Autosomal recessive
  • Cause: Lack of enzyme that converts phenylalanine to tyrosine
• What are the effects and treatment of Phenylketonuria (PKU)?

  • Effects: Damage to nervous system and mental retardation if not diagnosed
  • Treatment: Avoid foods with phenylalanine, especially during childhood & pregnancy

  
• What is the inheritance pattern and cause of Tay-Sach’s Disease?

  • Inheritance: Autosomal recessive
  • Cause: Lack of hexosaminidase A and storage of its substrate in lysosomes
• What are the effects of Tay-Sach’s Disease?

  • Common among United States Jews of central and eastern European descent
  • Affected infants develop neurological impairments and die by age three or four