Modification of Mendelian Ratios

• What is a wild-type allele?


  It is the most frequently encountered allele in a population, considered normal.
• How is a wild-type allele used in genetics?


  It serves as a standard to check if another allele has mutations.
• What is a mutation?


  A mutation is a modification of the genetic sequence.
• What is a mutant allele?


  A mutant allele is the product of a mutation that has altered genetic information.
• What is a loss of function mutation?


  A loss of function mutation diminishes the functionality of a gene.
• What happens if a gene responsible for synthesizing an enzyme has a loss of function mutation?


  The mutation can change the conformation of the enzyme and reduce its affinity for the substrate.
• What is a null allele?


  A null allele is the complete loss of function of a gene due to mutation.
• What is a gain of function mutation?


  A gain of function mutation increases the activity of a gene due to mutation.
• What can happen to protooncogenes if they undergo a gain of function mutation?


  They can be converted to oncogenes, leading to the creation of cancerous cells.
• What is a neutral mutation?


  A neutral mutation does not necessarily alter the activity of a gene and has no effect on the phenotype.
• What does hemizygous mean?

  Hemizygous refers to having no homolog or not being paired in diploid cells, usually in males.
• What is partial dominance and how was it studied?


  • Also known as incomplete dominance.
  • Studied by Carl Correns using the 4 o'clock or snapdragon plant.
  • Parent generation had red and white flowers; F1 generation had pink flowers.
• What occurs in a cross between parents with contrasting traits in partial dominance?


  It may generate offspring with an intermediate phenotype, falling between the contrasting traits.
• What is the phenotypic ratio in partial dominance?


  The phenotypic ratio is identical to the genotypic ratio.
• How are alleles represented in partial dominance?


  Neither allele is dominant or recessive, so uppercase and lowercase letters are not used as symbols.
• What is codominance?


  Codominance occurs when both alleles are dominant and expressed together as phenotypes.
• Who discovered the glycoprotein on red blood cells related to codominance?


  Karl Landsteiner and Philip Levin discovered the glycoprotein that acts as a native antigen.
• What is the MN Blood Group system?


  • It involves the inheritance of M and N substances (glycoproteins).
  • Genes at a locus in chromosome 4 regulate their production.
  • Inheritance of both genes leads to the production of both glycoproteins.
• What are the genotypes and phenotypes for the MN blood group?


  • Genotypes:
  • LMLM = M
  • LMLN = MN
  • LNLN = N
  • Phenotypes correspond directly to genotypes.
• How can mutations affect the number of alleles in a population?


  Mutations can produce different alleles, leading to a variety of alleles within a population.
• What is meant by multiple alleles?


  Multiple alleles refer to the presence of three or more alleles of the same gene in a population.
• What is an example of multiple alleles in humans?


  The ABO blood type system is an example of multiple alleles.
• What are the four different blood types in the ABO system?


  • Type A (dominant)
  • Type B (dominant)
  • Type AB (both A and B present)
  • Type O (silent/recessive allele)
• Who discovered the ABO blood types?


  Karl Landsteiner discovered the ABO blood types.
• Who discovered the AB blood type?


  Sturli and Von Decastello discovered the AB blood type.
• What are the antigens and phenotypes in the ABO blood group?


  • A antigen (A phenotype)
  • B antigen (B phenotype)
  • A and B antigen (AB phenotype)
  • Neither antigen (O phenotype)
• What are the alleles for the ABO blood types?


  IA = A, IB = B, and i = O.
• What are the genotypes for the ABO blood types?


  • IAIA = A
  • IBIB = B
  • IAIB = AB
  • IAi = A
  • IBi = B
  • ii = O
• Why can an individual only have two alleles from multiple alleles in a population?


  An individual can only have two alleles because they have two biological parents.
• Where is the ABO gene located?


  The ABO gene is located on chromosome 9.
• What are the blood types and genotypes based on parental blood types?


  Example 1:

  • Mom: AB, Dad: O
  • Possible blood types: 50% A, 50% B
  • Genotypic Ratio: 2:2 or 1:1

  
  

  Example 2:

  • Mom: A, Dad: AB
  • Possible blood types: 50% A, 50% AB
  • Genotypic Ratio: 2:2 or 1:1
• What are the antigens and antibodies in ABO blood types?


  • Blood types contain specific antigens: A, B, both, or neither.
  • The body produces antibodies to neutralize foreign particles.
• What is complete dominance in inheritance?

  Complete dominance occurs when one allele completely masks the effect of another allele.
• What is the Rhesus factor in blood types?


  The Rhesus factor determines whether blood type is positive or negative based on the presence of R genes.
• What genotypes indicate Rhesus positive blood type?


  RR or Rr indicates Rhesus positive blood type.
• What genotype indicates Rhesus negative blood type?


  rr indicates Rhesus negative blood type.
• What is the purpose of Anti-D in blood typing?


  Anti-D is used to test for the presence or absence of the Rhesus factor.
• What are the ABO blood types and their corresponding genotypes and Rhesus factors?


  • A+: AA, AO; Rhesus positive: RR, Rr
  • A-: AA, AO; Rhesus negative: rr
  • B+: BB, BO; Rhesus positive: RR, Rr
  • B-: BB, BO; Rhesus negative: rr
  • AB+: AB; Rhesus positive: RR, Rr
  • AB-: AB; Rhesus negative: rr
  • O+: OO; Rhesus positive: RR, Rr
  • O-: OO; Rhesus negative: rr
• What can mutations in essential genes lead to?


  Mutations in essential genes may lead to death.
• What is a heterozygous recessive lethal allele?


  A heterozygous recessive lethal allele has a lethal mutation but the individual can survive due to a non-lethal allele.