Autosomal Dominant Inheritance Flashcards
Define trait
Trait: feature or characteristic of an organism
Define autosomal trait
Autosomal trait: gene for the trait is localized to chromosomes 1-22 (NOT sex-linked or mitochondrial)
Define Mendelian (or Monogenic) trait
Mendelian/Monogenic trait: trait produced by a single gene
What are Mendel’s two Principles? Describe each
- Principle of Segregation (First Law): genes remains intact and distinct in the next generation, and intact genes can be transmitted to offspring (inherited) - genes are not blended
- Principle of Independent Assortment (Second Law): allele transmitted at one locus does not influence which allele is transmitted at another locus - genes at different loci are transmitted independently
What are the four types of alleles as classified by Mendel? Describe each
- Dominant allele: determines how a trait will appear in an organism
- Recessive: present in the genome but i phenotypically masked by the dominant allele when both are present
- Homozygous: having two identical alleles for a given gene (HH or hh)
- Heterozygous: having two different alleles for a given gene (Hh)
What is a Punnett Square used to predict?
Punnett Squares predict the outcome of a mating between individuals with specified genotypes
Differentiate between dominant disease and recessive disease in terms of Punnett Square. What are the three possible outcomes for each?
Dominant disease: disease allele is dominant (75% diseased)
- HH: homozygous for mutant allele (usually lethal)
- Hh affected heterozygote
- hh: homozygous or normal allele (unaffected)
Recessive disease: normal allele is dominant (75% not disease)
- HH: homozygous for normal allele (unaffected)
- Hh: carrier heterozygote (usually unaffected)
- hh: homozygous for mutant allele (disease)
What is probability and what is the principle utilized in genetics?
Probability: proportion of times a specific outcome occurs in a given number of events
- Principle of Independence: each event in a probability estimate is independent of every other
What are the two rules that arise from the Principle of Independence in probability?
- Multiplication rule (AND): ): in 2 independent trials, the probability of obtaining a given outcome in both trails is the product of their independent probabilities (ex. probability of 2 girls is ½ x ½ = ¼)
- Addition rule (OR): to find the probability of one outcome or another, add the probabilities together (ex. probability of having 2 girls or 2 boys is ¼ + ¼ = ½ )
Differentiate between gene frequency and genotype frequency
- Gene frequency: how often a particular gene sequence occurs in a population
- Genotype frequency: how often a given genotype occurs in a population
What is the proband in a pedigree?
Proband: first person in a pedigree to be identified clinically as having the disease
What are the three degrees of relatives in a pedigree? Describe each and provide a three examples for each
- 1st Degree relatives: related to proband as siblings, as parents or as child
- 2nd Degree relatives: persons separated from each other by one additional generational step (at least one person in between aka grandparents, aunts/uncles, nephews/nieces)
- 3rd Degree relatives: persons separated from each other by two additional generational steps (at least two people in between aka great grandchildren, great grandparents, first cousins)
How many disease alleles are required to manifest the disease phenotype in Autosomal Dominant diseases?
Only 1 disease allele is required for manifestation of the disease phenotype
What type of proteins are often involved in autosomal dominant diseases? Are AD diseases common or rare?
Non-enzymatic structural proteins are often involved in AD diseases
- AD diseases are relatively rare in humans
What are the five characteristics of an Autosomal Dominant disease?
- 2 sexes exhibit the trait in approximately equal proportions and are equally likely to transmit the trait to their offspring
- Affected individuals transmit the trait to approximately half of their offspring
- Unaffected individuals do not transmit the trait to their children
- No skipping of generations (only vertical transmission)
- Father-to-son transmission CAN occur
