8.19.16 Lecture Flashcards
Genetic variation originates from ___.
Heritable DNA mutations
What are the four general patterns of inheritance?
- Sex-linked (encoded on X or Y chromosome)
- Autosomal (encoded on numeric chromosomes)
- Recessive (both alleles must be affected for the phenotype to be conferred)
- Dominant (a single mutant allele confers a phenotype)
Draw the following pedigree symbols:
- Male
- Female
- Unspecified sex
- # of children of a certain sex
- Affected
- Nonpenetrant carrier (may manifest disease)
- Obligate carrier (will not manifest disease)
- Proband
- Deceased
- Marriage/union
- Divorced
- Consanguinity
- Monozygotic twins
- Dizygotic twins
- Twins, unknown zygosity
- Pedigree with generations and individuals numbered
- Still birth
- Adopted into family
- Adopted out of family
- Consultand
- Spontaneous abortion
- Miscarriage
- No offspring
- Multiple unions
- Pregnancy (with information)
- Termination of pregnancy

What is the genetic constitution of an individual or locus?
Genotype
What is the outward characteristics of an individual or gene product?
Phenotype
What is one of the alternative versions of a gene or DNA sequence at a given locus?
Allele
What is the position occupied by a gene on a chromosome?
Locus
What is a genotype with identical alleles at a given locus?
Homozygote
What is a genotype with different alleles at a given locus?
Heterozygote
What is a genotype with a single allele for a given chromosome segment?
Hemizygous
What is a genotype with two different mutant alleles at one locus?
Compound heterozygote
What is an alternate genotype present in a population at >1% frequency?
Polymorphism
What is the proportion of individuals manifesting disease?
Penetrance
What is the extent to which a mutation exhibits a phenotype?
Expressivity
What results from different mutations at one locus?
Allelic heterogeneity
What results from mutations at different loci?
Locus heterogeneity
What occurs when the same mutations manifest differently among individuals?
Phenotypic heterogeneity
What type of inheritance manifests only when there is no healthy allele present (for single gene disorders)?
Recessive inheritance
Individuals carry ___ recessive alleles that are lethal in homozygotes.
1-5
What is an example of a recessive disease?
Sickle cell anemia
What are the major characteristics of autosomal recessive inheritance?
- Only displayed in homozygotes
- Appears in more than one sibling of the proband, but not in parents, offspring, or other relatives (in other words, there is clustering among siblings and absence in ancestors)
- Males and females are affected equally
- Parents are asymptomatic carriers
- Parents may be consanguineous
- The recurrence risk for siblings = 1/4
- Carrier risk of unaffected siblings of proband = 2/3
What is a relationship resulting from common ancestry which increases the chance that both parents carry the same mutant allele?
Consanguinity
Risk of recessive genetic disease is affected by ___, ___, and ___.
Consanguinity; inbreeding; population carrier frequency
How is the degree of relationship to the proband calculated?
Degree of relationship = n = # of uninterrupted lines between proband and target