III. Penetrance and Expressivity Flashcards
___ is the ability of a given gene or gene combination to be expressed phenotypically to any degree; the extent to which a particular gene or set of genes is expressed in the phenotypes of individuals carrying it, measured by the proportion of carriers showing the characteristic phenotype.
Penetrance
___ refers to when most dominant and recessive genes in homozygous conditions and many completely dominant genes even in heterozygous conditions give their complete phenotypic expressions.
Complete Penetrance
___ refers to when some genes in homozygous as well as in heterozygous conditions fail to provide complete phenotypic expression of them.
Incomplete Penetrance
___ refers to the degree of the effect produced by a penetrant genotype; refers to variations in a phenotype among individuals carrying a particular genotype; determined by the proportion of individuals with a given genotype who also possess the associated phenotype.
Expressivity
Identical twins are derived from ___ zygote that splits during development.
1
Fraternal twins come from ___ different eggs fertilized separately at the same time.
2
Differentiate monozygotic from dizygotic twins.
Monozygotic twins are identical and develop from one egg and one sperm that split into two embryos.
Dizygotic twins are non-identical and develop from two eggs and two sperm that form two separate zygotes.
Monozygotic twins share one placenta, while dizygotic twins have two placentas.
___ is the probability that a pair of individuals will both have a certain characteristic, given that one of the pair has the characteristic.
Concordance
___ is the degree of dissimilarity in a pair of twins with respect to the presence or absence of a disease or trait.
Discordance
___ refers to when affected infants are considerably larger than normal (macrosomia) and tend to be taller than their peers during childhood.
Beckwith-Wiedemann Syndrome or Overgrowth Syndrome
____ is a growth disorder characterized by slow growth before and after birth.
Russell-Silver Syndrome
___ refers to genes on the same chromosome that are physically close to each other; they do not segregate independently but can be separated by recombination.
Linkage
____ is a representation of the distribution of a set of loci within the genome.
Genetic Map
___ is a method of mapping a gene to a particular band of the chromosome.
Cytogenetic Mapping
____ means crossing over; can occur between any 2 genes on a chromosome.
Recombination
___ refers to when 2 genes are on the same chromosome and are far enough apart that they undergo recombination at least 50% of the time.
Independent Assortment
___ refers to when 2 genes show linkage with a recombination level greater than 0% and less than 50%.
Incomplete Linkage
___ refers to two loci being so close together that alleles of these loci are virtually never separated by crossing over.
Complete Linkage
What are the factors that affect recombination frequencies? (3)
- Gender
- Region of the Chromosome Involved
- Increased Crossover Frequency
____ is the establishment of the sex of an organism, usually by the inheritance at the time of fertilization of certain genes commonly localized on a particular chromosome; results in the development of individuals with characteristics that allow them to be identified as males, females, or in some cases, hermaphrodites.
Sex Determination
____ is the phenotypic expression of an allele that is dependent on the gender of the individual and is directly tied to the sex chromosomes.
Sex Linkage
In a ____, the transmission is from the mother to the son.
Recessive X Linkage (X-linked Recessive Traits)
In ____, transmission is 100% to the daughters if only the father is affected and 100% to the sons if only the mother is affected.
X-linked Dominant Traits
___ are traits that are carried on the Y chromosome.
Y-linked Traits (Holandric Traits)
