Chapter 4b: X-Linkage, enviromental effects, cytonuclear inheritance Flashcards
males have XY sex determining chromosomes…they are referred to as being
hemizygous
define hemizygous
a condition in which only one copy of a gene or DNA sequence is present in diploid cells
x-linked traits are traits that are
controlled by the X chromosome
what is an example of an x-linked trait?
- color blindness
- hemophilia
2 characteristics of lethal x-linked recessive disorders
- observed only in males
2. females can be heterozygous carriers
sex-limited inheritance is the expression of specific phenotype but is
absolutely limited to one sex
example of a sex-limited trait is
feather plumage in chickens
sex-influenced inheritance means
sex of individual influences the expression phenotype
not limited to one or another sex
penetrance is…
the percentage of expression of mutant genotype in a population
expressivity is the range of
expression of mutant phenotype
expressivity is a result of
genetic background differences or environmental effects
during a conditional mutation enzymes that produce dark pigment…
lose catalytic function at higher temperatures
define genetic anticipation…
genetic disease has earlier onset and increases severity with each generation
extranuclear inheritance involves genes
not found in nucleus but rather in cytoplasmic organelles
organelle heredity indicates that
an organism’s phenotype can be affected by mitchondrial or chloroplast DNA
