Genetic Chapter 5

polygenic characteristics

Characteristics encoded by genes at many loci are called

incomplete dominance

When the heterozygote has a phenotype intermediate between the phenotypes of the two homozygotes

complimentation

___________has occurred if an individual organism possessing two recessive mutations has a wild-type phenotype, indicating that the mutations are nonallelic genes

anticipation

a genetic trait becomes more strongly expressed or is expressed at an earlier age as it is passed from generation to generation

2

an allele is recessive when ____ copies (homozygosity) is required for it to be expressed

temperature-sensitive allele

an allele whose product is functional only at certain temperatures

lethal allele

causes death at an early stage of development, usually before birth

cytoplasmic inheritance

characteristics that are encoded by genes located in the cytoplasm

continuous/quantitative characteristics

characteristics with many possible phenotypes

discontinuous characteristics

characteristics, which have a few easily distinguished phenotypes

multifactorial characteristics

continuous characteristics that are both polygenic and influenced by environmental factors;

complementation test

during _____________ parents that are homozygous for different mutations are crossed, producing offspring that are heterozygous.

[2(n+1)]/2

formula for # of genotypes where n = NUMBER OF ALLELES

3^n

forumla for # of genotype, n= the number of loci

turns off

genomic imprinting ________ specific genes

sex-influenced inheritances sex-limited characteristics

in _______ the trait has a higher penetrance in one of the sexes. in ______ the trait is only expressed in one sex, it has zero penetrance in the other sex

epistasis

one gene masks (hides) the effect of another gene at a different locus, not the same as dominance

epigenetics

reversible changes to DNA that influence the expression of traits are termed epigenetic marks

genetic conflict hypothesis

that there are different and conflicting evolutionary pressures acting on maternal and paternal alleles for genes (such as Igf2) that affect fetal growth

expressivity

the degree to which a character is expressed. EX. in polydactyl you can have a whole finger or just a nub

genomic imprinting

the differential expression of genetic material depending on whether it is inherited from the male or female parent

epistatic gene hypostatic gene

the gene that does the masking is called the ______ and the gene whose effect is masked is the _______________

penetrance

the percentage of individual organisms having a particular genotype that express the expected phenotype

codominance

the phenotype of the heterozygote is not intermediate between the phenotypes of the homozygotes; rather, the heterozygote simultaneously expresses the phenotypes of both homozygotes

genetic maternal effect

the phenotype of the offspring is determined by the genotype of the mother; nothing to do with cytoplasmic inheritance. Genes are inherited from both parents but the mother's genotype determines phenotype of the offspring

ressesive dominant

the precense of 2 ressesive aleles is required for ______ epistasis while _____ requires only one dominant allele

(1/2)^(2n)

the progeny proportions should be in fractions of ___________, where n equals the number of loci with two alleles segregating in the cross.

2:1

there is usually a _____ ratio for recessive lethal allele

duplicate recessive epistasis

two recessive alleles at either of two loci are capable of suppressing a phenotype

same

when a trait displays incomplete dominance; the phenotypic and genotypic ratios are the ____ because each genetype has its own phenotype

phenocopy

when environmental factors alone can produce a phenotype that is the same as the phenotype produced by a genotype; this phenotype is called ________

pleiotrophy

when one gene affects multiple characteristics

gene interaction

when the effects of genes at one locus depend on the presence of genes at other loci (NONALLELIC GENES). not the same as multiples alles which are allelic interactions at one locus.

incomplete penetrance

when the genotype does not produce the expected phenotype