Chapter three, test one Flashcards
who coined the terms genetics, allele, homozygote, and heterozygote
bateson
what is incomplete dominance
the relationship between two alleles of a gene where the heterozygote has a phenotype intermediate between that of the two homozygotes
does not resemble either pure bred parent
where do you see not complete dominance
in F1
if F1 of incomplete dominance self fertilize, what is the F2 phenotypic ratio
1:2:1
if F1 of incomplete dominance self fertilize, what is the F2 genotypic ratio
1:2:1
describe F2 ratio of incomplete dominance
1: parent
2: recombinant
1: parent
what is the biochemical explanation of incomplete dominance
each allele of the gene under analysis specifies an alternative form of a protein molecule with an enzymatic role in a certain production
homozygous recessive has nonfunctional enzyme
heterozygote has semifunctional enzyme that can produce a new phenotype
what does codominant mean
describes the relationship between two alleles of a gene where the heterozygote has the traits of both homozygotes
what are the phenotype ratios for the f2 generation of codominance
1:2:1
what are the genotype ratios for the F2 generation of codominance
1 homo dom: 2 both parents: 1 homo recess
what is an example of codominance
blood type
determinance of dominance relationships depends on what
the phenotype that appears in the F1 generation
what do the F1 generation look like for complete dominance
one of the true breeding parents
what do the F1 generation look like for incomplete dominance
resemble neither of parents
what do the F1 generation look like for codominance
both pure bred parents show
does codominance or incomplete affect law of segregation
no because it is based on proteins and enzymes present whether allele shows up in a certain way
is it possible to have more than two alleles
yes ex: blood type
but one person can only carry two alternatives
what examples shows that allele is codominant with every allele making a unique phenotype
histocompatibility antigens
how do multiple alleles on an allelic series arise
mutations
in what cells do mutations pass on
gamete producing cells
how can you calculate the number of genes based on people present
two genes per person
2 x # people
what is an allele frequency
the proportion of all copies of a gene in a population that are of a given allele type
what are wild type alleles
the most common alleles in a population
what makes an allele a wildtype
occurs in population at a frequency greater than 1%
what is monomorphic
a gene with only one wild type allele
what is polymorphic
more than one common allele
what is a common variant
high frequency alleles of a polymorphic gene
what is an example of a polymorphic gene
Histocompatibility antigens
what is pleiotropy
phenomenon in which a single gene determines a number of distinct and seemingly unrelated characteristics
what is a recessive lethal allele
an allele that prevent the birth or survival of homozygotes, though heterozygotes carrying the allele survive
in utero
how can lethal recessive or delayed lethality be passed on
from heterozygote carriers
how can delayed lethality be passed on
heterozygote carriers
or homozygote that live past puberty
dominant early lethal mutant alleles must be new
mutations because allele cant be passed on
how do you determine 2 genes affecting one trait
self fertilize F2
what shows that 2 genes affect one trait
presence or absence of dominant alleles of two genes
determines pheno and genotype
can the F2 genotypes be grouped in a 2 gene determine one trait if it is incomplete or codominance occur
no
give rise to more than four phenotypes
what biochemical pathway tells us about 2 gene affecting one trait
function additively in independent biochemical pathways
what is epistasis
a gene interaction in which the effects of alleles at one gene hide the effects of alleles at another gene
what is recessive epistasis
a gene interaction with which the effects of recessive alleles at one gene hide the effects of alleles at another gene
what is the ratio for the F2 generation in a recessive epistasis
9:3:4 4 represents (3+1) because ee masks the second gene
what is reciprocal recessive epistasis
an interaction between alleles of two different genes where the homozygous recessive genotype of each gene prevents the phenotypic expression of the dominant allele of the other gene
what is the ratio of the F2 generation for reciprocal recessive epistasis
9:7
what is dominant epistasis
a phenomenon where the effects of a dominant allele of one gene hide the effects of alleles at another gene
what is the F2 generation ratio for dominant epistasis
12: 3:1
13: 3
what are some important factors of epistasis
interaction between alleles of different genes
F2 pheno ratios depend on functions of specific alleles and their biochemical pathways
what does recessive epistasis reveal
dominant alleles of two genes function in same pathways to achieve a common outcome
what does dominant epistasis reveal
indicates dominant alleles of two genes have antagonistic functions
what is redundant gene action
a phenomenon where dominant, functional alleles of either or the other of two genes is required in the pathway
what is the F2 phenotypic ration showing redundancy
15:1
what is a heterogenous trait
a phenotype caused by a mutation in any one of a number of different genes
what is locus heterogeneity
describes a trait where mutations in any one of two or more genes results in the same mutant phenotype
what is a complementation test
method of discovering whether two mutations are in the same or separate genes
what is complementation
the process in which heterozygosity for loss of function mutant recessive alleles for two different genes produces a normal phenotype
what are multifactorial traits
traits determined be several factors, including multiple genes interacting with each other and one or more genes interacting with the environment
what factors can alter the phenotypic expression of a genotype
modifier genes
environment
chance
what is penetrance
in a population, the fraction of individuals with a particular genotype that show the associated phenotype
what is expressivity
the degree of intensity with which a particular genotype is expressed as a phenotype
what are modifier genes
genes that produce a subtle, secondary effect on phenotype
what is a phenocopy
a change in phenotype arising from environmental agents that mimics the effects of a mutation in a gene
are phenocopies heritable
no bc they do not result from a change in a gene
