beyond mendel Flashcards
what is a wild type allele
allele that occurs most frequently in the population, usually dominant but not always, responsible for most common phenotype
what is a mutant allele
contain modified genetic information compated to the wile type allele, responsible for mutant phenotypes
complete dominance
phenotypes of heterozygote and dominant homozygote are identical
incomplete dominance
heterozygote phenotype is intermediate between those of homozyotes (1:2:1 ratio)
codominance
two dominant alleles affect phenotype in seperate, distinguishable ways
what does it mean when a gene has multiple alleles
most genes have two alleles, they are the alternative forms of the same gene so they influnece the same trait; many variations of the gene present
ie blood groups in humans is determined by three alleles
what is polygenetic inheritance
results from the additive effect of multiple genes on one phenotype; many genes + enviornmental factors –> 1 characteristic
ie skin color
what is multifactoral inheritance
influenced by multiple genetic and enviornmental factors; ie. intelligence, cancer, diabetes, height, skin color
pedigree
family tree with genotypes and phenotypes used to trace inheritance patterns of particular traits; also used to make predicitions about the future
what are carriers
recessiviley inherited traits
individuals with normal phenotype but heterozygous geneotype for a reccessive disorder
phenotypes of autosomal recessive conditions
AA - wildtype
Aa - wildtype, carrier
aa - mutant
A=wildtype; a=mutant
phenotypes of autosomal dominant condition
AA - mutant (rare)
Aa - mutant (common)
aa- wildtype
A=mutant; a=wildtype
what are multifactorial disorders
many human diseases have both genetic and envionrmental factors; no clear cut pattern of inheritance; ie heart disease, diabetes, and cancer
what is the chromosome theory of inheritance
specific genes are located at specific loci on chromosomes which undergo segregation and independant assortment; the behavior of chomosomes during meiosis accounts for Mendels Law of segregation and independant assortment
chromosomes are vehicles of genetic hereditary
how was thomas hunt morgan able to show genes are on chromosomes
observed and noted wild-type allelesphenotypes in fruit fly populations; discovered a mutation that affected fruit fly color to provide evidence that genes are on chromosomes
linked genes
genes that are inherited together with other genes as they are located on the same chromosome, do not undergo homologous recombination and are inherited together; chance of inheriting is more than 50% (dihybrid cross 3:1)
unlinked genes
genes located father apart from each other, occur either in the same chromosome or in different chromosomes, undergoing homologous recombination, less likely to be inherited together; chance of inheriting is less than 50% (dihybrid cross 9:3:3:1
what are parental-type offspring
exhibit the same allele combination as their parents; chromosomes are similar to that of their parents
what are recombiant offspring
exhibit different allele combination from their parents; happens when crossing over occurs
how can you use recombination
frequencies to determine how close two linked genes are to each other on the
chromosome?
if genes are far apart on a chromosome the recombination frequenct is 50%, the inheritance of the alleles are independant; is the frequency is less than 50% the two loci are linked
what is x inactivation
mammalian XX individuals have one of two chromosomes in each cell randomly inactivated during embryonic development; XX individual heterozygous for x-linked gene will be mosiac
