Practice Exams Flashcards
what does a frequency of recombination of 25% indicate?
the 2 genes are likely to be located on the same chromosome
prophase I of meiosis
homologous chromosomes pair up to form tetrads
dihybrid cross
involved organisms that are heterozygous for 2 characters
monohybrid cross
involved organisms that are heterozygous for only one character
law of independent assortment
- it’s a method that can be used to determine the number of chromosomes in a plant
- can be used to predict the ratios of certain phenotypes
- requires the segregation of homologous chromosomes during meiosis
- can account for 9:3:3:1 ratio in f2 generations
pleiotropy definition
a single gene controls more than one character
novel phenotypes arise when
2 allelic pairs in a dihybrid cross affect the same phenotypic characteristic; and when there is incomplete dominance between 2 alleles of the same gene
nondisjunction definition
the failure of homolog or sister chromatid separation during cell division resulting in nuclei with the wrong number of chromosomes
the accuracy of map distances based on recombination frequencies
decreases as the chance of multiple crossovers increases, decreases as the distance between genes increases, is greatest when genes are at a distance of 7 mu or less
the frequency of crossovers increases
as the distance between genes increases
epistasis definition
an allele of one gene modifies or prevents the expression of alleles of enough gene
test cross is used for
determining whether an individual is homozygous or heterozygous
law of segregation
states that alleles become separated in meiosis and then come together randomly during fertilization
the frequency of crossing over between any 2 linked genes is
proportional to the distance between them and reproducible
positive interference
one crossover decreases the likelihood of crossovers in nearby regions
for a two-point test cross, if the percentage is 50%, then
the 2 genes may be not linked, distant from each other on the same chromosome, or on different chromosomes
an organism’s phenotype depends on
its genotype and its environment
incomplete dominance definition
phenotype occurring in heterozygous organisms is intermediate between the phenotype of homozygous organisms, but is more similar to one phenotype than the other
incomplete penetrance definition
occurrence of individual organisms that have a particular genotype or allele but not the corresponding phenotype
Chi-square test
statistical test used to determine if the actual results of a genetic cross are a good fit compared to the expected results
Mendel’s principle of segregation
idea that different variants of hereditary units are passed to offspring unaltered
three-point test crosses generate how many phenotypic classes?
(2)^3 = 8
