Practice Exams

Question 1

what does a frequency of recombination of 25% indicate?

Answer 1

the 2 genes are likely to be located on the same chromosome

Question 2

prophase I of meiosis

Answer 2

homologous chromosomes pair up to form tetrads

Question 3

dihybrid cross

Answer 3

involved organisms that are heterozygous for 2 characters

Question 4

monohybrid cross

Answer 4

involved organisms that are heterozygous for only one character

Question 5

law of independent assortment

Answer 5

1. it’s a method that can be used to determine the number of chromosomes in a plant
2. can be used to predict the ratios of certain phenotypes
3. requires the segregation of homologous chromosomes during meiosis
4. can account for 9:3:3:1 ratio in f2 generations

Question 6

pleiotropy definition

Answer 6

a single gene controls more than one character

Question 7

novel phenotypes arise when

Answer 7

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

Question 8

nondisjunction definition

Answer 8

the failure of homolog or sister chromatid separation during cell division resulting in nuclei with the wrong number of chromosomes

Question 9

the accuracy of map distances based on recombination frequencies

Answer 9

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

Question 10

the frequency of crossovers increases

Answer 10

as the distance between genes increases

Question 11

epistasis definition

Answer 11

an allele of one gene modifies or prevents the expression of alleles of enough gene

Question 12

test cross is used for

Answer 12

determining whether an individual is homozygous or heterozygous

Question 13

law of segregation

Answer 13

states that alleles become separated in meiosis and then come together randomly during fertilization

Question 14

the frequency of crossing over between any 2 linked genes is

Answer 14

proportional to the distance between them and reproducible

Question 15

positive interference

Answer 15

one crossover decreases the likelihood of crossovers in nearby regions

Question 16

for a two-point test cross, if the percentage is 50%, then

Answer 16

the 2 genes may be not linked, distant from each other on the same chromosome, or on different chromosomes

Question 17

an organism’s phenotype depends on

Answer 17

its genotype and its environment

Question 18

incomplete dominance definition

Answer 18

phenotype occurring in heterozygous organisms is intermediate between the phenotype of homozygous organisms, but is more similar to one phenotype than the other

Question 19

incomplete penetrance definition

Answer 19

occurrence of individual organisms that have a particular genotype or allele but not the corresponding phenotype

Question 20

Chi-square test

Answer 20

statistical test used to determine if the actual results of a genetic cross are a good fit compared to the expected results

Question 21

Mendel’s principle of segregation

Answer 21

idea that different variants of hereditary units are passed to offspring unaltered

Question 22

three-point test crosses generate how many phenotypic classes?

Answer 22

(2)^3 = 8