MT2

Question 1

linkage

Answer 1

the association of two genes on the same chromosome

Question 2

coupling configuration

Answer 2

arrangement of linked alleles in a dihybrid such that the two dominant
alleles are on a chromosome, the two recessive alleles are on the other chromosome (AB/ab)

Question 3

repulsion configuration

Answer 3

arrangement of linked alleles in a dihybrid such that a dominant and a
recessive allele are together on each chromsome (Ab/aB)

Question 4

cis dihybrid

Answer 4

a dihybrid in which the alleles are coupled (AB/ab)

Question 5

trans dihybrid

Answer 5

a dihybrid in which the alleles are in repulsion (Ab/aB)

Question 6

tetrad

Answer 6

(2) The four haploid product cells from a single meiosis (see the alternate definition provided
in Chapter 2)

Question 7

octad

Answer 7

an ascus containing eight ascospores, produced in species in which the tetrad normally
undergoes a postmeiotic mitotic division

Question 8

first division segregation

Answer 8

different alleles go into different nuclei at the first meiotic division
producing an MI division pattern of ascospores

Question 9

second division segregation

Answer 9

different alleles go into different nuclei at the second meiotic division
producing an MII division pattern of ascospores

Question 10

molecular marker

Answer 10

a site of DNA heterozgosity (difference), not necessarily associated with
phenotypic variation, used as a tag for a particular chromosomal locus

Question 11

single nucleotide polymorphism (SNP)

Answer 11

change in a single nucleotide that can be located within a gene or intergenic regions

Question 12

restriction enzyme

Answer 12

(restriction endonuclease) – an enzyme that will recognize specific target
nucleotide sequences in DNA and break the DNA chain at those points

Question 13

simple sequence length polymorphism (SSLP)

Answer 13

the presence of different numbers of short or simple
repetitive elements at one particular locus in different homologous chromosomes

Question 14

haplotype

Answer 14

a genetic class described by a sequence of DNA or of genes that are together on the same
physical chromosome (a chromosomal segment defined by the array of markers it carries)

Question 15

complete dominance

Answer 15

alleles which, when combined in the heterozygote show a phenotype
indistinguishable from one of the homozygotes

Question 16

haplosufficiency

Answer 16

one copy of the normal gene is able to confer a normal phenotype

Question 17

haploinsufficiency

Answer 17

one copy of the normal gene is unable to confer the normal phenotype

Question 18

codominance

Answer 18

alleles which, when combined in the heterozygote show phenotypic characteristics of
both homozygotes

Question 19

incomplete dominance

Answer 19

alleles which, when combined in the heterozygote show a phenotype
intermediate between the homozygotes

Question 20

lethal allele

Answer 20

an allele whose expression results in the death of the individual expressing it (may be
recessive or dominant)

Question 21

pleiotropic mutation

Answer 21

a mutation that affects several different phenotypic characteristics

Question 22

prototroph

Answer 22

an organism that will survive on minimal medium (carbon source, inorganic salts, water)

Question 23

auxotroph

Answer 23

an organism that will not survive on minimal medium, but whose growth depends on
supplementation of medium with a specific substance

Question 24

complementation test

Answer 24

a test for determining whether two mutations are in different genes (they
complement) or the same gene (they fail to complement)

Question 25

heterokaryon

Answer 25

cell with 2 nuclei in a common cytoplasm (results from fusing two haploid cells)

Question 26

epistasis

Answer 26

the phenotype of a mutant allele at one gene overrides the phenotype of a mutant allele at
another gene, such that the double mutant has the same phenotype as the first mutant

Question 27

suppression

Answer 27

a mutation in one gene can cancel the effect of a mutation in a second gene, resulting in
a wild type phenotype

Question 28

genetic redundancy

Answer 28

(duplicate genes) – Two independent genes that produce the same phenotypic
effect when present individually or when present together

Question 29

penetrance

Answer 29

the proportion of individuals with a specific genotype who show that genotype phenotypically

Question 30

expressivity

Answer 30

the degree to which a particular genotype is expressed in the phenotype

Question 31

chromosomes break and re-join during pairing, what is the visual evidence of that?

Answer 31

chiasmata

Question 32

crossing over occurs where?

Answer 32

chromatids (genes on the same chromosome)