MT1

Question 1

chromatin

Answer 1

the substance of chromosomes; now known to include DNA and chromosomal proteins

Question 2

histone

Answer 2

a type of basic protein that forms the unit around which DNA is coiled in the nucleosomes of
eukaryotic chromosomes

Question 3

nucleosome

Answer 3

the basic unit of eukaryotic chromosome structure; a ball of eight histone molecules that
is wrapped by two coils of DNA

Question 4

dominant phenotype

Answer 4

the parental phenotype that is expressed in a heterozygote

Question 5

dominant allele

Answer 5

an allele that expresses its phenotypic effect even when heterozygous with a
recessive allele; thus, if A is dominant over a, then A/A and A/a have the same phenotype

Question 6

recessive phenotype

Answer 6

– the parental phenotype that is not expressed in the heterozygote

Question 7

recessive allele

Answer 7

an allele whose phenotypic effect is not expressed in a heterozygote

Question 8

first filial generation (F1)

Answer 8

the first generation resulting from a controlled cross between two known
parents (P)

Question 9

second filial generation (F2)

Answer 9

the second generation resulting from a controlled cross between two
known parents (P), generated by selfing/intercrossing the F1 generation

Question 10

heterozygous

Answer 10

a cell/organism having different alleles at a given gene(s) (e.g. A/a)

Question 11

homozygous

Answer 11

(= true-breeding) – a cell/organism having identical alleles at a given gene(s) (e.g. A/A or
a/a)

Question 12

monohybrid

Answer 12

an individual heterozygous at one gene (e.g. A/a)

Question 13

monohybrid cross

Answer 13

a cross between two individuals identically heterozygous at one gene pair, e.g. A/
a x A/a

Question 14

product rule

Answer 14

the probability of two independent events occurring simultaneously is the product of
their individual probabilities

Question 15

sum rule

Answer 15

the probability that one or the other of two mutually exclusive events will occur is the sum
of their individual probabilities

Question 16

test cross

Answer 16

– a cross of an individual organism of unknown genotype or a heterozygote with a tester

Question 17

tester

Answer 17

an individual organism homozygous for one or more recessive alleles; used in a test cross

Question 18

gamete

Answer 18

a specialized haploid cell that fuses with a gamete of the opposite sex or mating type to form
a diploid zygote; in mammals, an egg or a sperm

Question 19

diploid

Answer 19

a cell having two chromosome sets or an individual organism having two chromosome sets in
each of its cells

Question 20

haploid

Answer 20

a cell having one chromosome set or an organism composed of such cells

Question 21

chromatid

Answer 21

one of the two side by side replicas produced by chromosome replication

Question 22

sister chromatids

Answer 22

the juxtaposed pair of chromatids arising from the replication of a chromosome

Question 23

homologous chromosomes

Answer 23

chromosomes that pair with each other during meiosis and (usually) have
the same genetic loci (may have different alleles)

Question 24

meiocyte

Answer 24

a cell in which meiosis takes place

Question 25

dyad

Answer 25

a pair of sister chromatids joined at the centromere

Question 26

tetrad

Answer 26

(1) four homologous chromatids in a bundle in the first meiotic prophase and metaphase

Question 27

chiasma

Answer 27

– a cross-shaped structure commonly observed between nonsister chromatids in meiosis; the site of crossing over

Question 28

molecular marker

Answer 28

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

Question 29

sex chromosome

Answer 29

a chromosome whose presence is correlated with the sex of an individual autosome – any chromosome that is not a sex chromosome

Question 30

homogametic sex

Answer 30

the sex with (homologous) homomorphic sex chromosomes (e.g., XX)

Question 31

heterogametic sex

Answer 31

the sex that has heteromorphic sex chromosomes (e.g., XY)

Question 32

hemizygous gene

Answer 32

a gene that is present in only one copy in a diploid organism

Question 33

reciprocal cross

Answer 33

a pair of crosses of the type genotype A (female) x genotype B (male) and B (female) x A (male)

Question 34

sex linkage

Answer 34

the location of a gene on a sex chromosome

Question 35

genetics

Answer 35

experimental study of genes/hereditary

Question 36

gene

Answer 36

fundamental unit of hereditary

Question 37

genome

Answer 37

complement of all genes in an organism; the genetic material of a chromosome set

Question 38

mutation

Answer 38

a change in DNA sequence (as compared to wild type)

Question 39

allele

Answer 39

an alternate form of a gene (resulting from a mutation)

Question 40

genotype

Answer 40

the specific allele composition of a genep

Question 41

phenotype

Answer 41

outward manifestation of a specific genotype

Question 42

independent assortment

Answer 42

(Mendel's 2nd Law) – unlinked or distantly linked segregating gene pairs assort independently at meiosis

Question 43

dihybrid

Answer 43

an individual heterozygous at two genes (e.g. A/a.B/b)

Question 44

dihybrid cross

Answer 44

a cross between two individuals identically heterozygous at two gene pairs, e.g. A/a.B/b x A/a.B/b

Question 45

chi-squared test

Answer 45

a statistical test used to determine the probability of obtaining observed proportions by chance, under a specific hypothesis

Question 46

null hypothesis

Answer 46

a hypothesis that proposes no difference between two or more data sets

Question 47

recombination

Answer 47

the process that generates a haploid product of meiosis whose genotype is different from either of the two haploid genotypes that constituted the meiotic diploid

Question 48

recombinant gamete

Answer 48

any gamete with a genotype that differs from the genotypes of the two haploid parents that fused to form the diploid meiocyte

Question 49

parental gamete

Answer 49

any gamete with a genotype identical to one of the haploid parents that fused to form the diploid meiocyte

Question 50

maternal inheritance

Answer 50

a type of uniparental inheritance in which all the progeny have the genotype and phenotype of the parent acting as the female