Chapter 14

Question 1

‘Particulate’ hypothesis

Answer 1

model in which parents pass down heritable units that retain separate identities in offspring
o Genes can be shuffled and passed along

Question 2

character

Answer 2

a heritable feature that varies among individuals

Question 3

trait

Answer 3

each variant for a character

Question 4

true-breeding

Answer 4

varieties that, over many generations of self-pollination, produce the same variety of parent plant (same phenotype)

Question 5

hybridization

Answer 5

the crossing of two true-breeding varieties

Question 6

P generation (true-breeding)

Answer 6

the true-breeding parents

Question 7

F1 generation (true-breeding)

Answer 7

the hybrid offspring of the P generation

Question 8

F2 generation (true-breeding)

Answer 8

results when F1 hybrids self-pollinate

Question 9

alleles

Answer 9

alternative versions of genes

Question 10

law of segregation

Answer 10

2 alleles for a heritable character segregate during gamete formation and end up in different gametes

Question 11

testcross

Answer 11

when you breed an organism of an unknown genotype with a recessive homozygote
o This will reveal the genotype of the organism

Question 12

monohybrids

Answer 12

heterozygous for one particular character in the cross

Question 13

monohybrid cross

Answer 13

a cross between two heterozygotes for one character

Question 14

dihybrids

Answer 14

individuals heterozygous for 2 characters in a cross

o Ex: YyRr

Question 15

dihybrid cross

Answer 15

a cross between F1 dihybrids

Question 16

law of independent assortment

Answer 16

states that 2 or more genes assort independently; each pair of alleles segregates independently of each other pair of alleles during gamete formation
o This applies only to allele pairs located on different chromosomes or
o Genes very far apart on the same chromosome

Question 17

multiplication rule

Answer 17

for determining the probability that 2 or more independent events will occur together, multiply the probability of one event by the probability of the other event
o Ex: events occurring on two different chromosomes

Question 18

addition rule

Answer 18

to find the probability that any 1 of 2 or more mutually exclusive events will occur, add the individual probabilities

Question 19

complete dominance

Answer 19

when the F1 offspring looks like 1 of the two parental varieties
o Phenotypes of heterozygote and dominant homozygote are indistinguishable

Question 20

incomplete dominance

Answer 20

when neither allele is completely dominant
o F1 phenotype is somewhere between the 2 parental varieties
o Ex: when R and W flowers produce pink

Question 21

codominance

Answer 21

when two alleles each affect the phenotype in separate, indistinguishable ways
o Both phenotypes are exhibited by heterozygotes since both molecules are present
o Ex: RR & WW combine to make RW (roan)

Question 22

Tay-Sachs disease

Answer 22

inherited disorder in which afflicted has brain cells which cannot metabolize certain lipids
o Lipid accumulation results in blindness, seizures, poor motor performance
o Due to incomplete dominance, but codominance at the molecular level

Question 23

pleitropy

Answer 23

genes which have multiple phenotypic effects

o Responsible for hereditary diseases such as cystic fibrosis and sickle-cell anemia

Question 24

epistasis

Answer 24

when the phenotypic expression of a gene at a locus alters that of a gene at a second locus

Question 25

quantitative characteristics

Answer 25

characters that are not one of two discrete characters, but vary in populations along a continuum
o Usually indicates polygenic inheritance
o Ex: skin color and height

Question 26

polygenic inheritance

Answer 26

an additive effect of 2 or more genes on a single phenotypic character

Question 27

multifactorial characteristics

Answer 27

when many factors, both genetic and environmental, influence phenotype

Question 28

pedigree

Answer 28

family tree describing the traits of parents and children across generations

Question 29

cystic fibrosis

Answer 29

common lethal genetic disease
o Results in abnormally high concen. of extracellular chloride, producing mucus
o Results from two recessive alleles

Question 30

sickle-cell disease

Answer 30

caused by substitution of single amino acid in hemoglobin protein of red blood cells
o 2 sickle-cell alleles required for full-blown manifestation (codominance)
o One copy of sickle-cell allele can have issues as well, protects against malaria

Question 31

huntington’s disease

Answer 31

caused by lethal dominant allele, deterioration of nervous system

Question 32

amniocentesis

Answer 32

test during the 14th-16th week of pregnancy
o Can determine if fetus has Tay-Sach’s disease
o Extract amniotic fluid

Question 33

chorionic villus sampling (CVS)

Answer 33

when physician gets tissue from placenta

o Advantage- rapid cell proliferation