Chapter 9: Mendelian Genetics And Mutation

Question 1

theory of blending inheritance

Answer 1

proposed that traits present on the parents mixed together like paint to produce a new combination in the offspring

Question 2

horticulture

Answer 2

the artificial selection of plants

Question 3

hybridizing

Answer 3

the process of crossing two different types of plants

Question 4

true breeding

Answer 4

strains of plants that contain only one form of a trait

Question 5

reciprocal cross

Answer 5

an experimental cross in which 2 different forms of a trait are interchanged between male and female plants

Question 6

monohybrid cross

Answer 6

an experiment that uses parent varieties (or strains) differing in a single trait

Question 7

self-crossing/self-fertilization

Answer 7

a plant is pollinated with its own pollen as opposed to pollen from another plant

Question 8

genes

Answer 8

heritable factors; discrete unit of hereditary information

Question 9

alleles

Answer 9

alternate forms of a gene

Question 10

homozygous

Answer 10

has two identical alleles for a given trait

Question 11

heterozygous/hybrid

Answer 11

has two different alleles for a given trait

Question 12

genotype

Answer 12

an allelic combination

Question 13

phenotypes

Answer 13

the physical expression of genes

Question 14

recombination

Answer 14

the occurrence of an offspring whose phenotype differs from that of the parent

Question 15

test-cross

Answer 15

crossing an organism of an unknown genotype with a homozygous recessive individual to determine the unknown genotype; the ratio of phenotypes in the offspring determines the unknown genotype

Question 16

inheritance

Answer 16

the way traits are passed on from generation to generation

Question 17

back cross

Answer 17

a test cross with the homozygous recessive parent (a reverse test cross)

Question 18

Punnett square

Answer 18

invented by Reginald Punnett in 1905. It is a grid that shows all the possible gametes formed by each of the parents and all of the possible genotypes and phenotypes in the offspring.

Question 19

dihybrid

Answer 19

a breeding experiment that uses parental varieties differing in two traits

Question 20

independent assortment

Answer 20

the alleles for the two different traits must assort independently with respect to one another

Question 21

meiosis

Answer 21

a type of cell division in sexually reproducing organisms which results in gametes with half of the chromosome number of the original cell

Question 22

recombination

Answer 22

a process in meiosis that results from homologous chromosomes segregating into different gametes, resulting in multiple possible allele combinations

Question 23

the multiplicative law of probability

Answer 23

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

Question 24

trihybrid

Answer 24

a breeding experiment that uses parental varieties differing in three traits

Question 25

sickle cell anemia

Answer 25

caused by a defective hemoglobin protein in red blood cells which causes the cells to deform to a sickle shape and triggers blood clotting and other symptoms

Question 26

the additive rule

Answer 26

the probability of one or another of two mutually exclusive (or separate) events occurring equals the sum of their individual probabilities

Question 27

intermediate inheritance

Answer 27

the heterozygote genotype has a unique phenotype which is intermediate to the two parental phenotypes; neither allele dominates

Question 28

codominance

Answer 28

both alleles of a heterozygote are distinctly expressed

Question 29

antigen

Answer 29

a foreign substance that does not belong to a particular host organism and elicits an immune response

Question 30

antibody

Answer 30

an immunoglobulin produced by B cells which binds to antigens, and in doing so function in immune response

Question 31

pedigree

Answer 31

information categorized into a family tree which traces the inheritance of various traits (including disorders) throughout generations

Question 32

Mendel's 3:1 ratio

Answer 32

describes that in the F2 generation, dominant and recessive traits will occur 3-to-1

Question 33

Mendel's 9:3:3:1 ratio

Answer 33

the result of a dihybrid cross, where out of 16 individuals, 9 represent both dominant traits, 3 represent one dominant trait, 3 represent another dominant trait, and 1 represents the recessive traits.

Question 34

epistasis

Answer 34

one gene's expression modifies or suppresses another gene

Question 35

albino

Answer 35

characterized by a complete lack of pigment

Question 36

quantitative characters

Answer 36

traits that vary in population along a continuum, because there is more than one existing phenotype

Question 37

polygenic inheritance

Answer 37

two or more genes have an additive affect on one phenotypic character

Question 38

locus

Answer 38

the location of a gene

Question 39

pleiotropy

Answer 39

one gene can affect many traits

Question 40

lethal recessive

Answer 40

a condition that is lethal in the homozygous condition

Question 41

dominant allele

Answer 41

in the heterozygote, the allele that is fully expressed

Question 42

recessive allel

Answer 42

in the heterozygote, the allele that is completely masked

Question 43

mutation

Answer 43

a recessive allele results in a defective enzyme

Question 44

structural disorder

Answer 44

one defective, dominant allele results in a phenotypic effect

Question 45

over-dominance

Answer 45

a population level phenomenon where the heterozygote has a selective advantage over either homozygote (ex: those will sickle-cell anemia are resistant to malaria)

Question 46

linked genes

Answer 46

genes that stay on the same chromosomes

Question 47

parental phenotypes

Answer 47

the offspring have an appearance which is identical to one of the parents

Question 48

recombinant phenotypes

Answer 48

the offspring have an appearance which differs from either of the parents

Question 49

map unit

Answer 49

a way of calculating the relative distance between genes, calculated by dividing the number of recombinants by the total number of offspring times 100

Question 50

sex chromosomes

Answer 50

the pair of chromosomes that determine the sex of an organism

Question 51

sex-linked gene

Answer 51

a gene located on a sex chromosome

Question 52

chromosome theory

Answer 52

the theory that Mendel's heritable factors are located on chromosomes

Question 53

hemizygous

Answer 53

having a total of one allele for a given trait; a condition that is associated with genes located on sex chromosomes

Question 54

Barr bodies

Answer 54

the inactive X chromosome present in each cell of the female which has been condensed into a compact object

Question 55

mosaic

Answer 55

in art, the term is used to describe a pattern; in biology, it is used to describe patchiness in a characteristic

Question 56

autosome

Answer 56

a chromosome that is not directly involved in sex determination; in humans there are 22 of these chromosomes

Question 57

sex chromosomes

Answer 57

the chromosomes that are responsible for sex determination; in humans there is only one pair of these chromosomes

Question 58

aneuploidy

Answer 58

a deviation in the chromosome number such that certain chromosomes are present in extra copies or are absent

Question 59

polyploidy

Answer 59

a deviation in the chromosome number such that the organism has more than two complete sets of chromosomes

Question 60

nondisjunction

Answer 60

a pair of homologous chromosomes or sister chromatids fail to separate properly during meiosis or mitosis

Question 61

karyotype

Answer 61

a technique in which an individual's metaphase I chromosomes are examined in order to determine their number and characteristics

Question 62

deletion

Answer 62

the loss of a piece of chromosome during cell division, resulting in a fragment which lacks a centromere

Question 63

syndrome

Answer 63

having a number of phenotypic effects

Question 64

point mutation

Answer 64

a mutation that affects a single nucleotide of the DNA strand

Question 65

silent mutation

Answer 65

the base pair substitution has no phenotypic effect

Question 66

missense

Answer 66

the base pair substitution causes one amino acid to be substituted for another amino acid

Question 67

nonsense

Answer 67

the base pair substitution causes an amino acid-specifying codon to be changed to a stop codon; the prematurely shortened protein is usually not functional

Question 68

frameshift

Answer 68

if the number of nucleotides, inserted or deleted, is not a multiple of three, this can occur. The result is an improper grouping of codons leading to a changed protein product.