CH 12

Question 1

What two concepts were the basis for ideas about heredity?

Answer 1

1) Heredity occurs within species
2) Traits are transmitted directly from parent to offspring

Question 2

What did Josef Kolreuter do?

Answer 2

crossed tobacco strains to produce hybrids

Question 3

What did Josef Kolreuter observe?

Answer 3

-Hybrid offspring differed from both parents
-Additional variation observed in 2nd generation offspring contradicts direct transmission

Question 4

What did T.A. Knight do?

Answer 4

crossed two varieties of garden pea, Pisum sativa

Question 5

What did T.A. Knight observe?

Answer 5

Crossed two true-breeding strains: self fertilization produces one type

1st generation resembled only 1 parent strain

2nd generation resembled both

Question 6

Pea plants were optimal because:

Answer 6

1. Other research showed that pea hybrids could be produced
2. Many pea varieties were available
3. Peas are small plants and easy to grow
4. Peas can self-fertilize or be cross-fertilzed

Question 7

What were the three stages of Mendel’s experimental method?

Answer 7

1. Produce true breeding strains for each trait he was studying
2. Cross-fertilize true breeding strains having alternate forms of a trait
   (also perform reciprocal crosses to ensure source of pollen is from both types (for ex white and purple)
3. Allow the hybrid offspring to self fertilize for several generations and count the number of offspring showing each form of the trait

Question 8

monohybrid cross

Answer 8

used to study only two variations of a single trait

Question 9

F1

Answer 9

first filial generation

Question 10

In the F1 generation, offspring is produced by…

Answer 10

crossing two true-breeding strains

Question 11

For every trait Mendel studied, all F1 plants resembled…

Answer 11

the same parent

Question 12

dominant

Answer 12

expressed

Question 13

recessive

Answer 13

hidden by a dominant allele

Question 14

F2

Answer 14

-second filial generation
-produced from the self-fertilization of F1 plants

Question 15

Although masked in the F1 generation the ____ _____ reappeared among some F2 individuals

Answer 15

recessive trait

Question 16

F2 generation ratio

Answer 16

3:1

Question 17

In F2 plants,
__ plants with the dominant form
___ plants with the recessive form
The dominant recessive ratio was ___

Answer 17

3/4; 1/4; 3:1

Question 18

Mendel discovered the ratio is actually
__ true breeding dominant plant
__ not true-breeding dominant plants
__ true breeding recessive plant

Answer 18

1; 2; 1

Question 19

Mendel’s conclusions
-each trait was _____, _____
-for each pair, one trait was ______, the other ______
-pairs of alternative traits examined were segregated among the progeny of a particular cross
-alternative traits were expressed in the F2 generation in the ratio of 3/4 dominant to 1/4 recessive

Answer 19

intact, discrete
dominant, recessive

Question 20

Mendel’s five-element model

Answer 20

1. Parents transmit discrete factors (genes)
2. Each individual receives one copy of a gene from each parent
3. Not all copies of a gene are identical
4. Alleles remain discrete - no blending
5. Presence of allele does not guarantee expression

Question 21

allele

Answer 21

alternative form of a gene

Question 22

homozygous

Answer 22

two of the same allele

Question 23

heterozygous

Answer 23

different alleles

Question 24

genotype

Answer 24

an individual’s complete set of alleles

Question 25

phenotype

Answer 25

an individual’s physical appearance

Question 26

principle of segregation

Answer 26

two alleles for a gene segregate during gamete formation (one from each parent) and are rejoined at random during fertilization

Question 27

dihybrid cross

Answer 27

used to study two variations of two traits in a single cross

Question 28

Dihybrid cross ratio

Answer 28

9:3:3:1

Question 29

Principle of Independent Assortment

Answer 29

In a dihybrid cross, the alleles of each gene assort independently

Question 30

The segregation of different allele pairs is ____ - for ex, seed shape is independent of seed color

Answer 30

independent

Question 31

Independent alignment of different homologous chromosome pairs during metaphase 1 leads to the _____ ______ of the different allele pairs

Answer 31

independent segregation

Question 32

testcross

Answer 32

used to determine the genotype of an individual with an unknown phenotype

Cross the unknown genotype with a homozygous recessive