Chapter 12

Question 1

Parental generation P0

Answer 1

plants used in the initial crosses

Question 2

F1

Answer 2

first generation of plants resulting from the original cross

Question 3

F2

Answer 3

seeds resulting from the self pollination of F1

Question 4

Trait

Answer 4

variation in the physical appearance of a heritable characteristic

Question 5

reciprocal cross

Answer 5

breeding plants with the contrasting traits

Question 6

allele

Answer 6

gene variants

Question 7

phenotype

Answer 7

observable physical trait expressed by the organism

Question 8

genotype

Answer 8

the underlying genetic alleles (visible and non-expressed)

Question 9

incomplete dominance

Answer 9

a heterozygote is a mix between the parental phenotypes

Question 10

codominance

Answer 10

both alleles in a heterozygote are fully expressed

Question 11

wild-type

Answer 11

most common combination of alleles in a population (+)

Question 12

variants

Answer 12

other alleles besides the wild type

Question 13

X-linked

Answer 13

gene is present of the X chromosome but not the Y

Question 14

Hemizygosity

Answer 14

only one allele for the X-linked genes

Question 15

Carriers

Answer 15

heterozygous for the trait

Question 16

lethal allele

Answer 16

mutation that results in a non-functional allele for an essential gene

Question 17

linkage

Answer 17

genes that are close together are likely to be inherited together

Question 18

hypostatic

Answer 18

allele that is being masked

Question 19

epistatic.

Answer 19

allele doing the masking

Question 20

Who is Johann Gregor Mendel and what is he known for?

Answer 20

Teacher, scientist, and abbot of a monastery, conducted experiments with pea plants which forms the basis of genetics

Question 21

What type of plant did Mendel work with and why?

Answer 21

Pea plants, self-fertilize and can cross-fertilize

Question 22

Understand and describe the experiments performed by Gregor Mendel at the P0, F1, and F2 levels.

Answer 22

True breeding is parental, one cross in F1, self pollination from F1 makes F2

Question 23

What does it mean if plants are bred “true” for a trait?

Answer 23

When self fertilized, all of the offspring had the same trait

Question 24

In Mendel’s crosses between true breeds that differed in one trait, what were the genotypic and phenotypic characteristics of the F1 generation?

Answer 24

100 percent of the plants had the dominant phenotype

Question 25

When Mendel then allowed the F1 generation to self-pollinate, what were the genotypic and phenotypic characteristics of the F2 generation?

Answer 25

the genotypic was 1:2:1 and phenotypic was 3:1

Question 26

What was the purpose of performing the reciprocal crosses for each of the seven traits?

Answer 26

this showed that the trait did not disappear as it was found in the F2 generation

Question 27

What are dominant and recessive traits and how did Mendel demonstrate this?

Answer 27

expressed are dominant and latent are recessive this was shown by recessive being seen in F2

Question 28

How did Mendel know that the traits were “discrete” and separate from one another?

Answer 28

Recessive was found in F2

Question 29

How did Mendel come to understand that his plants possessed two copies of each of the seven traits, and that one parent transmitted one of its copies to the next generation?

Answer 29

some plants were able to produce all dominant when self fertilized while others were a mix and some were only recessive offspring

Question 30

The fact that each of his plants possessed two copies of each trait meant that plants showing the recessive trait had what genotype? What did Mendel conclude about
the genotypes of plants showing the dominant trait?

Answer 30

rr, they could either be Rr or RR

Question 31

What are alleles and how do they arise in a population?

Answer 31

gene variants that arise by mutation and lead to different characteristics of the same trait

Question 32

How is an organism’s phenotype related to it’s genotype?

Answer 32

the genotype codes for the phenotype

Question 33

What does it mean if an organism is homozygous or heterozygous? How does this relate to Mendel’s P0, F1, and F2 generations?

Answer 33

all parental were homozygous, F1 were heterozygous, and F2 was a mixture of the two

Question 34

Name and describe the two genotypic conditions under which an organism could display the dominant characteristic.

Answer 34

RR or Rr

Question 35

When is a test cross used? How is it performed?

Answer 35

a way to figure out if homozygous or heterozygous, cross unknown individual with a homozygous recessive

Question 36

What is the Law of Segregation? When is it physically manifested during meiosis?

Answer 36

paired genes segregate equally into gamete such that offspring have an equal likelihood of inheriting either one (meiosis I division)

Question 37

What is the Law of Independent Assortment? When is it physically manifested during meiosis?

Answer 37

every possible combination of alleles for every gene is equally likely to occur (metaphase one)

Question 38

What is incomplete dominance? How does it differ from the simple dominant/recessive inheritance pattern?

Answer 38

a heterozygote is an intermediate phenotype between the two parent types (Red+White=pink)

Question 39

What is codominance? How does it differ from the simple dominant/recessive inheritance pattern?

Answer 39

A heterozygote results in a phenotype where both alleles are fully expressed (blood groups)

Question 40

What is a “wild-type” and what are “variants?” How do they relate to one another?

Answer 40

most common in a population is the wild type (+) and variants are other genotypes and phenotypes; the two can be either dominant or recessive to each other

Question 41

What are sex-chromosomes? How are they different from autosomes?

Answer 41

X and Y, shorter and determine the sex

Question 42

How are the X and Y chromosomes the same? How are they different?

Answer 42

determine sex but Y is much smaller

Question 43

What does it mean if a trait is X-linked?

Answer 43

it is more likely that men will have it and women can be carriers

Question 44

What is hemizygosity? Do males or females display hemizygosity and why?

Answer 44

only one allele for X-linked genes, males are hemizygotes

Question 45

What is a female “carrier?”

Answer 45

a female where one x has the allele and the other does not

Question 46

What is lethality? Under what types of conditions might these alleles survive in a population?

Answer 46

results in a nonfunctional allele for an essential gene; if the presence of a wild type allele functions well enough to maintain life and is dominant to the lethal allele

Question 47

How do situations of recessive lethal alleles differ from dominant lethal alleles?

Answer 47

if dominant, one lethal allele would be deadly

Question 48

What law is supported by the fact that a dihybrid cross may be broken down into two separate monohybrid crosses with the same frequencies of genotypes?

Answer 48

independent assortment

Question 49

What are linked genes and how do they cause exceptions to the Law of Independent Assortment?

Answer 49

genes that are close to each other on homologous chromosomes

Question 50

Understand the concept of epistasis. Why did Mendel not see patterns of epistasis in his work?

Answer 50

the interaction of one gene masks or interferes with the expression of another, it did not occur with the traits he was examining

Question 51

What is the relationship between hypostatic and epistatic alleles?

Answer 51

The hypostatic alleles are being masked while the epistatic alleles are doing the masking