Chapter 3

Question 1

Gene

Answer 1

An inherited factor that determines a characteristic

Question 2

Allele

Answer 2

One of two or more alternative forms of a gene

Question 3

Locus

Answer 3

A specific place on a chromosome where the alleles are located

Question 4

Genotype

Answer 4

A set of alleles that an individual organism possesses. Only the alleles of the genotype are inherited.

Question 5

Homozygous

Answer 5

A diploid organism with a genotype consisting of 2 identical alleles

Question 6

Heterozygous

Answer 6

A diploid organism with a genotype consisting of 2 different alleles

Question 7

Phenotype

Answer 7

The manifestation or appearance of a characteristic/trait. Can be physical, physiological, biochemical, or behavioral.

A phenotype arises from a genotype that develops in a certain environment.

How the phenotype develops is determined by the effect of other genes and environmental factors.

Organisms do NOT transmit their phenotypes to the next generation.

Question 8

Monohybrid cross

Answer 8

A cross between parents that only differ by a single characteristic.

Ex: homozygous plants for round seeds crossed with homozygous plants for wrinkled seeds

RRxrr

Genotypic ratio 1:2:1
Phenotypic ratio 3:1

Question 9

P generation

Answer 9

The first generation of a cross. Parental generation.

Question 10

F1 generation

Answer 10

Filial 1 cross. The offspring of the P generation.

Only express one of the phenotypes present in the parental generation.

Question 11

F2 generation

Answer 11

Filial 2 generation. The offspring of the F1 generation.

Both traits from the P generation are observed.

Question 12

Dominant

Answer 12

An allele or phenotype that is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in the heterozygous phenotype.

Traits that appeared unchanged in the F1 heterozygous offspring.

Question 13

Recessive

Answer 13

An allele or phenotype that is expressed only when the recessive allele is homozygous. The recessive allele is not expressed in the heterozygote phenotype.

Traits that disappeared in the F1 heterozygous offspring

Question 14

Principle of segregation

Answer 14

Mendel’s 1st law.

Each individual diploid organism possesses 2 alleles for any particular characteristic. These 2 alleles segregate when gametes are formed and 1 allele goes into each gamete in equal proportions during anaphase I.

Question 15

Concept of dominance

Answer 15

When 2 different alleles are present in a genotype, only the trait encoded by the dominant allele is observed by the phenotype

Question 16

Punnett square

Answer 16

A way to predict the outcomes of genetic crosses.

Each cell contains a allele from each of the corresponding gametes, generating the genotype of the fusion of those gametes.

Question 17

Probability

Answer 17

Expresses the likelihood of the occurrence of a particular event.

# of times particular event occurs
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

of possible outcomes

Question 18

Multiplication rule

Answer 18

The probability of 2 or more independent events occurring together is calculated by multiplying their independent probabilities.

The outcome of one must not influence the outcome of the other.

AND

Question 19

Addition rule

Answer 19

The probability of any one of two or more mutually exclusive events is calculated by adding the probability of these events

The events must be mutually exclusive - one event excludes the possibility of the occurrence of the other event.

OR

Question 20

Testcross

Answer 20

A useful tool for analyzing genetic crosses. One individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question.

Any recessive allele in the unknown genotype is expressed in the progeny (children gametes) because it will be paired with a recessive allele from the homozygous recessive parent

Question 21

Incomplete dominance

Answer 21

The phenotype of a heterozygote that is intermediate between the phenotypes of the two homozygotes.

Ex: BB - black fur
bb - white fur

Bb - grey fur

Question 22

Wild type

Answer 22

The phenotype or allele that is most commonly found in natural (wild) populations.

Question 23

Dihybrid cross

Answer 23

Cross between substances that differ in 2 characteristics.

Phenotypic ration 9:3:3:1

Ex: AABBxaabb

Question 24

Principle of independent assortment

Answer 24

Mendel’s 2nd law

Alleles at different loci separate independently of one another during anaphase I.

This is an extension of the principle of segregation.

Based o the behaviors of chromosomes in meiosis. Homologous chromosomes separate independently of all others in anaphase I so genes located on different pairs of homologs will assort independently. Genes located on the same chromosome do NOT assort independently.