Chapter 12: Patterns of Inheritance

Question 1

monohybrid cross

Answer 1

A mating between individuals who have different alleles at one genetic locus of interest. The character(s) being studied in a monohybrid cross are governed by two alleles for a single locus.

Question 2

F2 generation

Answer 2

The second filial generation, which is comprised of offspring(s) resulting from a cross of the members of F1 generation. The result of a cross between two F1 individuals (from F1 generation).

Question 3

homozygous

Answer 3

A genetic condition where an individual inherits the same alleles for a particular gene from both parents.

Question 4

punnett square

Answer 4

a diagram that is used to predict an outcome of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach. The diagram is used by biologists to determine the probability of an offspring having a particular genotype.

Question 5

rule of addition

Answer 5

If you add up the individual probabilities of two or more mutually exclusive events, you can predict the probability for any one of them to occur.

Question 6

codominance

Answer 6

The equal expression of both of the alleles.

ex: an individual will have an AB blood type. Theses two alleles are expressed equally.

Question 7

continuous variation

Answer 7

Variation in phenotypic traits such as body weight or height in which a series of types are distributed on a continuum rather than grouped into discrete categories.

Question 8

F1 generation

Answer 8

First filial generation (the word filial from the Latin word for “son”), the hybrid offspring of the P generation.

Question 9

segregation

Answer 9

Mendel’s first law, stating that each allele in a pair separates into a different gamete during gamete formation.

Question 10

heterozygous

Answer 10

An organism that has two different alleles for a gene.

Question 11

pedigree

Answer 11

Official record of the genetic history of an animal (family tree).

Question 12

rule of multiplication

Answer 12

To determine the probability of two or more independent events, you multiply the probability of one event by the probabilities of the other events.

Question 13

quantitative trait

Answer 13

A measurable phenotype that depends on the cumulative actions of many genes and the environment. These traits can vary among individuals, over a range, to produce a continuous distribution of phenotypes. Examples include height, weight and blood pressure.

Question 14

multiple alleles

Answer 14

Some traits are the product of many different alleles that occupy a specific gene locus (or location).
ex: ABO blood group system- 3 alleles determine blood type.

Question 15

dominant gene

Answer 15

An individual with one dominant and one recessive allele for a gene will have the dominant phenotype. They are generally considered “carriers” of the recessive allele: the recessive allele is there, but the recessive phenotype is not.

Question 16

genotype

Answer 16

The genetic makeup of a cell, an organism, or an individual usually with reference to a specific characteristic under consideration.

Question 17

dihybrid cross

Answer 17

A cross between two pure lines (varieties, strains) that differ in two observed traits. In Mendelian sense, between the alleles of both these loci there is a relationship of complete dominance - recessive. For example: RRYY/rryy parents result in F1 offspring that are heterozygous for both R and Y (RrYy).

Question 18

testcross

Answer 18

A way to explore the genotpye of an organism. Early use of the test cross was as an experimental mating test used to determine what alleles are present in the genotype.

Question 19

pleiotropy

Answer 19

One gene can account for many different phenotypes.
ex: In sickle-cell anemia, multiple symptoms (pneumonia, heart failure, and limited mental functioning) are caused by a single pair of elleles.

Question 20

epistasis

Answer 20

one gene controls the expression of a second gene
ex: two genes effect the color of a mouse. If a mouse inherits allele pair ‘cc’, it will be white regardless of the inherited ‘BB’ (black) or ‘bb/ Bb’ (brown)

Question 21

recessive allele

Answer 21

Either of a pair (or series) of alternative forms of a gene that can occupy the same locus on a particular chromosome and that control the same character; “some alleles are dominant over others.”

Question 22

phenotype

Answer 22

An organism’s traits.

Question 23

independent assortment

Answer 23

Each pair of alleles segregates independently of other pairs of alleles during gamete formation and combines independently of each other.

Question 24

polygenic inheritance

Answer 24

Polygenic inheritance combined effect of two or more genes on a single character
ex: skin color (bell curve distribution)

Question 25

incomplete dominance

Answer 25

The blending of traits.

ex: red snapdragon plant and white snapdragon plant produce pink snapdragon plant.

Question 26

environmental factors

Answer 26

When two different genotypes respond to environmental variation in different ways. A norm of reaction is a graph that shows the relationship between genes and environmental factors when phenotypic differences are continuous.