Genetics Vocab Ch. 3 Of Pierce 3Rd Ed

Front 1

addition rule

Back 1

states that the probability of any of two or more mutually exclusive events occurring is calculated by adding the probabilities of the individual events

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allele

Back 2

one of two or more alternate forms of a gene

Front 3

backcross

Back 3

cross between an F1 individual and one of the parental (P) genotypes

Front 4

chromosome theory of heredity

Back 4

states that genes are located on chromosomes

Front 5

concept of dominance

Back 5

principle of heredity discovered by Mendel stating that, when two different alleles are present in a genotype, only one allele may be expressed in the phenotype. The dominant allele is the allele that is expressed, and the recessive allele is the allele that is not expressed

Front 6

dihybrid cross

Back 6

a cross between two individuals that differ in two characteristics - more specifically, a cross between individuals that are homozygous for different alleles at the two loci (AA BB x aa bb);also refers to a cross between two individuals that are both heterzygous at the loci (Aa Bb x Aa Bb)

Front 7

dominant

Back 7

refers to an allele or a phenotype that is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote phenotype

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F1 (filial 1) generation

Back 8

offspring of the initial parents (P) in a genetic cross

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F2 (filial 2) generation

Back 9

offspring of the F1 generation in a genetic cross; the third generation of a genetic cross

Front 10

gene

Back 10

genetic factor that helps determine a trait; often defined at the molecular level as a DNA sequence that is transcribed into an RNA molecule

Front 11

genotype

Back 11

the set of genes possessed by an individual organism

Front 12

goodness-of-fit chi-square test

Back 12

statistical test used to evaluate how well a set of observed values fit the expected values. The probability associated with a calculated chi-square value is the probability that the differences between the observed and the expected values may be due to chance

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heterozygous

Back 13

refers to an individual organism that possesses two different alleles at a locus

Front 14

homozygous

Back 14

refers to an individual organsim that possesses two identical alleles at a locus

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incomplete dominance

Back 15

refers to the phenotype of a heterzygote that is intermediate between the phenotypes of the two homozygotes

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locus

Back 16

position on a chromosome where a specific gene is located

Front 17

monohybrid cross

Back 17

a cross between two individuals that differ in a single characteristic - more specifically, a cross between individuals that are homozygous for different alleles at the same locus (AA x aa); also refers to a cross between two individuals that are both heterozygous for two alleles at a single locus (Aa x Aa)

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multiplication rule

Back 18

states that the probability of two or more independent events occurring together is calculated by multiplying the probabilities of each of the individual events

Front 19

P (parental) generation

Back 19

first set of parents in a genetic cross

Front 20

phenotype

Back 20

appearance or manifestation of a characteristic

Front 21

principle of independent assortment (Mendel's second law)

Back 21

important principle of heredity discovered by Mendel that states that genes encoding different characteristics (genes at different loci) separate independently; applies only to genes located on different chromosomes or to genes far apart on the same chromosome

Front 22

principle of segregation (Mendel's first law)

Back 22

important principle of heredity discovered by Mendel that states that each diploid individual possesses two alleles at a locus and that these two alleles separate when gametes are formed, one allele going into each gamete

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probability

Back 23

likelihood of a particular event occurring; more formally, the number of times that a particular event occurs divided by the number of all possible outcomes. Probability values range from 0 to 1.

Front 24

Punnett square

Back 24

shorthand method of determining the outcome of a genetic cross. On a grid, the gametes of one parent are written along the upper edge and the gametes of the other parent are written along the left-hand edge. Within the cells of the grid, the alleles in teh gametes are combined to form teh genotypes of teh offspring

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recessive

Back 25

refers to an allele or phenotype that is expressed only when homozygous. The recessive allele is not expressed in the heterzygote phenotype.

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reciprocal crosses

Back 26

crosses in which the phenotypes of the male and female parents are reversed. For example, in one cross, a tall male is crossed wit ha short female and, in the other cross, a short male is crossed with a tall female

Front 27

testcross

Back 27

a cross between an individual with an unknown genotype and an individual with the homozygous recessive genotype

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wild type

Back 28

the trait or allele that is most commonly found in natural (wild) populations