Chapter 2 - Patterns Of Inheritance

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Variant

Back 1

an individual organism that is recognizably different from an arbitrary standard type in that species

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Autosome

Back 2

any chromosome that is not a sex chromosome

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Self

Back 3

to fertilize eggs with sperms from the same individual

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Cross

Back 4

the deliberate mating of two parental types of organisms in genetic analysis

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Pure breeding line

Back 5

a group of identical individual organisms that always produce offspring of the same phenotype when intercrossed

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Character difference

Back 6

alternative forms of the same attribute within a species

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Recessive allele

Back 7

an allele whose phenotypic effect is not expressed in a heterozygote

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Parental generation (P)

Back 8

the two strains or individual organisms that constitue the start of a genetic breeding experiment; their progeny is the F1 generation

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First filial generation (F1)

Back 9

produced by crossing two parental lines

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Reciprocal crosses

Back 10

a pair of crosses of the type genotype A(female) x genotype B (male) and B (female) x A (male)

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Dominant allele

Back 11

an allele that expresses its phenotpic effect even when heterozygous with a recessive allele; thus, if A is a dominant over a, then A/A and A/a have the same phenotype

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Dominant phenotype

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the phenotype of a genotype containing the dominant allele; the parental phenotype that is expressed in a heterozygote

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Equal segregation

Back 13

equal numbers of progeny genotypes attributable to the seperation of two alleles of one gene at meiosis

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Mendel's first law

Back 14

the two members of a gene pair segregate from each other in meiosis; each gamete has an equal probability of obtaining either member of the gene pair

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Heterozygote

Back 15

an individual organism having a heterozygous gene pair

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Recessive phenotype

Back 16

the phenotype of a homozygote for the recessive allel; the parental phenotype that is not expressed in a heterozygote

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Hybrid

Back 17

a heterozygote;
an individual progeny from any cross between parents of different genotypes

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Homozygote

Back 18

an individual organism that is homozygous

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Homozygous dominant

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refers to a genotype such as A/A

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Homozygous recessive

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refers to a genotype such as a/a

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Meiosis

Back 21

two successive nuclear divisions (with corresponding cell divisions) that produce gametes (in animals) or sexual spores (in plants and fungi) that have one-half of the genetic material of the original cell

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Monohybrid

Back 22

a single-locus heterozygote of the type A/a

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Monohybrid cross

Back 23

a cross between two individuals identically heterozygous at one gene pair - for example, A/a x A/a

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Dihybrid

Back 24

a double heterozygote such as A/a ; B/b

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Dihybrid cross

Back 25

a cross between two individuals identically heterozygous at two loci - for example, A B/a b x A B/a b

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Mendel's second law

Back 26

the law of independent assortment; unlinked or distantly linked segregating gene pairs assort independently at meiosis

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Testcross

Back 27

a cross of an individual organism of unknown genotype or a heterozygote (or a multiple heterozygote) with a tester

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Tester

Back 28

an individual organism homozygous for one or more recessive alleles; used in a testcross

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Product rule

Back 29

the probability of two independent events occuring simultaneously is the product of the individual probabilities

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Sum rule

Back 30

the probability that one or the other of two mutually exclusive events will occur is the sum of their individual probabilities

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Chi-square test

Back 31

a statistical test used to determine the probability of obtaining observed proportions by chance, under a specific hypothesis

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Pedigree

Back 32

a "family tree," drawn with standard genetic symbols, showing inheritance patterns for specific phenotypic characters

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Propositus

Back 33

in a human pedigree, the person who first came to the attention of the geneticist

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Sex chromosome

Back 34

a chromosome whose presence or absence is correlated with the sex of the bearer; a chromosome that plays a role in sex determination

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X chromosome

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one of a pair of sex chromosomes, distinguished from the Y chromosome

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Y choromosome

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one of a pair of sex chromosomes, distinguished from the X chromosome

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Homogametic sex

Back 37

the sex with homologous sex chromosomes (XX)

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Heterogametic sex

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the sex that has heteromorphic sex chromosomes (XY) and hence produces two different kinds of gametes with respect to the sex chromosomes

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Hemizygous gene

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a gene present in only one copy in a diploid organism - for example, an X-linked gene in a male mammal

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X linkage

Back 40

the inheritance pattern of genes found on the X chromosome but not on the Y chromosome

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Y linkage

Back 41

the inheritance pattern of genes found on the Y chromosome but not on the X chromosome (rare)

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Sex linkage

Back 42

the location of a gene on a sex chromosome

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SRY gene

Back 43

the maleness gene, residing on the Y chromosome

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Maternal inheritance

Back 44

a type of uniparental inheritance in which all progeny have the genotype and phenotype of the parent acting as the female

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Cytoplasmic segregation

Back 45

segregation in which genetically different daughter cells arise from a progenitor that is a cytohet

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Cytohet

Back 46

a cell containing two genetically distinct types of a specific organelle