Chapter 15 - The Chromosomal Basis Of Inheritance

Front 1

Chromosome theory of inheritance

Back 1

according to this theory, Mendelian genes have specific loci on chromosomes and it is the chromosomes that undergo segregation and independent assortment

Front 2

Sex-linked genes

Back 2

genes located on a sex chromosome

Front 3

Linked genes

Back 3

genes located on the same chromosome that tend to be inherited together in genetic crosses because the chromosome is passed on as a unit

Front 4

Genetic recombination

Back 4

the general term for the production of offspring with new combinations of traits inherited from two parents

Front 5

Parental types

Back 5

offspring of a testcross that inherit a phenotype that matches one of the parental phenotypes

Front 6

Recombinants

Back 6

offspring of a testcross that inherit a completely different phenotype than either parent

Front 7

Genetic map

Back 7

an ordered list of the genetic loci along a particular chromosome; first devised by Alfred Sturtevant

Front 8

Linkage map

Back 8

a genetic map based on recombination frequencies; portrays the sequence of genes along a chromosome, but it does not give the precise location of genes

Front 9

Cytological maps

Back 9

a genetic map that locates genes with respect to chromosomal features, such as stained bands, that can be seen in the microscope

Front 10

Barr body

Back 10

in female mammals, often one of the two X chromosomes becomes inactivated and condenses into this compact object, which lies along the inside of the nuclear envelope; occurs during embryonic development

Front 11

Nondisjunction

Back 11

a meiotic mishap in which the members of a pair of homologous chromosomes do not move apart properly during meiosis I, or in which sister chromatids fail to separate during meiosis II; results in one gamete receiving two copies of the chromosome and one gamete receiving none; can also occur during mitosis

Front 12

Aneuploidy

Back 12

an abnormal chromosome number

Front 13

Trisomic

Back 13

an aneuploid cell with a 2n+1 chromosome count

Front 14

Monosomic

Back 14

an aneuploid cell with a n chromosome count

Front 15

Polyploidy

Back 15

a mutant characteristic of some organisms in which they have more than two complete chromosome sets

Front 16

Deletion

Back 16

occurs when a chromosomal fragment lacking a centromere is lost during cell division; results in a chromosome that is missing certain genes; especially likely to occur during meiosis

Front 17

Duplication

Back 17

a fragment of a chromosome breaks off and joins another section, thereby forming a duplicate section on the new chromosome; especially likely to occur during meiosis

Front 18

Inversion

Back 18

occurs when a chromosomal fragment breaks off and reattaches to the original chromosome in the reverse orientation

Front 19

Translocation

Back 19

occurs when a chromosomal fragment breaks off and joins to a nonhomologous chromosome

Front 20

Genetic imprinting

Back 20

known to occur in mammals, a process by which certain genes are imprinted in some way in each generation, with the imprinting status of a given gene depending on whether the gene resides in a female or in a male