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Chapter 15 - The Chromosomal Basis of Inheritance


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Chromosome theory of inheritance
according to this theory, Mendelian genes have specific loci on chromosomes and it is the chromosomes that undergo segregation and independent assortment
Sex-linked genes
genes located on a sex chromosome
Linked genes
genes located on the same chromosome that tend to be inherited together in genetic crosses because the chromosome is passed on as a unit
Genetic recombination
the general term for the production of offspring with new combinations of traits inherited from two parents
Parental types
offspring of a testcross that inherit a phenotype that matches one of the parental phenotypes
offspring of a testcross that inherit a completely different phenotype than either parent
Genetic map
an ordered list of the genetic loci along a particular chromosome; first devised by Alfred Sturtevant
Linkage map
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
Cytological maps
a genetic map that locates genes with respect to chromosomal features, such as stained bands, that can be seen in the microscope
Barr body
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
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
an abnormal chromosome number
an aneuploid cell with a 2n+1 chromosome count
an aneuploid cell with a n chromosome count
a mutant characteristic of some organisms in which they have more than two complete chromosome sets
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
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
occurs when a chromosomal fragment breaks off and reattaches to the original chromosome in the reverse orientation
occurs when a chromosomal fragment breaks off and joins to a nonhomologous chromosome
Genetic imprinting
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

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