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Chapter 15 - Chromosome Inheritance

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Chromosome theory of inheritance
Mendelian genes ave specific loci on chromosomes, and it's the chromosomes that undergo segregation and independent assortment
Wild type
Normal phenotype for a character (most common in natural populations)
Sex-linked genes
Genes located on the sex chromosome
Linked genes
genes located on the same chromosome
Genetic recombination
Production of offspring with new combinations of traits inherited from two parents
Parental types
offspring that inherit a phenotype that matches one of the parental phenotypes
Recombinants
Offspring with new combinations of characters
Genetic map
ordered list of genetic loci along a particular chromosome
Linkage map
genetic map based on recombination frequencies
Map units
1% recombination frequency
Cytological maps
locate genes with respect to chromosomal features (locations)
Barr body
compact object (inactive X chromosome condenses to)
Nondisjunction
occaional mishap, members of homologous chromoses don't move apart properly during meiosis I : sister chromatids don't separate during meiosis II
Aneuploidy
Offspring having abnormal chromosome number
Trisomic
Chromosome present in triplicate (aneuploid cell)
Monosomic
Chromosome is missing
Polyploidy
Chromosome alteration
Deletion
Chromosmal fragment lacking a centromere is lost during cell division
Duplication
Fragment becoming attached as an extra segment to a sister chromatid
Inversion
Chromosomal fragment reattaching to the original chromosome (reverse orientation)
Traslocation
Fragment joins a nonhomologous chromosome
Genomic imprinting
A gene on one chromosome is silenced: allele on homologous chromose is free to be expressed
Fragile X syndrome
Physical appearance of abnormal X chromosome