Genetics Vocabulary Flashcards
Phenotype
the observable expression of a genotype as a physical, medical, cellular, or biochemical trait
Aneuploidy
any abnormal number of chromosomes (other than 46 in humans)
Monosomy
having one less than the normal number of chromosomes (45 in humans)
Trisomy
having one more than the normal number (47 in humans)
Haploid
the normal number of chromosomes in a gamete (egg or sperm) (23 in humans)
Diploid
the normal number of chromosomes in somatic cells (46 in humans)
Disomy
the normal number of homologous chromosomes (2) per cell
Triploid
three homologous chromosomes in each set (69 in humans)
Chromatids
copies of chromosomes arising from DNA replication early in the cell cycle. (These become the chromosomes of the daughter cells.)
Nondisjunction
meiotic error in which homologs (meiosis I) or chromatids (meiosis II) fail to separate, resulting in abnormal chromosome segregation in the gametes.
Mosaicism
the presence of two or more different chromosome complements in an individual, can occur as the result of nondisjunction in mitosis or trisomy rescue
Trisomy rescue
the postzygotic loss of an extra chromosome, resulting in reversion of a trisomic cell to the disomic state
Reciprocal translocation
an exchange of material between two nonhomologous chromosomes
Balanced translocation
one with no net gain or loss of genetic material
Unbalanced translocation
one which results in partial monosomy and/or trisomy
Robertsonian translocation
a fusion of the long arms of two acrocentric chromosomes (4-5% cases of Down syndrome are due to Robertsonian translocations between chromosome 21 and chromosome 13, 14, or 15)
Deletion
loss of some chromosomal material resulting in partial monosomy
Duplication
presence of an extra copy of a portion of a chromosome resulting in partial trisomy
Inversion
rearrangement of chromosomal material in which a portion is placed “upside down” as a result of two breaks within that chromosome
