| Term | Definition |
|---|
| Diploid (2n) | 46 chromosomes, 22 pairs of autosomes and XX in females and XY in males |
| Gametes | Eggs and sperm, 23 chromosomes, 22 autosomes and X or Y |
| Karyotypes | Chromosomes stained and photographed during metaphase and arranged in a standard sequence |
| Centromere | Divides the chromosome into 2 arms |
| G-bands (by Giemsa Stain) | The system of naming chromosome bands |
| G-banding | Common staining method, treat chromosome with trypsin, stained with Giemsa stain |
| Karyotype Analysis | Total number of chromosomes, sex chromosomes' content, presence or absence of individual chromosomes, nature or extent of chromosomal aberrations |
| Chromosome Painting | Chromosomes are "painted" in different colors, very easy to identify chromosome and detect chromosome translocation, very expensive and not used commonly |
| Lymphocytes, Skin Cells, Tumor Cells | Cells used for chromosomal analysis after birth |
| Amniotic Cells, Chorionic Villi, Fetal Cells from Maternal Blood | Cells used for chromosomal analysis before birth |
| Amniocentesis | Most common way to collect fetal cells, for chromosomal and biochemical test, generally performed in the 16th week if there is enough amniotic fluid, less than 1% increase of spontaneous abortion, can test more than 100 disorders |
| Chorionic Villus Sampling | Cells are taken from placenta by catheter, can be done at 8-10 weeks, higher risk to mother and fetus at sampling, can help earlier decision to terminate pregnancy, used less often but recommended when early decision is important for mother's health |
| Fetal Cells from the Mother's Blood | New method, small number of fetal cells go into mother's blood stream, it should be safer for both mother and fetus than other methods, however it is difficult to isolate fetal cells |
| Polyploidy | A chromosome number that is a multiple of the normal haploid set, more than 3n of chromosome |
| Aneuploidy | Chromosome number varies by something less than a set, for example a chromosome 21 trisomy while all other chromosomes have 2 copies |
| Triploidy | 3 sets of chromosomes (69), 99% results in spontaneous abortion |
| Tetraploidy | (4) Consists of about 5% of spontaneous abortions, caused by the first cell division after fertilization |
| Monosomy | Having only 1 of a homologous half |
| Trisomy | Having 3 copies of a single chromosome |
| Autosomal Monosomy | Lethal condition, rarely seen in spontaneous abortions and live births, majority are lost early in development |
| Autosomal Trisomy | Most are lethal, are the cause of 50% of cases of chromosomal abnormalities resulting in fetal deaths, however, varies by chromosome |
| Patau Syndrome | (47, +13) Lethal, mean survival time is 6 months, causes facial malformations, eye defects, extra fingers or toes, severe malformations of brain, nervous system, and heart |
| Edwards Syndrome | (47, +18) Average survival time is 2-4 months, small at birth, mentally retarded, grow slowly, malformations of heart, hands, and feet, for unknown reasons, 80% are female |
| Down Syndrome | (47, +21) Leading cause of mental retardation and heart defects in the U.S. |
| Turner Syndrome | (45, X) Monosome X, female, short, wide chest, rudimentary ovaries and abnormal sexual development, puffiness of hands and feet at birth, abnormalities of the aorta, but no mental retardation |
| Klinefelter Syndrome | (47, XXY) Affected individuals are male with low fertility and may have mental disfunction, other forms XXYY, XXXY, or XXXXY |
| XYY Syndrome | (47, XYY) Males who may have antisocial, violent behavior |
| Egg development and sperm development have different time table, or maternal selection to refuse abnormal embryo may become less effective by maternal aging | Why is maternal (not paternal) age a big risk factor? |
| Nondisjunction | Most common cause of aneuploidy in meiosis, is the failure of homologs or sister chromatids' chromosomes to separate in meiosis or mitosis, produces abnoraml gametes |
| Deletions | Loss of chromosomal material, most on a large-scale are lethal |
| Translocations | Exchange of chromosomal segments between nonhomologous chromosomes |
| Viable Chromosomal Deletions | Cri du chat syndrome, Wilms tumor, retinoblastoma, Prader-Willi syndrome |
| Cri du chat syndrome | (5 p-) Deletion of short arm of chromosome 5, affects several functions including mental, intestinal, and throat, infant cry resembles a meowing cat, researchers have identified regions with genes involved in larynx and nervous system development |
| Reciprocal Translocation | 2 nonhomologous chromosomes exchange parts, no genetic information is gained or lost, may cause nothing, cancer, or abnormal offspring |
| Robertsonian Translocation | 5% of Down syndrome cases involve a translocation between chromosomes 21 and 14, centromeres from 2 chromosomes fuse and chromosomal material from the short arms are lost, carrier of the translocation can live normal life |
| Uniparental Disomy | Both copies of a chromosome are inherited from a single parent, expresses all recessive diseases |
| Fragile Sites | Certain part of chromosome is easily broken, most common is X |
Combine with other sets
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