Term
|
Definition
13, 14, 15, 21, 22
Share the same P sequence |
|
|
Term
|
Definition
|
|
Term
|
Definition
| One extra individual chromosome |
|
|
Term
|
Definition
| Abnormal number of chromosomes |
|
|
Term
| Tissue for chromosome analysis |
|
Definition
Any viable tissue with intact nucleus
Not RBCs
Not fixed |
|
|
Term
| Use of lymphocytes vs bone marrow in chromosome analysis |
|
Definition
Lymphocytes: not spontaneously dividing but can be triggered with PHA. Can be used for postnatal diagnosis of congenital anomalies (except for PUBS, and acquired abnormalities such as leukemia)
Bone marrow: used for acquired abnormalities in leukemia |
|
|
Term
| Chromosome preparation for analysis |
|
Definition
Done during metaphase
1. Culture cell
2. Colcemid - spindle fiber poison
3. Hypotonic solution
4. Fixed
5. Protease, Giemsa stain |
|
|
Term
|
Definition
| Homologous recombination, cross over, and independent assortment happen |
|
|
Term
| Differences in meiosis between sexes |
|
Definition
Male: all 4 daughter cells become viable gametes, meiosis starts in puberty
Female: only 1 daughter cell becomes viable gamete, meiosis begins during fetal development and is arrested at birth in prophase I, during ovulation MI resumes until metaphase II, at fertilization MII is completed |
|
|
Term
|
Definition
Abnormal # of chromosomes
Occurs with 3-4% of all pregnancies
Occurs due to non-disjunction |
|
|
Term
|
Definition
Can occur in either MI or MII - although most of the time it occurs in MI
Acrocentric chromosomes - 90% of the time NDJ is maternal and 3/4 occur in MI |
|
|
Term
| Autosomal chromosome abnormalities |
|
Definition
Phenotype usually involves developmental delay/MR
Facial features more characteristic of the syndrome than the family members
Growth delay
Congenital malformations |
|
|
Term
| Sex chromosome abnormalities |
|
Definition
Usually milder symptoms because Y chromosome only has ~50 genes
And X inactivation in females |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| Robertsonian translocation |
|
Definition
Exchange of whole arms between two acrocentric chromosomes (13, 14, 15, 21, 22)
Break is always around the centromere
Balanced: 45
Unbalanced: 46
Joining of both centromeres and Q arms |
|
|
Term
| Parent with balanced Robertsonian translocation reproduces: |
|
Definition
| Can lead to monosomy, trisomy, normal, or balanced carrier |
|
|
Term
|
Definition
Any translocation that is not Robertsonian
Exchange between two, non homologous, chromosomes
Usually p arm of one chromosome combines with q arm of another
Balanced: 46
Unbalanced: 46 or 47 |
|
|
Term
| Parent with reciprocal translocation reproduces: |
|
Definition
| Can lead to normal, translocation carrier, or duplication-deletions |
|
|
Term
|
Definition
Ring - 2 breaks at ends, ends rejoin to form ring
Terminal - 1 break at an end
Interstitial - 2 breaks somewhere in middle |
|
|
Term
|
Definition
<5Mb deletion, usually cannot be seen with G banding
Ex. PWS/AS, RB, William, DiGeorge, VCFS |
|
|
Term
|
Definition
Two P arms and two Q arms joined together
ex. Xq - leads to Turner syndrome |
|
|
Term
|
Definition
Includes centromere, both arms have breaks
Recombinant chromosome
Duplication and deletion of ends can happen
Viable, abnormal offspring |
|
|
Term
|
Definition
Does not contain centromere - 2 breaks in same arm
Usually non viable - if viable it will be normal phenotype
Either has 2 or 0 centromeres in offspring |
|
|
Term
| Frequency of chromosomal mosaicism |
|
Definition
Newborns: 0.1%
Amniotic fluid: 0.25%
CVS: 1-2% |
|
|
Term
|
Definition
Occurs through MITOTIC nondisjunction
or
Meiotic NDJ + trisomy rescue |
|
|
Term
| Idiopathic intrauterine growth retardation (IUGR) |
|
Definition
| 20% of IUGR has placental mosaicism |
|
|
