Chapter 6 Flashcards
Nodisjunction
When chromosomes fail to separate properly
Aneuploid
Having an abnormal number of chromosomes (normally individual chromosomes)
Uniparental disomy
When both copies of a homologous pair of chromosomes are inherited from a single parent
*not detected by karyotype
Euploid
Having the correct number of chromosomes
Trisomy
The gain of a single chromosome (3 in total)
Monosomy
The loss of a single chromosome (1 total chromosome)
Polyploid
Possessing more than two complete SETS of chromosomes
Genomic imprinting
A process by which only one copy of a gene is expressed while the other copy is suppressed, based on the parent of origin (whether it is the maternal or parental copy)
What segment is the arrow pointing to?
1q2.4
What are the viable trisomies in humans?
13, 18, 21, X
What are the viable monosomies in humans?
There are NO viable autosomal monosomies.
X monosomy is the only one period
Deletion
The loss of part of a chromosomes (can be intercalary aka in the middle or terminal aka at the end)
Duplication
Additional copies of a region of a chromosome (includes copy number variants)
*can be caused by unequal crossing over
Inversion
Rearrangement of genetic segments within the same chromosome
What are the two types of inversion?
Pericentric: inversion that includes centromere
Paracentric: inversion that does NOT include centromere
*will have 2 normal homologs and 2 homologs that have both deletions and duplications
Translocation
Exchange of genetic segments between two nonhomologous chromosomes
3 types of translocation
Reciprocal, nonreciprocal, and robertsonian
Reciprocal translocation
Equal part exchange of genetic info between two nonhomologous chromosomes (they both get some)
Nonreciprocal translocation
An unequal exchange of genetic info between nonhomologous chromosomes (one doesn’t get any)
Robertsonian translocation
When two nonhomologous, acrocentric chromosomes’ q arms fuse and create one chromosome (p arms don’t really carry genetic info so no genetic info is lost)
*creates 3 lethal gametes and 3 viable gametes. 1 normal, 1 translocation carrier, and 1 translocation Down syndrome
When does an inversion loop occur?
During prophase I
Nondisjunction in Meiosis I vs Meiosis II
Meiosis I: failure of homologous chromosomes to seperate. Normally results in heterozygous copy (Aa). Results in 4 aneuploid gametes
Meiosis II: failure of sister chromatids to separate. Normally results in homozygous copy (aa). Results in 2 normal and 2 aneuploid gametes
