19 Questions
Which type of chromosome abnormality is characterized by an exact multiple of the haploid gamete number?
Euploidy
What type of cells contain an extra set of the entire genome?
Tetraploid cells
In humans, which type of chromosome abnormality is considered lethal and rare?
Polyploidy
What type of chromosome abnormality involves any chromosome number that is not an exact multiple of the number in a haploid gamete (n)?
Aneuploidy
Which term describes the presence of two or more genetically different cell lineages within one individual?
Mixploidy
What is the most common cause of triploidy?
Fertilization by two sperm (dispermy)
Tetraploidy is commonly seen in which of the following?
Spontaneous abortions
What is the term for the failure of chromosomes to separate normally during meiotic or mitotic cell divisions?
Nondisjunction
Which condition is characterized by one extra chromosome?
Trisomy
What term describes a chromosome disorder involving one chromosome missing?
Monosomy
Which type of Aneuploidy is associated with Turner Syndrome?
Monosomy
Which type of chromosome rearrangement involves the removal of a chromosome segment and its insertion into a different chromosome?
Insertion
What is the most common mechanism of formation for isochromosomes?
Misdivision through the centromere in meiosis II
In which type of unbalanced rearrangement does a chromosome fuse end to end with loss of their acentric fragments?
Dicentric chromosome
What kind of mutation involves the production of one or more copies of any piece of DNA, including a gene or even an entire chromosome?
Duplication
Which type of unbalanced rearrangement involves the loss of a chromosome segment?
Deletion
What is the term for unidentified chromosomes, referred to as supernumerary chromosomes or extra structurally abnormal chromosomes?
Marker chromosomes
What type of rearrangement results in a chromosome where one arm is missing and the other arm is duplicated in a mirror-image fashion?
Isochromosome
Which type of rearrangement involves one arm of a chromosome and its homolog at the proximal edge of the arm exchanging positions?
"Paracentric Inversion"
Study Notes
-
Mixploidy: Two or more genetically different cell lineages within one individual (2n/3n)
- Mosaicism: genetically different cell populations from one zygote (45,X/46,XX)
- Chimerism: genetically different cell populations from different zygotes
-
Euploidy Triploidy: Three sets of chromosomes (3n)
- Most common cause: fertilization by two sperm (dispermy)
- Less common cause: failure of one meiotic division
- Phenotype depends on the source of extra set of chromosomes
- Extra paternal chromosomes: partial hydatiform moles
- Extra maternal chromosomes: spontaneously aborted earlier in pregnancy
-
Euploidy Tetraploidy: Four sets of chromosomes (4n)
- Common in spontaneous abortions (5%)
- Rare in live births
- Seen at tumors
- Mosaics: mixture of diploid and tetraploid cells
- Mostly from failure of cell division in first mitotic division
-
Aneuploidy: Chromosome number not a multiple of basic chromosomes (2n-1, 2n+1)
- Monosomy: one chromosome missing
- Trisomy: one extra chromosome
- Clinically significant type of human chromosome disorders
-
Aneuploidy Formation: Nondisjunction
- Failure of chromosomes to separate normally during meiotic or mitotic cell divisions
- Meiosis I: one gamete with 24 chromosomes contains both paternal and maternal members
- Meiosis II: one gamete with extra chromosome contains both copies
-
Aneuploidy: Mosaicism
- Clinically significant if it occurs early in cleavage divisions
-
Aneuploidy: Anaphase lag
- One homologous chromosome or one chromatid fails to join to the daughter cell
- Causes one normal and one monosomic cell
-
Aneuploidy: Kinds of Aneuploidy
- Monosomy: Turner Syndrome (45,X)
- Trisomy: Trisomy 21 (Down Syndrome), Trisomy 18 (Edwards Syndrome), Trisomy 13 (Patau Syndrome), Klinefelter Syndrome (47,XXY), Trisomy XYY, Trisomy XXY
-
Abnormalities of Chromosome Structure: Balanced rearrangements
- No loss or gain of genetic information
- Change in chromosomal gene order
- Inversions, translocations, insertions
- Carrier of balanced chromosome rearrangement usually phenotypically normal
-
Abnormalities of Chromosome Structure: Unbalanced rearrangements
- Net gain or loss of DNA
- Deletions and duplications
- The larger the deletion or duplication, the greater the chance of phenotypic consequences
-
Abnormalities of Chromosome Structure: Robertsonian translocations
- Two acrocentric chromosomes fuse near the centromere region
- Loss of short arms
- Karyotype is considered balanced from having only 45 chromosomes.
Test your knowledge on chromosome abnormalities and chromosomal disorders with this quiz. Explore the major categories of genetic diseases, the role of specific chromosome abnormalities in syndromes and their impact on reproductive health and malignancy.
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