Chromosomes & Chromosomal Abnormalities Flashcards
Somatic nondisjunction during mitosis contributes to aneuploidy in cancer cells. This results from the failure of what cell cycle checkpoint?
Spindle assembly checkpoint in M phase
How are the short and long arms of chromosomes identified?
Short arm - p
Long arm - q
What is the most common cause of trisomies?
Nondisjunction
What clinical features are associated with Down Syndrome?
Decreased intellectual ability, severe hypotonia in newborns, congenital abnormalities, increased risk of acute leukemia, abnormal immune response
A cell has 69 chromosomes. Is this cell euploid or polyploid?
The cell is both euploid (multiple of 23 chromosomes) and polyploid (one complete set of extra chromosomes).
Haploid gametes and diploid cells are euploid, but not polyploid.
Prader-Willi and Angelman syndromes may be associated with what chromosomal abnormality?
Microdeletions
How do microdeletions differ from deletions?
In deletions, an entire chromsomal arm is deleted. In microdeletions, only a region or band is deleted.
What are the structural chromosomal abnormalities?
Inversions, ring chromosomes, isochromosomes, translocations, deletion, microdeletions
True/False. Phenotypes on ring chromosomes are associated with deleted genes.
True. Deletion of genes during formation of the ring chromosome results in phenotypic changes. If no genes are deleted then there will be no phenotypic changes.
Differentiate between a submetacentric and acrocentric chromosome.
In a submetacentric chromosome, the centromere is located near the middle of the chromosome, but is not exactly in the center. This results in a short and a long arm.
In an acrocentric chromosome, the centromere is located at one end of the chromosome. This results in a short and a long arm. The short arm also contains satellites.
What process takes place during meisos to increase genetic diversity of gametes by allowing for different combinations of traits?
Recombination via crossing over between homologous chromosomes
True/False. Robertsonian translocations always result in mutant phenotypes.
False. Individuals with a Robertsonian Translocation are phenotypically normal. They are are increased risk of producing abnormal gametes, also increasing risk for chromosomal disorders such as Down Syndrome.
What are the clinical features of Klinefelter syndrome?
In males - hypogonadism, gynecomastia, sparse body hair, reduced muscle mass
Infertility, normal IQ but predisposition for learning disabilities
What are the sex chromosome aneuploidies?
Klinefelter Syndrome (XXY)
Turner Syndrome (45,X)
Trisomy X (XXX)
Jacob Syndrome (XYY)
A newborn has rocker-bottom feet, a small head, and clenched fists. As the newborn ages, significant developmental disabilities and a congenital heart defect are noted. What disorder is causing the observed symptoms?
Edwards Syndrome - Trisomy 18
Chromosome loci are named based on chromosome number, arm, region, and band. Identify the circle loci on the chromosome.
Xp11
How can aneuploidy result from nondisjunction in meiosis?
Failure of homologous chromosomes to separate in meiosis I
OR
Failure of sister chromatids to separate during meiosis II
What is an unbalanced chromosomal abnormality with loss of one arm and duplication of the other?
Isochromosome
Flip to view a normal male karyotype.
What are the two classes of chromosomal abnormalities?
Structural & numerical
What is mosaicism?
Mosaicism is the concept that cells in the body may sometimes be genetically different than other cells, with different genotypes and phenotypes. The mature organism is a mosaic of mutated and non-mutated cells.
What is a Robertsonian translocation?
Translocation involving two acrocentric chromosomes. The short arm of one chromosome is exchanged for the long arm of another to create a larger metacentric chromosome. Offspring are phenotypically normal. Any chromosome fragments that fail to integrate at degraded.
What characteristics are associated with Trisomy X?
Sterility, irregular menses, mildly decreased IQ
Why is the incidence of certain single-gene disorders associated with greater paternal age?
Primary spermatocytes undergo cell division beginning at puberty until death. The greater the number of cell divisions, the more likely point mutations and thus single-gene disorders are to occur.
