30 Questions
What is the term for chromosomes that are classifed based on the position of the centromere?
Metacentric
Which enzyme maintains chromosome integrity by replacing the 5′ end of the long strand during DNA replication?
Telomerase
How many divisions can most cells undergo before becoming senescent due to a critical length of chromosomes?
50 to 60 divisions
What is the diploid number of chromosomes in humans?
46
Which organism has 54 chromosomes?
Sheep
What type of chromosome has the centromere located at an intermediate position?
Submetacentric
What parameters were used by early pioneers of cytogenetics to classify individual chromosomes?
Length, position of the centromere, and presence or absence of satellites
In which condition might a man with Klinefelter's disease go undiagnosed until puberty or adulthood?
Infertility
What labels were used to subdivide chromosomes into groups based on overall morphology?
A to G
When might a genetic karyotype be done for infertility?
When the cause of infertility is unknown
In what scenario might a woman with Turner syndrome or a man with Klinefelter's be unaware of their condition?
While coping with infertility
Why might infants or children with certain medical conditions need karyotyping?
To identify any chromosomal abnormalities
What is the estimated frequency of triploidy in live births?
1 in 10,000
Why might parents undergo testing if a child is born with translocation Down syndrome?
To determine if the condition is hereditary
What percentage of miscarriages are thought to be caused by chromosomal abnormalities like trisomy 16?
50%
What type of leukemia may be diagnosed by looking for the Philadelphia chromosome?
Chronic myelogenous leukemia
What is the main reason for conducting karyotype testing following a stillbirth?
To determine the cause of the stillbirth
What is the term used for cells that have more than two sets of chromosomes?
Polyploid
What is the most common cause of intellectual disability?
Trisomy 21
Which chromosomal disorder has the widest phenotypic variation affecting almost every organ?
Trisomy 21
In which type of meiosis does about 75% of maternal nondisjunctions leading to Trisomy 21 occur?
Meiosis I
What is the most common trisomy among the ones mentioned in the text?
Trisomy 18
What is the primary cause of Trisomy 21 (Down Syndrome)?
Non disjunction
Which trisomy has a survival rate of less than 3 days after birth?
Trisomy 13 (Patau Syndrome)
What is the main characteristic feature of Trisomy 21 on examination?
Short neck
Which syndrome is characterized by short stature, sexual infantilism, and webbed neck?
Turner Syndrome
What percentage of Trisomy 21 cases have the extra chromosome contributed by the mother?
90% to 95%
What is a common feature of Trisomy X syndrome?
Increased risk of learning disabilities
Which syndrome results in a mild phenotype in comparison with the other syndromes mentioned?
Trisomy X
What is a common consequence of Translocations?
Learning disabilities
Test your knowledge on prenatal testing, genetic disorders, and the role of karyotype testing in cases of translocation Down syndrome, stillbirth, and recurrent miscarriages.
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