Chromosomal disorders -MCQs
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
ANSWER -B.
Metaphase.
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Usual procedure to examine chromosomes is to arrest dividing cells in metaphase with mitotic spindle inhibitors and then to stain the chromosomes.
Mitotic spindle inhibitors – N-diacetyl-N-methylcolchicine
A. C banding
B. Q banding
C. G banding
D. T banding
ANSWER -C.
G banding.
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G-banding- technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes.
It is the most common chromosome banding method.
It is useful for identifying genetic diseases through the photographic representation of the entire chromosome complement.
The metaphase chromosomes are treated with trypsin (to partially digest the chromosome) and stained with Giemsa stain.
A. Gene mapping
B. DNA profiling
C. DNA fingerprinting
D. DNA barcoding
ANSWER -A.
Gene mapping
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Gene mapping describes the methods used to identify the locus of a gene and the distances between genes.
DNA profiling is also called DNA fingerprinting
DNA fingerprinting – is a forensic technique in criminal investigations, comparing criminal suspects’ profiles to DNA evidence so as to assess the likelihood of their involvement in the crime
A. X2.12p
B. X21.p2
C. pX21.2
D. Xp21.2
ANSWER -D.
Xp21.2
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Notation Xp21.2 refers to a chromosomal segment located on the short arm of the X chromosome, in region 2, band 1, and sub-band 2.
A. Translocation between two acrocentric chromosomes
B. Most common form of chromosomal translocation in humans
C. Does not usually cause health difficulties
D. Result in a increase in the number of chromosomes
ANSWER -D.
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Robertsonian translocation -result in a reduction in the number of chromosomes
A. Turner syndrome
B. Down syndrome
C. Klinefelter syndrome
D. Edwards syndrome
ANSWER -B.
Down syndrome
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Down syndrome is the most common of the chromosomal disorders
A. Fragile X syndrome
B. Phenylketonuria
C. Fetal alcohol syndrome
D. Down syndrome
ANSWER -D.
Down syndrome
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Down syndrome is the most common cause of the mental retardation
A. Paternal meiotic error
B. Maternal meiotic error
C. Paternal mitotic error
D. Maternal mitotic error
ANSWER -B.
Maternal meiotic error
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90% of free trisomy 21 is due to a maternal meiotic error
A. Reciprocal translocation
B. Point Mutation
C. Meiotic nondisjunction
D. Maternal Mitotic error
ANSWER -C.
Meiotic nondisjunction
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Most common cause of trisomy and Down syndrome is meiotic nondisjunction
In-Shorts
Humans have 5 autosomal chromosomes with arms that are particularly discordant in length, known as acrocentric chromosomes.
These are 13, 14, 15, 21 and 22.
When these chromosomes break at their centromeres, the two resulting long arms may fuse.
The result is a single, large chromosome with a metacentric centromere.
This form of rearrangement is a Robertsonian translocation.
