32 Questions
The length of each chromosome is expressed as a percentage of the total length of a diploid set.
False
The centromeric index is expressed as the ratio of the length of the longer arm to the whole length of the chromosome.
False
Bands that stain darkly with one method may stain lightly with other methods.
True
There are defined interbands between the light and dark bands on a chromosome.
False
Q-staining methods use the Giemsa dye mixture as the staining agent.
False
G-staining methods produce a fluorescent banding pattern.
False
The numbers assigned to each chromosome were based on the G-banding pattern.
False
The chromosomes are visualized as consisting of a continuous series of dark and light bands.
True
The human chromosome nomenclature is based on the results of a single international conference.
False
The autosomes are numbered from 22 to 1 in decreasing order of length.
False
The sex chromosomes are referred to as X and Z.
False
Group A chromosomes are the shortest in the karyogram.
False
The X chromosome resembles the shorter chromosomes in group C.
False
Group G chromosomes have satellites on their short arms in every cell.
False
The Y chromosome has satellites.
False
The group letter designations were agreed upon at the Paris Conference.
False
R-bands have the same staining intensity as G-bands.
False
C-banding methods can identify every chromosome in the somatic cell complement.
False
The Q-banding method demonstrates patterns of DNA replication.
True
X-chromatin is found on the short arm of the Y chromosome.
False
Nucleolus organizing regions are revealed by R-banding methods.
False
Telomeric bands are revealed by C-banding methods.
False
Each human chromosome is composed of distinct bands with no unbanded areas.
True
The patterns obtained with Q-banding methods are identical to those obtained with G-banding methods.
False
The bands and regions are numbered from the ends of the chromosome arms outward.
False
The karyotype describes the diagrammatic representation of a chromosome.
False
The group letter designations were agreed upon at the Paris Conference (1971).
False
The centromeric index is expressed as the ratio of the length of the longer arm to the whole length of the chromosome.
False
All chromosomes in the D and G groups show satellites on their short arms in a single cell.
False
The tertas karygram is a systematized array of the chromosomes prepared by drawing, digitized imaging, or photography.
True
The idiogram is used to describe the normal or abnormal chromosomal complement of an individual.
False
The length of each chromosome is expressed as a percentage of the total length of a diploid set.
False
Study Notes
Normal Chromosomes
- Human chromosome nomenclature is based on the results of several international conferences (Denver 1960, London 1963, Chicago 1966, Paris 1971, Paris 1975, Stockholm 1977, Paris 1980, Memphis 1994, Vancouver 2004).
- The current nomenclature incorporates and supersedes all previous ISCN recommendations.
Chromosome Number and Morphology
- Autosomal chromosomes are numbered from 1 to 22 in decreasing order of length.
- Sex chromosomes are referred to as X and Y.
- Chromosomes can be arranged into seven readily distinguishable groups (A-G) based on descending order of size and the position of the centromere.
Non-Banding Techniques
- Group A (1-3): Large metacentric chromosomes readily distinguished from each other by size and centromere position.
- Group B (4-5): Large submetacentric chromosomes.
- Group C (6-12, X): Medium-sized metacentric or submetacentric chromosomes.
- Group D (13-15): Medium-sized acrocentric chromosomes with satellites.
- Group E (16-18): Relatively short metacentric or submetacentric chromosomes.
- Group F (19-20): Short metacentric chromosomes.
- Group G (21-22, Y): Short acrocentric chromosomes with satellites.
Banding Techniques
- A band is defined as the part of a chromosome that is clearly distinguishable from its adjacent segments by appearing darker or lighter with one or more banding techniques.
- Q-staining methods: Produce a fluorescent banding pattern using quinacrine mustard or quinacrine dihydrochloride.
- G-staining methods: Use Giemsa dye mixture as the staining agent, producing an almost identical pattern of dark and light bands.
- R-bands: Produced using reverse staining methods, resulting in opposite staining intensity to G-staining methods.
- C-bands: Reveal constitutive heterochromatin, and can be used to identify specific chromosomes.
X-and Y-Chromatin
- Inactive X chromosomes and the heterochromatic segment on the long arm of the Y chromosome appear as distinctive structures in interphase nuclei, referred to as X-chromatin (Barr body, sex chromatin, X-body) and Y-chromatin (Y-body), respectively.
Chromosome Band Nomenclature
- Each chromosome is considered to consist of a continuous series of bands, with no unbanded areas.
- A band is a part of a chromosome clearly distinguishable from adjacent parts by virtue of its lighter or darker staining intensity.
- Bands are allocated to various regions along the chromosome arms, and regions are delimited by specific landmarks.
- Landmarks include the ends of the chromosome arms, the centromere, and certain bands.
Karyotype and Idiogram
- Karyogram: A systematized array of the chromosomes prepared either by drawing, digitized imaging, or by photography.
- Karyotype: The use of nomenclature to describe the normal or abnormal, constitutional or acquired, chromosomal complement of an individual, cell line, or species.
- Idiogram: A diagrammatic representation of a karyotype.
Learn about the international conferences that established the nomenclature system for human chromosomes and how it is used in other species.
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