Variation in chromosome structure and number - Microscopic examination of eukaryotic chromosomes

8 important questions on Variation in chromosome structure and number - Microscopic examination of eukaryotic chromosomes

Why do cytogeneticists usually analyzes chromosomes in actively dividing cells?

Because chromosomes are more compact and microscopically visible during cell division.

Which 4 different positions of the centromeres in chromosomes are possible?

- Metacentric (centromere is near the middle);
- Submetacentric (centromere is slightly off center);
- Acrocentric (centromere is significantly off center but not at the end);
- Telocentric (centromere is at one end).

How are the small and large arm of chromosomes designated?

The short arm is designated with the letter p, and the long arm with the letter q.
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What is a karyotype?

A photographic representation in which all of the chromosomes within a single cell have been arranged in standard fashion.

How are the chromosomes numbered?

They are numbered according to their size (1 is the largest, 22 the smallest).

Beside size and centromeric location, which other method do geneticists use to identify each type of chromosome within a karyotype?

They add a stain called Giemsa. Some chromosomal regions bind the stain heavily and produce dark bands, in other regions, the stain hardly binds at all, and they produce light bands.

In which phase of the cell cycle can be observed the most G bands?

The prometaphase (the chromosomes are then less compacted).

For which three things is the banding pattern of chromosomes useful?

- Individual chromosomes can be distinguished from each other;
- Changes in chromosome structure can be detected;
- Evolutionary relationships between species can be assessed.

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