Chromosomal Analysis: The normal human karyotype

Question 1

Normal karyotype of a female?

Answer 1

22 pairs of autosomes
XX sex chromosomes
one of each pair comes from each parent

Question 2

Normal karyotype of a male?

Answer 2

22 autosomes
XY sex chromosomes
one of each autosomes comes from each parent; Y is of paternal origin; X is of maternal origin

Question 3

Each chromosome has a narrow waist called the ____, which is the site of attachment of the spindle fibres by which the two chromatids are drawn to opposite poles of the spindle during cell division.

Answer 3

centromere

Question 4

What are the metacentric chromosomes?

Answer 4

Chromosomes 1, 3, 16, 19 and 20

Question 5

What are the acrocentric chromosomes?

Answer 5

Chromosomes 13, 14, 15, 21, 22 and Y

Question 6

Metaphase chromosomes often show a lack of condensation in the NOR of the short arms of chromosomes 13–15, 21 and 22 due to activity of their clustered ribosomal genes in the formation of the nucleoli. Thus, the ends of the short arms appear as _____, separated from the rest of the chromosome arm by narrow stalks, also known as _____.

Answer 6

‘satellites’; secondary constrictions

Question 7

This shorthand system of symbols is used to describe Karyotype.

Answer 7

Paris nomenclature (total number of chromosomes, sex chromosome constitution and a description of any abnormality)

Question 8

A standardised numbering system is used for the bands seen with G - banding and this is shown diagrammatically in the human ____.

Answer 8

idiogram

Question 9

Each chromosome in the idiogram is divided into a number of chromosome regions using the ____,_____, and most prominent _____ as landmarks.

Answer 9

Ends; centromere; G - bands

Question 10

The centromere divides the chromosome into ____ and ____.

Answer 10

short (p) and long (q) arms.

Question 11

Interpret this band location: band Xp21.1

Answer 11

short arm of X chromosome, region 2, band 1, sub-band 1