Cytogenetic Techniques and Karyotyping

Question 1

What are the four parts to a chromosome?

Answer 1

• Contromere
• Short (p) arm
• Long (q) arm
• Telomere

Question 2

What is a Karyotype?

Answer 2

A Karyotype is a complete set of chromosomes from a cell usually photographed during metaphase of mitosis and arranged in a standard sequence

Question 3

What useful information do karyotypes provide?

Answer 3

They provide:

• Number of chromosomes present
• Number and type of sex chromosomes
• Presence or absence of individual chromosomes (of parts of)
• Detectable structural abnormalities

Question 4

What is Chromosome painting and how does it work?

Answer 4

Chromosome painting is an easier method (than traditional methods) to identify small changes in chromosomes via a karyotype.

• Fluorescent dyes are attached to DNA-specific sequences, which attach to their target chromosomes, ‘painting’ them with their distinctive colour
• Combinations of different DNA sequences and fluorescent dyes –> each chromosome shows a unique pattern
• The pattern highlights any translocations, duplications, deletions, inversions and aneuploidies

Question 5

What is Fluorescent in Situ Hybridisation (FISH) and how does it work?

Answer 5

• Mitotic or Interphase cells are fixed to a slide with the hybridisation method using fluorescently labelled tags.
• Can identify the morphology and population

Question 6

What is DNA Microarray and how does work?

Answer 6

Microarray typically is used to compare two different cell types.

• SS (single-stranded) fragments of DNA are attached to a glass slide at a pot called a field which contains many copies of the SS sequence
• For expression analysis different coloured fluorescent tags are added to complementary DNA (cDNA) derived from mRNA extracted from both types of cells