Question

Come up with an analogy comparing cytogenetic mapping, to genetic mapping, to DNA sequence mapping. Be able to describe it. Don't use a country map as an analogy.

an analogy that compares cytogenetic mapping, genetic mapping and dna sequence

Answer 1

• Sequencing refers to the determination of sequence of DNA, RNA or protein.
• DNA sequencing helps in the knowledge of the genetic code, which will further determine the expressed products and their properties.
• DNA sequence refers to arrangement of nucleotides.
• Thus, DNA sequence may be compared to words made of chronological arrangement of alphabets (where alphabets are analogous to nucleotides).

• Location of a gene in a chromosome is called its locus. The location of the gene determines its traits, evolutionary variations, mutations, recombination, linkages, and several other important aspects.

  Gene location on a chromosome may be determined by genetic mapping.

• 1. Cytogenic mapping for gene location:

  In this method, the chromosome is stained, and bands are obtained, in form of dark and light bands and sub-bands. The location of the gene is indicated by the position of the band in relative to the centromere, and location of gene in short or long arm (p or q) arm of the chromosome. A number is used to designate the position on the autosome (1 to 22) or X and Y to represent sex chromosome.

  Example: If a gene location is indicated as 14p11, this indicates that the gene is on 14th autosomal chromosome on the p arm. Abbreviations may be used like: “cen”- if the gene is close to centromere, “ter”- if gene is near terminus, “tel” -indicating telomere.

  2. Molecular mapping for gene location.

  Molecular location is based on sequence or base pair of a gene. Molecular mapping may be either be in form of genetic map or physical map.

  A. Physical map helps in determining the actual location of the gene on the chromosome, measured in terms of gene distance as base pairs. It may use molecular tags Expressed tag sequence (ETS) or radio-hybrids or radio isotopes of nucleotides.

• Thus, the genetic mapping is like finding a sentence with the words of interest.

• While cytogenetic mapping is like the index refering to chapters.

The entire analogy is:

• Nucleotides forming DNA sequence- alphabets forming words. Example thw word gene.

• Genetic mapping- scanning for sentences with the word "gene".

• Cytogenetic mapping: The chapters with the word and sentence with gene.