MadSci Network: Genetics

Re: What is the difference between an animals DNA and a plants DNA?and

Date: Sun Nov 19 21:04:22 2000
Posted By: Matthew Champion, Grad student, Biochemistry/Biophysics Texas A&M University
Area of science: Genetics
ID: 973782060.Ge


     This is a very good question.  there are lots of differences between 
animal & plant DNA, but what they are depends on at what you are looking.  
Chemically, plant, human, animal, bacteria, fungi, and even many viruses 
have identical DNA.  DNA is composed of a backbone made from deoxyribose 
(A sugar) and phosphate.  The individual base pairs that encode the 
genetic information are adenine, guanine, cytosine, and thymine (AGCT).  A 
base pairs with T, and G base pairs with C, which defines specificity for 
DNA, and allows one strand to direct the replication of an exact 
complementary strand, so an organism can make another set of DNA and 
divide/reproduce.  This was elegently demonstrated by Meselson & Stahl, a 
observation for which they recieved a Nobel Prize, and it agreed perfectly 
with the Watson & Crick model of DNA.  
     So, in many ways, structurally, chemically, and in the nature of 
reproduction/synthesis, plant DNA and animal DNA are very similar, if not 
identical.  So much so, that when we place genes from plants and animals 
inside of bacteria, they will often follow those instructions and produce 
a foreign protein instead.  This is how human insulin for the treatment of 
diabetes is produced in a bacteria.
     The main difference between plant and animal DNA is in the 
organization of genes and the size of the total genome, or how many base 
pairs of DNA the organism has.  As a rule, plants tend to have much larger 
genomes than their animal counterparts, and they have a lerger portion of 
garbage and intron DNA.  Very few genes are present in this DNA, and it 
tends to contain regions that are spliced out, or perhaps serve a 
structural role in the shape, packing, and placement of the genome.
     In terms of size for example, the human genome contains about 3-4 
billion base pairs of DNA, whereas corn or maize, is perhaps a less 
complex organism contains a similar number of base pairs.  Some pine trees 
and lilly plants contain 10-100 times as much DNA as a human, most of 
which does not appear to encode any genes.
     The manner in which DNA is chemically modified in the cell is 
different in plants and animals.  Although many of the same modifications 
occur in both plants and animals, such as adding methyl (CH3) groups to 
the DNA, occurs under different circumstances or for different reasons.
     I hope this is helpful to you for your project.  Let us know if there 
is anything else we can answer for you.  Thanks.

-Matt Champion-

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