MadSci Network: Genetics Query:

Mallory: 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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