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Name: Cheryl C.
Status: Educator
Age: 60s
Location: N/A
Country: N/A
Date: March 2004


Question:
Is there a difference in the amount of DNA in animal cells vs plant cells,specifically in cells such as liver cells, onion cells, pea cells, and chicken cells?



Replies:
Interesting question...All forms of life on Earth contain DNA. The amount of DNA and the code that is held within that DNA directs the respective organism's development, function and form. The more differences there are between two organisms, the more we can expect that there are differences in the DNA. There are two basic variables in DNA ...amount, as you suggest, or the sequence of the 4 bases that are the lettered code of DNA. As you might suspect, the amount of DNA is quite different amongst organism. But some rather complex organisms do not have more DNA than the less complex organisms. What is interesting is the enormous variety of amounts and sequences in the bases of DNA that leads to the variety in life- forms. Plants often have multiple copies of chromosomes and since chromosomes contain DNA plants often have quite large amounts of DNA.

A single plant cell can have over 100 chromosomes. In the end it is not simply the amount of DNA but how that DNA is used, what other regulators of DNA are involved etc. There are an enormous host of complexities I have not mentioned that present scientists with an overwhelmingly complex puzzle. One thing is certain...science has a very, very, long way to go to understand just how a single human cell actually does what it does under the control of genes and the proteins that are the products of those genes.

pf


Recall that chromosomes are made of DNA. Different species have different chromosome numbers and therefore, in general, different amounts of DNA. That is not entirely true however because if one organism has a small chromosome number and another a large number, it may just be that the one with few chromosomes has very large chromosomes and the one with many has lots of very small chromosomes. But, there is no real difference between the amount of DNA in a plant cell vs. an animal cell. Also, recall that all organisms start out as one cell and that the DNA is replicated before the cell divides so that it can pass on an exact copy to the next cell. So within any one organism, every cell has the same amount of DNA in it, except in the gametes of sexually reproducing organisms where there is half the amount in those cells. So in humans, every cell has the same amount of DNA in it as every other cell, except eggs and sperm which have half the amount.

vanhoeck



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