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Dear Dr. Pat,

I am in grade 10 science and we are almost finished the biology unit.

We have a big unit exam tomorrow and I need some help. In the animal cell (not sure if it's in the plant cell or not) there is a thing called the "centrosome" I was wondering if you could tell me what it's function is in the cell. I have no idea, and probably should know.

Thanx a lot.   Lesia

Hi Lesia,

A centrosome is the system of microtubules and centrioles that pull the pairs of chromosomes apart when plant and animan cells divide. The centromere is a very important reason why all daughter cells have the same chromosomes and genes as the parent cell.

Think of the difficulty in making cell division work perfectly each and every time. You must figure out a way to duplicate, exactly, 5 feet of DNA, wind it into chromosomes and last but not least, make sure that each daughter cell gets one copy of each chromosome. The centromeres are invaluable in that last step.

The centromere is usually somewhat near the middle of the chromosome, although its exact position varies from chromosome to chromosome. Once you complete the duplication of the DNA, the two identical DNA duplexes are held together by the centromere. The DNA winds up into a chromosome that has two 'sister chromotids' which are the two identical chromosomes. The centrosome hooks up with the centromere, pulling the sister chromotids to the center of the cell. The centromere duplicates itself and, finally, the centrosome pulls the two sister centromeres apart and the chromatids (new chromosomes) apart with it. The sisters move into different ends of the cell and the cell pinches down in the middle to create the two new cells.

I hope this helps. Good luck. I just know you will do a great job on your test.

Thanks for asking,

Dr. Pat

Hi Dr. Pat,
You have a great site with wonderful information. But I have a  question.  I have to make a cell model and I was wondering what kind of things that I can use to represent things in the cell like, cell membrane, cytoplasm, nucleus, etc.  It has to be things from our home and creative and also different.  Can you help me?

Hi Loni,
I can only pass on some ideas I have seen used by students such as yourself.
One young lady wrote that they had to make a model of a cell used things that suggested the function of the cell part. For instance, a battery for a mitochondria.
I have seen kids use only pieces of candy that reflect the shape of the cell part. Such as, a gum ball for the nucleus.
I have also seen models made of pasta and others of small toys, such as one of those balls with the long, flexible rays of plastic (squish or kwish or something ball) for the nucleus.
Here are some alternative ways to think of the functions of the various organelles. These descriptions may lead you to think of some cell model that is creative and new. Lets begin with the organelles (parts of the eukaryotic cell) that both plant and animal cells have. Nucleus: brain or library. Mitochondrion: battery or power plant. Golgi Apparatus: mail sorting room. Granules: special equipment closet. All membranes: import/export customs office. Endoplasmic Reticulum: kitchen or construction site. In plants only, we have the Chloroplast: sugar factory or transformer and the vacuole: stomach.
Hope this is enough to get you started. I know you will come up with something surprising.
Dr. Pat

Hi my name is Phillip and I am in the sixth grade and I am doing a  project on fingerprints and I was wondering if you were cloned wouldn't your clone have the same fingerprints as you?
Thanks,  Phillip

Hi Phillip,
Twins and triplets are natural clones of human beings. The fertilized egg splits all the way in two by accident, when it divides. When you look at human twin, you see that, although they have identical DNA sequences, there are many things that are different. That is because not every detail about a person is determined by their genes. For instance, the personality of two twins is often very different. So, too, are their fingerprints. The DNA determines that you will have fingerprints on the tips of your fingers, to help with touch and picking up things. But the DNA does not determine exactly what that pattern will be.
This is an excellent question to pose. You are obviously very bright and could easily be a scientist when you grow up. Keep thinking and asking.
Dr. Pat

Because of this page I was able to learn a lot more about Bacteria Cells. This page also helped me in a small presentation on Bacteria Cells, and how to describe them to the class so they would understand. Thanks a lot.

Thank you so much for your kind e-mail. We are very pleased that our information on Bacterial cells was of interest and of use to you. Science is full of fun stuff just like that. Maybe some day you will discover something in science that school kids the world over will have to learn about.
Enjoy your school year. And, again, thank you.
Dr. Pat

Dr. Pat,
What are genes made of?

Hi Sue,
What an excellent question! Genes are made of DNA. A gene is small strand of DNA. A long strand of many genes (like a necklace with many beads strung together) is called a chromosome. DNA is made by linking many thousands of 'nucleotides' together to make a string of DNA. A nucleotide is made of sugar, phosphate, and a base. These are all made of carbon, hydrogen, oxygen, phosphate, and nitrogen atoms. This is all shown in the web pages: and
Dr. Pat


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