I read from an article that many bony fish which include Nemo, the clownfish, change sex throughout their life-spans. How does changing sex impact their DNA? Were they born with both X and Y chromosomes or somehow they were changed when the sex wa

-A curious adult from California June 25, 2004 It is amazing the variety of ways Mother Nature has come up with to determine whether an animal is going to have a boy or a girl. As you know, for humans, sex is determined by the presence of a Y chromosome -- humans with an X and a Y chromosome are male and those with two X chromosomes are female.

I have a bunch of questions about genes, their locations on chromosomes, and \"junk\" DNA. Do genes on one chromosome have some functional characteristic or are genes scattered across chromosomes without regard to their function? How important is

-A curious adult from California

June 16, 2004

First off, it doesn't really matter on which chromosome a gene is located. The best evidence for this is found by comparing mouse and human chromosomes. What you can quickly see is that at a high level, mouse chromosomes are really just mixed up bits of human chromosomes. In other words, you can mix and match parts of chromosomes and everything works out OK.

How does DNA replicate itself?

-A middle school student from Michigan

June 14, 2004

Cells need to copy their DNA when they divide. This process is called DNA replication. To understand how DNA is copied, we first need to understand the structure of DNA.

DNA is made of two long strands that wrap around each other to make the famous double helix. Each strand is composed of a sequence of molecules called nucleotides. Bases are a part of the nucleotides.

The other night on CSI they used a medical term (I think it started with a C) for a person that had two different DNA\'s. Have you ever heard of this?

-A curious adult from Alabama June 8, 2004 What you are thinking of is "chimera." In the TV show, CSI, a woman claimed a man raped her, but DNA taken from his blood did not match the DNA of the suspect. The test also revealed that the most likely suspect was a relative of the man. When further DNA tests cleared his relatives, the man's DNA was tested again. This time it was from a hair sample and this time it was a perfect match to the suspect's DNA. Can one person have two types of DNA in different parts of his body?

What is the difference between dominant vs. recessive? Can you tell me what I could do to show my class about this without this being long?Thank you.

-A middle school student from New York

June 4, 2004

Good question. Remember that for most genes, you have two copies of each gene that you inherited from your mother and your father.

Each copy of the gene could be different. For example one copy may give you blue eyes while another may give you brown.

So, what color are your eyes if you have both the brown and blue eye version of the eye color gene? Brown. This is where the idea of dominant and recessive comes in.

What will be the effect on our body if chromosome number is altered from 46?

-A high school student from Pakistan

June 3, 2004

If a body has too few or too many chromosomes, it usually won't survive to birth. Getting the number of chromosomes right is so complicated that nature often makes mistakes. Believe it or not, around 10% of sperm and 50% of eggs contain abnormal chromosomes and more than half of first trimester spontaneous abortions are due to chromosome abnormalities.

How does a paternity test work?

-A curious adult from California

June 1, 2004

Did I find my real dad? Is that really my son? Did Michael Jackson really father Billie Jean's kid? Questions like these used to be very hard to answer. In the past, people used a blood test. This might rule out that you were the father but couldn't prove that you were.

Nowadays, DNA technology is used to figure out who is the father of a child. DNA paternity testing makes it possible to determine a child's biological father to a very high degree of certainty.

What is DNA made of?

-2 middle school students from Michigan

May 28, 2004

You may have heard of the "double helix" of DNA. Double helix refers to the shape of DNA, which is a ladder-like molecule that looks like the picture to the right. In DNA, two long strands (shown in yellow) wind around each other. These strands, the backbones of the ladder, are two long chains made of phosphate molecules.

The rungs of the ladder? Well, attached to each of these phosphates is the sugar that gives DNA its name, deoxyribose.

What does DNA do?

-A middle school student from Michigan

May 28, 2004

DNA is information. Think of DNA as a collection of cookbooks that contains all the recipes for making and running living things like worms, plants, birds, and people.

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