1. Why we look somewhat like our parents, but not exactly.
Human Chromosomes
Why we look somewhat like our parents, but not exactly.

2. Think about the picture matching activity.
Everyone in the class is alike, but different.
How are we alike?
How are we different?
Click here and then on “Find out more about Heredity!”
Remember when we did the picture matching activity? You matched kids with their parents by looking at how they were alike and different. You may have seen similarities in eye color, shape of the face, how far the ears stick out and the shape of noses. You also saw that people have their head in the same place, one nose on the front of the head, two ears sticking out either side of the head and a mouth below the nose.
How do we get to be the way we are? The study of genetics looks at how we inherit traits from our parents.

3. DNA: One section of DNA is a gene
The code for traits is contained in the nucleus of each cell of our body.
Inside the nucleus are chromosomes which are made of DNA. This is the code to make you you.
Nucleus
Cell
There is a code for out traits contained in each cell of out body. We each have the same basic set of instructions, but with slightly different information. This coded information is found in the nucleus of cells on structures called chromosomes. It would be interesting to look at your own chromosomes, but that requires very careful laboratory work. So, instead of looking at our own chromosomes, imagine that you are looking at someone else’s through a microscope with a 100 power objective. First, using the low power objective, you peer through the eyepiece. Carefully, you focus and slowly move the slide until you find a cell. Switching to medium power, you focus on the nucleus. Now, you are ready to use the high power objective (1000 power-our microscopes only go up to 500 power.) As you focus, the contents of the nucleus become visible. You can now see chromosomes.
Chromosome
DNA: One section of DNA is a gene

4. Click here for an animation showing the relationship between cells, nuclei, chromosomes and DNA.
Then click on “What is DNA?”
Then “Cellular Journey”
Then Nucleus and
Then “DNA Basics”
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Put the following items in order from largest to smallest: chromosomes, DNA, cell, nucleus

5. Chromosomes are very small.
Here is what they look like when you see them through a microscope.
Chromosome smear

6. Click here to see more about chromosomes
Click here to see more about chromosomes. Then click on “What are Chromosomes?
List three words that describe a chromosome. a. b. c.

7. A karyotype is when chromosomes are grouped from largest to smallest.
They are also grouped by the centromere position and the banding patterns.
These chromosomes are incredibly small. If they are to be studied, the pictures can be cut up and the chromosomes arranged and glued down as shown in a karyotype. We now do this on the computer with digital pictures. A karyotype is a picture of the chromosomes arranged in order from largest to smallest. They are also grouped in order by the centromere position. (The centromere is where the two sides of the chromosomes come together.) A third thing to look at when arranging chromosomes on a karyotype is the banding patterns.

8. List at least 3 chromosomes characteristics that are used to make a karyotype. (What features of the chromosomes do people look at to help them put the chromosomes in the proper order?) a. b. c.
Why do you think researchers and doctors would rather look at a karyotype than at the chromosomes smear as they appear through a microscope?

9. Compare the karyotypes for a male and a female.
Compare these two karyotypes. The chromosomes in the first picture came from the nucleus of a cell of a female. The chromosomes in the second picture came from the nucleus in the cell of a male. Can you find the difference between a male karyotype and a female karyotype?
A female karyotype
A male karyotype

10. Compare the male and female karyotypes.
How are they alike?
How are they different?
How can you tell a female karyotype from a male karyotype?

11. Body Cells
Body cells are all cells in the body, except the egg and sperm
Lung cells
Liver cells
Bone cells
Nerve cells
Skin cells
Muscle cells, etc., etc., etc.
Remember, every cell in the body has a set of chromosomes. Lung cells, lilver cells, bone cells and brain cells. Old cells and new cells-all of them have chromosomes. Where do all of these chromosomes come from?

12. Where do we get new body cells?
Write where you think that we get new cells.
What do you think happens to the number of chromosomes in these new cells?

13. Before a body cell divides it copies every one of the chromosomes.
When the body cell divides, each new body cell gets a copy of each chromosomes.
The new body cell is exactly like the original cell!! They have the same number and same type of chromosomes.
Chromosomes are made inside the cells. Just before a cell divides, it copies every one of its chromosomes. In this way, the two new cells are identical to the original cell. They have the same number and same type of chromosomes. In this way, the two new cells are identical to the original cell. They have the same number and same type of chromosomes.
The whole process is amazing if you stop to think about it. Normally, a human cell has 46 chromosomes. Right before the cell divides, it contains 92 chromosomes. All of these chromosomes have to be equally shared so that each new cell gets 46 of them-two chromosomes 1s, two number, 2s etc. Just any combination of 46 chromosomes won’t do.
Click here to see an animation of this.

14. Look at this body cell. How many chromosomes does it contain? _____
How many pairs of chromosomes? __
Sketch the body cells that will result after this one divides.
Draw the new cell here:

15. One section of DNA is a gene
Imagine that you are looking at a set of chromosomes through a high power microscope. This time focus on one single chromosome. If the magnification were high enough, you would see that the chromosome looks like it is made up of coils of coils. If it were possible to unwind a coil, you would find yourself looking at DNA. Again, chromosomes are made of DNA and sections of DNA are called genes. Some genes have a code in its DNA that makes a protein to tell you body to do at least one, and sometimes more than one, thing. Sometimes genes act together to code for a trait. There are also genes that control other genes by acting as “switches” to turn other genes on and off. Many of these control genes, which are basically the same in all animals, act while an embryo is developing and determine the size, structure and building of our bodies. A small difference in these genes can make a large difference in body form.
One section of DNA is a gene

16. Scientists are finding out more about DNA each day.
Human Genome Project:
found the gene (code) for each chromosome in our body
don’t know exactly how each gene (code) works.