Name: Date: Chromosome Webquest (35 points)

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1 Name: Date: Chromosome Webquest (35 points) This is due by 11:59pm Monday January 9th on google classroom. This is an individual assignment. If you have questions, please me and I will try to answer them. Background Information: Read this and use it to answer questions #1-10! Deoxyribonucleic acid (DNA) contains the genetic instructions for the development and functioning of all living organisms. DNA is found in the nucleus of a cell in two different forms, depending on whether or not the cell is going through mitosis (cell division). When a cell is not going through mitosis, DNA is in a long, loosely coiled form called chromatin. Chromatin includes DNA and its associated proteins. Chromatin cannot be seen with a microscope because of its loosely coiled state. During mitosis (cell division), chromatin becomes tightly coiled. Protein is a molecule found in the body that creates our body structure and controls bodily functions. The total length of chromatin in each cell has been estimated to be approximately 2 meters, or 6 feet 8 inches. A tightly coiled strand of chromatin is known as a chromosome. Because chromosomes are shorter and fatter (more condensed) than chromatin, they can be seen with a microscope. Walther Flemming, a German scientist, was the first man to observe chromosomes while studying the division of salamander larvae cells in Most organisms have a characteristic number of chromosomes in their cells. For organisms that sexually reproduce, the characteristic number of chromosomes is called the diploid number. Diploid means two or double. Humans are diploid, meaning there are two copies of each chromosome in each cell. A child inherits half of her chromosomes from her father and half from her mother during reproduction, so each parent passes 23 chromosomes to the child. Two inherited chromosomes with the same genes (one chromosome from the mother and one chromosome from the father) form homologous pairs. Humans have 46 chromosomes, meaning humans have 23 homologous pairs. Therefore, the diploid number for humans is

2 written 2n = 46. The diploid number for an organism with 8 chromosomes is written as 2n = 8. The haploid number is written in this form: n=number of chromosomes. The diploid number is usually written in this form: 2n=number of chromosomes. By studying chromosomes, and knowing an organism s diploid number, scientists can determine whether an organism is 1) male or female, 2) has certain health conditions and/or 3) is related to another organism. Comparison of Chromatin and Chromosomes Chromatin Made of DNA and its associated proteins DNA strands are long and loosely coiled around proteins. Chromatin is string-like Found in the nucleus when a cell is not going through mitosis (cell division) Not visible with a microscope Chromosomes Made of DNA and its associated proteins DNA strands are condensed and tightly coiled around proteins. Chromosomes are short and fat Formed by chromatin when a cell is going through mitosis (cell division) Visible with a microscope Answer the following questions based on the passage above: (10 points) 1. What is DNA?

3 2. What is chromatin? 3. What is the length of chromatin in each cell? 4. What is a chromosome? 5. Why can chromosomes be seen under a microscope? Who was the first person to observe them? 6. What is meant by diploid number? 7. What is meant by haploid number? 8. How many chromosomes are found in human gametes? Write the haploid number in the correct form. 9. How many chromosomes are found in human somatic cells? Write the diploid number in the correct.

4 10. What three types of information can be gathered from knowing an organism s diploid number?. Go to: and answer the following questions: (3 points) 1. What three key features do scientists use to identify chromosomes similarities and differences? 2. What do these key features allow scientists to do? 3. What are centromeres used for? Go to: and answer the following questions: (3 points) 1. What is a Karyotype? 2. How are the chromosomes arranged? 3. Match up the chromosomes and finish the Karyotype (you can use the hints if you want.) Is this Karyotype human? How do you know? Is it male or female? How do you know?

5 Go to: and answer the following questions: (9 points) 1. What are autosomes? How many does a human cell have? 2. How many sex chromosomes does a human cell have? What do they do? 3. What are homologous chromosomes? 4. How do cells get 46 chromosomes? 5. Summarize the process of mitosis in one or two sentences. 6. Summarize the process of meiosis in one or two sentences. 7. How can a cell end up with too few or too many chromosomes? 8. What is a reciprocal translocation?

6 9. What is a Robertsonian translocation? Go to: and answer the following questions: (10 points) 1. What is the function of telomeres? Where are they located? Be detailed in your explanation. 2. What happens to telomeres every time a cell divides? How many times can a cell divide before a cell dies? 3. When can a cell no longer divide? 4. What are telomeres made of? 5. What are the type of cells in which telomeres do not shorten? 6. Why do chromosomes have telomeres? 7. Why do telomeres get shorter every time a cell divides?

7 8. What prevents telomeres from shortening? 9. How are telomeres related to cancer? 10. How are telomeres related to aging? What are four factors in aging?