| A | B |
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| Compare prokaryotic and eukaryotic DNA. | See page 295 in your text; you may also want to look back at pages 172-175. Make a chart to compare them. |
| Is the number of chromosomes in eukaryotic DNA the same from species to species? | No. Examples: humans have 46; Drosophila have 8; giant sequoia tree cells have 22. |
| Why must DNA in a prokaryotic bacterium be folded so compactly? | The DNA in a bacterium is about 1000 times as long as the bacterium itself, so it must fit into a space that is 1/1000 of its own length! |
| Eukaryotic cells must pack more tightly than prokaryotic ones. Why? | Example: human cell has 1000 times as many base pairs of DNA as a bacterium; the greater number require more tight "packing". |
| What is chromatin? | It's a granular material visible within the nucleus; it consists of DNA tightly coiled around proteins called histones. So, it is DNA and protein tightly packed together. |
| What are histones? | They're globular protein molecules around which DNA is tightly coiled in chromatin. |
| What is a nucleosome? | It's the beadlike structure formed by DNA and histone molecules in a cell; they pack with one another to form a thick fiber, which is shortened by a system of loops & coils. (see picture pg. 297) |
| It is theorized that nuclosomes have changed very little during evolution; why? | It's thought that they are so important that mistakes in DNA folding could harm a cell's ability to reproduce. |
| What do you call each DNA-histone complex? | It is a nucleosome. |
| In a larger eukaryotic chromosome, where does replication happen? | It occurs at hundreds of places in both directions until each chromosome is completely copied. |
| What is a replication fork? | It's a site where separation and replication occur in a larger eukaryotic chromosome. |
| What happens during DNA replication? | 1) The DNA molecule separates into 2 strands; 2) 2 new complementary strands are produced following the rules of base pairing (adenine + thymine pair; guanine + cytosine pair). (see picture on 298) KNOW HOW TO DO COMPLEMENTARY BASES! |
| How is DNA replication carried out (what is necessary for it to happen)? | A series of enzymes enable replication to happen (299). |
| What is DNA plymerase? | It's an enzyme that "proofreads" new DNA strands, helping to ensure that each molecule is a nearly perfect copy of the original DNA. |
