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Biology Chapter 14
DNA Structure and Function part 1. (14.1-14.2)
| Question | Answer |
|---|---|
| What began our understanding of DNA? | The discovery of nucleic acids followed by the development of double-helix model. (Fredrich Miescher discovered nucleic acids) |
| What is transformation? | A process in which external DNA is taken up by a cell. |
| What bacteria did Fredrich Griffith use in his experiment of bacterial transformation? | Streptococcus pneumoniae. He used two strains known as rough (R) and smooth (S). |
| Which strain was pathogenic? | The S-strain was pathogenic whereas the R-strain was non-pathogenic. |
| In Griffith's transformational experiments, what was the informational component transferred? | DNA. |
| What is a bacteriophage? | A virus that infects bacteria. |
| What is the structure of a virus? | A protein coat (capsid), and a nucleic acid core containing the genetic material of DNA or RNA. |
| What are Chargaff's rules? | This states that the amount of Adenine=amount of Thymine and amount of Cytosine=amount of Guanine. Different species had equal amounts of purines and pyrimidines but different ratios of A+T and G+C. |
| What are the building blocks of DNA? | Nucleotides. |
| What are the important components of a nucleotide? | The nitrogenous base (nitrogen-bearing), a 5-carbon sugar (pentose), and a phosphate group. |
| What is a purine? | These are the nitrogenous base of a nucleotide. They have a double ring structure with a six-membered ring fused to a five-membered ring. (Adenine and guanine are purines.) |
| What is a pyrimidine? | These are another form of the nitrogenous base. They have a single six-membered ring structure. (Cytosine, Thymine, and Uracil are pyrimidines) |
| Where is the phosphate connected in DNA and RNA? | It's connected to the 5' carbon of the sugar by an ester (acid+alcohol) linkage between phosphoric acid and 5'-OH group. |
| Who discovered the structure of DNA? | Watson, Franklin, and Crick used X-ray crystallography and X-ray diffraction methods to piece together the double-helix model. |
| What pairs together in the DNA helix? | Base pairing occurs between pyrimidines (T and C) and purines (A and G), so that A pairs with T, and C pairs with G. |
| How do these pairs bond with each other? | The base pairs form hydrogen bonds to link together. A and T form 2 hydrogen bonds while C and G form 3 hydrogen bonds. |
| How are the DNA connections arranged? | The two strands run anti-parallel, meaning the 3' end of one strand faces the 5' end of the other strand. |
| Describe the construction of the DNA helix. | The sugar and phosphate of the nucleotides form the backbone of the structure and the nitrogenous bases are stacked inside. Each base pair is separated from the next pair by a 0.34 nm and each turn of the helix measures 3.4 nm. |
| How many base pairs are present per turn of the helix? | 10 |
| What is the dideoxy chain termination method of DNA sequencing? | It uses a chain of terminators known as dideoxynucleotides (ddNTPs). These are different from deoxynucleotides by the lack of a free 3' OH group on the 5-carbon sugar. When ddNTP is added to growing DNA it will stop bc free 3'OH group needs a nucleotide |
| Define gel electrophoresis. | It is a technique used to separate DNA fragments of different sizes. |
| How does all the necessary DNA fit inside a prokaryote's nucleoid region? | By supercoiling. That means the DNA is either over wound or under wound. |
| How does the DNA fit inside a eukaryote's nucleus? | The DNA is wrapped around proteins called histones to form structures call nucleosomes. |
| How is the nucleosome linked to the next one? | By a "linker DNA" molecule. This is known as beads on a string structure. |
| When are chromosomes most compact? | During metaphase measuring 700 nm in width. |
| What are the names of the different regions on a eukaryotic chromosome in interphase? | The tightly packaged region is called heterochromatin. The less dense region is called the euchromatin. |
| Describe heterochromatin. | This contains genes that are usually not expressed and is found in the regions of the centromere and telomere. |
| Describe the euchromatin. | This contains the genes that are transcribed with DNA packaged around nucleosomes but not further compacted. |
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tali_Alley
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