Download DNA - The Double Helix

G1 Retesting Assignment
Nucleic acids
DNA - The Double Helix
Recall that the nucleus is a small spherical, dense body in a cell. It is often called the "control center"
because it controls all the activities of the cell including cell reproduction, and heredity. Chromosomes are
microscopic, threadlike strands composed of the chemical DNA (short for deoxyribonucleic acid). In simple terms,
DNA controls the production of proteins within the cell. These proteins in turn, form the structural units of cells
and control all chemical processes within the cell. Think of proteins as the building blocks for an organism, proteins
make up your skin, your hair, and parts of individual cells. The proteins that are made largely determine how you
look. The proteins that will be made for your body are determined by the sequence of DNA in the nucleus.
What important polymer is located in the nucleus? _______________
___________ is the instructions for making a cell's ______________.
Chromosomes are composed of genes, which is a segment of DNA that codes for a particular protein, which
in turn codes for a trait. Hence you hear it commonly referred to as the gene for baldness or the gene for blue
eyes. Meanwhile, DNA is the chemical that genes and chromosomes are made of. DNA is called a nucleic acid
because it was first found in the nucleus. We now know that DNA is also found in some organelles such as the
mitochondria and chloroplasts. It is the DNA in the nucleus that actually controls the cell's workings.
_______ on chromosomes code for specific ___________ in a cell.
DNA is also found in _____________ and ____________.
In 1953, James Watson and Francis Crick established the structure of DNA. The shape of DNA is a
double helix, which is like a twisted ladder. The sides of the ladder are made of alternating sugar and phosphate
molecules. The sugar is a pentose called deoxyribose. Color all the phosphates pink (one is labeled with a "p").
Color all the deoxyribose sugars blue (one is labeled with a "D").
What is meant by a double helix? ____________________________
Name a pentose sugar. _________________
The sides of DNA are made of _____________ and ______________.
The rungs of the ladder are pairs of 4 types of nitrogen bases. The bases are known by their coded
letters --- A, G, T, and C. These bases always bond in a certain way. Adenine will only bond to thymine. Guanine
will only bond with cytosine. This is known as the "Base-Pair Rule." The bases can occur in any order along a
strand of DNA. The order of these bases is the code that contains the instructions. For instance, ATGCACATA
would code for a different gene than AATTACGGA. A strand of DNA contains millions of bases. (For simplicity,
the image only contains a few.)
What makes up the "rungs" of DNA? ____________________
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G1 Retesting Assignment
What will pair with adenine? _____________
Color the thymines orange.
Color the adenines green.
Color the guanines purple.
Color the cytosines yellow.
Note that that the bases attach to the sides of the ladder at the sugars and not the phosphate.
The DNA helix is actually made of repeating units called nucleotides. Each nucleotide consists of three
molecules: a sugar (deoxyribose), a phosphate, which links the sugars together, and then one of the four bases.
Two of the bases are purines - adenine and guanine. The pyrimidines are thymine and cytosine. Note that the
pyrimidines are single ringed and the purines are double ringed. Color the nucleotides using the same colors as you
colored them in the double helix.
Nucleotides are made of a pentose ___________, a ____________, and a nitrogen-containing __________.
Name 2 bases with double C-N rings. ____________________
The two sides of the DNA ladder are held together loosely by hydrogen bonds. The DNA can actually
"unzip" when it needs to replicate - or make a copy of itself. DNA needs to copy itself when a cell divides, so that
the new cells each contain a copy of the DNA. Without these instructions, the new cells wouldn't have the correct
information. The hydrogen bonds are represented by small circles. Color the hydrogen bonds grey.
____________ bonds between bases must be broken to copy DNA.
Copying DNA to make two, identical DNA molecule is called ____________.
Messenger RNA
So, now, we know the nucleus controls the cell's activities through the chemical DNA, but how? It is the
sequence of bases that determine which protein is to be made. The sequence is like a code that we can now
interpret. The sequence determines which proteins are made and the proteins determine which activities will be
performed. This is how the nucleus is the control center of the cell. The only problem is that the DNA is too big
to go through the nuclear pores so a chemical is used to read the DNA in the nucleus. That chemical is messenger
RNA (mRNA). The messenger RNA (mRNA) is small enough to go through the nuclear pores. It takes the
"message" of the DNA to the ribosomes and "tells them" what proteins are to be made. Recall that proteins are
the body's building blocks. Imagine that the code taken to the ribosomes is telling the ribosome what is needed like a recipe.
Messenger RNA is similar to DNA, except that it is a single strand, and it has NO thymine. Instead of
thymine, mRNA contains the base Uracil. In addition to that difference, mRNA has the sugar ribose instead of
deoxyribose. RNA stands for Ribonucleic Acid. Color the mRNA as you did the DNA, except Color the ribose a
DARKER BLUE, and the uracil brown.
mRNA has a ____________ strand of nucleotides.
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G1 Retesting Assignment
__________ replaces __________ on RNA.
_________ is the pentose sugar on RNA.
__________, not DNA can leave the nucleus through ________ in the nuclear envelope.
Proteins are made at the _____________.
The Blueprint of Life
Every cell in your body has the same "blueprint" or the same DNA. Like the blueprints of a house tell the
builders how to construct a house, the cellular DNA "blueprint" tells the cell how to build the organism. Yet, how
can a heart be so different from a brain if all the cells contain the same instructions? Although much work
remains in genetics, it has become apparent that a cell has the ability to turn off most genes and only work with
the genes necessary to do a job. We also know that a lot of DNA apparently is nonsense and codes for nothing.
These regions of DNA that do not code for proteins are called "introns," or sometimes "junk DNA.” The sections
of DNA that do actually code for proteins are called "exons."
__________ are non-coding segments of DNA.
Questions:
1. Write out the full name for DNA.
2. What is a gene?
3. Where in the cell are chromosomes located
4. DNA can be found in what organelles in the cell?
5. What two scientists established the structure of DNA?
6. What is the shape of DNA?
7. The sides of the DNA ladder are composed of what?
8. The "rungs" of the DNA ladder are made of what?
9. What sugar is found in DNA? In RNA?
10. How do the bases bond together?
A bonds with _____
G bonds with _______
11. The two purines in DNA are_____________ and ___________.
12. DNA is made of repeating units called _______________.
13. Why is RNA necessary to act as a messenger? Why can't the code be taken directly from the DNA?
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G1 Retesting Assignment
14. Proteins are made where in the cell?
15. How do some cells become brain cells and others become skin cells, when the DNA in ALL the cells is exactly
the same?
16. Why is the DNA molecule referred to as the "blueprint of life"?
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G1 Retesting Assignment
DNA Molecule
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G1 Retesting Assignment
DNA and Genes
1. What are genes and what do they code for?
2. Proteins are made of chains of _______________.
3. How do cells use proteins?
4. The subunits making up polypeptides are called _________________.
5. How many amino acids exist?
6. Sketch and label the basic structure of an amino acid.
7. The group that makes amino acids different from each other & gives the amino acid its unique properties is
called the ___________ group.
8. DNA is found in the ____________ of a cell and begins the process of making a _______________.
9. Where are proteins made?
10. Describe the two types of ribosomes.
11. The first step in making a protein is to make a copy of ___________ in the nucleus.
RNA
12. What nucleic acid contains the master code for making proteins?
13. What nucleic acids acts as a blueprint in copying the master code?
14. Compare and contrast the sugars on DNA and RNA.
15. Compare and contrast the nitrogen bases on DNA and RNA.
16. RNA is made of a ____________ strand, while DNA is a ___________ stranded molecule.
17. What base replaces thymine on RNA?
18. Name the 3 types of RNA molecules.
19. What is the function of mRNA?
20. What is the function of rRNA?
21. What is the function of tRNA?
22. Describe the shape of mRNA.
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G1 Retesting Assignment
23. How does mRNA get out of the nucleus once it has copied DNA's instructions?
24. What bases pair together on RNA?
25. How long is mRNA?
26. What is a codon?
27. Methionine is called the __________ codon & is represented by the bases ________.
28. Name the 3 stop codons.
29. How long in rRNA?
30. What is the shape of rRNA?
31. What two things make up ribosomes?
32. What process occurs at the ribosomes?
33. Each codon stands for an _______________.
34. Can amino acids have more than one codon?
35. There are ______ amino acids and ______ possible codons.
36. How do you read the circular genetic codon table?
37. Use the genetic codon table and name these amino acids:
GGG?
UCA?
CAU?
GCA?
AAA?
38. Name the complementary bases on DNA.
39. Name the complementary bases on RNA.
40. What is the shape of tRNA?
41. What can attach to one end of a tRNA molecule for transport?
42. Opposite the attachment site on tRNA are 3 nucleotide bases called the ______________.
43. Make a sketch of a tRNA molecule with its attachment site and anticodon labeled.
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G1 Retesting Assignment
44. A codon on mRNA is complementary to an _____________ on tRNA.
45. What anticodon is complementary to the codon - ACU?
Transcription and Translation
46. Sketch the pathway to making a protein.
47. define protein synthesis.
48. Name the 2 phases of protein synthesis.
49. Before mRNA can leave the nucleus it must be _______________ in order to correctly make proteins.
50. Define transcription and tell where it occurs.
51. What RNA copies DNA?
52. Are both strands of DNA copied?
53. What enzyme is required to copy DNA?
54. The DNA strand that is copied is called the _____________ strand.
55. What would be the complementary RNA sequence for the DNA sequence- 5'- GCGTATG-3'?
56. What enzyme separates the DNA strands in transcription?
57. RNA polymerase adds complementary ____________ to the DNA template strand.
58. ___________ are regions on DNA where RNA polymerase binds to start transcription.
59. The promoter contains a sequence called the _________ box.
60. Other sequences on DNA called __________ signals tell the RNA polymerase when to stop transcribing.
61. Newly made mRNA must be _________ to make the nucleic acid functional.
62. What are introns & what happens to them during mRNA processing?
63. What are exons and what happens to them during mRNA processing?
64. Describe the cap that is added to the new mRNA transcript.
65. What type of tail is added to the mRNA transcript?
66. The new mRNA transcripts is made of _____________ with a 5' _________ and a 3' ____________ tail.
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G1 Retesting Assignment
67. What happens next to the newly made mRNA?
68. Define translation & tell where it occurs?
69. How do ribosomes read mRNA?
70. Describe the structure of a ribosome.
71. Ribosomes are composed of ________ rRNA and ________ protein.
72. Ribosomes have 2 tRNA sites called _______ and ______ along with an exit site.
73. The first part of translation is called ____________.
74. The small ribosomal subunit attaches to what codon on mRNA?
75. Once the mRNA and small subunit attach, what happens next?
76. Sketch an label a ribosome with both its subunits, its 2 tRNA sites, and the attached mRNA transcript.
77. The ______________ moves along the mRNA strand ________ codon at a time.
78. How many tRNA's will fit into a ribosome at one time?
79. What happens to the two amino acids carried by the 2 tRNA's inside a ribosome?
80. The joining of amino acids by ___________ bonds is the second part of translation called ______________.
81. Once an amino acid is joined to the growing polypeptide chain, the tRNA leaves the _______________ to pick
up another ________________.
82. When a tRNA leaves the ribosome, the ribosome moves down the _________ strand allowing another
________ and its amino acid to enter.
83. each time the ribosome moves, it moves over _________ codon.
84. The last stage of translation is called _______________.
85. Name the 3 termination codons.
86. The sequence of amino acids in the polypeptide chain is called the ____________ protein structure.
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