Name: ______Period: ______
DNA/RNA structure and DNA replication
1. What type of macromolecule is DNA? A NUCLEIC ACID
2. Why is the DNA molecule known as the molecule of inheritance?
BECAUSE IT CONTAINS THE GENETIC CODE OF A SPECIES, WHICH IS TRANSFERRED TO FUTURE GENERATIONS OF INDIVIDUALS THROUGH CELL DIVISION (MITOSIS AND MEIOSIS)
3. What does D.N.A. mean? DEOXYRIBONUCLEIC ACID
4. What are genes? SEQUENCES IN THE DNA THAT CODE (CONTAIN THE INFORMATION) FOR THE SYNTHESIS OF A PROTEIN
5. What are the subunits of DNA called? NUCLEIC ACIDS
6. What are the subunits of DNA composed of?
A 5-CARBON SUGAR (RIBOSE), A PHOSPHATE GROUP, AND A NITROGEN BASE (A, T, G OR C)
7. Draw this subunit and label all 3 parts.
8. What part of a nucleotide makes up the handrails (sides) of DNA? THE SUGAR/PHOSPHATE GROUP
9. What part of a nucleotide makes up the rungs of the DNA structure? THE COMPLEMENTARY BASE PAIRS A-T, G-C
10. What are the four nitrogen bases in DNA? A, T, G, C
11. What nitrogen base is present in DNA but is not present in RNA? What nitrogen base is used in RNA instead? THYMINE (T) IS PRESENT IN DNA BUT NOT IN RNA. RNA CONTAINS URACIL (U) INSTEAD OF THYMINE (T)
12. Describe the double helix. What kind of chemical bond is formed between the bases? THE DOUBLE HELIX IS LIKE A SPIRAL STAIRCASE: THE RAILS REPRESENT THE OUTER SUGAR/PHOSPHATE BACKBONE, AND THE BASE PAIRS (A-T, G-C), REPRESENT THE “RUNGS” OF THE LADDER. BETWEEN ADENINE (A) AND THYMINE (T) THERE ARE 2 HYDROGEN BONDS, AND BETWEEN GUANINE (G) AND CYTOSINE (C), THERE ARE 3 HYDROGEN BONDS.
13. Give the “complementary base pairs” of the DNA molecule that make up the “base pairing rule”.
A-T, G-C
14. What are the complementary base pairs of RNA? A-U, G-C
15. Describe 3 differences between the nucleic acids DNA and RNA.
DNA / RNASUGAR / DEOXYRIBOSE / RIBOSE
BASES / A, T, G, C / A, U, G, C
BASE PAIRS / A-T, G-C / A-U, G-C
NO. OF STRANDS / TWO STRANDS / ONE STRAND
SIZE / LARGE / SMALL
True or False:
16. F The order of the phosphate group is what makes two DNA molecules different. BASE
17. T The bases of all DNA molecules are the same no matter the species.
18. F The DNA molecule always leaves the nucleus. DNA NEVER LEAVES THE NUCLEUS
19. During what phase of the cell cycle does DNA replication occur? DURING THE SPHASE OF INTERPHASE.
20. How do base-pairing rules make DNA replication possible?
IT ALLOWS FOR THE DNA TO MAKE EXACT COPIES OF ITSELF; THE ORIGINAL STRAND IN REPLICATION SERVES AS A PATERN FOR THE NEW STRAND TO BE MADE.
21. Why is DNA replication “semi conservative”? SEMI CONSERVATIVE: OF THE TWO NEW DNA MOLECULES PRODUCED AT THE END OF DNA REPLICATION, EACH CONTAINS ONE ORIGINAL STRAND, AND ONE NEW STRAND (MADE OF FREE NUCLEOTIDES ADDED IN BY POLYMERASE)
22. Why does the DNA need to replicate? TO MAKE COPIES OF ITSELF; EACH COPY WILL BE PLACED IN A DIFFERENT DAUGHTER CELL AT THE END OF MITOSIS OR MEIOSIS.
23. Which enzyme opens the DNA double strand in the beginning of replication? How does it open the DNA strand?
HELICASE UNZIPS DNA BY BREAKING THE HYDROGEN BONDS BETWEEN THE COMPLEMENTARY BASE PAIRS.
24. In what direction is the new DNA strand synthesized by polymerase? IN THE 5’ TO 3’ DIRECTION
25. DNA polymerase can’t attach new nucleotides to a free 3’ end of DNA by itself. Which enzyme attaches RNA (the primer) to the DNA so polymerase can attach, and start adding DNA nucleotides?
RNA POLYMERASE ATTACHES A PRIMER TO THE DNA SO POLYMERASE CAN ATTACH AND START ADDING NEW DNA NUCLEOTIDES
26. Describe:
Leading Strand: DNA STRAND CONTIUOUSLY MADE IN THE 3’ END OF THE ORIGINAL DNA.
Lagging Strand: DNA STRAND MADE DISCONTINUOUSLY IN THE 3’ END OF THE ORIGINAL DNA BUT CLOSER TO THE REPLICATION FORK. CONTAINS OKAZAKI FRAGMENTS THAT WILL THEN BE CONNECTED BY LIGASE.
Okazaki fragments: FRAMENTS OF DNA IN THE LAGGING STRAND OF DNA.
27. What is the function of:
a. Helicase: TO UNZIP THE DNA STRAND AND EXPOSE BASES ON EITHER SIDE
b. RNA primase: TO ADD RNA PRIMER TO 3’ END OF ORIGINAL DNA
c. Polymerase: ATTACHES TO PRIMER AND ADDS FREE NUCLEOTIDES TO 3’ END OF ORIGINAL DNA TO BUILD LEADING AND LAGGING STRANDS
28. How many DNA strands (handrails!) does replication produce?
2 NEW STRANDS
29. Directions: Below are five (3) different DNA sequences:
· In the original DNA row of each table, rewrite the sequence in the form of three (3) bases per box.
This will help you for when you move on to the steps to Protein Synthesis on the next assignment.
DNA sequence #1: ACCGTAGGTCGAAAT
Original DNA / ACC / GTA / GGT / CGA / AATNew Copy of DNA / TGG / CAT / CCA / GCT / TTA
DNA sequence #2: TACCGAGCTAGCTAT
Original DNA / TAC / CGA / GCT / AGC / TATNew Copy of DNA / ATG / GCT / CGA / TCG / ATA
DNA sequence #3: CTCATTTGACTAACC
Original DNA / GAG / ATT / TGA / CTA / ACCNew Copy of DNA / CTC / CAA / ACT / GAT / TGG
30. Identify the structure marked with an “x”: NUCLEOTIDE (CONTAINS A PHOSPHATE GROUP, A SUGAR RIBOSE, AND A NITROGEN BASE)