Download My DNA RNA and Protein Notes

Name: ____________________________________________ Date: ___________________________ Period: _____
Unit 6 Notes, Part A: DNA, RNA, and Proteins (Chapter 16)
Ms. Ottolini, AP Biology, 2012-2013
Nucleic Acids (DNA and RNA): “Information molecules”
1. Parts of a Nucleotide (phosphate group, pentose
sugar, and nitrogenous base)
2. Nucleotides link together in two strands to form a
______________________
3. Chargaff’s Rules: A bonds with T and G bonds with C ;
a _________ (2 rings) always binds to a __________
(1 ring)
Comparison between DNA and RNA
Ribonucleic Acid (RNA)
• Single stranded
• Sugar = ribose
• Nitrogenous bases
= A, U, G, C (NO T)
• Can fold up in 3D
shape
Beginning Replication (DNA  DNA)
4. Site on the DNA where it starts = Origin of Replication
Place where nucleotides add = ___________________
5. Prokaryotes- single starting spot
Eukaryotes-multiple sites
Deoxyribonucleic Acid (DNA)
• Double stranded
• Sugar = deoxyribose
• Nitrogenous bases =
A, T, G, C (NO U)
• Strands run in
opposite directions
(________________)
• Ladder twists into a
double helix
• Backbone = sugars
and phosphates
• Rungs of ladder =
nitrogenous bases
• ________________
between nitrogenous
bases hold sides of
ladder together
Notes
The Steps of DNA Replication
6. The most important enzyme in DNA replication is DNA polymerase
7. The main job of DNA polymerase is to read one strand of DNA and add
complementary nucleotides to make a copy of this template strand. It reads the template
strand in the 3’ → 5’ direction. It builds a new strand in the 5’→3’ direction (adds onto 3’
end of sugar in previous nucleotide)
The Enzymes Involved in DNA Replication
8. _______________- untwists double helix to open strands at replication forks
9. _______________- relieves strain caused by untwisting
10. ___________________________- stabilize unpaired strands to hold them open
11. ______________- starts segment by adding RNA primer sequence (because DNA
polymerase cannot start the chain by itself…it can only add nucleotides to the 3’ end of
an existing DNA or RNA chain)
12. _______________- removes RNA primers and replaces them with DNA bases by
adding to the 3’ end of the previous fragment
13. _______________- joins Okazaki fragments together to make a continuous copied
strand
Differences in Replication using Different Template Strands
14. The leading strand runs (3’  5’), so a new strand can be built from this template
strand (5’  3’) heading into the replication fork… Primase adds an RNA_________ to
start the chain and DNA polymerase adds nucleotides in the 5’  3’ direction
15. The lagging strand runs (5’  3’), so a new strand built from this template strand
must copy (5’  3’) heading out of the replication fork… Primase adds RNA primers at
various spots as the fork opens and DNA polymerase adds nucleotides in 5’  3’
direction, which creates short segments called _____________ fragments… Ligase
connects Okazaki fragments together
16. Important: because DNA polymerase can’t fill in last section when primer is removed
from lagging strand, the code shortens with each replication
17. _______________ sequences at ends of chromosomes prevent erosion of essential
information in code with each replication…contain repeats of useless nucleotide
sequences
18. Telomerase = enzyme that lengthens telomeres ; found in eukaryotic germ cells that
divide frequently to produce gametes ; misfunction of this enzyme may play a role in
aging and cancer
Final Product of Replication
18. Two full double helices
19. Replication is _________________________…
meaning one strand serves as a template for a new
complementary strand  each double helix has one
old strand and one new strand
20. The other two possible models (now known to
be incorrect) are conservative replication and
dispersive replication (see right)
Proofreading and Repair
21. Mistakes in final DNA after replication: 1 in 10 billion
22. Mistakes in initial base pairing during replication 1 in 100,000
23. _____________________ proofreads each base as it’s added
& fixes errors
24. Errors can come from “proofreading mistakes” that are not
caught OR environmental damage (ex: X-rays, UV light, chemical
mutagens/carcinogens)
Nucleotide Excision Repair
25. Cells continually monitor DNA and make repairs that
proofreading does not catch
26. ________________- DNA cutting enzymes that remove errors
27. DNA polymerase fills in gap using complimentary strand
28. Ligase seals ends
29. Example error = ____________________ ; when two thymine
nucleotides are right next to each other in the same strand ;
caused by damage due to UV light ; can be repaired using excision
repair
30. Example disorder involving repair enzymes = xeroderma
pigmentosum (genetic disorder ; mutation in DNA enzymes that
repair DNA  increased skin cancer and cataract risk)