“DNA is the code of instructions for cells” Name: _______________________ Date: _________________ Period: __________ DNA & Gene Expression Review/Study Guide DNA Structure Name the following structures. Phosphate Nitrogen base 1. Deoxyribose (sugar) 2. 3. 4. Nucleotide 5. If the above structure is part of DNA, then what is the specific name for part #2? Deoxyribose 6. If the above structure is part of RNA, then what is the specific name for part #2? Ribose 7. When part #3 is abbreviated A, it stands for __Adenine__. 8. When part #3 is abbreviated T, it stands for __Thymine______. 9. When part #3 is abbreviated C, it stands for __Cytosine__. 10. When part #3 is abbreviated G, it stands for ___Guanine___. 11. When part #3 is abbreviated U, it stands for _Uracil______. 12. 13. 14. 15. What is the name of the DNA molecule’s shape? Double Helix What is one unit of DNA called? Nucleotide What are the parts of the nucleotide? Sugar, phosphate, nitrogen base What types of bonds hold together nitrogen bases? Hydrogen bonds 16. What is the base-pairing rule? A bonds with T and G bonds with C 17. What is a gene? A section of DNA that codes for a protein DNA DNA Replication 18. How does a DNA molecule unzip? Helicase unzips the molecule by breaking H bonds between nitrogen bases 19. What role does helicase play in DNA replication? Helicase unzips the molecule by breaking H bonds between nitrogen bases 20. What role does DNA polymerase play in DNA replication? DNA Polymerase builds the new half of DNA out of nucleotides during replication 21. How many copies of DNA are made during replication? One DNA is made into 2 DNA molecules, each one is ½ original and ½ newly built. This is referred to as semi- conservative. 22. What do the copied DNA molecules look like compared to the original? See above 23. What do leading strand and lagging strand have to do with DNA replication? What are Okazaki fragments and DNA ligase? After the DNA unzips, DNA polymerase builds a new half on each of the halves of DNA. The DNA polymerase can only build the new half in the 3’ to 5’ direction. Since the two halves of DNA are opposite each other, one side can be built quickly in one complete strand (called leading strand) as the DNA unzips but the other side (the lagging strand) has to be built in little fragments in the opposite direction (called Okazaki fragments) and those fragments are stitched together by ligase DNA vs. RNA 24. According to Chargraff, amount of A=T, amount of C=G. So if 20% of bases are A, 1. how much are T? 20% 2. how much are C? 30% 3. how much are G? 30% function DNA Code for how to make proteins RNA makes proteins # of strands 2 1 Sugar deoxyribose ribose bases A,T,G,C A,U,G,C mRNA rRNA tRNA stands for Messenger RNA Transfer RNA function Is a copy of DNA code for making protein original location Is built in nucleus DURING TRANSCRIPTION will move to ribosome Ribosomal RNA Reads mRNA codons and matches them with tRNA anticodon Is the ribosome (on rough ER or free floating in cytoplasm Stays in cytoplasm Brings the amino acid to ribosome Free floating in cytoplasm Goes to ribosome RNA strand Protein Synthesis 25. What is the relationship between genes and proteins? The gene is a code for how to make a protein 26. What are the building blocks of proteins? Amino acids 27. What type of molecules are helicase and RNA polymerase? They are a type of protein called enzymes 28. What does helicase do? It breaks H bonds between nitrogen bases to unzip DNA 29. What does RNA polymerase do? Builds mRNA using DNA as template during transcription 30. What does tRNA do? Brings the amino acid to the ribosome where the tRNA anticodon is matched to the mRNA codon 31. What type of bond holds amino acids together? peptide 32. Where does protein synthesis take place in a cell? Transcription takes place in the nucleus and translation takes place in the cytoplasm 33. What is a codon? An anticodon? Codon is a sequence of three nitrogen bases in mRNA, an anticodon is a sequence of three nitrogen bases in tRNA that match up to the anticodon to deliver the correct amino acid 34. Describe Protein synthesis (transcription and translation. )Be able to transcribe DNA into mRNA and translate mRNA into amino acids. TRANSCRIPTION 1. The DNA code is copied by building an mRNA using the DNA as a template. 2. The mRNA then leaves the nucleus (leaving the DNA protected in the nucleus) TRANSLATION 3. The mRNA goes to the ribosome (rRNA) where the codons (on the mRNA) are matched with anticodons of tRNA 4. Amino acids attached to tRNA are linked together using peptide bonds and forming a chain of amino acids Amino acid chain is folded into a protein 35. Place the following words in order of size from largest to smallest: Chromosome, Cell, Nucleotide, DNA Molecule, Nucleus Cell, nucleus, chromosome, DNA, nucleotide MUTATIONS 36. List and define 3 types of mutations. Substitution- one nucleotide in the DNA is reoplaced with another (example: A replaced by G) Insertion: An extra nucleotide is inserted into a DNA strand Deletion: A nucleotide is deleted from a DNA strand Examples: Original DNA sequence: ATTGGCA Substitution: GTTGGCA Insertion AATTGGCA Deletion: ATGGCA 37. Which type(s) can cause the most damage and why? Indertion and deletion both cause a frameshift mutation which changes the amino acid sequence from the mutation on 38. Many amino acids have more than one codon. For example if a section of DNA mutates from GAA to GAC the corresponding mRNA codon will change from CUU to CUG and if you look those up on the mRNA codon chart, they both code for Leucine so it doesn’t change the protein at all. 39. GULO gene: A deletion occurred in the DNA of the third protein (GULO) needed to syntheisze vitamin C in the ancestor of most primates, so primates decended from this common ancestor inherited this mutated GULO gene, including humans The deletion caused a frameshift mutation in the DNA sequence, changing the amino acid chain and causing a premature stop codon. This exact same mutation of the same single nitrogen base (out of over 1300 possible bases that could have mutated) to make this disfunctional gene is present in all primates decended from this ancestor, showing the mutation must have been inherited by primates from a common ancestor rather than happening independently in each species. PSEUDOGENE: A DNA sequence that resembles a gene but has been mutated into an inactive form over the course of evolution. Though genetically similar to the original functional gene, pseudogenes do not result in functional proteins, although some may have regulatory effects.
