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Unit 5: DNA – Study Guide
Name__________________________________ Hr. __________
3.3.B.a Describe the chemical and structural properties of DNA
-DNA is composed of linked nucleotides; each nucleotide is composed of a phosphate, a sugar and one of 4 nitrogen bases
(adenine, thymine, guanine and cytosine)
- DNA is double-stranded, in the shape of a double helix (phosphates and sugars make up the outside, nitrogen bases,
make up the rungs)
- A and T always pair up, C and G always pair up (held together by hydrogen bonds)
Practice:
1. Write the complementary strand to AGGTCACTA:
____________________________
2. Where is DNA stored in cells? ________________________________
3. Draw and label 2 joined nucleotides in the box below.
Label the phosphates, sugars, nitrogen bases and
hydrogen bonds:
3.3.B.d Explain how an error in the DNA molecule (mutation) can be transferred during replication
- Replication is the process of making a new copy of DNA
-Steps: 1. DNA unzips 2. The new bases pair up with the original strand 3. The new strand coils back up
- DNA polymerase (an enzyme) helps bind the correct nucleotides and finds and fixes errors, but it may not catch
everything
Practice:
4. What is the name of the process that creates a new strand of DNA? ______________________________________
5. In what part of the cell does replication occur? _________________________________
6. What enzyme helps the new bases pair up correctly? _____________________________
7. Why is DNA replication called “semiconservative”? ______________________________________________________
8. What is the first step of replication? ________________________________________
3.2.E.a Explain how the DNA code determines the sequence of amino acids necessary for protein synthesis
- Transcription is the process of copying the original strand of DNA to produce a complementary strand of RNA
- Three types of RNA: mRNA, rRNA, tRNA
- RNA does not contain thymine (T), it is replaced by uracil (U). A =U
- RNA is single stranded
G=C
Practice
9. Label the steps represented by each letter:
DNA------------(A)
DNA ------------(B)--------------RNA ---------------(C)----------------- Protein
(A)_______________________
(B)________________________
10. Replication creates more ___________. Transcription creates ____________
(C) _________________________
11. In the ‘T-Chart’ list three additional differences of DNA and RNA
DNA
-Permanent
Genetic Info.
RNA
-Temporary Genetic
Info.
3.3.B.b Recognize that DNA codes for proteins, which are expressed as the heritable characteristics of an organism
- Translation occurs inside of the ribosome
- Translation is the process that converts mRNA into a protein.
- Translation uses the codons on the mRNA to code for amino acids that create proteins.
Practice
12. In what organelle does transcription occur? _________________________________________
13. A codon is made up of ________________ nucleotides. Create ONE codon ______________
(number)
14. What amino acid does your CODON translate to? ______________________________
3.3.D.b Describe how genes can be altered and combined to create genetic variation within a species (e.g. mutation,
recombination of genes)
- A mutation is any change in an organism’s DNA sequence. May or may not affect the amino acid sequence.
- Two types of mutations: Point Mutation – effects one nucleotide or codon
Frameshift Mutation – effects more than one codon
-Occur during replication or from the environment (mutagens)
Practice
15. During what process do mutations occur? _________________________________________
16. Are all mutations bad? EXPLAIN! ____________________________________________________________________
_________________________________________________________________________________________________
17. Give an example of a mutagen. _____________________________________________________________________
18. What is the job of DNA polymerase during replication?___________________________________________________
__________________________________________________________________________________________________
19. Complete the chart below to compare the original and mutated DNA strand
Original Strand: A T G G G C C A T A T A C A A
DNA Template
Complimentary
Base
mRNA
Amino Acid
Mutated Strand: ADD an ‘A’ after the 6th base.
DNA Template
mRNA
Amino Acid
20. Is this a point mutation or frameshift mutation? _____________________________ EXPLAIN! __________________
__________________________________________________________________________________________________
21. How is the mutated strand different from the original? __________________________________________________
Mutated Strand: CHANGE the 9th base from a ‘T’ to a ‘C’.
DNA Template
mRNA
Amino Acid
22. Is this a point mutation or frameshift mutation? _____________________________ EXPLAIN! __________________
__________________________________________________________________________________________________
23. How is the mutated strand different from the original? __________________________________________________