SBI4U - Molecular Genetics Exam Questions with
Correct Answers
1. Double Helix correct answers: two strands of nucleotides wound about each other; structure of
DNA
2. Deoxyribose sugar correct answers: sugar used in DNA to make up the "backbone"
3. Nitrogenous base correct answers: An organic base that contains nitrogen, a subunit of a
nucleotide in DNA and RNA
4. Purine correct answers: double-ring nitrogenous base; adenine and guanine
5. Pyrimidines correct answers: Cytosine and Thymine/uracil, single ring
6. phosphate group correct answers: Component of DNA and RNA backbone along with 5-C
sugar
7. Nucleotide correct answers: monomer of nucleic acids made up of a 5-carbon sugar, a
phosphate group, and a nitrogenous base
8. Glycosyl Bond correct answers: nitrogenous base is attached to 1' carbon
9. phosphodiester bond correct answers: a bond that is responsible for the polymerization of
nucleic acids by linking sugars and phosphates of adjacent nucleotides
10. 3' end of DNA correct answers: Unbound OH on the 3' carbon of deoxyribose
11. 5' end of DNA correct answers: Unbound OH on the 5' carbon of deoxyribose
12. 4 bases of DNA correct answers: Adenine, Thymine, Cytosine, Guanine
13. 4 bases of RNA correct answers: Adenine, Uracil, Cytosine, Guanine
14. Histones correct answers: 8 protein molecules around which DNA is tightly coiled in
chromatin. Positively charged _> more tightly bonded to DNA.
15. Nucleosomes correct answers: DNA coiled around histones
16. Supercoiling correct answers: Extremely tight coiling of nucleosomes. (First coiling =
double helix structure. Second = Nucleosomes. 3rd= Supercoiling. 4 = Supercoil into
chromatid.)
17. Distance between base pairs correct answers: 0.34 nm
18. Distance between double helix twists correct answers: 3.4 nm (10
bases/twist)
19. initiation of transcription correct answers: Attachment of RNA polymerase to
the promoter. Unwinds the DNA and breaks the H bonds between strands. RNA polymerase
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, binds to the template (3'-5') strand of DNA.
20. elongation (transcription) correct answers: RNA polymerase reads 3'-5', starts
mRNA synth when it finds beginning of the gene. mRNA is synthesized w/ uracil in 5'-3' direction
forming phosphodiester bonds.
21. template strand correct answers: The DNA strand that provides the template for
ordering the sequence of nucleotides in an mRNA transcript. 3'-5'.
22. coding strand correct answers: the strand of DNA that is not used for transcription
and is identical in sequence to mRNA, except it contains uracil instead of thymine. Genetic code
version. 5'-3'.
23. termination of transcription correct answers: rna polymerase finds terminator
sequence in template dna. single strand of mrna and rna poly released. dna h bonds reform,
dna recoils
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Correct Answers
1. Double Helix correct answers: two strands of nucleotides wound about each other; structure of
DNA
2. Deoxyribose sugar correct answers: sugar used in DNA to make up the "backbone"
3. Nitrogenous base correct answers: An organic base that contains nitrogen, a subunit of a
nucleotide in DNA and RNA
4. Purine correct answers: double-ring nitrogenous base; adenine and guanine
5. Pyrimidines correct answers: Cytosine and Thymine/uracil, single ring
6. phosphate group correct answers: Component of DNA and RNA backbone along with 5-C
sugar
7. Nucleotide correct answers: monomer of nucleic acids made up of a 5-carbon sugar, a
phosphate group, and a nitrogenous base
8. Glycosyl Bond correct answers: nitrogenous base is attached to 1' carbon
9. phosphodiester bond correct answers: a bond that is responsible for the polymerization of
nucleic acids by linking sugars and phosphates of adjacent nucleotides
10. 3' end of DNA correct answers: Unbound OH on the 3' carbon of deoxyribose
11. 5' end of DNA correct answers: Unbound OH on the 5' carbon of deoxyribose
12. 4 bases of DNA correct answers: Adenine, Thymine, Cytosine, Guanine
13. 4 bases of RNA correct answers: Adenine, Uracil, Cytosine, Guanine
14. Histones correct answers: 8 protein molecules around which DNA is tightly coiled in
chromatin. Positively charged _> more tightly bonded to DNA.
15. Nucleosomes correct answers: DNA coiled around histones
16. Supercoiling correct answers: Extremely tight coiling of nucleosomes. (First coiling =
double helix structure. Second = Nucleosomes. 3rd= Supercoiling. 4 = Supercoil into
chromatid.)
17. Distance between base pairs correct answers: 0.34 nm
18. Distance between double helix twists correct answers: 3.4 nm (10
bases/twist)
19. initiation of transcription correct answers: Attachment of RNA polymerase to
the promoter. Unwinds the DNA and breaks the H bonds between strands. RNA polymerase
1/
13
, binds to the template (3'-5') strand of DNA.
20. elongation (transcription) correct answers: RNA polymerase reads 3'-5', starts
mRNA synth when it finds beginning of the gene. mRNA is synthesized w/ uracil in 5'-3' direction
forming phosphodiester bonds.
21. template strand correct answers: The DNA strand that provides the template for
ordering the sequence of nucleotides in an mRNA transcript. 3'-5'.
22. coding strand correct answers: the strand of DNA that is not used for transcription
and is identical in sequence to mRNA, except it contains uracil instead of thymine. Genetic code
version. 5'-3'.
23. termination of transcription correct answers: rna polymerase finds terminator
sequence in template dna. single strand of mrna and rna poly released. dna h bonds reform,
dna recoils
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