BIOB111 - Tutorial activity for Session 13

Transcription

1 BIOB111 - Tutorial activity for Session 13 General topics for week 7 Session 13: Types of nucleic acids, DNA replication Useful links: 1. Visit this website and use its menu to locate information and practice questions: (link verified 1 st February 2017) 2. Visit this website and click play to see DNA replication, Okazaki fragments and other excellent animations: (link verified 1 st February 2017) 3. Performing a cheek swab to extract DNA from human cells (virtual lab): (link verified 1 st February 2017) 4. Use the following link to learn the procedure for extracting the DNA from frozen green peas or a banana: General tutorial questions: 1. Discuss and define each of the following: a) Nitrogen bases: purines and pyrimidines Which category do adenine, thymine, guanine, cytosine and uracil fit into? b) Nucleoside c) Nucleotide Last updated on 23-Feb-18 Page 1 of 10

2 d) Genetic code 2. Select the components that are present in the different nucelic acids: DNA contains a) Ribose b) Deoxyribose c) Phosphate d) Adenine e) Guanine f) Thymine g) Cytosine h) Uracil RNA contains a) Ribose b) Deoxyribose c) Phosphate d) Adenine e) Guanine f) Thymine g) Cytosine h) Uracil Last updated on 23-Feb-18 Page 2 of 10

3 3. Matching: 1.DNA 2. Messenger RNA 3. Codon 4. trna 5. Mutation 6. Ribosomal RNA 7. Gene 8. Translation 9. Transcription a) Deoxyribonucleic acid; the genetic material that carries information about an organism that is passed from parent to offspring AND is used by an individual as the recipe for making proteins b) A alteration in a cell's genetic material c) RNA that copies the coded message from DNA in the nucleus and carries the message into the cytosol d) Protein synthesising machinery that forms the ribosome e) Sequence of three bases that codes for a specific amino acid f) Carries a specific amino acid and deposits to the ribosome during protein synthesis g) Segments of DNA that contains the information to make a specific protein h) Process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA i) Decoding of a mrna message to create a chain of amino acids (protein) 4. In DNA, guanine pairs with: a) Thymine b) Adenine c) Cytosine d) Guanine 5. The sugar present in each nucleotide of a DNA strand is: a) Ribose b) Fucose c) Arabinose d) Deoxyribose 6. The backbone of nucleic acids consists of: Last updated on 23-Feb-18 Page 3 of 10

4 a) The nitrogen containing bases b) The phosphate and sugar components in each of the nucleotides c) The sugar component of the nucleotide d) The phosphate component of the nucleotide 7. Which of the following statements concerning the double helix structure present in DNA molecules is correct? a) The two DNA strands are identical to each other b) Hydrogen bonds between sugar units hold the two DNA strands together c) Hydrogen bonds between the nitrogen containing bases hold the DNA strands together, with the bonds forming between one pyrimidine base and one purine base d) The base pairing combinations are always A-G and C-T 8. In DNA replication the unwinding of the double helix: a) Only occurs at the 5 end of the DNA double helix b) Only occurs at the 3 end of the DNA double helix c) Occurs at multiple points within the DNA helix at the same time d) Requires DNA ligase 9. A three-nucleotide sequence on a messenger RNA that codes for a single amino acid: a) Operon b) Codon c) Intron d) Exon 10. The process of copying a gene's DNA sequence onto a sequence an mrna is called: a) Replication b) Transcription c) Translation d) Transposition 11. When a DNA strand with the sequence AACGTAACG is transcribed, what is the sequence of the synthesised mrna? a) AACGTAACG Last updated on 23-Feb-18 Page 4 of 10

5 b) UUGCAUUGC c) AACGUAACG d) TTGCATTGC 12. All of the following are directly involved in translation EXCEPT: a) mrna b) trna c) ribosomes d) DNA 13. Modification of a DNA sequence within a gene is called a: a) Intron b) Replication c) Mutation d) Anticodon Conceptual multiple choice questions: 14. Concept: Primary structure of DNA Context: Each nucleotide unit within DNA contains a deoxyribose sugar connected to both a phosphate & a nitrogen containing base. A single strand of DNA is composed of many nucleotides units, which are connected via chemical bonds. When two DNA strands come together the interactions between nitrogen containing bases (on separate strands) induce a helical coil, where the DNA strands resemble a spiral stair-case like structure. Question: Which of the following accurately describes the primary structure of DNA? a) Primary structure is the sequence of nucleotides within a single strand of DNA b) Primary structure is the sequence of deoxyribose sugars within a single strand of DNA c) Primary structure consists of the interactions between the nitrogen containing bases within two different DNA strands that results in a helical coil d) Primary structure consists of the interactions between the nitrogen containing bases within a single DNA strand that results in a helical coil 15. Concept: Secondary structure of DNA Last updated on 23-Feb-18 Page 5 of 10

6 Context: Each nucleotide unit within DNA contains a deoxyribose sugar connected to both a phosphate & a nitrogen containing base. A single strand of DNA is composed of many nucleotides units, which are connected via chemical bonds. When two DNA strands come together the interactions between nitrogen containing bases (on separate strands) induce a helical coil, where the DNA strands resemble a spiral stair-case like structure. Question: Which of the following accurately describes the secondary structure of DNA? a) The secondary structure of DNA is the sequence of nitrogen containing bases within a single strand of DNA b) The secondary structure of DNA is the helical coil of the double stranded DNA helix that is made possible by the hydrogen bonds between the nitrogen bases on the separate strands of the helix c) The secondary structure of DNA is the sequence of nucleotides within a single strand of DNA d) The secondary structure of DNA is the helical coil of the double stranded DNA helix that is made possible by the covalent bonds between the ribose sugars on the separate strands of the helix 16. Concept: Interactions between two separate DNA strands to form a DNA helix Context: The two DNA strands within a double stranded DNA helix are connected via interactions between the nitrogen containing bases located on different DNA strands. Each interaction between the DNA strands relies on a complementary pairing between one purine and one pyrimidine base. Question: Which of the following accurately describes the interactions between the nitrogen containing bases that hold together a double stranded DNA helix? a) A small base (pyrimidine) from one DNA strand forms multiple hydrogen bonds with a large base (purine) from another DNA strand b) A large base (pyrimidine) from one DNA strand forms a single covalent bond with a small base (purine) from another DNA strand c) A large base (pyrimidine) from one DNA strand forms a single hydrogen bond with a small base (purine) from another DNA strand d) A small base (pyrimidine) from one DNA strand forms multiple covalent bonds with a large base (purine) from another DNA strand Last updated on 23-Feb-18 Page 6 of 10

7 17. Concept: Purpose of DNA replication Context: An organisms DNA contains all of the instructions necessary for its life. Each cell that contains a nucleus possesses its own DNA. Cells routinely undergo mitosis to produce two identical daughter cells from the parent cell. Question: Which of the following best describes the purpose of replicating DNA? a) Each cell requires at least half the organisms DNA in its nucleus to properly carry out its role and contribute to keeping the organism alive b) DNA replication is required only to allow the organism to grow larger by increasing the number of cells within the organism c) Each cell requires the entire complement of the organisms DNA in its nucleus to properly carry out its role and contribute to keeping the organism alive d) DNA replication is required only for regulation of cellular processes to ensure that the organism remains healthy 18. Concept: Result of DNA replication Context: To begin DNA replication the DNA helix is unwound using a helicase enzyme to exposure the nitrogen containing bases within both the leading and lagging DNA strands. Both the leading and lagging strands are used as templates during DNA replication process. Question: What is produced after one round of DNA replication? a) One double stranded helix that contains both of the original template strands & the other helix that contains both of the newly formed strands b) Two double stranded DNA helices, each containing one strand from the original DNA helix and a second newly formed strand c) The two new double stranded DNA helices may either contain both template, both new strands or one of each d) Two double stranded DNA helices, each containing two newly formed DNA strands, with the original templates discarded 19. Concept: Role of DNA in the cell Last updated on 23-Feb-18 Page 7 of 10

8 Context: Despite the similar structures of DNA and RNA, their roles in the cell are very different. The main difference between the nucleic acids, DNA and RNA, lies in the structure of the sugars within each of the nucleotides. DNA contains the deoxyribose sugar, whereas RNA contains the ribose sugar. Question: What is the major role of DNA in the cell? a) DNA contains long stretches of nucleotides but no genes, and it must be replicated before the DNA can be used to create a specific protein b) There are three types of DNA with each playing an important role in the process of converting a nucleotide sequence into a specific protein c) There are two types of DNA, with one used in transcription and one used in translation to generate specific proteins d) Specific regions within DNA called genes are used as the genetic instructions to create specific proteins that have specific functions 20. Concept: Role of RNA in the cell Context: Despite the similar structures of DNA and RNA, their roles in the cell are very different. The main difference between the nucleic acids, DNA and RNA, lies in the structure of the sugars within each of the nucleotides. DNA contains the deoxyribose sugar, whereas RNA contains the ribose sugar. Question: What is the major role of RNA in the cell? a) RNA contains long stretches of nucleotides but no genes, and it must be split in half before the RNA can be used to create a specific protein b) There are three types of RNA with each playing an important role in the process of converting a nucleotide sequence into a specific protein c) There are two types of RNA, with one used in transcription and one used in translation to generate specific proteins d) Specific regions within RNA called genes are used as the genetic instructions to create specific proteins that have specific functions 21. Concept: Role of the mrna in the cytosol Context: In order to create a specific protein, the first step is for a specific region of DNA called a gene to be copied (transcribed) onto a messenger RNA (mrna). The Last updated on 23-Feb-18 Page 8 of 10

9 transcription of the mrna occurs in the nucleus, but the mrna moves out of the nucleus after it has been transcribed. Question: Why is it essential that the mrna transcript moves out of the nucleus into the cytosol? a) After transcription of the mrna, the mrna must move out into the cytosol where it can be broken down and recycled b) After transcription of the mrna, the mrna must move into the mitochondria (via the cytosol), where the mrna is required for translation of a specific protein c) After transcription of the mrna, the mrna must move out into the cytosol so that more copies of the mrna can be made in preparation for transcription where a specific protein is created d) After transcription of the mrna, the mrna must move into the cytosol where the nucleotide code on the mrna is used to create a specific protein through translation 22. Concept: Genetic code Context: The genetic code explains which combinations of nucleotides code for specific amino acids. Each set of three nucleotides, called codons, in DNA and mrna code for a specific amino acid. For example, AUG in mrna specifies that a methionine will be added to the amino acid chain (protein) during translation. Question: What does the genetic code reveal about a gene (part of the DNA) with a known nucleotide sequence? a) The genetic code specifies how many nucleotides are present in a particular gene b) The genetic code specifies which amino acids are used to build a specific protein based on the unique sequence of nucleotides within a gene c) The genetic code specifies how often the gene will be used to create a protein d) The genetic code specifies the nucleotide sequence of the mrna created from the nucleotide sequence of the gene 23. Concept: DNA mutations Context: A DNA strand contains a huge number of nucleotides. For example, a short region of a DNA strand may have the base sequence GACGGTAATAG. Problems can Last updated on 23-Feb-18 Page 9 of 10

10 arise when mutations occur, which change one type of nucleotide to another. For example, a mutation may cause an adenine to be replaced by a thymine. Question: What would happen if a DNA mutation caused a large change to the structure of the protein created from the DNA? a) Large structural changes to proteins usually enhance the function of the protein, making the protein more efficient b) Large structural changes to proteins do not affect their function c) Large structural changes will be tolerated by some proteins but not others, so the protein may either lose or retain its function d) Large structural changes to proteins usually cause the protein to become non-functional, as is seen in many genetic disorders Last updated on 23-Feb-18 Page 10 of 10