Molecular Biology and Genetics Exam January 2023 PDF

## Molecular Biology and Genetics Exam January 2023 ### **Question 1** A mutation that occurs when a base is inserted into or deleted from a DNA sequence completely altering an entire amino acid sequence is called: * Frameshift Mutation ### **Question 2** DNA glycosylases are involved specificall...

## Molecular Biology and Genetics Exam January 2023 ### **Question 1** A mutation that occurs when a base is inserted into or deleted from a DNA sequence completely altering an entire amino acid sequence is called: * Frameshift Mutation ### **Question 2** DNA glycosylases are involved specifically with which of the following repair mechanisms? * Base excision repair ### **Question 3** When a mutation in a gene that alters a codon, but the resulting new codon translates for the same amino acid, it can be referred to as a: * silent mutation * synonymous mutation * single nucleotide polymorphism ### **Question 4** The post-replicative DNA repair pathway is also referred to as: * Mis-match repair pathway ### **Question 5** A mutation in the P53 gene increases the risk of developing cancer because: * The P53 protein is responsible for slowing down the cell cycle to allow time for DNA repair to take place. * Damaged cells cannot enter into programmed cell death. * P53 is a tumour suppressor gene. ### **Question 6** Which of the following statements regarding the function and characteristics of P53 protein are true? * It can activate apoptosis * It activates P21 protein * It carries out specific gene transcription * It forms a tetramer complex ### **Question 7** DNA damage caused by UV radiation usually results in: * Dimers forming between adjacent pyrimidines ### **Question 8** A 10-year-old Caucasian girl is brought in by her parents for evaluation of a skin disorder. The child has freckles on her face, arms, and legs. The parents were told that she suffers from Xeroderma pigmentosum and should limit her sun exposure. What is the most likely etiology of this disorder? * Impaired DNA repair by the nucleotide excision repair ### **Question 9** Okazaki fragments are joined together by: * DNA Ligase ### **Question 10** A base pair substitution is referred to as a transversion when? * A pyrimidine substitutes for a purine ### **Question 11** The protein P53 is important in preventing somatic mutations because: * It slows down the cell cycle which allows time for the repair systems to correct DNA damage. * It induces apoptosis. ### **Question 12** The phosphate group on the DNA nucleoside is located on which number carbon on the sugar residue? * 5 ### **Question 13** The various tautomeric forms of DNA bases can alter which type of bond in the DNA molecule? * Hydrogen ### **Question 14** Which of the following can increase the induced mutation rate in DNA? * Alterations to bases as a result of chemical exposure * Exposure to intense sunlight * Working as a biomedical scientist in a clinical laboratory ### **Question 15** DNA polymerase reads DNA in the 3 prime to 5 prime direction? * True ### **Question 16** How are the chromosomes of a eukaryote cell replicated? * The linear DNA molecules are replicated from multiple origins of replication bidirectionally. ### **Question 17** In this diagram of DNA replication, the segments labelled F are responsible for: * Forming the replication fork ### **Question 18** Enzymes called **topoisomerases** form breaks in the DNA molecules to prevent the formation of super-coiling(knots) in the DNA helix during replication. ### **Question 19** DNA gyrase (a topoisomerase) is an enzyme that **relieves stress upstream from the replication fork** ### **Question 20** The structures represented by the Letter E are called: * Okazaki fragments ### **Question 21** Nucleotides can be produced by the cell ... * From the breakdown products of earlier nucleic acids via salvage pathways * By synthetic pathways involving phosphate, pentose sugar, and nitrogen base ### **Question 22** Which enzyme is responsible for strand separation during the process of replication? * Helicase ### **Question 23** Why does DNA synthesis only proceed in the 5' to 3' direction? * Because DNA polymerases can only add nucleotides to the 3' end of a polynucleotide strand ### **Question 24** DNA replication in the human cell occurs: * On both strands but in opposite directions. ### **Question 25** The DNA replication fork: * Is a Y-shaped structure, where both DNA strands are replicated simultaneously. ### **Question 26** Which of the following enzymes are capable of adding new nucleotides to a growing DNA chain? * DNA polymerase * Taq polymerase ### **Question 27** Primase is the enzyme responsible for: * making short strands of RNA at the site of replication initiation ### **Question 28** Agarose gel electrophoresis resolution of DNA molecules is facilitated by the negative charge conferred by the presence of which chemical group? * Phosphate groups ### **Question 29** How is the chromosome of a bacterial cell replicated? * The circular DNA molecule is replicated from one origin of replication bidirectionally ### **Question 30** In replication, once the DNA strands have been separated, reformation of the double helix is prevented by: * Single-strand binding proteins ### **Question 31** The 5' end of each Okazaki fragment begins with: * a separate RNA primer ### **Question 32 ** Complete the following statement. There are **1 start codon and 3 stop codons** found in the human genetic code. ### **Question 33** A newly-formed protein's N-terminal amino acid is virtually always **methionine** as its codon is the used as the start codon by virtually all organisms. ### **Question 34** Ribosomes are composed of: * rRNA and protein ### **Question 35** The anticodon is a physical component of which molecule? * tRNA ### **Question 36** In the DNA sequence below: 5'GCG ATA AGC TGC GAA3' 3'CGC TAT TCG ACG CTT5' The lower strand can be referred to as the **template strand**. ### **Question 37** Protein synthesis begins at the "start codon" which normally coded for the amino acid **methionine**. ### **Question 38** Elongation factor, EF-Tu, uses the energy released from GTP Hydrolysis to catalyse: * The delivery of an aminoacyl-tRNA to the 'A' side of the ribosome ### **Question 39** How many different aminoacyl tRNA synthetases are there? * 20 ### **Question 40** The net effect of Histone Deacetylase action is to: * Suppress gene expression by altering histone binding to genes. ### **Question 41** The antibiotic Puromycin inhibits which of the following processes? * Translation ### **Question 42** One of the mRNA codons specifying the amino acid leucine is 5'-CUA-3'. Its corresponding anticodon is: * 3'-GAU-5' ### **Question 43** The "Wobble" hypothesis in protein synthesis states that: * Only the first 2 nucleotides of the codon determine the specificity of the tRNA molecule. ### **Question 44** How does the first nucleotide at the 5' end of a new mRNA chain differ from the other nucleotides in the chain? * The first nucleotide retains its triphosphate group, while others do not. ### **Question 45** Where is the amino-acid binding site located on the tRNA molecule? * At the end of the 3' end of the molecule ### **Question 46** Following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site: * Moves to the P site of the ribosome ### **Question 47** Which statement/s about the lac operon is/are incorrect? * It regulates the production of a series of five enzymes. * It is normally turned off if tryptophan is present. * Lactose binds to the repressor protein and this inactivates the operon. ### **Question 48** Which of the following are important in the control of eukaryotic gene expression? * Control of the rate in which genes are transcribed. * Control of mRNA processing after it has been transcribed from DNA. * Changes in the activity of DNA polymerase. ### **Question 49** Using the following numbered terms below, what is the correct order that best represents the sequence structure of a typical mRNA molecule in a prokaryotic cell as it is synthesized? * 3' trailing sequences * Coding sequences * Leader sequences * Termination signals The correct sequence is **3-2-4-1** ### **Question 50** In the function of the lac operon in E.coli, the lac genes are transcribed in the presence of lactose because: * Isomer of lactose binds to the repressor ### **Question 51** In a bacterial operon, the location of the regulatory region usually occurs **at the 5' end of** and **upstream of** the structural genes. ### **Question 52** A mutation in the I gene of the lac operon could directly affect: * The repressor gene ### **Question 53** In the usual flow of genetic information, which of the following best represents the expression of genes? * DNA - RNA - protein ### **Question 54** RNA polymerase binds to a sequence called a/an **promoter** before beginning transcription. ### **Question 55** The expressed sequences within eukaryotic mRNA that code for gene products are called **exons**. ### **Question 56** Why can only one of the DNA strands of a specific gene be used for transcription? * Because RNA polymerase only reads in the 3-5 prime direction. ### **Question 57** Which of the following statements are false about DNA transcription? * Only the exons are transcribed. * Introns are transcribed separately to exons. ### **Question 58** The 3' end of eukaryotic pre-mRNA molecules are changed by: * Cutting and adding 100-250 adenine nucleotides. ### **Question 59** Which of the following is true about introns found within human genes? * They are sequences that do not code for proteins but can be alternatively spliced during mRNA processes to generate different protein products. * Usually longer in length compared to exons. * They are sometimes present in messenger RNA due to a mutation at the splicing site. ### **Question 60** The transcription process as outlined below begins at the area labelled **E**. ### **Question 61** The use of histone acetylases can influence DNA structure by: * Opening DNA conformation. ### **Question 62** If thymine makes up 25% of the bases in a certain DNA sample, what percentage of the bases must be cytosine? * 25% ### **Question 63** Which of the following DNA sequences are complimentary sequences of 5'TATTCGCTTA3'? * 5'TAAGCGAATA3' * 3'ATAAGCGAATS' ### **Question 64** The DNA bases Guanine and Cytosine are: * A purine and a pyrimidine respectively. ### **Question 65** Which of the following DNA nucleotide sequences represents the complement to the DNA strand 5'AGATCCG-3'? * 3'-TCTAGGC-5' ### **Question 66** A 28-year-old man was diagnosed with an abnormal form of P53 protein which is shorter than the normal protein. Which of the following point mutations in the DNA is consistent with the abnormality? (You will need to use the amino acid coding table below to answer this question) * TAT changes to TAA ### **Question 67** Which of the following DNA codons could code for the following the amino acid glycine (gly) (You will need to use the amino acid coding table below to answer this question)? * 5'GGT-3' * 5'GGC-3' * 3'CGG-5' ### **Question 68** Which of the following sugars is found in RNA? * D-Ribose ### **Question 69** The following molecules are nucleosides except: * Inosine ### **Question 70** Which one of the following facts about the mitochondrial DNA are false? * It is only found in mammalian cells. ### **Question 71** Approximately how many genes do humans have in their genome? * 20000-25000 ### **Question 72** Which of the following features is atypical (not present) in a normal eukaryotic gene? * An operator region ### **Question 73** In a nucleosome structure, to what does the DNA helix attached itself? * Histone proteins ### **Question 74** Which one for the following gene components are incorrectly matched with their function? * Regulator gene binds to the repressor protein. ### **Question 75** RNA polymerase reads the template strand in the **3' to 5'** direction and makes mRNA in the **5' to 3'** direction ### **Question 76** The 5-primed (5') carbon in DNA refers to the carbon on the **5th carbon on the ribose sugar counter in order from the carbon attached to the nucleotide** and **the carbon on the ribose sugar which is attached to the phosphate group**. ### **Question 77** DNA can be visualised by UV light on agarose gel using which one of the following dyes? * Ethidium bromide ### **Question 78** When sister chromatids separate, what name is given to the genetic strands of separation? * Daughter chromosomes ### **Question 79** Agarose gel electrophoresis resolution of DNA molecules is facilitated by the negative charge conferred by the presence of which chemical group? * Phosphate groups. ### **Question 80** During which stage of meiosis do bivalent chromosomes occur? * Prometaphase * Metaphase ### **Question 81** What event during meiosis produces trisomies and monosomies? * Non disjunction ### **Question 82** What protein(s) is/are involved in the spindle assembly checkpoint? * Cohesin * Securin * Separase ### **Question 83** Which is NOT correct regarding nondisjunction? * Separates maternal from paternal chromatids ### **Question 84** Which of the following descriptions of DNA sequences does NOT reflect a true binding region for DNA-protein interaction? * Adrenaline Response Element ### **Question 85** Which of the following human diseases is least likely to be caused by aneuploidy? * Fragile X syndrome ### **Question 86** On which number carbon is the hydroxyl group (on the sugar residue of a DNA nucleoside) which binds to the incoming phosphate of another nucleoside, located on? * 3 ### **Question 87** Which of the following is NOT due to anomalies in autosomal chromosomes? * Turner syndrome ### **Question 88** Which of the following karyotypes is not compatible with survival to birth? * 45,Y ### **Question 89** Some rare cases of Down's syndrome are caused by a translocation between which chromosomes? * 21 and 14 ### **Question 90** Which phrase best describes polyploidy? * An extra set of chromosomes. ### **Question 91** A volume of 1ul of a DNA solution (100ng/ul) is added to a 25ul PCR reaction, what is the final amount of DNA template in the PCR reaction? * 100 ng * 0.1 ug ### **Question 92** What volume (ul) of a 1M MgCl2 stock solution needs to be added to a 25ul PCR reaction to reach a final concentration of 8mM MgCl2? Give your answer to two decimal places. * 0.20 ### **Question 93** If the stock concentration of forward primer is 5.6uM, what volume (ul) of forward primer needs to be added in a total PCR reaction volume of 25ul to obtain a working concentration of 200nM? (Given you answer to 2 decimal places) * 0.89 ### **Question 94** The presence of a 350bp Alu insertion in the human ACE gene increases the risk of developing late onset heart disease. The image below shows the PCR amplification products for this genotype in 6 patients. Based on the banding patterns of the PCR products (no Alu insertion = 250bp, Alu insert = 700bp), which patients are at greatest risk of developing heart disease? * Patients 2, 4, and 5 ### **Question 95** The gel electrophoresis image below shows the PCR amplification products for the genetic analysis of the PV92 Alu repeat polymorphism in 6 human subjects. Lane M contains the 100bp molecular weight ladder. The (+) allele containing the Alu insert and the (-) allele (no Alu repeat), produce PCR products of approximately 650bp and 250bp respectively. How many of the 6 samples contain at least one copy of the Alu repeat allele? * 5 ### **Question 96** The gel image below shows the PCR products for amplification of the PV92 Alu repeat in 6 samples. Lane 7 is the negative control sample. What reagent/s would you leave out of the PCR reaction mixture when setting up a negative control tube? * DNA template ### **Question 97** Using the NCBI website to retrieve the human BRCA1 gene sequence, what is the 3 letter stop codon at the end of this gene? * TAG ### **Question 98** Using the NCBI website to view the entry for the human BRCA1 gene sequence, what is the length of the mRNA sequence for isoform NM_007294? (Give number of nucleotides only, do not include any units or letters) * 7088 ### **Question 99** Use the NCBI website to retrieve the human BRCA1 gene sequence. What is the 3rd amino acid coded for in the gene? * Alanine ### **Question 100** Using the NCBI website to retrieve the human Insulin gene sequence, what is the 3 letter stop codon at the end of the gene? * TAG