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Question 1
Incorrect
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In which phase do chromosomes in the nucleus become condensed into well-defined chromosomes?
Your Answer: Prophase
Correct Answer: Metaphase
Explanation:Prophase begins when the nucleus envelope disintegrates and the chromosomes start to condense. The chromosomes consist of two sister chromatids that are joined at a constriction known as centromere. When the cell reaches the metaphase the chromosomes are completely condensed and ready to align on the equatorial plate
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This question is part of the following fields:
- Genetics
- Medicine
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Question 2
Correct
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The enzyme responsible for telomeres maintaining their length after cell division is called:
Your Answer: Telomerase
Explanation:Telomerase is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences. Telomerase activity is exhibited in gametes and stem and tumor cells.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 3
Incorrect
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With regard to X linked disorders which of the following are true
Your Answer: They are relatively common but their expression is variable
Correct Answer: X linked recessive disorders usually present in males and only very rarely present in homozygous females
Explanation:All are true for autosomal recessive disorders. Dominance rules for sex-linked gene loci are determined by their behaviour in the female: because the male has only one allele (except in the case of certain types of Y chromosome aneuploidy), that allele is always expressed regardless of whether it is dominant or recessive.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 4
Incorrect
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When during the cell cycle do the centrioles replicate?
Your Answer: S phase
Correct Answer: G1 phase
Explanation:During G1 phase the cell will prepare for cell division. All the organelles will start to duplicate in this phase and the cell will begin to grow whilst proteins are also synthesized.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 5
Correct
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In which phase do chromosomes in the nucleus become completely condensed into well-defined chromosomes?
Your Answer: Metaphase
Explanation:Prophase begins when the nucleus envelope disintegrates and the chromosomes start to condense. The chromosomes consist of two sister chromatids that are joined at a constriction known as centromere. When the cell reaches the metaphase the chromosomes are completely condensed and ready to align on the equatorial plate
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This question is part of the following fields:
- Genetics
- Medicine
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Question 6
Incorrect
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Under normal conditions (where n represents the number of chromosome pairs), just before mitosis begins, how many chromosomes are contained in the nucleus of each somatic cell:
Your Answer: 2n
Correct Answer: 4n
Explanation:In a normal somatic cell there are 2n chromosome but in a replicating cell just before mitosis the chromosomes duplicate but are still joined via the centrosome. Thus there are 4n chromosomes. After completion of mitosis the number goes back to 2n.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 7
Incorrect
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Which of the following is not true regarding mitochondrial chromosome disorders?
Your Answer: Most mitochondrial diseases are myopathies and neuropathies with a maternal pattern of inheritance.
Correct Answer: Because mitochondrial chromosomes have no introns in their genes, any point mutation has a low likelihood of having an effect.
Explanation:Mitochondrial DNA (mtDNA) does indeed lack introns, meaning that its genes are closely packed with coding sequences. This actually means that any point mutation in the mtDNA is more likely to have an effect, not less. The lack of introns means there are fewer non-coding regions where mutations can occur without affecting gene function. Thus, mutations in mtDNA often have significant consequences because they are more likely to alter essential coding sequences.
The other statements are true:
- Most mitochondrial diseases are myopathies and neuropathies with a maternal pattern of inheritance: This is correct because mtDNA is inherited maternally, and many mitochondrial disorders affect muscle and nerve function.
- Retinal degeneration, diabetes mellitus, and some forms of hearing loss are some of the other diseases attributed to mitochondrial chromosome defects: These are indeed conditions associated with mitochondrial defects.
- Mitochondrial chromosome defects are inherited from one’s mother: This is correct, as mtDNA is passed from mother to offspring.
- Leber’s hereditary optic neuropathy (LHON), the commonest cause of blindness in young men, is an example of a mitochondrial chromosome defect: This is true; LHON is a well-known mitochondrial disorder.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 8
Correct
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Which of the following is an incorrect statement regarding the structure of DNA?
Your Answer: The two strands of DNA are held together by cysteine bonds.
Explanation:The two strands of DNA are held together by hydrogen bonds formed between the nucleotide bases.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 9
Correct
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What is the structure of nucleosomes?
Your Answer: Strands of double strand DNA + histones
Explanation:DNA is packed and condensed by binding to histone proteins. The double stranded DNA forms a complex with histone proteins which is called a nucleosome. There are 8 histone proteins contained in one core of nucleosome.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 10
Correct
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“Ploidy” is a term used to refer to the number of chromosomes in cells. Cancer cells are commonly:
Your Answer: Aneuploidy
Explanation:Cancer cells most commonly undergo disordered cell growth and cell division. This results in an additional number of chromosomes called aneuploidy. This is a characteristic of cancer cells along with variation in differentiation of the cells.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 11
Correct
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When during the cell cycle does DNA replication occur?
Your Answer: S phase
Explanation:The S phase is known as the synthesis phase. During this phase DNA will begin to replicated, as well as the synthesis of the centrosomes and associated proteins.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 12
Correct
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Regarding restriction fragment length polymorphisms (RFLP) and Gene Knockout Mouse Models. All are true except:
Your Answer: In knockout mouse models a gene is turned on through targeted mutation
Explanation:In RFLP, polymorphism occurs in 98% of the non coding genome, resulting in no phenotypical change in the organism. A gene is not turned on by a mutation, rather the mutation at the restriction site will alter the DNA and the DNA will now form fragments of different lengths. PCR is a better technique than RFLP.
A knockout, as related to genomics, refers to the use of genetic engineering to inactivate or remove one or more specific genes from an organism. Scientists create knockout organisms to study the impact of removing a gene from an organism, which often allows them to then learn something about that gene’s function.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 13
Incorrect
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Southern Blotting and DNA probes:
Your Answer: Localisation of native nucleic acid sequences within cells is part of insitu hybridisation
Correct Answer: DNA fragments are separated by gel electrophoresis and transferred onto membrane sheets in southern blotting
Explanation:A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. The other forms of blotting involve the use of RNA and proteins.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 14
Correct
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Normal parents have a child with a recessive condition, Tay Sachs. The chance of them having a normal child is?
Your Answer: 75%
Explanation:The chance for normal parents having a child with a recessive disease is 1:4 or 25%. As both the parents are heterozygous for this condition. They have a 3:4 chance of having a normal child or 75%.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 15
Incorrect
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With regards to P53, which statement is NOT true?
Your Answer: P53 activates many gene expression pathways
Correct Answer: P53 is a RNA binding protein
Explanation:P53 is a tumour suppressor gene. It is not an RNA binding protein. It has been implicated in almost all tumours. It regulates the progression from G1 to the S phase of the cell cycle and is activated in response to damaged DNA.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 16
Incorrect
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During which phase of meiosis does exchange of genetic material occur accounting for genetic diversity between individuals:
Your Answer: Metaphase 2
Correct Answer: Prophase 1
Explanation:Prophase 1 has been divided into five different stages ( laptotene, zygotene, pachytene, diplotene ans diakinesis). In prophase 1 chromosomes are going to condense to become visible, each chromosome will contain two chromatids that are joined at the centromere. the nucleolus and nuclear envelope are going to disintegrate. the homologous chromosomes will form tetrad and crossing over will occur between the chromosomes (random exchange of genes), the point of exchange is known as the chiasmata, this increases genetic diversity.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 17
Correct
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Which statement about X linked dominant disorders is FALSE?
Your Answer: Heterozygous females tend to have the disease more severely than affected males.
Explanation:Women who have the affected X chromosome will be affected, but the severity will be less than that in males as they have a normal X chromosome to counter the effect of the mutated X chromosome. Affected males will pass on the defect to their daughters 100% of the time but not to their sons.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 18
Incorrect
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Mutation in RB can lead to the formation of which cancer?
Your Answer: Osteosarcoma
Correct Answer: Retinoblastoma
Explanation:Patients with a history of autosomal dominant familial retinoblastoma have at least one mutated copy of the RB gene. This predisposes the patient to develop retinoblastoma in one or both the eyes. Patients with a family history should be screened properly so that it can be detected and treated as early as possible.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 19
Incorrect
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Which of the following statements is true regarding chromosomes?
Your Answer: The centromere divides the chromosome into the long (q) and short (p) arms
Correct Answer: All are true
Explanation:All of the above mentioned statements are true regarding chromosomes.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 20
Incorrect
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Which of the following are true with regard to autosomal recessive disorders:
Your Answer: These disorders only manifest themselves where an individual is homozygous for the disease allele
Correct Answer: All are true
Explanation:All are true for autosomal recessive disorders.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 21
Incorrect
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Regarding Southern Blotting and DNA probes, which answer is FALSE
Your Answer: DNA fragments are separated by gel electrophoresis and transferred onto membrane sheets in southern blotting
Correct Answer: RNA fragments are separated by gel electrophoresis and transferred onto membrane sheets in southern blotting
Explanation:Restriction enzymes always cut at different positions. There are different restriction endonucleases for different nucleotide sequences.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 22
Incorrect
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Which of the following with regard to DNA mutations does not fit:
Your Answer: Splicing mutations may alter which amino acids are incorporated into the polypeptide chain
Correct Answer: All gene mutations cause clinical disease entities
Explanation:All gene mutations do not cause a clinical manifestation of the disease, some gene mutations are silent mutations. They are present but do not cause any disease.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 23
Incorrect
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Three adjacent nucleotides code for a particular amino acid. These are called codons. How many common amino acids are there and how many potential codon combinations make up the genetic code?
Your Answer: 12 amino acids, 64 codon combinations
Correct Answer: 20 amino acids, 64 codon combinations
Explanation:There are around 20 amino acids and 61 out of the 64 combinations of codon code for these 20 common amino acids.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 24
Incorrect
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Which of the following conditions results from chromosomal ‘non-disjunction’?
Your Answer: Edward syndrome
Correct Answer: All of the options
Explanation:Non-disjunction can result in aneuploidy i.e. abnormal number of chromosomes in a cell. It results due to uneven division of chromosomes in the meiosis 1 or 2 phase. All the above mentioned examples are of non-disjunction.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 25
Incorrect
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In most somatic cells telomeres progressively shorten as:
Your Answer: None of the above
Correct Answer: The cell divides
Explanation:Telomerase activity is seen in germ cells and is absent in somatic cells. A somatic cell is any biological cell forming the body of an organism, other than a gamete, germ cell, gametocyte or undifferentiated stem cell. i.e. liver cells. Telomeres prevent the chromosomes from shortening and prevent the coding portion of the DNA from being lost, thus allowing the cell to replicate indefinitely. During replication telomeres may be lost resulting in cell death.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 26
Correct
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The process whereby DNA fragments are separated by size and charge is called:
Your Answer: Gel electrophoresis
Explanation:Fragments of DNA of varying length can be separated on the basis of their charge and their size by a process called gel electrophoresis. Because DNA contains negatively charged phosphate groups, it will migrate in an electric field toward the positive electrode. Shorter chains migrate more rapidly through the pores of the gel, and thus separation depends on length. DNA bands in the gel can be visualized by various techniques including staining with dyes and autoradiography.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 27
Incorrect
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In a knockout mouse model the process used to combine the new DNA sequence and the stem cells is known as:
Your Answer: Electroporation
Correct Answer: Insertion
Explanation:Chimerisation is also known as the formation of recombinant DNA. When a foreign DNA sequence is inserted into a plasmid or other DNA sequence, this process is known as insertion.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 28
Incorrect
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The length of DNA is generally measured in terms of the number of:
Your Answer: Hydrogen bonds
Correct Answer: Base pairs
Explanation:As DNA is made up of nucleotides, its length is measured by the number of base pairs in the DNA molecules.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 29
Incorrect
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What is the protective hexametric sequence at the ends of chromosomes called?
Your Answer: Histone
Correct Answer: Telomere
Explanation:Telomeres are non coding DNA plus proteins that are found at the end of the linear chromosomes. They maintain the integrity of the chromosomes and prevent their shortening.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 30
Incorrect
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Telomerase is active in all of the following cells, except:
Your Answer: Certain cancer cells
Correct Answer: Certain liver cells
Explanation:Telomerase is an enzyme that adds repetitive nucleotide sequences to the ends of chromosomes (telomeres), preventing their shortening during cell division. Telomerase activity is crucial for cells that divide frequently and need to maintain their telomere length for continued proliferation. These include:
- Stem cells: They have high telomerase activity to maintain their long-term proliferative capacity.
- Germ cells: These cells also have active telomerase to ensure the stability of genetic material across generations.
- Certain white blood cells: Some immune cells, particularly those that need to proliferate in response to infection, show telomerase activity.
- Certain cancer cells: Many cancer cells reactivate telomerase, which contributes to their uncontrolled growth and immortality.
However, most somatic cells, including certain liver cells, do not exhibit significant telomerase activity. While some liver cells might show low levels of telomerase activity during regeneration, it is not generally active in normal, differentiated liver cells.
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This question is part of the following fields:
- Genetics
- Medicine
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SESSION STATS - PERFORMANCE PER SPECIALTY
