This set of Bioinformatics Question Paper focuses on “Genome Anatomy-3”.
1. More than _____ of the human genome consists of interspersed repetitive sequences derived from TEs (transposable elements).
Explanation: The presence of these elements may be demonstrated using programs for detection of low-complexity regions in sequences. For e.g. in the fruit fly Drosophila has 15% of genome that is made up of transposable elements.
2. The retroposons include short _________ interspersed nuclear elements (SINES).
a) 90–4000 bp long
b) 80–500 Mbp long
c) 80–300 bp long
d) 100–3000 bp long
Explanation: There exists also (6–8 kbp long) interspersed nuclear elements (LINES). Different types of transposable elements are present in high copy numbers in mammalian genomes in varying manner.
3. _____ of the human genome comprises one particular family of the SINE Element, designated Alu (1.2 million copies).
Explanation: Ten percent of the human genome comprises one particular family of the SINE Element. And 14.6% of one particular LINE designated LINE1 (593,000 copies) are present.
4. Vertebrate chromosomes have long (>300 kb) regions of distinct GC richness, repeat content, and gene density, designated isochores in a model of genome organization proposing that genomes are made up of distinct segments of unique composition.
Explanation: Human and mouse chromosomal regions that have a low density of genes are AT-rich and have more Alu or B1/B2 (SINES) than LINE1 elements. Whereas the reverse is true for regions that have a high gene density, and those regions are more GC-rich.
5. The human genome contains about _________ of class II of elements that probably predate human evolution (Smit 1996).
a) 2,000 copies
b) 200,000 copies
c) 2,00,00,000 copies
d) 20,00,000 copies
Explanation: The class of TEs, class II, is made up of elements that employ a DNA-based mechanism of transposition. Class II elements also include the Activation-Dissociation (Ac-Ds) family in maize and the P element in Drosophila.
6. A third category of TEs has features of both class I and class II TEs. These miniature, inverted repeat TEs (MITES) are ________ in length.
a) 400 bp
b) 500 Mbp
c) 300 kbp
d) 600 kbp
Explanation: They were discovered in diverse flowering plants where they are frequently associated with regulatory regions of genes. Hence, they could be exerting an influence on regulation of gene expression.
7. Which of the given features is incorrect?
a) TEs are present in few particular chromosomes
b) TEs are present in all of the chromosomes
c) Abundance of TEs varies
d) TEs can comprise a large portion of the genomes of higher eukaryotes, both plants and animals
Explanation: TEs are present in all of the chromosomes, ranging from bacteria to humans, but their abundance varies. They can comprise a large portion of the genomes of higher eukaryotes, thus, only a small fraction of the genome of these organisms carries gene sequences.
8. Eukaryotic genes that encode proteins are interrupted by ________
a) exons of varying length and number
b) introns of varying length and number
c) exons of varying length and but same number
d) introns of varying number but same length
Explanation: In S. cerevisiae (budding yeast), only a small fraction of the genes contain introns, and there are a total of 239 introns in the entire genome. In contrast, in individual human genes, introns may be present in numbers exceeding 100 and comprise more than 95% of the gene.
9. Introns can remain at a corresponding position in a eukaryotic gene for long periods of evolutionary time.
Explanation: The origin of introns in eukaryotic genes is not understood but has been accounted for by two models. The “introns-early” view proposes that introns were used to assemble the first genes from sets of ancient conserved exons, whereas the “introns-late” view proposes that introns broke up previously continuous genes by inserting into them.
10. The intron structure of genes in a particular eukaryote is used for predicting the location of genes of genome sequences.
Explanation: Other features of eukaryotic genes in a particular organism that are useful for gene prediction include the consensus sequences at exon–intron and intron–exon splice junctions, base composition, codon usage, and preference for neighboring codons. Computational methods incorporate this information into a gene model that may be used to predict the presence of genes in a genome sequence.
Sanfoundry Global Education & Learning Series – Bioinformatics.
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