Biology Study Set 13

Biology

Quiz 14 :

From Dna to Protein

Quiz 14 :

From Dna to Protein

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Using Figure 14.6, translate this nucleotide sequence in part of an mRNA transcript into an amino acid sequence: img
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Following are the steps involved in the conversion of a nucleotide sequence to amino acid sequence.
1. Write the complementary bases for the given nucleotide sequence in order to complete the DNA sequence.
5' GGTTTCTTCAAGAGA 3'
3' CCAAAGAAGTTCTCT 5' (complementary base sequence)
2. Now consider previous half of the DNA sequence and replace its bases as per the bases couples involved in mRNA. (G-C/A-U)
5' GGTTTCTTCAAGAGA 3'
3' CCAAAGAAGUUCUCU 5' (mRNA)
3. Below given mRNA sequence enters the ribosome and then further band into transfer RNA sequence.
5' GGUUUCUUCAAGAGA 3' (mRNA)
3' CCAAAGAAGTTCUCU 5' (tRNA)
4. Through tRNA sequence we can easily decode the amino acid sequence (codon), because it is responsible for carrying the amino acids to the ribosome. Here, each pair of three bases in the tRNA sequence carries an amino acid that codes for a particular amino acid. After pairing them, we make use of a codon table in order to identify the codons and produce an amino acid sequence.
5' GGU UUC UUC AAG AGA 3' (mRNA)
3' CCA AAG AAG TTC UCU 5' (tRNA)
img img img img img Amino acids
img GFFKR
(Amino acid sequence)
5. Therefore, the above sequence represent amino acid sequence and the codons present in the amino acid sequence are glycine (G), phenylalanine (F), phenylalanine (F), lysine (K) and arginine (R).

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Antisense drugs may help us fight cancer and viral diseases, including SARS. These short mRNA strands are complementary to mRNAs that have been linked to these illnesses. Speculate on how these drugs work.
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Antisense drugs are made up of synthetic compounds that interact with other natural genetic material in order to retain the information for the production of proteins. These are usually short strands complementary to their target mRNAs. When they bind with each other, it forms a DNA/RNA hybrid which is further degraded by RNAase-H enzyme. This enzyme catalyzes the cleavage of RNA by means of hydrolytic mechanism resulting in the cleavage of phosphodiester bonds. This event makes mRNA unavailable for translation and would lead to methylation of promoter and coding regions of normal gene resulting in silencing of that particular gene. That is how such drugs help in fighting against various contagious diseases.

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Cigarette smoke is mostly carbon dioxide, nitrogen, and oxygen. The rest contains at least fifty-five different chemicals identified as carcinogenic, or cancer-causing, by the International Agency for Research on Cancer (IARC). When these carcinogens enter the bloodstream, enzymes convert them to a series of chemical intermediates that are easier to excrete. Some of the intermediates bind irreversibly to DNA. Propose one mechanism by which smoking cigarettes can cause cancer.
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Cigarette smoking is main cause of lip cancer and lung cancer. Smokers are more prone to mouth cancer. It is also a cause of laryngeal, oral, oesophageal and gall bladder cancer in men and women. It is important contributory factor for the development of kidney and pancreatic cancer. It is also associated with cancer of stomach and uterine cervix.
There are various chemicals such as benzopyrene and many other substances present in cigarette smoke which are carcinogenic. Reverse smoking cause's oral cancer. In reverse smoking the burning end of cigarette is kept in mouth. Lip cancer is caused by constant irritation by cigarette and pipes. Cigarette smoking mutates and inactivates P53 (tumour suppressor gene) which checks cancer growth. Loss of these suppressor genes can lead to cancer which is regarded as an uncontrolled cell growth. In healthy cells, cell growth is regulated by proto-oncogenes and tumour suppressor proteins. Mutation can be caused by variety of factors that stimulate the development of proto-oncogenes into oncogenes and can affect the availability of tumour suppressor proteins. This is how; many other chemicals in cigarette can lead to cancer.

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________ can cause gene mutations.
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Briefly review Section 13.3. Now suppose that DNA polymerase made a wrong base pairing while a crucial gene region of DNA was being replicated. DNA repair mechanisms did not kick in to fix the mistake. Here is the part of the DNA strand that contains the error: img After the DNA molecule is replicated, two daughter cells form. One daughter cell is carrying the mutation and the other cell is normal. Develop a hypothesis to explain this observation.
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________ different codons represent a near-universal genetic code.
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Anticodons pair with ________.
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Match the terms with the most suitable description. img
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An mRNA molecule is synthesized by _________.
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An RNA molecule is typically _______.
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DNA contains many different gene regions that are transcribed into different ________.
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In some cases, the termination of transcription of prokaryotic DNA depends on the structure of the newly forming RNA transcript. The terminal end of an mRNA transcript often folds back tightly on itself and makes a hairpin-looped structure, like the one shown at right. Why do you suppose that a "stem-loop" structure such as this stops transcription of prokaryotic DNA when the RNA polymerases reach it img
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Neurofibromatosis is a human autosomal dominant disorder caused by mutations in the gene. It is characterized by the formation of soft, fibrous tumors in the peripheral nervous system and skin as well as abnormalities in muscles, bones, and internal organs Because the mutant allele is dominant, an affected child usually has an affected parent. Yet in 1991, scientists reported that a boy developed neurofibromatosis even though his parents did not. When they examined both copies of the boys NF1 gene, they found that the gene on the chromosome he inherited from his father contained a transposon. Neither father nor mother had a transposon in any of the copies of their genes. Explain the cause of neurofibromatosis in the boy and how it arose.
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Each codon specifies a(n) __________.
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