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163766512065Biological Basis of Inheritance00Biological Basis of Inheritance-720090-368935Name:____________________Class:____________________Date:____________________00Name:____________________Class:____________________Date:____________________45707308255Biology Gr11F 00Biology Gr11F Read the passage below. Then answer the questions that follow.Mutation 48342553766820Reading CheckWhat is a mutagen?________________________________00Reading CheckWhat is a mutagen?________________________________483489066040Vocabulary DevelopmentCopy the key vocabulary written in bold in the space provided below.____________________________________________________________________________________00Vocabulary DevelopmentCopy the key vocabulary written in bold in the space provided below.____________________________________________________________________________________Mutation is defined as an alteration in the nucleotide sequence of DNA (deoxyribonucleic acid) of an organism. The structure of DNA consists of nitrogenous bases (purines and pyrimidines), glucose and phosphate. Purine consists of adenine (A) and guanine (G) bases, whereas pyrimidine bases are cytosine(C) and thymine (T). The bases are arranged as codons (three bases) that describe the coding of proteins for expression of cells. Mutation occurs when the sequence of nitrogenous base is changed, either due to copying errors during the replication or an exposure to mutagens such as chemicals, pollution, cigarette smoke, viruses, radiation and sunlight. The outcome of mutation is a change in the genetic message coded by the gene. In general, mutation is classified into two types based on the cells that are getting affected, namely, germ line and somatic. In the former case, mutation occurs in the reproductive cells (egg and sperm), which is then inherited from the parents to the offspring. This germ line mutation is responsible for causing hereditary diseases and/or genetic disorders. Somatic mutation, on the other hand, takes place in body cells like skin. It is not inherited to the descendants. Table shows some examples of human diseases that are caused by inherited mutations.Depending upon the effect of mutation on the structure of DNA, mutation can be further divided into several types namely substitution (exchanging base between two DNA strands), insertion (extra base is inserted in a DNA strand), deletion (loss of base pairs), inversion (reverse of base sequence) and frame-shift (insertion and deletion of one or more base pairs). Let's discuss in brief about single-base substitution or point mutation. When a single base in the nucleotide sequence is replaced by another, then it is known as point mutation. Point mutations also include insertion and/or deletion of a single base in the DNA strand. Usually, they are caused due to error in DNA replication. At times, it occurs after exposure to mutagens like heat and radiation. 4780915252095 Looking closer A gene has a nonsense mutation. Will the protein it produces be longer, shorter, or the same length as the protein produced by the normal gene?(hint: what does a stop codon do?)________________________________________________________________________________________________________________________________________________________________________________________________________00 Looking closer A gene has a nonsense mutation. Will the protein it produces be longer, shorter, or the same length as the protein produced by the normal gene?(hint: what does a stop codon do?)________________________________________________________________________________________________________________________________________________________________________________________________________The effects of point mutation can vary depending upon the site of mutation on the gene. If point mutation occurs in the coding sequence of DNA, then the protein coded by the altered gene is changed. Some other possible outcomes of point mutations include a failure of DNA transcription (conversion of messenger RNA to proteins), alteration of regulatory responses and other genetic changes. Hence, based on the functional changes of the gene, point mutations are divided into three types, namely, nonsense (failure of expression), missense (base code for a different protein) and silent (no significant change). The diseases like sickle cell anemia and thalassaemia are caused due to missense mutation in the coding sequence of a gene. With a missense mutation, the new nucleotide alters the codon so as to produce an altered amino acid in the protein product.-635105600500In HYPERLINK "" sickle-cell anemia, the replacement of A by T at the 17th nucleotide of the gene for the beta chain of hemoglobin changes the codon GAG (for glutamic acid) to GTG (which encodes valine). Thus the 6th amino acid in the chain becomes valine instead of glutamic acid. 2362835104140Critical ThinkingHow can a positive mutation lead to evolution of a certain population?______________________________________________________________________________________________________________________00Critical ThinkingHow can a positive mutation lead to evolution of a certain population?______________________________________________________________________________________________________________________Although mutations that change in protein sequences can be harmful to an organism; on occasions, the effect may be positive in a given environment. In this case, the mutation may enable the mutant organism to withstand particular environmental stresses better than wild-type organisms, or reproduce more quickly. In these cases a mutation will tend to become more common in a population through natural selection. Nylonase is an example of beneficial mutation in bacteria. The nylonase bacteria can eat short molecules of nylon (nylon-6). The mutation in these bacteria involves insertion of a single nucleotide in the genetic material. It is estimated that this frameshift mutation might have occurred in the 1940s when nylon was invented. Nylonase can be used in wastewater treatment plants.Skill: Reading EffectivelyIn the space provided, explain how the terms in each pair differ in meaning.1.Mutation, mutagen2.Point mutation, silent mutationComplete each statement by underlining the correct term in the brackets.1.If a mutation causes a sequence of nucleotides to change from ACGAGA to ACGAGGA, the mutation is called a(n) [insertion / deletion] mutation.2.Mutations that change one or just a few nucleotides in a gene on a chromosome are called [random / point] mutations.3.If a point mutation is such that it causes a codon to specify a different amino acid, the mutation is called a [missense / silent] mutation. 4.If a mutation causes a sequence of nucleotides to change from ACGAGA to ACGGA, the mutation is called a(n) [insertion / deletion] mutation.In the space provided, write the letter of the term or phrase that best completes each statement.1.Point mutations occur whena.one nucleotide is replaced with a different nucleotide.b.a gene’s location changes.c.long segments of a gene are lost.d.gametes are forming during meiosis.2.Somatic mutations area.heritable.c.in the germ cells.b.not heritable.d.Both (a) and (c)3.Germ cell mutations area.not heritable.c.in the body cells.b.heritable.d.Both (a) and (c)4.If a deletion mutation eliminated all of the guanine bases from the codon sequence GAT-CGC-CAA-TAG, the altered sequence would reada.ATC-TCA-ATA.c.ACC-CAA-ATA.b.ATC-CCA-ATA.d.AAT-CCA-TAC.In the space provided, write T if the statement is true or F if it is false.1.An insertion is the change of one nucleotide from one kind of base to another.2.A missense mutation has no effect on the resulting amino acid sequence.3.A frameshift mutation causes a change in the reading frame of a DNA sequence.4.A deletion can occur as a small change in the DNA or a larger change in the chromosome.Skill: Reading EffectivelyRead each question, and write your answer in the space provided.1.How is a missense mutation different from a nonsense mutation? How are they similar? 2.Explain the difference between insertion and deletion mutations.3.List the possible causes of mutation.4.What is the difference between the gene coding for normal hemoglobin and that coding for sickle-cell hemoglobin?5.Skin cancer can occur if the DNA in skin cells is mutated by ultra-violet radiation in sunlight. Can the mutation that causes skin cancer be passed on to offspring? Explain your answer.6.Give two examples of recessive genetic disorders and one example of a dominant genetic disorder.7.You read in a book that all mutations are bad. Do you agree? Explain. 8. What are the different types of point mutation? 9. Give two examples of missense point mutation ................
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