BIOLOGY III - Mutation and Gene Function 1
In biology, mutations are changes to the nucleotide sequence of the genetic material
of an organism. Mutations can be caused by copying errors in the genetic material
during cell division, by exposure to ultraviolet or ionizing radiation, chemical
mutagens, or viruses, or can be induced by the organism, itself, by cellular processes
such as hypermutation. In multicellular organisms with dedicated reproductive cells,
mutations can be subdivided into germ line mutations, which can be passed on to
descendants through the reproductive cells, and somatic mutations, which involve
cells outside the dedicated reproductive group and which are not usually transmitted
to descendants. If the organism can reproduce asexually through mechanisms such as
cuttings or budding the distinction can become blurred. For example, plants can
sometimes transmit somatic mutations to their descendants asexually or sexually
where flower buds develop in somatically mutated parts of plants. A new mutation
that was not inherited from either parent is called a de novo mutation. The source of
the mutation is unrelated to the consequence, although the consequences are related to
which cells are affected.
Mutations create variation within the gene pool. Less favorable (or deleterious)
mutations can be reduced in frequency in the gene pool by natural selection, while
more favorable (beneficial or advantageous) mutations may accumulate and result in
adaptive evolutionary changes. For example, a butterfly may produce offspring with
new mutations. The majority of these mutations will have no effect; but one might
change the color of one of the butterfly's offspring, making it harder (or easier) for
predators to see. If this color change is advantageous, the chance of this butterfly
surviving and producing its own offspring are a little better, and over time the number
of butterflies with this mutation may form a larger percentage of the population.
Neutral mutations are defined as mutations whose effects do not influence the fitness
of an individual. These can accumulate over time due to genetic drift. It is believed
that the overwhelming majority of mutations have no significant effect on an
organism's fitness. Also, DNA repair mechanisms are able to mend most changes
before they become permanent mutations, and many organisms have mechanisms for
eliminating otherwise permanently mutated somatic cells.
Mutation is generally accepted by the scientific community as the mechanism upon
which natural selection acts, providing the advantageous new traits that survive and
multiply in offspring or disadvantageous traits that die out with weaker organisms.
SOURCE: https://www.amazines.com/Mutations_related.html
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Mutation and Gene Function
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Define genetic screening
Discuss three advantages and disadvantages of genetic screening
Define the Human Genome Project:
State that the Human Genome project is an international cooperative venture to
sequence the complete human genome
Discuss two possible advantages of this project
Define clone
Outline a technique used in the cloning of farm animals
Discuss the ethical issues of cloning human embryos
Discuss the results of crop plant and animal breeding
Define Gene Mutation
Outline the difference between an insertion and a deletion
Explain the consequence of a base substitution mutation in relation to the process
of transcription and translation (You may use the example of sickle cell anaemia)
Gene Mutation
Read the text and choose an appropriate word to complete the
gaps:
Mutations are changes to the ……….sequence of the genetic material of an organism.
a. chromosome
b. nucleotide
c. base
d. protein
Due to copying errors in the genetic material during cell ………. and by exposure to
ultraviolet or ionizing radiation, chemical mutagens, or carcinogens, mutations can
occur deliberately during processes such as hypermutation,
a. distinction
b. division
c. separation
d. isolation
In multicellular organisms, mutations can be subdivided into germ line mutations, ,
and somatic mutations. ……………….. mutations can be passed on to descendants.
a. germ line
b. somatic
c. asomatic
d. genetic line
Plants sometimes can transmit somatic mutations to their descendants sexually or
………
a. with union
b. unsexually
c.without union
d. asexually
A new mutation that was not inherited from either parent is called a de ……mutation.
A. novel
b. novo
c. new
d. anew
Mutations create variation within the gene pool. Deleterious mutations can be reduced
in frequency in the gene pool by natural selection, while more beneficial mutations
may accumulate and result in adaptive ………..changes.
a. evolved
b. evolution
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c. evolutionaryd. evolving
Match the types of mutation with their description: frameshift, adaptive, silence,
nonsense, missence, back, neutral, point.
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……………………. mutation is what renders mutagenesis non-random in many ways
and increases the rate of beneficial mutations arising.
……………………. or reversion is a change in a nucleotide pair of a point-mutated DNA
sequence that restores the original sequence and hence the original phenotype.
…………………….. is a mutation caused by indels, ie. inserts or deletes a number of
nucleotides that is not evenly divisible by three from a DNA sequence. Due to the
triplet nature of gene expression by codons, the insertion or deletion can disrupt the
reading frame, or the grouping of the codons, resulting in a completely different
translation from the original. The earlier in the sequence the deletion or insertion
occurs, the more altered the protein produced is.
………………………or non-synonymous mutations are types of point mutations where a
single nucleotide is changed to cause substitution of a different amino acid. This in
turn can render the resulting protein non-functional. Such mutations are responsible
for diseases such as epidermolysis bullosa and sickle-cell disease.
……………………….. is a mutation that occurs in an amino acid codon (presumably
within an mRNA molecule) which results in the use of a different, but chemically
similar, amino acid. This is similar to a silent mutation, where a codon mutation may
encode the same amino acid (see Wobble Hypothesis); for example, a change from
AUU to AUC will still encode leucine, so no discernible change occurs.
…………………………is a point mutation in a sequence of DNA that results in a
premature stop codon.
……………………..or substitution, is a type of mutation that causes the replacement of
a single base nucleotide with another nucleotide. Often the term point mutation
also includes insertions or deletions of a single base pair (which have more of an
adverse effect on the synthesized protein due to nucleotides still being read in
triplets, but in different frames- a mutation called a frameshift mutation).
…………………..mutations are DNA mutations that do not result in a change to the
amino acid sequence of a protein. They may occur in a non-coding region (outside of
a gene or within an intron), or they may occur within an exon in a manner that does
not alter the final amino acid sequence.
Gaucher disease as a paradigm of current issues
regarding single gene mutations of humans
E Beutler, Department of Molecular and Experimental Medicine,
Scripps Research Institute, La Jolla, CA 92037.
Gaucher disease is a glycolytic storage disease caused by a deficiency in activity of
the catabolic enzyme glucocerebrosidase. Over 35 different mutations have been
documented, including missense and nonsense point mutations, splicing mutations,
deletions and insertions, a fusion gene, and examples of gene conversion. Gaucher
disease is most common in the Ashkenazi Jewish population, in which just five of the
mutations in this population account for 98% of the disease-producing alleles. Each of
these mutations is found in the context of a single haplotype, a finding consistent with
a single origin of each mutation. Although it is clear that these mutations provide a
selective advantage in the Jewish population and thus constitute a balanced
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polymorphism, the nature of the advantage is unknown. Gaucher disease can be
treated symptomatically, by administration of the missing enzyme, by allogeneic bone
marrow transplantation, and potentially by gene transfer into hematopoietic stem
cells. Increasing understanding of this disease has, as in other genetic disorders,
created a host of social and ethical dilemmas regarding matters such as the cost of
treatment for rare diseases and the advantages and disadvantages of populationtargeted genetic screening.
Taking into account the points raised in the abstract, write an essay discussing
the advantages and disadvantages of genetic screening. (200-250 words)
You may use some of the following words:
Genetic defects recognition
identification of pregnancy complications
May prevent premature death
invasion of personal privacy
epidermolysis bullosa disease
sickle-cell anaemia disease
blood relatives
participate in clinical trials
for insurance purposes
insurance premiums
for the defective breast cancer alleles
insurance discrimination
likelihood of a disease
family history
ramifications of test results
social discrimination
breast and ovaries surgically removed
inconclusive results
mandatory testing
the sickle cell anaemia screening
change of lifestyle
kept confidential
limited to life threatening diseases
family relationships change
opportunity to seek medical help
stigmatization
loss of employment
reduction in cancer-related mortality
cost-ineffective
advantages outweigh the disadvantages
a feeling of relief or anxiety
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