Key Area 1.6 (a) and (b) Gene Mutations. Learning Outcomes.
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Transcript of Key Area 1.6 (a) and (b) Gene Mutations. Learning Outcomes.
![Page 1: Key Area 1.6 (a) and (b) Gene Mutations. Learning Outcomes.](https://reader035.fdocuments.net/reader035/viewer/2022062523/5a4d1acb7f8b9ab05996f994/html5/thumbnails/1.jpg)
Key Area 1.6 (a) and (b)
Gene Mutations
![Page 2: Key Area 1.6 (a) and (b) Gene Mutations. Learning Outcomes.](https://reader035.fdocuments.net/reader035/viewer/2022062523/5a4d1acb7f8b9ab05996f994/html5/thumbnails/2.jpg)
Learning Outcomes
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Genetic Variation• Within the human population, there
are many different types of variation in the genomes.
• These difference are the result of mutations and rearrangements of parts of the sequence of bases.
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Mutations• Mutations are changes in the
genome that can result in no protein or an altered protein being expressed.
• Mutations arise spontaneously and at random but only occur rarely.
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Single Gene (point) Mutations
• A single gene (point) mutation involves a change in one of the base pairs in the DNA sequence of a single gene.
• A point mutation can alter the expression of the gene.
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Single Gene Mutations• Three types of single gene mutation are:
1) Substitution2) Insertion3) Deletion
Each of these results in one or more codons for one or more amino acids being altered.
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Task• Using the text book (page 61), add a
diagram of each type of mutation into your notes.
• Ask your partner to check over it to make sure it is fully completed and to a high standard.
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Impact of Protein Structure• Single-nucleotide substitutions brings
about only a minor change (one different amino acid).
• Single-nucleotide substitutions include:
1) Missense2) Nonsense3) Splice-Site
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Missense• Following a substitution, the altered
codon codes for an amino acid which still makes sense but not the original sense.
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Nonsense• As a result of a substitution, a codon
that used to code for an amino acid becomes changed into one that acts as a stop codon.
• It causes protein synthesis to be halted prematurely and results in the formation of a polypeptide chain which is shorter than the normal one.
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Splice-Site• A molecule of primary mRNA
transcript is spliced to remove introns and seal exons together.
• A splice-site mutation substitutes, inserts or deletes one or more nucleotides at a site where introns are normally removed.
• Splice-site mutations can alter post-transcriptional processing.
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Research Task• Research reasons for geographical
variation in incidence of post-weaning lactose tolerance or sickle-cell trait in humans.
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Frame-shift Mutations• Insertion and deletion both lead to
major changes since each cause a large portion of gene’s DNA to be misread.
• The protein produced differs from the normal protein by many amino acids and it is usually non-functional.
• Frame-shift mutations can also result in an expansion of a nucleotide sequence repeat.
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Starter/Task
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Key Area 1.6 (c), (d) and (e)Chromosome Mutations
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Learning Outcomes
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Chromosome Mutations• These mutation alter the structure of
one or more chromosomes.• There are four types of chromosome
mutations:1) Duplication2) Deletion3) Inversion4) Translocation
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Duplication• A segment of genes is repeated.
• Some duplication of genes may have a detrimental effect or be of an advantage.
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Deletion• A segment of genes becomes
detached and the two remaining ends join giving a shorter chromosome lacked the detached genes.
• Deletion normally has drastic effects on the organism involved.
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Inversion• A segment of genes is reversed.
• This results in non-viable gametes.
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Translocation• A section of one chromosome breaks
off and attaches to another chromosome that is not it’s matching partner.
• Translocation leads to non-viable gametes.
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Task• Using page 67-69, add diagrams of
each type of chromosome mutation to your notes.
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Importance of Mutations • Mutation is the only source of new
variation.• New alleles of genes arise.• Most mutations are harmful or lethal,
but rarely, can be advantageous. • Mutations are the raw material of
evolution!!!
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Polyploidy• Polyploidy is the result of an error
occurring during gamete formation or cell division and all the matching chromosomes fail to separate.
• Polyploidy is a mutation where cells receive one or more extra sets of chromosomes.
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Think and Discuss• Would you ever eat a polyploidy fruit
or vegetable?• What do you think it would look
like/taste like?
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Polyploidy in Plants• Approximately 50% of plant species
are polyploid, due to duplication of entire genomes millions of years ago, in their common ancestors.
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Importance of Polyploidy• Polyploid plants are larger, have
increased seed and fruit size, and higher yields.
• Polyploid plants with an uneven number of sets of chromosomes are sterile so produce seedless fruit.
• Advantages are increased vigour, crop quality and resistance to disease.
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Examples of Polyploid• Banana – a triploid, originated from a
cross between two species or wild banana. Bananas are propagated asexually.
• Potato – a tetraploid, native to South America.
• Other examples include swede, oil seed rape, wheat and strawberry.