Biology Mutations 14-15 SNL Biology Copyright Pearson Prentice Hall

Mutations Copyright Pearson Prentice Hall

What is the first thing you think of when you hear the word mutation? Copyright Pearson Prentice Hall

The reality Copyright Pearson Prentice Hall

What is a mutation Mutations are changes in genetic material – changes in DNA code – thus a change in a gene(s) In gene mutations, the DNA code will have a base (or more) missing, added, or substituted in a codon. Copyright Pearson Prentice Hall

How common are mutations? Mutations occurs at a frequency of about 1 in every 1 billion base pairs Everybody has about 6 mutations in each cell in their body! If I have that many mutations, why don’t I look weird? Mutations are not always seen. The affected gene may still function. Mutations may be harmful . Mutations may be beneficial . Mutations may have no effect on the organism Copyright Pearson Prentice Hall

How common are mutations Mutations are a major source of genetic variation in a population increasing biodiversity. Some variations may help them to survive better . Create your own REALISTIC example How do mutations affect a population? Copyright Pearson Prentice Hall

Normal Gene DNA (sense strand) mRNA Polypeptide Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons Pro-Glu-Glu-Cys-Gly Amino acids The sense strand is the DNA strand which acts as the template for mRNA transcription © 2010 Paul Billiet ODWS

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Types Of Gene Mutations Point mutations occur when one base in sequence of a codon is changed(ex: GCA is changed to GAA) There are 3 Types Substitution Deletion Also Called Insertion (aka addition) Frameshift Mutations

Gene- Segment of DNA that codes for making a specific protein/trait Copyright Pearson Prentice Hall

Substitution Mutation Kinds of Mutations -Substitutions will only affect a single codon -Their effects may not be serious unless they affect an amino acid that is essential for the structure and function of the finished protein molecule (e.g. sickle cell anaemia) Gene mutations result from changes in a single gene. In a substitution, one base replaces another. Copyright Pearson Prentice Hall

Mutations: Substitutions Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons Pro-Glu-Glu-Cys-Gly Amino acids Substitution mutation GGTCACCTCACGCCA ↓ CCAGUGGAGUGCGGU Pro-Arg-Glu-Cys-Gly © 2010 Paul Billiet ODWS

No change Normal gene Substitution mutation GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons Pro-Glu-Glu-Cys-Gly Amino acids Substitution mutation GGTCTTCTCACGCCA ↓ CCAGAAGAGUGCGGU Pro-Glu-Glu-Cys-Gly © 2010 Paul Billiet ODWS

Disaster Normal gene Substitution mutation GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons Pro-Glu-Glu-Cys-Gly Amino acids Substitution mutation GGTCTCCTCACTCCA ↓ CCAGAAGAGUGAGGU Pro-Glu-Glu-STOP © 2010 Paul Billiet ODWS

Kinds of Mutations Frameshift mutations- Addition/deletion of a nucleotide -shifts the grouping of codons. -May change every amino acid that follows the point of the mutation. -Can alter a protein so much that it is unable to perform its normal functions. Gene mutations result from changes in a single gene. In an insertion, an extra base is inserted into a base sequence. Copyright Pearson Prentice Hall

Kinds of Mutations In a deletion, the loss of a single base is deleted and the reading frame is shifted. Gene mutations result from changes in a single gene. The loss of a single letter in a sentence models the effects of the deletion of one base in a DNA sequence. Copyright Pearson Prentice Hall

Mutations: Additions A frame shift mutation Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons Pro-Glu-Glu-Cys-Gly Amino acids Addition mutation GGTGCTCCTCACGCCA ↓ CCACGAGGAGUGCGGU Pro-Arg-Gly-Val-Arg © 2010 Paul Billiet ODWS

Mutations: Deletions A frame shift mutation Normal gene GGTCTCCTCACGCCA ↓ CCAGAGGAGUGCGGU Codons Pro-Glu-Glu-Cys-Gly Amino acids Deletion mutation GGTC/CCTCACGCCA ↓ CCAGGGAGUGCGGU Pro-Gly-Ser-Ala-Val © 2010 Paul Billiet ODWS

HUNTINGTON’S DISEASE Copyright Pearson Prentice Hall

How are mutations passed on? Only mutations in gametes (egg & sperm) are passed onto offspring. Has greatest impact in early embryonic development(in stem cells or first few days) Mutations in body cells only affect the organism in which they occur and are not passed onto offspring . How are mutations inherited? Copyright Pearson Prentice Hall

Mutagens What causes mutations? Natural errors in replication/transcription and/or environmental factors (What enzyme molecule would be responsible for errors during replication and/ transcription? What is a mutagen Something that causes the DNA code to change(mutate); x-ray, chemicals, UV light, radiation Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Although the haploid human genome consists of 3 billion nucleotides, changes in even a single base pair can result in dramatic physiological malfunctions. For example, sickle-cell anemia is a disease caused by the smallest of genetic changes. Here, the alteration of a single nucleotide in the gene for the beta chain of the hemoglobin protein (the oxygen-carrying protein that makes blood red) is all it takes to turn a normal hemoglobin gene into a sickle-cell hemoglobin gene. This single nucleotide change alters only one amino acid in the protein chain, but the results are devastating. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Summary Human Genome- 3,000,000,000 nucleotides Hemoglobin Gene- 73,308 nucleotides Mutation- 1 base (in a sequence of 147 between nucleotides 62,137-63,660) Location-Tip of Chromosome 11 Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Sequence Normal Hemoglobin Transcribe: (DNA) ATG GTG CAC CTG ACT CCT GAG GAG AAG TCT GCC GTT ACT  (mRNA)UAC CAC GUG GAC UGA GGA CUC CUC UUC AGA CGG CAA UGA Amino- Start Val  His  Leu  Thr  Pro  Glu  Glu  Lys  Ser  Ala  Val  Thr Sequence for Mutant (Sickle-Cell) Hemoglobin-Transcribe:  (DNA)ATG GTG CAC CTG ACT CCT GTG GAG AAG TCT GCC GTT ACT (mRNA)UAC CAC GUG GAC UGA GGA CAC CUC UUC AGA CGG CAA UGA AMINO Start Val  His  Leu  Thr  Pro  Val  Glu  Lys  Ser  Ala  Val  Thr Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Sequence Normal Hemoglobin Transcribe: (DNA) ATG GTG CAC CTG ACT CCT GAG GAG AAG TCT GCC GTT ACT  (mRNA)UAC CAC GUG GAC UGA GGA CUC CUC UUC AGA CGG CAA UGA Amino- Start Val  His  Leu  Thr  Pro  Glu  Glu  Lys  Ser  Ala  Val  Thr Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Sequence for Mutant (Sickle-Cell) Hemoglobin Transcribe:  (DNA)ATG GTG CAC CTG ACT CCT GTG GAG AAG TCT GCC GTT ACT (mRNA)UAC CAC GUG GAC UGA GGA CAC CUC UUC AGA CGG CAA UGA AMINO Start Val  His  Leu  Thr  Pro  Val  Glu  Lys  Ser  Ala  Val  Thr Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall -Result- The change from Glutamic acid to Valine (hydrophobic) causes the blood cell to become stiff and lose its round shape. -Clogs blood vessels, causing damaged organs Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall More than 10 years ago, scientists discovered that mutations in a gene called BRCA1 lead to a particularly deadly type of breast cancer. Now scientists have found another gene that may explain why. The gene PTEN has instructions to produce a protein that stops the uncontrolled cell growth of cancer. But BRCA 1 prevents PTEN from doing its work of suppressing cancer. That could explain why the 15 - 20% of women who have the BRCA 1 mutation are at a higher risk of getting breast cancer. Copyright Pearson Prentice Hall