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MUTATIONS & HUMAN GENETICS Chapter 11.3, Chapter 12
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Mutations (11.3) Mutation = change in DNA sequence Mutations can be caused by errors in replication, transcription, translation, cell division, or external agents. Mutations in reproductive cells can affect potential offspring (ex: inheritable genetic disorders) Mutations in body cells do not get passed onto offspring (ex: if an individual develops skin cancer)
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MUTATIONS THE DOG RAN ALL DAY becomes THE DOG ANA LLD AY THE DOG ANA LLD AY or or THE DOG RAN ALL DAY becomes THE DOG SRA NAL LDA Y THE DOG SRA NAL LDA Y What happened in each sentence?
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Types of Mutations Types of Mutations Can alter the genetic code causing changes to amino acids and then protein produced. Frameshift Frameshift - moves reading frame to the left or right. Deletion = a base is deleted Insertion = a base is added
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Mutations THE DOG RAN ALL DAY becomes THE DOG RUN ALL DAY THE DOG RUN ALL DAY or or THE DOG RAN ALL DAY becomes THE DOG RAN THE DOG RAN or or
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Point Mutation/Substitution – One base is substituted in place of another possibly altering amino acids (a.a.) produced Missense Mutation – changes a.a. Silent Mutation – doesn’t change a.a. Nonsense Mutation – changes a.a. to a stop codon
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http://highered.mcgraw- hill.com/sites/0072556781/student_view0 /chapter11/animation_quiz_4.html http://highered.mcgraw- hill.com/sites/0072556781/student_view0 /chapter11/animation_quiz_4.html http://highered.mcgraw- hill.com/sites/0072556781/student_view0 /chapter11/animation_quiz_4.html
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Non Coding Chromosomal Mutations missing or extra pieces of chromosomes, switched pieces, extra chromosomes (nondisjunction) occurs frequently in plants, “super sized strawberries” Few chromosomal mutations get passed onto offspring because… The zygote dies or the mature offspring cannot reproduce and is sterile
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Mutation of genetic material will affect the proteins produced
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Sickle Cell – result from the change in one base on Chromosome 11.
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Cause & Repair Some mutations are spontaneous others can be the result of long term Mutagen = any agent that causes DNA change (ex: harmful chemicals, radiation) Cells have repair mechanisms and special enzymes that can fix incorrect DNA.
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HUMAN TRAITS Chapter 12, Section 1
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Pedigree Pedigree = map of inheritance of genetic traits from generation to generation
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Karyotype Chromosomes come in pairs, inherited from parents Karyotype = a chart of chromosome pairs, can be used to visualize chromosomal abnormalities Humans have 23 pairs of chromosomes, 46 total chromosomes
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Autosomes = any chromosome that isn’t a sex chromosome Sex Chromosome = genes that determine an individual’s gender (X and Y) Sex chromosomes are the last pair on the karyotype
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Recessive Heredity Caused by recessive alleles Attached earlobes, Cystic fibrosis (defective protein leads to excessive mucus production in lungs), Albinism Individual will only display the recessive phenotype if its genotype is homozygous recessive
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Dominant Heredity Caused by dominant allele Freckles, Widow’s peak, Hitchhickers thumb, Huntington’s disease (brain degeneration, doesn’t appear until later in age), immunity to poison ivy Individual will display the dominant phenotype if its genotype is heterozygous or homozygous dominant
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When Heredity Follows Different Rules Chapter 12, Section 2
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Incomplete Dominance Complete Dominance = one allele completely dominates over another Incomplete Dominance = phenotype of a heterozygote is in between the dominant & recessive phenotypes, appearance of a third phenotype
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Codominance Both alleles for a gene are expressed in a heterozygous individual Neither allele is dominant or recessive Ex: Blood type BLOOD TYPE.ppt BLOOD TYPE.ppt BLOOD TYPE.ppt
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Sex Determination & Sex- linked Inheritance Combination of sex chromosomes (X and Y) determine an individual’s gender Males XY, X chromosome comes from mom & Y chromosome comes from dad Females XX, both mom & dad give an X chromosome Sex-linked Traits = traits controlled by genes on sex chromosomes
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Red-Green colorblindness Hemophilia (blood doesn’t clot properly) Male Pattern Baldness Duchenne Muscular Distrophy (muscular degeneration leading to eventual paralysis)
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Most of sex-linked traits are found on genes on the X chromosome (X-linked trait) because it is larger than the Y chromosome X-linked traits display more in males because they only have 1 X chromosome, whereas females get 2 X chromosomes so they can be carriers of the trait but not display the phenotype
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Polygenic Inheritance Characteristics that are influenced by several genes
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