MUTATIONS & HUMAN GENETICS Chapter 11.3, Chapter 12

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)

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?

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

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

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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 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

 Mutation of genetic material will affect the proteins produced

Sickle Cell – result from the change in one base on Chromosome 11.

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.

HUMAN TRAITS Chapter 12, Section 1

Pedigree  Pedigree = map of inheritance of genetic traits from generation to generation

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

 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

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

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

When Heredity Follows Different Rules Chapter 12, Section 2

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

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

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

 Red-Green colorblindness  Hemophilia (blood doesn’t clot properly)  Male Pattern Baldness  Duchenne Muscular Distrophy (muscular degeneration leading to eventual paralysis)

 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

Polygenic Inheritance  Characteristics that are influenced by several genes