MUTATIONS Chapter 11.3, Chapter 12

Mutations  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)

Types of Mutations  Point Mutations (base substitutions)= a change in a single DNA base pair  Frameshift Mutations (addition or deletion)= a single base is added or deleted from DNA

 If a mutation causes a change in the a.a. it’s called a missense mutation  If a mutation does not change the a.a. it’s called a silent mutation  If a mutation changes the a.a. to a ‘stop’ codon it’s called a nonsense mutation.

Point Mutations (Base Substitutions)  THE BOY CUT HIS LIP AND ATE THE HOT DOG  Point mutation  THE BOY BUT HIS LIP AND ATE THE HOT DOG  GAC  TAC  GAC  GAG  Silent mutation is when mutation makes no amino acid change  CTT  CTG  Leucine  Leucine (No change!) Animation Quiz 14 - Mutation by Base Substitution Animation Quiz 14 - Mutation by Base Substitution

Frameshift Mutations  THE BOY CUT HIS LIP AND ATE THE HOT DOG  Insertion:  THE BOY CUT HIS SLI PAN DAT ETH EHO TDO G  Deletion:  THE BOY CUT HIS LIP ANA TET HEH OTD OG  hill.com/sites/ /student_view0/chapter9/animat ion_quiz_5.html hill.com/sites/ /student_view0/chapter9/animat ion_quiz_5.html hill.com/sites/ /student_view0/chapter9/animat ion_quiz_5.html

 Chromosomal Mutations = missing or extra pieces of chromosomes, switched pieces, extra chromosomes  occurs frequently in plants, “super sized strawberries”  Few C.M.’s get passed onto offpring because the zygote dies and doesn’t develop or the mature offspring cannot reproduce

 Mutation of genetic material will affect the proteins produced

Cause & Repair  Some mutations are spontaneous  Mutagen = any agent that causes DNA change (ex: 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

  ee_overview.htm ee_overview.htm

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  Human has 22 pairs (44 chromosomes)  Sex Chromosome = genes that determine an individuals gender (X and Y)  Male= XYFemale= XX  Sex chromosomes are the last pair on the karyotype  Human has 1 pair (2 chromosomes)

Common Chromosomal Disorders DisorderChromosome Abnormality Patau SyndromeTrisomy 13 Edwards SyndromeTrisomy 18 Down SyndromeTrisomy 21 Jacobs SyndromeXYY Turner SyndromeXO Kleinfelter SyndromeXXY Triple XXXX

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 homozygous phenotypes, appearance of a third phenotype  Do not use lower case letters, use prime instead (‘) apostrophe

Alleles: S= straight hair, S’= curly hair SS= straight, SS’=wavy, S’S’=curly  Cross a straight haired father with a wavy haired mother:

Codominance & Multiple Alleles  Both alleles for a gene are expressed in a heterozygous individual  Neither allele is recessive, both dominant  Ex: Blood type  BLOOD TYPE.ppt BLOOD TYPE.ppt BLOOD TYPE.ppt  Blood type also shows multiple alleles, more than 2 alleles: A, B, O  Eye color also shows multiple alleles

Erminette Chickens  F B = black, F W = white  F B F B = black; F W F W = white  F B F W = erminette (speckled)  Please cross a white chicken with a speckled chicken.

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 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

For the colorblindness trait, cross a normal dad with a heterozygous normal mom. X R = normal X r = red-green colorblind

Cross a colorblind dad with a normal mom whose father was colorblind. X R = normal X r = red-green colorblind

Polygenic Inheritance  Characteristics that are influenced by several genes