Chromosomal Mutations. Changes in Chromosome Number or Structure Alterations of Inheritance Patterns by Gender. Alterations in Chromosome Number . Polyploidy: one or more extra sets of chromosomes
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Chromosomal Mutations Changes in Chromosome Number or StructureAlterations of Inheritance Patterns by Gender
Alterations in Chromosome Number • Polyploidy: one or more extra sets of chromosomes • Aneuploidy: gain or loss of one chromosome or a small number of chromosomes
Non-disjunction in Meiosis II Normal Meiosis Non-disjunction in Meiosis I Aneuploidy • Arises by Non-disjunction • Non-disjunction = failure of homologues or chromatids to separate during meiosis
Human Chromosomal Aneuploids Autosomal Aneuploids Trisomy: three copies of one chromosome
Human Autosomal Abnormality How can Down Syndrome occur? Eg. Egg with 2 copies of #21 (24 chromosomes) + Sperm with 1 copy of #21 (23 chromosomes) = Embryo with 3 copies of #21 (47 chromosomes)
Karyotype for Down Syndrome Physical Features Eye fold Palm Crease
400 300 200 100 0 10 20 30 40 50 Incidence of Down Syndrome Increases with Maternal Age Number per 1000 Births Age of Mother (years)
Which one involves the loss of one chromosome? Which one describes the failure of chromatids to separate in Anaphase II? Which one involves the gain of an extra set of chromosomes? Which is the most specific description for the cause of Down Syndrome? Polyploidy Non-disjunction Aneuploidy Crossing-over Trisomy Applying Your Knowledge
Human Chromosomal Aneuploids Sex Chromosome Aneuploids Sterile female Fertile female Sterile male Fertile male
Human Sex Chromosome Abnormality How can Turner Syndrome occur? Eg. Egg with 0 copies of X (22 chromosomes) +Sperm with 1 copy of X (23 chromosomes)= Embryo with 1 copy of X (45 chromosomes)
Chromosome Deletion in Humans Cri-du-chat syndrome is correlated with a deletion at the end of chromosome 5.
Chromosome Duplication in Humans • Small duplications in chromosome 15 cause no symptoms • Large duplication (with inversion) causes seizures and mental retardation
Chromosome Translocation in Humans • Reciprocal Translocation involves exchange between two non-homologous chromosomes • Reciprocal translocation between chromosomes 2 and 20 causes Alagille Syndrome
Chromosome Translocation in Humans • Robertsonian Translocation involves a fusion of the long arms of two different chromosomes • Translocation Down Syndrome involves a Robertsonian Translocation between chromosomes 14 and 21
Applying Your Knowledge • Deletion • Duplication • Inversion • Translocation • Which type of structure change • represents an exchange between two non-homologous chromosomes? • represents a reversal of a chromosome segment? • represents a loss of a chromosomal segment?
John Adams BB or Bb bb BB or Bb bb John Quincy Adams Interaction between Gender and Heredity Example: Pattern BaldnessCaused by a dominant allele in males,but a recessive allele in females