Changes in Chromosome Number or StructureAlterations of Inheritance Patterns by Gender
2 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
Arises by Non-disjunction
Non-disjunction failure of homologues or chromatids to separate during meiosis
4 Human Chromosomal Aneuploids Autosomal Aneuploids Trisomy three copies of one chromosome 5 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) 6 Karyotype for Down Syndrome Physical Features Eye fold Palm Crease 7 Incidence of Down Syndrome Increases with Maternal Age Number per 1000 Births Age of Mother (years) 8 Applying Your Knowledge
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
9 Human Chromosomal Aneuploids Sex Chromosome Aneuploids Sterile female Fertile female Sterile male Fertile male 10 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) 11 Karyotype for Turners Syndrome Non-functional Ovaries From Adult Female with Turners Syndrome Normal uterus tubes and ovaries 12 Human Chromosomal Aneuploids How can XYY Syndrome occur One Copy of the X chromosome Two Copies of the Y chromosome Eg. Egg with 1 copy of X (23 chromosomes) Sperm with 2 copies of Y (24 chromosomes) Embryo with XYY (47 chromosomes) 13 X-Chromosome Inactivation in Females
Inactivation of one of the X chromosomes in each cell of an adult female balances the sex chromosome/autosome ratio.
Either the maternal or paternal chromosome is inactivated.
The arrow shows a Barr body or inactivated X.
The number of Barr bodies equals the number of X chromosomes minus one.
female male 14 Applying Your Knowledge Determine how many Barr bodies would be found in each cell of someone with 0 2 1 0 15 Chromosome Structure Changes 16 Chromosome Deletion in Humans
is correlated with
a deletion at the end
of chromosome 5.
17 Chromosome Duplication in Humans
Small duplications in chromosome 15 cause no symptoms
Large duplication (with inversion) causes seizures and mental retardation
18 Chromosome Translocation in Humans
Reciprocal Translocation involves exchange between two non-homologous chromosomes
Reciprocal translocation between chromosomes 2 and 20 causes Alagille Syndrome
19 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
20 Chromosome Inversions Lead to Unbalanced Meiotic Products A paracentric inversion does not include the centromere A pericentric inversion includes the centromere 21 Applying Your Knowledge
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
22 Interaction between Gender and Heredity Example Pattern BaldnessCaused by a dominant allele in malesbut a recessive allele in females 23 Interaction between Gender and Heredity Cock-feathered male Hen-feathered female Hen-feathered male Cock feathering autosomal recessive Expressed only in males 24 Interaction Between Gender and Heredity Angelman SyndromeDeletion on chromosome 15 inherited from mother Prader-Willi SyndromeDeletion on chromosome 15 inherited from father
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