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The Human GenomeChapter 12
Karyotypes and Pedigrees
The Human Genome In humans, diploid (2n) = 46
That means somatic cells have 46 chromosomes 44 autosomal chromosomes and a pair of sex
chromosomes
Pedigrees
A pedigree is a diagram that traces a single trait through several generations
Individuals shaded in have attached earlobes. Is this trait dominant or recessive?
RECESSIVE!! Partially shade carriers and label genotypes
Solution:
A Pedigree for a sex-linked recessive trait:
Shade in known carriers and label genotypes.
Solution:
The Human GenomeChapter 12
Blood Typing and Chromosomal Genetic Disorders
Blood Typing ChartBlood Type
Genotypes Antigens AntibodiesDonate
toReceive
fromReaction to
Anti-AReaction to
Anti-B
Reaction to
Anti-Rh
A B
AB O
Rh+
Rh-
Use only to type blood in lab
(serum reacts to antigens present)
Blood Typing ChartBlood Type
Genotypes Antigens AntibodiesDonate
toReceive
fromReaction to
Anti-AReaction to
Anti-B
Reaction to
Anti-Rh
A
IAIA, IAi
B
IBIB, IBi
AB
IAIB
O
ii
Rh+
++, +-dominant
Rh-
--recessive
Use only to type blood in lab
(serum reacts to antigens present)
Blood Typing ChartBlood Type
Genotypes Antigens AntibodiesDonate
toReceive
fromReaction to
Anti-AReaction to
Anti-B
Reaction to
Anti-Rh
A
IAIA, IAi A Anti-B
B
IBIB, IBi B Anti-A
AB
IAIB AB none
O
ii none Anti-AAnti-B
Rh+
++, +-dominant
Rh none
Rh-
--recessive
none*only if exposed
to antigen
*Rh- mothers can be exposed to the Rh antigen if the fetus is Rh+
Use only to type blood in lab
(serum reacts to antigens present)
Blood Typing ChartBlood Type
Genotypes Antigens AntibodiesDonate
toReceive
fromReaction to
Anti-AReaction to
Anti-B
Reaction to
Anti-Rh
A
IAIA, IAi A Anti-B A,AB A,O
B
IBIB, IBi B Anti-A B,AB B,O
AB
IAIB AB none AB AB,A, B,O
O
ii none Anti-AAnti-B
A,B,AB,O O
Rh+
++, +-dominant
Rh none pos pos or
neg
Rh-
--recessive
none*only if exposed
to antigen
pos or
neg
neg only
*Rh- mothers can be exposed to the Rh antigen if the fetus is Rh+
Use only to type blood in lab
(serum reacts to antigens present)
Blood Typing ChartBlood Type
Genotypes Antigens AntibodiesDonate
toReceive
fromReaction to
Anti-AReaction to
Anti-B
Reaction to
Anti-Rh
A
IAIA, IAi A Anti-B A,AB A,O clumps -
B
IBIB, IBi B Anti-A B,AB B,O - clumps
AB
IAIB AB none AB AB,A, B,O clumps clumps
O
ii none Anti-AAnti-B
A,B,AB,O O - -
Rh+
++, +-dominant
Rh none pos pos or
neg
clumps
Rh-
--recessive
none*only if exposed
to antigen
pos or
neg
neg only -
Use only to type blood in lab
(serum reacts to antigens present)
*Rh- mothers can be exposed to the Rh antigen if the fetus is Rh+
Nondisjunction
Occurs when a chromosome or chromosomes fail to separate in meiosis
Individuals end up with the wrong number of chromosomes ( < or > 46 total)
Risk factor increases with age
Nondisjunction of Autosome
Down Syndrome
caused by trisomy 21 (3 copies of chromosome #21)
Nondisjunction of Sex Chromosomes
Turner Syndrome (karyotype 45, XO):
Female; sterile; sex organs do not develop at puberty
Klinefelter’s Syndrome (Karyotype 47, XXY):
Male; infertility; fewer secondary sex characteristics; variations are 48, XXXY and 49, XXXXY
