Human Heredity. 1) Autosomes –all the chromosomes except the sex chromosomes (in humans, there are...
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Transcript of Human Heredity. 1) Autosomes –all the chromosomes except the sex chromosomes (in humans, there are...
Human Heredity
• 1) Autosomes– all the chromosomes
except the sex chromosomes (in humans, there are 22 pair)
2) Sex chromosomes– The sex-determining
chromosomes, the X & Y
• 3) Karyotype– Pictures of paired
human chromosomes arranged by size, used to identify abnormalities in fetuses
– Cells from an amniotic fluid sample are cultured, stained & photographed
• 4) Nondisjunction– Failure of chromosomes to separate– May cause a variety of birth defects, including
trisomy 21 or Down syndrome
• Turner’s syndrome
XX
XX O
•Only 1 sex chromosome is present.
*Associated with underdeveloped ovaries, short stature, webbed neck, and broad chest.
*Individuals are sterile, and lack secondary sexual characteristics.
*Mental retardation typically not evident .
• Klinefelter’s syndrome
• 5) Pedigree5) Pedigree Chart showing family history of a traitChart showing family history of a trait– Solid lightSolid light = homozygous dominant, = homozygous dominant, – solid darksolid dark = homozygous recessive, = homozygous recessive, – half-circlehalf-circle = heterozygous = heterozygous
• 6) Genetic disorders– Harmful effects produced by mutated genes,
most are recessive and few are lethal– Example: sickle cell anemia
Genotypes
SS
Ss
ss
Normal, with malarial resistance
Same as parents ; normal, no resistance; sickle-cell anemia
• 7) Sex-linked traits– A recessive gene on the X chromosome– Examples: color-blindness & hemophilia
– Genotypes:Phenotypes:– XNY normal male– XnY colorblind– XNXN normal female– XNXn carrier female– XnXn colorblind
normal vision
“weak red”
“weak green”
Phenotypes???
Cross of carrier female & normal male
XN
Xn
XN XNXN XNY
XN Xn XnY
Y
HY
X H Xh XHXh
XHXh
XHXH XHXh XHY XhY
Carrier Mom
Royal Hemophilia
Sex linkage & calico cats
Polydactyly(multiple fingers and toes)