Transcript Pedigrees & Karyotypes

Pedigrees &
Karyotypes
Pedigrees
•Used to explore human genetics
•Circles = Female
•Squares = Male
•Traits:
– Not Shaded = Do not have
– ½ Shaded = Carrier
– Full Shade = Have
Modes of Inheritance
• Autosomal or Sex-Linked
– Autosomal –chromosomes other than sex
chromos.
– Sex linked – X or Y
• Dominant or Recessive
Autosomal Recessive
• ~equal in males & females
• Often skips generations
• May show carriers (half shaded)
but not always!
Autosomal Dominant
•Does not skip generations
•Affect crossed with unaffected =
50% of offspring are typically
affected
Sex-Linked Traits
–Mostly males
•Mother of affected male is a
carrier or affected.
–No male carriers, but can have
female carriers
Pedigree Flowchart
More Males
Sex Linked
Trait
How many
males &
females are
affected?
Affected
Males equal
Affected Females
Autosomal
No male
carriers?
Yes:
Recessive
No:
Does the trait
skip a
generation?
Are
carriers
present?
Yes:
Recessive
No:
Dominant
Human Karyotypes
• Number & appearance of chromosomes
in the nucleus of eukaryotes
• Diploid organisms
• 46 Chromosomes
– 23 homologous pairs
•2 sex chromos.
• Used to detected
aneuploidy associated
disorders
Nondisjunction
• Not coming apart
• Abnormal
chromosome #s in
gametes
– Causes: Aneuploidy
Down Syndrome
• Trisomy (Three bodies)
• Chromosome 21
– autosomal
• Most common serious birth defect
in the US
• 1/700 US births
Sex Chromosomes
Disorder
• Turner’s Syndrome
– Female with only one X
– XO
– Causes Sterility = no sex organ
development at puberty
– Short stature
– Webbed neck
• Klinefelter’s Syndrome
– Males with an extra X
– Reduced fertility
– Less testosterone
– 1/1000 males
• XYY
– Normal reproduction
– Delay motor skills
– temper
X Chromosome
• No cases of babies born
without an X chromosome
• X is vital for normal
development
Y Chromosome
• Important role in sex
determination
• Y presence creates a male no
matter how many extra Xs
– Exception : Swyer syndrome