Pedigrees & Karyotypes

Pedigrees•Used to explore human genetics•Circles = Female•Squares = Male•Traits:

– Not Shaded = Do not have – ½ Shaded = Carrier– Full Shade = Have

http://learn.genetics.utah.edu/content/addiction/pi/

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 FlowchartHow many males

& females areaffected?

More Males Sex Linked

Trait

Affected Males = Affected Females

Autosomal

Are carrier

s presen

t?

Yes:

Recessive

No:Does

the trait skip a

generation?

No male carriers?

Yes: Recess

ive

No: Domina

nt

Human Karyotypes• 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

•1/800 US births•Mild – severe

Sex Chromosomes Sex Chromosomes DisorderDisorder

•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