Pedigrees Karyotypes Pedigrees Used to explore human genetics

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: Recessiv e 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