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Notes #9. Baby Face Lab. Background. Gene: segment of DNA codes for a trait Allele: alternate forms of a gene Dominant: “more powerful” allele / most common (CAPITAL) Recessive: only expressed when no dominants present (lower case). Phenotype
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Notes #9 Baby Face Lab
Background • Gene: • segment of DNA codes for a trait • Allele: • alternate forms of a gene • Dominant: • “more powerful” allele / most common (CAPITAL) • Recessive: • only expressed when no dominants present (lower case)
Phenotype • how genes are expressed • Genotype • genetic makeup • letters representing a trait • Homozygous: • identical alleles (kk, KK) • Heterozygous: • different alleles (Kk)
I. Sex • 1 pair of sex chromosomes • X and Y • XX = female • XY = male
X X P(male) = P(female)= X Y
X X P(male) = P(female)= X Y XX XX XY XY
Which sex is more responsible for sex of the baby? • Mom can only give X’s, males can give X or Y. • Sex linked trait • Trait that is on a sex chromosome
Hemophilia XH X P(male) = P(female)= X Y
Find out the genotypes for a hemophiliac boy’s parents. XH X P(male) = P(female)= X Y XH X XX XH Y XY
Color Blindness X X Xc Y
Color Blindness X X Xc Y Xc X Xc X X Y XY
Make a color blind female Xc X Xc Y
Make a color blind female Xc X Xc Y Xc Xc Xc X Xc Y XY
Hairy Ears: located on Y chromosome X X X Ye X X X X XYe XYe
Incomplete dominance • Blending of traits • Skin, hair, eye color • Hair type • Codominance • Equally dominant • Dimples
Notes #4: Karyotyping
I. Karyotype • Map of chromosomes. • Purpose: • Count up and match chromosomes in a cell • See if there are any chromosomal abnormalities • Who do they test: • Anyone who they think could certain genetic diseases or could be a carrier • Unborn babies • How do they do it? • Blood cell • Baby cells acquired through amniocentesis
II. Amniocentesis • Amniotic fluid: • Fluid surrounding baby • Contains some of baby’s cells • Ultrasound: • Use sound waves to create image • Guide needle into placenta to acquire baby’s cells
III. Nondisjunction • During meiosis homologous chromosomes don’t separate evenly. • One gamete ends up with too many and the other one ends up with too few. • If this gamete is fertilized, all cells of baby will have wrong #
IV. Genetic Diseases caused by nondisjunction • Down’s Syndrome • Chromosomal problem: Extra #21 • Symptoms: mild to severe mental retardation, physical characteristics • Life expectancy: 49 years • 1/800-1000
Turner’s Syndrome • 45 X • Chromosomal problem: missing a sex chromosome • Life expectancy: Normal • Symptoms: mild to no mental retardation, sterility, short stature, sometimes heart & kidney problems • 1/2500
Trisomy XXY • Klinefelter Syndrome • Chromosomal problem: Extra sex chromosome(s) • Symptoms: • sterile, mild to severe mental retardation, feminized proportions, physical characteristics. • Life Expectancy: Normal • 1/500
Trisomy 18 • AKA Edward Syndrome • Chromosomal problem: Extra # 18 • 1/3000 • Symptoms: • Severe mental retardation • Severe physical deformities • Life expectancy – 1 week to a few months
Trisomy 13 • Patau Syndrome • Chromosomal problem: Extra #13 • Symptoms: • Polydactyly (extra fingers • Severe physical deformities • Life expectancy: • 1 week to a few months • 1/5000