Bio CH 13 chromosomes/mapping/genetics

• visual part of chromosome
• a)sex chromosomes (2) x and y
• xx-female
• xy-male
• b)autosomes (44)

• errors in meiosis -> nondisjunction
• Aneuploid= +1-1 chromosome (error in meiosis)
• a) Autosome error- Down syndrome 3 #21chromosomes instead of 2. (higher with age)
• b) sex chromosome error xxx,xxy,x,xyy

• Condition is gentetically caused:
• a) Few are caused by dominant allele

• b)Most are caused by recessive allele
• I)Cystic fibrosis - 1/2500 caucasion births. Gene therapy- attempt to replace defective allele w good one.

• II) Tay-sacks disease "lysosome storage disease"
• -lipid digestive enzyme is missing

III) Hemophilia- blood clotting issue

• IV)Sickle cell anemia- error in hemoglobin (changes shape beta chain)
• -High frequency in americans of african anscentry
• -If you are heterozygous resistant to maleria (700 or more hemoglobin variants)

• Heterogygous for the condition
• Example for Tay-sacks:
• Tt (t - carrier for tay sachs)
• carrier x carrier-->Tt x Tt--> 1TT:2Tt:1tt
• 20% have tt

used in prenatal diagnosis of chromosomal abnormalities and fetal infections,[2] in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for genetic abnormalities

a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus(placental tissue) and testing it for chromosomal abnormalities

• catolog of mutant alleles that have clinical symptoms.
• Many have enzyme coding
• Many are recessive
• (28,000)

• Genes on chromosome are "linked" (to some degree)
• Many travel together
• Mapping genes onto chromosome can be done looking at recombination frequency (how often they are seperated)
• 
• Genes clossser to centriole are more likely to stay together after crossover.