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- visual part of chromosome
- a)sex chromosomes (2) x and y
- b)autosomes (44)
Errors in chromosome #
- 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, 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
Human gene mutation database:
- catolog of mutant alleles that have clinical symptoms.
- Many have enzyme coding
- Many are recessive
Chromosomes / Genes:
- 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.