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14 (inherited disorders (sickle cell disease, affects one out 400 African…
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inherited disorders
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cystic fibrosis, strikes one out of every 2,500 people of European descent, and one out of 25 are carriers
the chloride transport channels are defective or absent in the plasma membrane of children who inherit two recessive alleles
having cystic fibrosis results in highly abnormal concentrations of extracellular chloride causing mucus to thicken and become stickier
so the mucus builds up in pancreas, lungs, digestive tract, and other organs
sickle cell disease, affects one out 400 African Americans. it is caused by a substitution of a single amino acid in the hemoglobin protein of red blood cells
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when oxygen content of an infected individual blood is low, the sickle cell hemoglobin aggregates into sickle shape
sickled cells clump and clog small blood vessels. leading to physical weakness, pain, organ damage, and paralysis
two sickle cell alleles are needed for full blown sickle cell, the presence of one can affect phenotype
Mendel's model
first, alternative versions of genes are called alleles
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third, two alleles differ, one is dominant allele determines the organism appearance, the recessive allele no effect on appearance
fourth, the law of segregation two alleles for a heritable character segregate during gamete formation ending up in different gametes
Punnett square, device for predicting the allele composition of offspring from a cross between two individuals of known genetic makeup
capital letter for dominant allele, and lower case for recessive allele
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dominance
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when two alleles have affected the phenotype separately in distinguishable ways, this leads to codominance
ex: MN blood group in humans, is codominant alleles for two specific molecules that are located on the surface of red blood cells
also the MN phenotype is not intermediate between MN so it is completely different from incomplete dominance
dominant allele (round) codes for an enzyme that converts the unbranched form of starch to a branched form in the seed
the recessive allele (wrinkled) codes for the defective form of the enzyme that leads to unbranched starch, causing excess water to enter the seed
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but if dominant allele is present then excess water there will not be excess water entering the seed and it will not wrinkles when dried
ex: Tay-Sachs disease, inherited disorder, the brain cannot metabolize certain lipids b/c a crucial enzyme doesn't work properly
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the intermediate phenotype observed at biochemical level is characteristic of incomplete dominance of either allele
also heterozygote condition does not lead to disease symptoms, b/c half the normal enzyme activity is sufficient preventing lipid accumulation in the brain
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P generation, are the true-breeding parents (parental generation)
F1 generation, is the hybrid offspring (first filial generation)
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the effects of dominant and recessive allele, the organism trait doesn't always reveal its genetic compostion
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genotype, the genetic makeup
in Mendel's inheritance, genes only affect one phenotypic character, but genes have multiple phenotypic effects called pleitropy
many pleiotropic alleles cause the symptoms for hereditary diseases. Ex: sickle-cell, and cystic fibrosis
dominance relationship, multiple alleles, and pleiotropy effect alleles of a single gene
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such as human skin and height vary in populations in gradations along continuum, quantitative characters are usually the effect
these character designate polygenic inheritance, in which two or more genes will be affected for a single phenotypic character
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phenotype is affected by many things, that include the environment and genetics, meaning they are multifactorial
family history/ tree describes the parents traits and children across the generation called a pedigree
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testing during pregnancy
in 14-16th week in pregnancy, amniocentesis can be performed to determine whether the fetus has a disease
this procedure a needle is inserted into the uterus and extracts amniotic fluid, the liquid that bathes the fetus
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heterozygous, has two different alleles for a gene
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character, heritable trait that varies in individuals
each variant for a character, as it being either purple or white color for flowers called a trait
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cross pollinating two different true breeding plants, when mating them or crossing them is hybrization
homozygous, pair of identical alleles for a character (ex: PP homozygous dominant, pp homozygous recessive)