Chapter 13: Patterns of Inheritance

dosage compensation that Barr bodiesensures an equal expression of genes from the sex chromosomes even though females above 2 X chromosomes and males have only 1mosiacismmammalian females may be mosaic for the expression of genes on the X chromosome due to inactivation in dosage compensationcalico cats have heterozygosityhaving two different alleles of the same gene; one for black fur and one for orange fur making a patchy distributionmendel's seven traits on five chromososmes-- the absolute LUCKassortment of genes is not independent; if genes are connected together on a chromosome they will tend to travel togethergenetic recombination most often is genes far apartthe farther apart 2 genes are, the more frequently recombination should occur between themfigure 13.2the chromosomal basis of sex linkagefigure 13.3are white-eyed females ever possible?figure 13.17obtaining fetal cellsmarkers that can be detected but dont cause phenotypegenetic markers that can be detected using molecular techniques but that do not cause a detectable phenotype.SNP's single nucletide--- millions of thema site present in at least 1% of all the population at which individuals differ by a single nucleotide. There can be used as genetic markers to map unknown genes or traits.nondisjunction and aneuploidythe failure of homologues or sister chromatids to separate properly during meiosis this failure leads to the gain or loss of a chromosomeMonosomics and trisomicsmonosomics- have lost one copy of an autosome and generally do not survive embryonic development trisomies- have gained an extra autosome and also do not survive.looking at five of the smallest human chromososmes13, 15, 18, 21, & 22 can be present as three copies and still allow the individual to survive, at least for a time.downs and moms 20 and younger and 3520 and younger risk 1 in 1700 and 35 risk 1 in 750female gamates arrested in meiosis 1chromosomal abnormalities arise more frequently on the female side where gametes are set aside in early development.XXX ( taller normal female) XXY (kinefelter and OX tunner) XO (genetotype turner) XYY (geneotype Jacod)XXX- develops into a female with one functional X chromosome and two Barr bodies, taller instate but otherwise normal in appearance. XXY- develops into a male who has many female body characteristics and in some cases diminished mental capacity. XO-sterile female, short in statue, webbed neck and sex organs that never fully mature during puberty. XYY- develop normal fertile males of normal appearancepedigrees: circles, squares, horizontal and vertical lines, colored inSquare shapes represent males; circles represent females. Filled-in shapes are individuals that have whatever trait is being shown in the pedigree. Two individuals connected together with a horizontal line between them are the parents of the individuals that are connected by vertical lines below them.looking at the pedifree of albinism (13.13) what three questions does a geneticist traditionally ask? what are the answers as they relate to albinism1. is albinism sex-linked or autosomal? 2. is albinism dominant or recessive? 3. is the albinism trait determined by a single gene or several? It is reasonable to assume that it is autosomal. It is consistent with a recessive mode of inheritance. One gene is segregated in the cross.Hemiphilia's are usually inherited asx-linked recessive patternsQueen Victoria's descendentsThe most famous instance of hemophilia, 3/9 of her children did receive the defective allele.why is it significant that it a valine and glumatic acid change (p. 249)it causes the hemoglobin molecules to aggregate into stiff rods, which deform blood cells into sickle shape that can no longer carry oxygen efficientlyIf Huntington's is dominant, what does the disorder persistthe disorder persists in human populations because its symptoms usually do not develop until the affected individuals are more than 30 years old, and by that time most of them have had children.Genetic counseling and amniocentesis and chorionic villus samplingtests used when identifying parents at risk of producing children with genetic defects or high risk pregnancies that assess the genetic state of the embryo at an early stageDescribe the three things that genetic counselors look at from cultures of cells obtained (amnio, CVS).1. chromosomal karyotype 2. enzyme activity 3. genetic markersPreimplantation genetic screeningscreening of embryo created in vitro at the 4- to 8-call stage for genetic disorders prior to implantationGenomic imprintingDescribes an exception to Mendelian genetics in some mammals in which the phenotype caused by an allele is exhibited when the allele comes from one parent, but not from the other.Maternal inheritance of mitochondria.mitochondria usually inherited from one parent generally the mother via the egg