PCB 3063 Detailed Exam 2 2025

Aromatase - -converts androgens to estrogens in temp dependent sex determination Pars - -on each end of y chromosome; synapse and recombine w X chromosomes in meiosis MSY - -male specific region of Y, middle section including SRY SRY - -sex determining region Y; controls sexual development, codes for testis determining factor (TDF) Males w two X chromosomes and no Y? - -one X contains SRY Females with one X and one Y? - -Y chromosome missing SRY TDF - -testes determining factor, on SRY, transcription factor Klinefelter syndrome - -More than 1 X chromie, (XXY) usually male, infertile, 47 XXY, Karyotype 47, XXX Syndrome (Triplo-X) - -(XXX) female differentiation, usually perfectly normal, also possible tetra and penta X, bc of nondisjunction during meiosis Turner Syndrome - -45, X0, female genitalia, short, skin flaps on back of neck, underdeveloped, normal intelligence, bc nondisjunction during meiosis Dosage compensation - -Mechanism in which X chromosome inactivation equalizes gene expression between males and females; deletion of extra genes when 2+ x chromosomes are present X:y chromosome ration for male drosophila - -0.5 X:y chromosome ration for metamale drosophila - -0.33 X:y chromosome ration for female drosophila - -1.0 X:y chromosome ration for metafemale drosophila - -1.5 X:y chromosome ration for intersex drosophila - -.75-.67 Barr body - -Inactivated X chromosome PCB 3063 PCB 3063 PCB 3063 Lyon hypothesis - -the proposal that dosage compensation in mammalian females is accomplished by partially and randomly inactivating one of the two X chromosome; why female cats can have random spots of different colors Mechanism of x inactivation - -DNA and/or histone proteins are chemically modified Mechanism of x inactivation - -DNA inactivated by splices in the genome Imprinting - -process whereby expression of genes on one homolog but the other in unaffected Xic (X inactivation center) - -Contains several genes important for X inactivation XIST (X inactive specific transcript) - -gene on Xic, critical for gene inactivation Possible explanations for conditions of people with abnormal numbers of sex chromosomes - -- inactivation doesn't take place early enough - not all x chromosomes are inactivated Aneuploidy - -the presence of an abnormal number of chromosomes in a cell but not a complete set Monosomy - -loss of a single chromosome from a diploid gene Trisomy - -gain of a single chromosome from diploid genome Euploidy - -complete haploid sent of chromosomes are present Polyploidy - -more than two sets of chromosomes are present Autoploidy - -Polyploid organism with multiple chromosome sets all from the same species Alloploidy - -Polyploid organism that contains the genomes of two or more different species Nondisjunction - -Error in meiosis in which homologous chromosomes fail to separate. 50% - -ratio of abnormal genes when nondusjunction occurs during meiosis II Not tolerated - -monosomy of autosomes Tolerated - -monosomy of sex chromosomes Haploinsufficiency - -a single copy of the recessive gene is insufficient to provide a life sustaining function for organism PCB 3063 PCB 3063 Down syndrome - -trisomy 21 (47, 21+) - higher risk of disease and cancers DSCR: Down syndrome critical region - -critical region on chromosome 21, responsible for many phenotypes of disorder Over age 35-40, because of increase in ovum - -chances of having a child with down syndrome increase (because?) Amniocentesis & chromic villus sampling - -fetal cells obtained from amniotic fluid or placental chorion Noninvasive prenatal genetic diagnosis - -deriving fetal cells and DNA from maternal circulation Patau Syndrome (47, 13+) and Edward syndrome (47, 18+) - -only viable human aneuploidy, autosomal trisomy, severe malformations, short lifespan/lethal Chromosome aberrations - -changes that delete, add, or rearrange substantial portions of one or more chromosomes Deletions and duplications - -changes in total amount of genetic info Inversions and translocations - -the genetic material remains the same but is rearranged Nonhomologous chromosomes - -translocation occurs between what Terminal deletion - -A deletion occurring near one end of the chromosome. Intercalary deletion - -deletion occurring on the interior of the chromosome Compensation loop - -Synapsis between chromosome with large intercalary deletion and normal complete homolog Requires unpaired region of normal homolog buckling out to loop out of linear structure into deletion Crui du chat syndrome - -loss/deletion of small variable part on short arm of chromosome 5, not inherited, mutation Duplications - -unequal crossing over between synapsed chromosomes during meiosis, replication error prior to meiosis Insertion and deletion - -compensation loops during prophase 1 could be due to ... Gene redundancy, phenotypic variation, source of genetic variability during evolution - the three aspects of gene duplications PCB 3063 Nucleolus organizer regions (NOR's) - -contain clusters of rdna repeat sequences The bar mutation in drosophila - -this duplication in drosophila causes phenotypic variation in the 16A region on the X chromosome, responsible for eye shape (slit or round) Inversions - -rearrangement of linear gene sequence; requires 2 breaks in chromosome and reinsertion of sequence; requires _____ loop; unusual synapsis during meiosis Reciprocal translocation - -exchange of segments between two nonhomologous chromosomes Familial Down Syndrome - -one parent has 14/21 translocation; during meiosis 1/4 gametes have two copies of chromosome 21 Linkage - -two genes on a single pair of homologs; exchange