Genetics Exam 2

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princesspink21
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Genetics Exam 2
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2011-10-09 15:47:44
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Genetics
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  1. Independent Assortment:
    2 genes on 2 different homologous pairs of chromosomes
  2. Linkage:
    2 genes on a single pair of homologs
  3. Complete linkage:
    • only parental gametes
    • very rare
  4. Drosophilia:
    crossing over occurs only in females
  5. What are the steps of two point mapping?
    • 1) Find and map the smallest distance.
    • 2) continue this process until the map is complete and all distance add up to observed recombination frequencies
  6. To find % of double crossover:
    % of SCO x % of SCO = DCO %
  7. 3-point mapping rules:
    • 1) individual must be heterozygous at all 3 loci
    • 2) must be able to determine genotype by examing phenotypes of offspring
    • 3) must have large # of offspring
  8. Interference:
    reduction in the number of DCO events relative to what is expected based on the map distance
  9. Heterokaryon:
    • a single hybrid cell with 2 nuclei
    • only 2 cells (mouse and human) can be induced to form heterokaryon
  10. Synkaryon:
    nuclei in heterokaryon will fuse to form synkaryon
  11. Isogamets:
    • reproductive cells
    • similar to our haploids
  12. Tetrad analysis:
    take a single gene and map according to the centromere
  13. Distance between gene and centromere:
    (1/2 2nd division segregant asci)/(total asci scored)
  14. Ordered Tetrad Analysis:
    • must know order
    • destinguishes 1st and 2nd division segregants which is necessary to map gene in relation to the centromere
  15. Unordered Tetrad Analysis:
    • determine if 2 genes are linked (occur on the same chromosome)
    • map distance between the two loci
  16. Male chromosome:
    22, XY
  17. Female chromosome:
    22, XX
  18. Klinefelter Syndrome:
    • 47, XXY
    • genetalia/internal ducts male
    • underdeveloped testes - cant produce sperm (sterile)
    • some masculine development
    • slight breast enlargement
    • 2/1000 male births
    • occur from nondisjunction of x-chromosome
  19. Turner Syndrome:
    • 45, X
    • female external genetaliea/internal ducts
    • underdeveloped ovaries
    • short
    • webbed neck
    • broad chest
    • 1/3000 female births
    • occur from nondisjunction of X-chromosome
  20. 47, XXX syndrome:
    • 1/1200 female births
    • highly variable:
    • - normal to underdeveloped secondary sexual characters
    • - sterility
    • - mental retardation
  21. 48, XXXX
    spontaneously aborted
  22. 49, XXXXX
    spontaneously aborted
  23. Jacob Syndrome:
    • 47, XYY
    • 9/315 males in Scottish Maximum Security proson
    • taller
    • criminal acts
    • 7/9 subnormal intelligence
    • all 9 personality disorder
    • known as the "criminal" phenotype
    • actually found that these individuals dont have antisocial behaviors and live normal lives
  24. Sexual differentiation in Humans:
    • every embryo goes through period when is hermaphrodite
    • 5th week --> gonadal tissue arise associated with kidney
    • primordial germ cells migrate to these ridges -- outer cortex and inner medulla form
    • 2 sets of undifferentiated male and female ducts exist
    • if cells have XY development into testes takes place - 7th week
    • testicular tissue secretes 2 hormones for continued male development
    • absences of Y - ovarian tissue forms
    • absence of male development oogonia begin meiosis and oocytes can be detected - 12th week
    • 25th week - all oocytes remain dormant untill puberty
    • males - spermatocytes are not produced until puberty
  25. Hermaphrodites:
    • 2% of live birth
    • 2 eggs are fertilized in womb - one XX and one XY
    • eggs merge to become one zygote
  26. Pseudoautosomal Regions (PAR):
    • shares homology with X-chromosome
    • synapses and recombines
  27. Nonrecombining Region of the Y (NRY):
    • 20 genes in this region
    • 12 groups into 2 different groups
    • 5 of 12 have homologs on X-chromosome
    • other 7 lack X -homologs - expressed only in testes
  28. Sex determining region of the Y (SRY):
    encodes TDF (testis determining factor)
  29. Sex ratio:
    • the actual proprtion of male to female offspring
    • 1:1
  30. Primary Sex Ratio:
    the proportion of males to females conceived in the population
  31. Secondary Sex Ratio:
    the proportion of males to females born in a population
  32. Why would fetal mortatliy be higher in males?
    Dosage Compensation
  33. Lyon Hypothesis:
    • inactivation is random
    • occurs early in embroyonic development
    • all progeny cells have the same X chromosoem inactivated
  34. Red-green color blindness:
    • hemizygous males are fully color-blind
    • heterozygous females display mosaic retinas - patches of defective color perception and surrounding areas of normal color
  35. anhidrotic ectodermal dysplasia:
    • Hemizygous males - absence of teeth, sparse hair growth, lack of sweat glands
    • heterozygous females - patches of tissues without sweat glands
  36. Genic Balance Theory:
    • a threshold for maleness is reached with X:A is 1:2
    • presence of additional X alters this balance and results in femaleness
  37. Sex-lethal (SXL):
    • master switch for activation of at least 4 separate regulatory genes
    • activated when X:A = 1 --> results in female development
    • if X:A = .5 --> results in male development
    • mutations of Sxl kill females but have no effects on males
  38. Dosage Compensation in Drosophila:
    • no X-chromosome inactivation
    • male X-linked genes transcribed at 2 times the level compared to females
    • dosage compensation is regulated by at least 4 autosomal male specific lethal genes
    • these genes are under the control of Sxl
    • mutations in these genes reduces the increased expression of X-linked genes in males --> causing lethality
  39. Euploid:
    • complete haploid sets of chromosomes are present
    • we are euploids
  40. Aneuploid:
    • organisim gains or losses one or more chromosomes but not a complete haploid set
    • monosomy - loss of a single chromosome (2n-1) - they die
    • trisomy - addition of a chromosome to a diploid complement
  41. polyploid:
    • 3 or more complete haploid sets of chromosomes
    • triploid = 3n
    • tetraploid = 4n
    • pentaploid = 5n
    • 2 types: autopolyploid & allopolyploid
  42. Cri-Du-Chat syndrome:
    • partial monosomy in humans
    • segmental deletion
    • chromosomal designation = 46, -5p
    • - have all 46, but missing part of chromosome 5
    • cardiac and gastrointestinal malfunctions
    • mentally retarted
    • abnormal development of glottis and larynx --> meowing cat sound
    • 1/50,000 live births
    • some can learn to develop self care skills and communication
  43. segmental deletion:
    only a part of a chromosome is lost
  44. Down Syndrome:
    • trisomy 21 = 47, 21+
    • mom age 20 = < 1/1000
    • mom age 30 = 1/1000
    • mom age 40 = 1/100
    • mom age 45 = 1/50 to 1/12
    • almond shape eyes
    • short
    • flat round heads
    • protruding tongue
    • characteristic palm and fingerprint
    • retardation
    • shortened life expectancy
    • prone to respiratory disease, heart malformation, leukemia, alzheimers disease
  45. Platau Syndrome:
    • trisomy 13 = 47, 13+
    • harelip
    • cleft palate
    • pplydactyly - extra finger
    • congenital malformations of most organs
    • abnormal development early in gestation
    • survive around 3 months
    • 1/19,000 live births
    • average mom age = 32
  46. Edward Syndrome:
    • tisomy 18 = 47, 18+
    • small newborn
    • elongated skulls
    • webbed neck
    • congenital disloaction of hips
    • receding chin
    • average survival time: 4 months
    • death usually caused by pneumonia or heart failure
    • 1/8000 live births
    • more common in female offspring
  47. Autopolyploid:
    • each additional set of chromosome is identical to parent species
    • autotriploid: AAA
    • autotetraploid: AAAA
    • produce by heat/cold shock during meiosis or apply colchicine to somatic cells undergoing mitosis
  48. Autotriploids examples:
    potatoes, winesap apples, commerical bananas, seedless watermelons
  49. autotetraploids:
    alfalfa, coffee, peanuts, mcintosh apples
  50. autooctoploids:
    • AAAAAAAA
    • commerical strawberries
  51. Allopolyploids:
    • polyploids that result from hybridization of two closely related species
    • may be sterile
  52. Endopolyploidy:
    cells in normal diploid organism becomes polyploid through the process of Endomitosis
  53. Deletion:
    • Deleting part of a chromosome
    • - Terminal Deletion: deleting at the end of the chromosome
    • - Intercalary Deletion: deleting in the middle of the chromosome
  54. Duplication:
    • duplication in a single allele on a chromosome
    • -Terminal Duplication: duplicating on the end of the chromosome
    • -Intercalary Duplication: duplicating in the middle of the chromosome
  55. Inversion:
    • taking a chunk of DNA and flipping it 180 degrees, then putting it back
    • -Paracentric inversion: does not include the centromere
    • -Pericentric Inversion: centromere is involved in inversion
  56. Dicentric Chromosome:
    • 2 centromeres in chromosomes
    • doesnt produce viable cells
  57. Acentric Chromosome:
    • no centromere in the chromosome
    • doesnt produce viable offspring

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