Chromosomal Basis of Inheritance (Chap 12)

Question 1

Eukaryotic

Answer 1

• diploid, 2n =zygote
  - >during meiosis : homologous(match pair) vs nonhomologous chromosome
• haploid, n
• sex chromosome= autosome

Question 2

Centromere positions

Answer 2

(constriction along chromosome)

• metacentric
• submetacentric
• acrocentric
• telocentric

Question 3

Chromosomal Theory of Inheritance

Answer 3

• sex chromo-> X and Y : male = heterogametic (XY) and female homogametic (XX)
• random fussion : F1(0.5XX, 0.5 XY)
• Sex linkage: on X chromo,
• -> hemizygous : Xlink gene in males
• -> crisscross inheritance : Pmale –> F1female–> F2 male
• Nondisjunction X chromo (autosome + sex chromo)
• ->chromo don’t migrate to pole during anaphase+telophase
• ->primary non chromosome: mei 1 both sister chromo in half of cells and mei 2 daughter chromo in 2/4 gametes
• -> X chromo: aneuploidy
• ->secondary: mei 1 each cell has one sister, mei2 2:0:1:1 in gamete

Question 4

Sex Chromosome

Answer 4

-plants can be dioecious or monoecious

Question 5

Sex determination

Answer 5

• genotypic:
• –> mammals: Y chromo mec = testis-determining fact (nondisjunction = Tuner Sundrom/ X0 or Klinefelter/ XXY)+ dosage compensation: barr bodies/Lyin hypothesis 1) Lyonixation 2) inactive X chromo
• –> Drosphilia+ Caenorhabditio: X chromo-autosome balance system= hermaphroditic (Y determines male fertility: 1=male, between 1 and 0= intersex)
• –> other/bird/butterfly: 1) male= homogametic (zz) 2) female= heterogamteic (zc) 3) Z-linked sim to X but reversed

Question 6

Analysis of Sex-linked traits in humans

Answer 6

• X-linked Recessive : appears more in males
• ”” Dominant –> trait: effects both sexs and all generations
• Y-linked -> holandric trait