lecture 21 – aberrant ploidy - indiana.eduforrl311/lecnotes/lec21.pdf · 1 lecture 21 –...
Post on 28-Apr-2018
221 Views
Preview:
TRANSCRIPT
1
Lecture 21 – Aberrant Ploidy I. Aberrant euploidy A. examples of differing ploidy monoploid 1x diploid 2x triploid 3x tetraploid 4x
pentaploid 5x hexaploid 6x octaploid 8x
B. in nature - in plants (and less commonly, animals) – 30 – 35% of naturally occurring plant
species are polyploid. - endopolyploidy – in many animals, some cells may be polyploid II. Monoploidy – 1n, rare result of errors in cell division A. Usually sterile B. in some species, some individuals are monoploid - males in social insects (ants, bees, wasps) - males produced by parthenogenesis - not sterile because C. useful experimentally and in agriculture - experimental use of monoploidy - but how do you get back to diploid?
diploidplant
meiotic productcells plated
haploidembryoids
grow haploidplantletsmonoploid
plantdiploidplant
diploidembryoids
grow diploidplantlets
monoploidplant(sterile)
treatwithcolchicine
2
III. Polyploids (odd vs. even chromosome #) A. Odd ploidies 1. origins of triploid
- odd ploidies are generally sterile
- why?
- triploidy can be very useful? B. Even ploidies and cell divisions - most natural polyploids are even in # homologues (i.e. 2x, 4x, 6x, 8x, etc) IV. Auto vs allopolyploids A. major types 1. autopolyploid 2. allopolyploid - homeologous
A1 A2 A3
A1 A2 A3
3
B. autopolyploid
- endoreduplication C. allopolyploidy
D. experimental allopolyploidy’ - way of producing useful plant varieties
2n 0n
0n 0n
2n 2n
meiosis
2n
4n
mitosisA1A1
A2 A2
A1A1
A2
A2
0n
2n
A1A1
A2 A2
A1A1
A2 A2
A1A1 A2A2
tall fescue Italian ryegrassisolate cells
remove cell wall
fuse protoplasts
heterokaryon
hybrid cell
regenerate plant
plant has characteristicsintermediate betweentwo parentsallotetraploid
4
IV. Aneuploidy A. polysomy 1. trisomy a. consequences b. human trisomies (most are inviable) - Klinefelter (XXY) - trisomy 21 (Down syndrome) - trisomy 13 (Patau syndrome) - trisomy 18 (Edwards syndrome) 2. monosomy a. human monosomies B. aneuploidy arises because of nondisjunction during meiosis
BB
AA
a a
bb
BBbb
a a
b
A
b
A
B B
a a
AA
top related