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Post zygotic isolation:Hybrid infertility and viability
- 1. Post-zygotic isolation • Inter-specific hybrid: Different species, same genus • Intra-specific hybrid:: Sub-species, one specie
- 2. Inter-specific hybridization 1. Unsuccessful Mostly 2. Successful If Success then • Healthy • Unhealthy • Fertile • Low fertility • Infertile
- 3. Hybrid Infertility • Mostly are sterile means they can’t produce viable gametes • Some have low fertility mean low quantity or quality of gametes • Few are Fertile Reasons of infertility • Incompatible gametes • Different size, shape and number of chromosomes • Extra chromosome can’t make homologous pair during meiosis e.g. donkey have 62 chromosome and horse have 64, resulting mule 63
- 4. Hybrid viability • Unhealthy individual • Having low life span • Premature death • Remain undeveloped • E.g. Goat × Sheep , normal embryo but die much before birth
- 5. Examples of hybrid Blood parrot cichlid • Intra-specific • 1986 in Taiwan • Midas cichlid × redheaded cichlid • Narrow mouth → feeding problem • Male → Sterile • Females → Fertile
- 6. Dzo or Yakow • Yak × Cow • Stronger and taller • High yield of milk and meat • Females mostly → fertile • Males → sterile • Hybrid can be back crossed Original specie • Crossed at Tibet and Mongolia
- 7. Zebroid • Male zebra × Female belong to equidae family(horses, donkeys, zebra, pony) • Zebroid is collective name for • Zorse (zebra × horse) • Zonkey (zebra × donkey) • Zony (zebra × pony) • Occur in nature • Sterile and dwarf • Stripes on some area
- 8. Cama • Dromedary male × Lama female • 14 January, 1998 in Dubai • High production of wool • Cama is always fertile ─ same no. of chromosomes • Lama is six times smaller and Lighter than camel • So artificial insemination is done
- 9. Grizzly-Polar bear • 1st hybrid was seen in 1964 • Grizzly bear live in forested area and breed on land • Polar bear live on ice and breed on ice • Scientist suggest ice melt polar move toward forested area • 2nd case in Victoria, After DNA analysis, hybrid’s mother → Polar, Father → Grizzly
- 10. Savannah cat • Domestic cat × wild African serval • More social and loyal • Highest jumpers, tall, large, slim body • Varies in coloration depending on parents • Always have spotted and marbled appearance • Look like small version of cheetah