Editing Kākāpō (section)

===Genetics===
Because kākāpō passed through a [[Population bottleneck|genetic bottleneck]], in which their world population was reduced to 49 birds, they are extremely inbred and have low genetic diversity. This manifests in lower disease resistance and in fertility problems: 61% of kākāpō eggs fail to hatch.<ref>{{Cite journal |last1=Savage |first1=J.L. |last2=Crane |first2=M.S. |last3=Hemmings |first3=N. |date=2021 |title=Low hatching success in the critically endangered kākāpō is driven by early embryo mortality not infertility |journal=Animal Conservation |volume=25 |issue=3 |pages=352–360 |doi=10.1111/acv.12746|s2cid=244579763 |doi-access=free }}</ref><!--

See https://zslpublications.onlinelibrary.wiley.com/doi/full/10.1111/acv.12746

--> Beginning in 2015, the Kākāpō 125+ project has sequenced the [[genome]] of all living kākāpō, as well as some museum specimens.<ref>{{Cite web |first= |date=2023 |title=Kākāpō gene sequencing |url=https://www.doc.govt.nz/our-work/kakapo-recovery/what-we-do/research-for-the-future/kakapo125-gene-sequencing/ |website=Department of Conservation, New Zealand Government}}</ref> The project is a collaboration led by Genomics Aotearoa and a collaboration with a team of international collaborators.<ref name="White20160">{{Cite journal |last=White |first=Rebekah |date=Sep–Oct 2016 |title=Decoding Kākāpō |url=https://www.nzgeo.com/stories/decoding-kakapo/ |journal=New Zealand Geographic |volume=141}}</ref><ref>{{Cite web |first= |date=2023 |title=Kākāpō125+ gene sequencing |url=https://www.doc.govt.nz/our-work/kakapo-recovery/what-we-do/research-for-the-future/kakapo125-gene-sequencing/ |website=Department of Conservation, New Zealand Government}}</ref>

A [[DNA sequencing|DNA sequence analysis]] was performed on 35 kākāpō genomes of the surviving descendants of an isolated island population, and on 14 genomes, mainly from museum specimens, of the now extinct mainland population.<ref name = Dussex2021>{{Cite journal | last1=Dussex | first1=N. | last2=van der Valk | first2=T. | last3=Morales | first3=H.E. | last4=Wheat | first4=C.W. | last5=Díez-del-Molino | first5=D. | last6=von Seth | first6=J. | last7=Foster | first7=Y. | last8=Kutschera | first8=V.E. | last9=Guschanski | first9=K. | last10=Rhie | first10=A. | last11=Phillippy | first11=A.M. | last12=Korlach | first12=J. | last13=Howe | first13=K. | last14=Chow | first14=W. | last15=Pelan | first15=S. | last16=Mendes Damas | first16=J.D. | last17=Lewin | first17=H.A. | last18=Hastie | first18=A.R. | last19=Formenti | first19=G. | last20=Fedrigo | first20=O. | last21=Guhlin | first21=J. | last22=Harrop | first22=T.W.R. | last23=Le Lec | first23=M.F. | last24=Dearden | first24=P.K. | last25=Haggerty | first25=L. | last26=Martin | first26=F.J. | last27=Kodali | first27=V. | last28=Thibaud-Nissen | first28=F. | last29=Iorns | first29=D. | last30=Knapp | first30=M. | last31=Gemmell | first31=N.J. | last32=Robertson | first32=F. | last33=Moorhouse | first33=R. | last34=Digby | first34=A. | last35=Eason | first35=D. | last36=Vercoe | first36=D. | last37=Howard | first37=J. | last38=Jarvis | first38=E.D. | last39=Robertson | first39=B.C. | last40=Dalén | first40=L. | date=2021 | title=Population genomics of the critically endangered kākāpō | journal=Cell Genomics | volume=1 | issue=1 | pages=100002 | doi=10.1016/j.xgen.2021.100002 | pmid=36777713 | pmc=9903828 | doi-access=free }}</ref> An analysis of the long-term genetic impact of small population size indicated that the small island kākāpō population had a reduced number of harmful [[mutation]]s compared to the number in mainland individuals.<ref name = Dussex2021/>  It was hypothesized that the reduced mutational load of the island population was due to a combination of [[genetic drift]] and the purging of deleterious mutations through increased [[inbreeding]] and [[Negative selection (natural selection)|purifying selection]] that occurred since the isolation of this population from the mainland about 10,000 years ago.<ref name = Dussex2021/>  Purging of deleterious mutations occurs when there is selection against recessive or partially recessive detrimental [[allele]]s as they are expressed in the [[zygosity|homozygous state]].<ref name = Dussex2021/>