遺傳度

遺傳度（粵拼：wai4 cyun4 dou6；參見英文：heritability）係遺傳學同心理學等領域上常用嘅指標，用嚟量度一個表現型（某隻生物嘅某一個特定外形或者成份，例如係身高或者智能）特徵有幾受遺傳因素影響。遺傳度研究問嘅問題如下^[1]^[2]：攞一個生物群體入面嘅某個特徵，個體之間喺呢個特徵上嘅差異有幾多唔係因為環境性或者隨機性差異而起嘅呢？

數值

遺傳度數值會喺 0 同 1 之間。遺傳度接近 0 就表示個體喺呢個特徵上嘅差異近乎完全係由環境因素而起嘅；而遺傳度接近 1 就表示個體喺呢個特徵上嘅差異近乎完全係由遺傳因素決定嘅，後者嘅例子有多種嘅遺傳病。

好多行為同心理特徵都會一定程度上受遺傳因素影響，例如大人嘅智商（IQ）嘅遺傳度估計超過 60% ^[3]，噉係因為遺傳因素可以影響腦各部份嘅結構同特性，而腦嘅結構同特性就會影響行為^[4]。

研究

遺傳度可以靠研究孖胎嚟估計：同卵孖胎喺遺傳上近乎完全一樣，而異卵孖胎喺遺傳上平均會有 50% 一樣；如果有某個特徵，同卵性孖胎喺呢個特徵上嘅差異細過異卵性孖胎嘅（假設每對孖胎都係喺同一個環境大，或者每對孖胎都係細細個分開咗）就表示呢個特徵會受遺傳因素影響。於是研究者就可以靠研究孖胎嚟估計個特徵嘅遺傳度^[5]^[6]。

好似下圖噉：

孖胎研究嘅方法：每隻 trait 係一種特性，Y 軸表示統計相關，而當中

紅色棒表示同卵孖胎之間喺 $X$ 上嘅統計相關，
綠色棒表示唔係同卵孖胎但親生嘅兄弟姊妹之間喺 $X$ 上嘅統計相關，
藍色棒表示養兄弟姊妹之間喺 $X$ 上嘅統計相關，

Trait B 似乎遺傳度零舍高：同卵孖胎明顯會喺 $X$ 上相似（相關值高）但養兄弟姊妹唔會明顯喺 $X$ 上相似（相關值低）－由藍色棒到綠色棒到紅色棒（兩兄弟姊妹之間遺傳相似度升）會令兩兄弟姊妹之間喺 $X$ 上嘅統計相關明顯噉升。

睇埋

參考

Lynch M, Walsh B (1998). Genetics and analysis of quantitative traits. Sunderland, Mass.: Sinauer Assoc. ISBN 978-0-87893-481-2.
Johnson W, Penke L, Spinath FM (2011). "Understanding Heritability: What it is and What it is Not". European Journal of Personality. 25 (4): 287–294. doi:10.1002/per.835. ISSN 0890-2070.

引咗

↑ Wray N, Visscher P (2008). "Estimating Trait Heritability". Nature Education. 1 (1): 29. Retrieved 24 July 2015.
↑ Kempthorne O (1957). An introduction to genetic statistics (1st ed.). Ames, Iowa: Iowa State Univ. Press.
↑ Panizzon, Matthew S., et al. "Genetic and environmental influences on general cognitive ability: Is g a valid latent construct?." Intelligence 43 (2014): 65-76.
↑ Trut, Lyudmila (1999). "Early Canid Domestication: The Farm-Fox Experiment". American Scientist. 87 (2): 160. doi:10.1511/1999.2.160. Archived from the original on 23 June 2011.
↑ Wahlsten, Douglas (1994). "The intelligence of heritability". Canadian Psychology. 35 (3): 244–260.
↑ Johnson, W., Turkheimer, E., Gottesman, I. I., & Bouchard Jr, T. J. (2009). Beyond heritability: Twin studies in behavioral research. Current directions in psychological science, 18(4), 217-220.

拎

（英文） Stanford Encyclopedia of Philosophy entry on Heredity and Heritability

[1] Wray N, Visscher P (2008). "Estimating Trait Heritability". Nature Education. 1 (1): 29. Retrieved 24 July 2015.

[2] Kempthorne O (1957). An introduction to genetic statistics (1st ed.). Ames, Iowa: Iowa State Univ. Press.

[3] Panizzon, Matthew S., et al. "Genetic and environmental influences on general cognitive ability: Is g a valid latent construct?." Intelligence 43 (2014): 65-76.

[4] Trut, Lyudmila (1999). "Early Canid Domestication: The Farm-Fox Experiment". American Scientist. 87 (2): 160. doi:10.1511/1999.2.160. Archived from the original on 23 June 2011.

[5] Wahlsten, Douglas (1994). "The intelligence of heritability". Canadian Psychology. 35 (3): 244–260.

[6] Johnson, W., Turkheimer, E., Gottesman, I. I., & Bouchard Jr, T. J. (2009). Beyond heritability: Twin studies in behavioral research. Current directions in psychological science, 18(4), 217-220.

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