(Bilingual Post) Athletes, why your mom deserves a big hug from you?
文長慎入，內容三個重點如下 Long post with TOC here:
1. Discovery of DNA in mitochondria 線粒體中DNA的發現2.Functions of mitochondria and mtDNA 線粒體和mtDNA的功能
3.How and why DNA functions differently in mitochondria? (and why you should thank your mom.) DNA在線粒體中的運作方式為什麼跟在細胞核裡的運作方式不同？(為什麼你必須感謝你的母親)
Let’s dive in… 進一步了解…
- Discovery of DNA in mitochondria
線粒體中DNA的發現
“For a long time, biologists thought our DNA resided only in the control center of our cells, the nucleus. Then, in 1963, a couple at Stockholm University discovered DNA outside the nucleus. They noticed DNA fibers in structures called mitochondria, the energy centers of our cells. “
(Source: https://www.nytimes.com/…/sc…/mitochondrial-dna-mothers.html)
長期以來，生物學家認為我們的DNA僅存在於我們細胞的控制中心 – 也就是細胞核。然後，在1963年，斯德哥爾摩大學的一對夫婦在細胞核外發現了DNA。 他們在線粒體的結構中發現了DNA纖維；線粒體是我們細胞的能量中心。 - “Functions of mitochondria and mtDNA – the power plants of human physiology
線粒體和mtDNA的功能 – 人體內所有生理運作的能量來源 (發電廠)
Mitochondria are structures within cells that convert the energy from food into a form that cells can use (Note: Without mitochondria, each cell and every function win your body will stop immediately, so does your life.). Each cell contains hundreds to thousands of mitochondria, which are located in the fluid that surrounds the nucleus (the cytoplasm). Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA. This genetic material is known as mitochondrial DNA or mtDNA.
線粒體是每個細胞內都有的結構，可將食物中的能量轉化為細胞可以使用的形式 (小編註：所以，如果沒有線粒體，人體內所有的生理功能會立即停止，所有的生命跡象也會立即停止)。 每個細胞包含成百上千的線粒體，位於圍繞細胞核（細胞質）的液體中。 儘管人體大多數DNA都被包裝在細胞核內的染色體中，但線粒體卻具備有少量自己的DNA。 這種遺傳物質被稱為 “線粒體DNA” 或mtDNA。
Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation. Oxidative phosphorylation is a process that uses oxygen and simple sugars to create adenosine triphosphate (ATP), the cell’s main energy source.
線粒體DNA包含37個基因，所有這些基因對於正常的線粒體功能都是必不可缺的。 這些基因中的十三種提供了 “製造 [參與氧化磷酸化所需的酶] 的關鍵資訊” (小編註：如果把人體功能運作比喻成是在跑支電腦程式，那麼DNA就是這支程式的程式碼 source code)。 “氧化磷酸化” 是利用氧氣和單醣產生 “三磷酸腺苷”（ATP, 一種細胞的主要能源）的過程。
The remaining genes provide instructions for making molecules called transfer RNA (tRNA) and ribosomal RNA (rRNA), which are chemical cousins of DNA. These types of RNA help assemble protein building blocks (amino acids) into functioning proteins.
另外的24個基因提供了 製造 “轉移RNA (tRNA)” 和 “核醣體RNA (rRNA)” 的分子的關鍵資訊。這兩種RNA有助於將蛋白質構件(氨基酸)組裝成 “功能蛋白”。
(Source: https://ghr.nlm.nih.gov/mitochondrial-dna) - How and why DNA functions differently in mitochondria? (and why you should thank your mom.) DNA在線粒體中的運作方式為什麼跟在細胞核裡的運作方式不同？(為什麼你必須感謝你的母親)
Unlike nuclear DNA, which comes from both parents, mitochondrial DNA comes only from the mother. Nobody fully understands why or how fathers’ mitochondrial DNA gets wiped from cells.
在遺傳上，人體所有細胞核內的DNA都來自雙親，但是 線粒體內的DNA卻僅來自母親。 沒有人理解父親的線粒體DNA是如何從(新生兒胚胎的)細胞中被清除掉的，也不知道為什麼。
An international team of scientists recently studied mitochondria in the sperm of a roundworm called C. elegans to find answers. Their results, published in the journal Science, show that paternal mitochondria in this type of roundworm have an internal self-destruct mechanism that gets activated when a sperm fuses with an egg. Delaying this mechanism, the scientists found, led to lower rates of embryo survival. (https://science.sciencemag.org/content/353/6297/394, 2016-07-22)
一個國際科學家團隊最近研究了一種叫做”秀麗隱桿線蟲”的線蟲的精子中的線粒體，以尋找答案。 他們的結果發表在2016年7月的《科學》雜誌上
…
It’s well known that the transfer of mitochondrial DNA from mother to offspring, often called maternal inheritance, occurs in humans and most multicellular organisms.
眾所周知，線粒體內的DNA從母親到後代的轉移(通常稱為“母體遺傳”)發生在人類和大多數多細胞生物中。
…
Before this research, it had been thought that maternal inheritance was orchestrated by processes in the mother’s egg cells… Large structures called autophagosomes, for instance, are known to engulf paternal mitochondria shortly after a sperm penetrates an egg… however, the paternal mitochondria in the roundworms actually started to break down before any autophagosomes reached them. It’s like a suicide mechanism…
在進行這項研究之前，曾有人認為母體的遺傳是由母親卵細胞中的過程所編排的。例如，有一個大的結構稱為自噬體，在精子穿透卵子後不久會吞噬父體的線粒體。 但在線蟲的實驗裡，父體的線粒體在任何自噬體到達它們之前就開始自行分解。 有點像是一個自殺機制…
The big mystery that remains is why maternal inheritance occurs so consistently across organisms… One theory has to do with the fact that sperm must generate a lot of energy when competing to fertilize an egg. During this time, sperm mitochondria are overworked, which could possibly damage their DNA and lead to mutations (hence the suicide).
(Note: Hence my reminder for you to give your dad a bug hug, on the upcoming Father’s Day, for his sacrifice. )
為什麼“母體遺傳”在不同物種的生物體之間如此一致地發生，目前仍然是一個大謎團… 有一種理論指出可能是因為精子在競爭讓卵子受精的過程裡必須消耗大量能量，導致精子線粒體過度操勞，可能會破壞其DNA並導致突變（因此選擇自殺）。
(Source of section 3 and the photo)
(小編註：所以當你因為自己優秀的體能而在母親節特別感謝母親之餘，別忘了在父親節那天也要感念把拔在你生命的第一瞬間為你做的犧牲和配合喔～)
