The social geneThe social gene

鄭先祐鄭先祐靜宜大學 生態學系靜宜大學 生態學系

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The social geneThe social gene 12.1 Introduction12.1 Introduction 12.2 Genes as strategists (12.2 Genes as strategists ( 基因作為策略者基因作為策略者 )) 12.3 Variant genes12.3 Variant genes 12.4 The reach of the strategic gene (12.4 The reach of the strategic gene ( 策略性基策略性基

因因 )) 12.5 The prokaryotic firm: managing a cytoplas12.5 The prokaryotic firm: managing a cytoplas

mic commons (mic commons ( 原核公司：經營一個細胞質公共原核公司：經營一個細胞質公共財財 ))

12.6 Dangerous liaisons (12.6 Dangerous liaisons ( 聯繫聯繫 )) 12.7 Plasmid protection rackets 12.7 Plasmid protection rackets 12.8 Team substitutions12.8 Team substitutions

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12.9 Multicellular corporations12.9 Multicellular corporations 12.10 A chimeric menagerie 12.10 A chimeric menagerie (( 供展覽用的野生動物供展覽用的野生動物 )) 12.11 The nuclear citadel (12.11 The nuclear citadel ( 要塞要塞 )) 12.12 The sexual revolution12.12 The sexual revolution 12.13 The open society and its enemies12.13 The open society and its enemies 12.14 The eukaryotic alliance12.14 The eukaryotic alliance 12.15 Sex chromosomes12.15 Sex chromosomes 12.16 Genomic imprinting and the altercatio12.16 Genomic imprinting and the altercatio

n of generationsn of generations 12.17 Reprise (12.17 Reprise ( 再出現再出現 ))

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12.1 Introduction12.1 Introduction

於天擇下演化的複雜行為和構造，可視為於天擇下演化的複雜行為和構造，可視為對適應的基因的選擇，而不是對個體對適應的基因的選擇，而不是對個體 (vehi(vehicles) cles) 的選擇。的選擇。 個體只是基因遺傳個工具。個體只是基因遺傳個工具。

對這樣的說法之批評：個體才是一個生命對這樣的說法之批評：個體才是一個生命體，其體內的某個基因，倘若沒有其他許體，其體內的某個基因，倘若沒有其他許多基因的協助，往往無法遺傳下去。多基因的協助，往往無法遺傳下去。

然而，個別基因可視為整體基因然而，個別基因可視為整體基因 (( 個體和群個體和群體體 )social groups)social groups 的成员。的成员。

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This chapter emphasizes the current stThis chapter emphasizes the current state of genetical systems, and ask why cate of genetical systems, and ask why conserved feature of organisms are evolonserved feature of organisms are evolutionarily stable relative to conceivablutionarily stable relative to conceivable(e( 可理解的可理解的 ) alternatives.) alternatives.

Gene-centred theories are often revileGene-centred theories are often reviled(d( 謾罵謾罵 ) because of their perceived im) because of their perceived implications for human societies.plications for human societies.

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12.2 Genes as strategists12.2 Genes as strategists

Gene are catalysis.Gene are catalysis. 基因所獲取的利益是在個體上，個體的基因所獲取的利益是在個體上，個體的 reprorepro

ductive successductive success ，以及這個個體的大部份基，以及這個個體的大部份基因的遺傳。因的遺傳。

倘若再加上個體與其親緣關係的個體，整體的倘若再加上個體與其親緣關係的個體，整體的某個基因的某個基因的 inclusive fitnessinclusive fitness ，這時個體的，這時個體的利益和基因的利益就不一定一致。利益和基因的利益就不一定一致。

這時基因可以扮演 這時基因可以扮演 strategistsstrategists ，而不是個體。，而不是個體。

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12.3 Variant genes12.3 Variant genes

個體的基因，如同一本書的文字。個體的基因，如同一本書的文字。 這本書有多少字？ 這本書有多少字？ Material genesMaterial genes 使用多少字彙？ 使用多少字彙？ Informational genesInformational genes

於 於 informational genes informational genes 中，有部份是中，有部份是 strstrategic gene(ategic gene( 策略性基因策略性基因 )) ，可於 ，可於 evolutioevolutionary gamenary game 中，扮演 中，扮演 strategist (strategist ( 策略者策略者 )) 。。

A strategic gene corresponds to a set of A strategic gene corresponds to a set of material genes and can be considered tmaterial genes and can be considered the unit of adaptive innovation.he unit of adaptive innovation.

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12.4 The reach of the 12.4 The reach of the strategic genestrategic gene

Dawkins (1976) a thought-experimentDawkins (1976) a thought-experiment Considered the possibility of a gene that causeConsidered the possibility of a gene that cause

d its possessors to develop a green beard and td its possessors to develop a green beard and to be nice to other green-bearded individuals.o be nice to other green-bearded individuals.

綠鬍子效應綠鬍子效應 (green-beard effect)(green-beard effect) ，策略性基，策略性基因因

因為選擇性的差異，而形成 因為選擇性的差異，而形成 linkage disequililinkage disequilibrium (Box 12.1)brium (Box 12.1)

Species boundaries are a major cause of LiSpecies boundaries are a major cause of Linkage disequilibrium.nkage disequilibrium.

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Linkage disequilibriumLinkage disequilibrium

1.1. A new mutation A new mutation 2.2. Epistatic selection generates linkage Epistatic selection generates linkage

disequilibrium because it causes a gedisequilibrium because it causes a gene to leave more descendants when it ne to leave more descendants when it is present in some combinations than is present in some combinations than in others.in others.

3.3. Sampling effects can cause linkage diSampling effects can cause linkage disequilibrium in small populations.sequilibrium in small populations.

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12.5 The prokaryotic firm: man12.5 The prokaryotic firm: managing a cytoplasmic commonsaging a cytoplasmic commons

原核公司：經營細胞質公共財原核公司：經營細胞質公共財 Genetic replication makes use of energy anGenetic replication makes use of energy an

d substrates that are supplied by the metabd substrates that are supplied by the metabolic economy in much greater quantities tholic economy in much greater quantities than be possible without a genetic division of an be possible without a genetic division of labour.labour.

These materials are common goods (These materials are common goods ( 公共公共財財 ), available to every gene in the cytoplas), available to every gene in the cytoplasm.m. Thus, genetic communities are potentially vulnThus, genetic communities are potentially vuln

erable to free-riders, genes that take more than erable to free-riders, genes that take more than they contribute.they contribute.

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DNA-based replicators are believed to hDNA-based replicators are believed to have evolved from RNA-based replicators,ave evolved from RNA-based replicators, possibly because DNA is copied with gr possibly because DNA is copied with greater fidelity (eater fidelity ( 忠誠忠誠 ) than RNA (Lazcano, ) than RNA (Lazcano, et al., 1988).et al., 1988).

The change also had implications for celThe change also had implications for cellular security.lular security.

DNADNA 運用運用 m-RNAm-RNA ，且需要隨時清除，且需要隨時清除 m-RNm-RNAA ，如此可以避免有 ，如此可以避免有 RNA-based parasite.RNA-based parasite.

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12.6 Dangerous liaisons (12.6 Dangerous liaisons ( 聯聯繫繫 ))

Cosmides and Tooby (1981) called a set oCosmides and Tooby (1981) called a set of genes that replicated together, and whof genes that replicated together, and whose fitness was maximized in the same wase fitness was maximized in the same way, a coreplicon.(y, a coreplicon.( 核心組核心組 ))

倘若一個個體內有兩個以上的 倘若一個個體內有兩個以上的 corepliconcoreplicon ，，這將會有利益的衝突。這將會有利益的衝突。

細菌有多個細菌有多個 circular genomescircular genomes One is the bacterial chromosomeOne is the bacterial chromosome The extra circles are called plasmids.The extra circles are called plasmids.

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細菌的細菌的 plasmid plasmid 通常是一些特別的 通常是一些特別的 metabmetabolic skills. olic skills. 譬如：譬如： antibiotic resistanceantibiotic resistance Such a plasmid may be essential in the presSuch a plasmid may be essential in the pres

ence of antibiotics but a burden in their absence of antibiotics but a burden in their absence.ence.

於細菌交接的過程，通常只有於細菌交接的過程，通常只有 plasmidplasmid 傳送。傳送。 這是有風險的交接 這是有風險的交接 (( 譬如有病毒譬如有病毒 ))

細菌的細菌的 plasmidplasmid 的遺傳，可以有的遺傳，可以有 vertical avertical and horizontalnd horizontal 兩種。兩種。

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12.7 Plasmid protection 12.7 Plasmid protection racketsrackets

Plasmid once acquired, are difficult to Plasmid once acquired, are difficult to discard.discard.

Many plasmids encode a persistent Many plasmids encode a persistent “poison” and its short-lived “antidote”.“poison” and its short-lived “antidote”.

Thus, if a cell segregates without the Thus, if a cell segregates without the plasmid, it is cut off from its supply of plasmid, it is cut off from its supply of antidote and succumbs to the poison.antidote and succumbs to the poison.

The gene for the poison can be said to The gene for the poison can be said to recognize the presence or absence of recognize the presence or absence of the gene for the antidote.the gene for the antidote.

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Mitochondria Mitochondria Mitochondria contain a large DNA maxi-cMitochondria contain a large DNA maxi-c

ircle and many small mini-circles.ircle and many small mini-circles. The maxicircle encodes essential genes iThe maxicircle encodes essential genes i

n garbled form (n garbled form ( 斷章不全的形式斷章不全的形式 ), wherea), whereas the minicircles encode guide RNAs.s the minicircles encode guide RNAs.

Could RNA enditing have evolved as a miCould RNA enditing have evolved as a minicircle maintenance system?nicircle maintenance system? If so, one would predict that minicircles can If so, one would predict that minicircles can

also edit DNS and encrypt maxicircle genes ialso edit DNS and encrypt maxicircle genes in ways that only they can decipher (n ways that only they can decipher ( 解讀解讀 ).).

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12.8 Team substitutions (12.8 Team substitutions ( 換換組员組员 ))

A non-recombining bacterial chromosomA non-recombining bacterial chromosome is a team that does not change its membe is a team that does not change its members (except by mutation).ers (except by mutation).

Its social contract is ‘all for one, and onIts social contract is ‘all for one, and one for all’, not ‘every gene for itself’.e for all’, not ‘every gene for itself’.

細菌的細菌的 chromosomal recombination chromosomal recombination 只有只有在結合在結合 (conjugation)(conjugation) 或是病毒感染或是病毒感染 (transd(transduction)uction) 時，才有可能生。時，才有可能生。

但有些細菌演化出可以從環境取用但有些細菌演化出可以從環境取用 DNADNA 取代取代其內的某段相同的部份。其內的某段相同的部份。 (( 這有這有 recombinatirecombination)on)

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Uptake of DNA is induced under conditions Uptake of DNA is induced under conditions of nutritional stress and may have evolved of nutritional stress and may have evolved primarily as a means of gaining nutrients.primarily as a means of gaining nutrients.

Why should a team replace one of its membWhy should a team replace one of its members?ers?

The repair hypothesis views transformation The repair hypothesis views transformation as a means of replacing injured team membas a means of replacing injured team members (damaged DNA).ers (damaged DNA). 但是這個假說難成立，因為但是這個假說難成立，因為 uptake of DNA is not iuptake of DNA is not i

nduced by damage to the chromosome.nduced by damage to the chromosome. The recombinant-progeny hypothesis views The recombinant-progeny hypothesis views

transformation as a means of trying out netransformation as a means of trying out new players. (w players. ( 於惡劣的環境，更換不同的組员於惡劣的環境，更換不同的組员 ))

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12.9 Multicellular corporati12.9 Multicellular corporationsons

The development of resistant spores by The development of resistant spores by BBacillus subtilisacillus subtilis illustrates the differentiati illustrates the differentiation of soma and germ line in simple form.on of soma and germ line in simple form.

某個細菌進行某個細菌進行 unequal cell division unequal cell division 產生產生 a a mother cell (soma) and a prespore (germ mother cell (soma) and a prespore (germ line).line).

The mother cell engulfs the prespore, assiThe mother cell engulfs the prespore, assists in formation of the spore coat and is tsts in formation of the spore coat and is then discarded.hen discarded.

當環境營養缺乏時，細菌會犧牲當環境營養缺乏時，細菌會犧牲 mother cell mother cell (soma)(soma) ，而投入 ，而投入 spore (germ line).spore (germ line).

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多細胞公司多細胞公司 生物發展生物發展 somas to gain the benefits of a somas to gain the benefits of a

cellular division of labour (cellular division of labour ( 分工分工 ).). 但是但是 soma soma 是擁有資源者，可能被其他是擁有資源者，可能被其他 germ germ

lines lines 剝削資源。剝削資源。 因此因此 soma soma 必要對其產出的必要對其產出的 germ linesgerm lines 有有

「信心」「信心」 (( 基因必要是相同基因必要是相同 )) 當當 soma soma 愈來愈大愈複雜，愈來愈大愈複雜， soma soma 和 和 gerger

m lines m lines 的關係愈來愈不直接，這讓的關係愈來愈不直接，這讓 paraparasites sites 有機可趁。因此免疫機制 有機可趁。因此免疫機制 (immune (immune surveillance) surveillance) 必要產生。必要產生。

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於於 vertebrate immune system vertebrate immune system 發展出 發展出 T-cell receptors, major histocompatibilT-cell receptors, major histocompatibility complex (MHC) antigens and immuity complex (MHC) antigens and immunoglobulinsnoglobulins

補充資料 補充資料 (( 生物學 免疫系統生物學 免疫系統 ))

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Specific responsesSpecific responses

Two kinds of Two kinds of lymphocyteslymphocytes play a criti play a critical role in the specific responses.cal role in the specific responses. These are the These are the B-cellsB-cells and the and the T-cellsT-cells..

B-cellsB-cells are specialized to do two thing are specialized to do two thingss plasma cells make antibodies to combat plasma cells make antibodies to combat

the invader. (the invader. (humoral immunityhumoral immunity)) memory B-cells memory B-cells 記憶過去曾經產生過的抗記憶過去曾經產生過的抗

體資料。 體資料。

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cellular immunitycellular immunity

T-cells are involved inT-cells are involved in cellular immuni cellular immunityty..

There are three basic kinds of T-cells.There are three basic kinds of T-cells. Helper T-cellsHelper T-cells ( ( 幫助者幫助者 ), interact with othe), interact with othe

r cells to enhance the immune response.r cells to enhance the immune response. cytotoxic T-cellscytotoxic T-cells ( ( 殺手殺手 ), identify infected ), identify infected

cells and rupture their membranescells and rupture their membranes suppressor T-cellssuppressor T-cells ( ( 壓抑壓抑 ), help call off the ), help call off the

body's defenses.body's defenses.

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抗原抗原 -- 抗體反應抗體反應 Antigens are Antigens are

foreign molecules foreign molecules that elicit an that elicit an immune response immune response in the host in the host organism.organism.

Antibodies are Antibodies are proteins produced proteins produced by the host by the host plasma cells that plasma cells that identify and help identify and help destroy antigens, destroy antigens, including the cells including the cells that bear that bear antigens.antigens. Fig. 20.4

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When a specific antigen is encountered, the When a specific antigen is encountered, the recognition regions of the antibody molecules recognition regions of the antibody molecules attach to specific binding sites on the antigen attach to specific binding sites on the antigen that can be engulfed by a macrophage.that can be engulfed by a macrophage.

Fig. 20.5

巨喫細胞

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Fig. 20.6 In the Fig. 20.6 In the ongoing combat ongoing combat against invaders.against invaders.

巨喫細胞吞食抗原，巨喫細胞吞食抗原，再將抗原送至膜外。再將抗原送至膜外。

Helper T-cell Helper T-cell 受到激受到激發，分泌發，分泌 interleukininterleukin 。。

InterleukinInterleukin刺激刺激 cytocytotoxic T-cellstoxic T-cells 和和 memmemory cellsory cells 的的 productiproduction.on.

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Fig. 20.7 Fig. 20.7 B-cells begin their own B-cells begin their own

arousal by capturing arousal by capturing antigen and preparing a antigen and preparing a recognition site that will recognition site that will match that of a chosen match that of a chosen helper T-cell.helper T-cell.

When they bind together, When they bind together, interleukin secreted by interleukin secreted by the helper T-cell activated the helper T-cell activated the B-cell and plasma, the B-cell and plasma, and memory cells are and memory cells are produced.produced.

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Primary and secondary Primary and secondary responseresponse

Those defenses can be divided into two Those defenses can be divided into two stages: the primary response and stages: the primary response and secondary response.secondary response.

Primary response occurs when a Primary response occurs when a foreign substance is encountered for foreign substance is encountered for the first time.the first time.

The secondary response is the sequence The secondary response is the sequence that is triggered by the army of memory that is triggered by the army of memory cells produced by the primary response.cells produced by the primary response.

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Self-tolerance and Self-tolerance and autoimmunityautoimmunity

All the cells of the body bear their own molecAll the cells of the body bear their own molecular "markers" embedded in their membranes.ular "markers" embedded in their membranes.

所有的免疫細胞巡邏全身，只要有這些所有的免疫細胞巡邏全身，只要有這些 markersmarkers的細胞，就不會攻擊。的細胞，就不會攻擊。

This acceptance by the body's immune cells is This acceptance by the body's immune cells is called-tolerance.called-tolerance.

In some case, the immune system can turn agIn some case, the immune system can turn against its own body, the reaction is called autoiainst its own body, the reaction is called autoimmunity.mmunity.

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Interferon (Interferon ( 干擾素干擾素 ) ) Interferon causes cells to become resistant to Interferon causes cells to become resistant to

attacks by other viruses.attacks by other viruses. It does not act against specific viruses but will It does not act against specific viruses but will

inhibit any viral attack.inhibit any viral attack. Given interferon in a nasal spray Given interferon in a nasal spray 可以避免感可以避免感冒。冒。

Interferon reduced brain tumor size.Interferon reduced brain tumor size. Side effects: it triggers irregular heartbeats, it Side effects: it triggers irregular heartbeats, it

may also complicate liver or kidney problems.may also complicate liver or kidney problems.

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Essay 20.3 How African Essay 20.3 How African crocodiles defend against crocodiles defend against

Texan rabbitsTexan rabbits If you take hemoglobin from a If you take hemoglobin from a

rabbit and inject it into a rabbit and inject it into a crocodile, the crocodile will form crocodile, the crocodile will form antibodies against the rabbit antibodies against the rabbit hemoglobin.hemoglobin.

Why can this be?Why can this be? There are only about 300 DNA There are only about 300 DNA

segments that code for the segments that code for the variable DNA segments of variable DNA segments of antibodies.antibodies.

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Recombination of DNARecombination of DNA

Only 300 DNA segments clearly not enOnly 300 DNA segments clearly not enough to provide an antibody response ough to provide an antibody response against every possible antigen.against every possible antigen.

However, these regions are extremely However, these regions are extremely unstable. They break apart and rejoin unstable. They break apart and rejoin endlessly, providing a virtually infinite endlessly, providing a virtually infinite number of combinations (in humans, number of combinations (in humans, about 180about 180 億億 ).).

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AIDSAIDS AIDSAIDS ：： acquired immuno-deficiency syacquired immuno-deficiency sy

ndrome (ndrome (後天免疫失調症候群後天免疫失調症候群 )) The first case of AIDS in the United StatThe first case of AIDS in the United Stat

es appeared in 1979, followed by a half-es appeared in 1979, followed by a half-dozen cases reported in Los Angeles in dozen cases reported in Los Angeles in 1981.1981.

In early 1989, the world Health OrganizIn early 1989, the world Health Organization estimated that over one new case ation estimated that over one new case of AIDS was developing each minute, wof AIDS was developing each minute, worldwide.orldwide.

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In 1995, it was reported between 63In 1995, it was reported between 63萬 萬 and 89and 89萬萬 77千人感染千人感染 AIDSAIDS 。。

It is estimated that between 6 and 10 million peIt is estimated that between 6 and 10 million people are presently affected with the virus but dople are presently affected with the virus but do not yet show symptoms.o not yet show symptoms.

Many people carry antibodies to the virus that Many people carry antibodies to the virus that causes AIDS, showing that they have been expocauses AIDS, showing that they have been exposed to it, without developing the symptoms.sed to it, without developing the symptoms.

The syndrome, once full blown, is incurable anThe syndrome, once full blown, is incurable and virtually always cause death within a few yead virtually always cause death within a few years (fewer than 14% of victims survive past three rs (fewer than 14% of victims survive past three years).years).

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Fig. 20.8 AIDS Fig. 20.8 AIDS manifests itself in manifests itself in numerous ways, all numerous ways, all

marked by a marked by a deteriorating deteriorating

immune system.immune system.

Early signs of AIDS inclEarly signs of AIDS include a series of lingerinude a series of lingering(g(慢性的慢性的 ), simple colds,), simple colds, night sweats, persisten night sweats, persistent fever, swollen glands, t fever, swollen glands, and coughing.and coughing.

More serious conditionMore serious conditions follow, including at les follow, including at least three forms of cancast three forms of cancer and destruction of ther and destruction of the lungs and brain (Fig. e lungs and brain (Fig. 20.8)20.8)

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Fig.20.9 AIDS is especially prevalent Fig.20.9 AIDS is especially prevalent among needle-sharing addicts.among needle-sharing addicts.

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Dependence on condoms Dependence on condoms as a protectionas a protection

Some types of condoms are not Some types of condoms are not completely effective.completely effective.

For example, those made of animal For example, those made of animal membranes, rather than rubber, do membranes, rather than rubber, do not block the passage of viruses.not block the passage of viruses.

Also some men simply do not know Also some men simply do not know how to use them safely.(The condom-how to use them safely.(The condom-sheathed penis must be withdrawn sheathed penis must be withdrawn immediately after ejaculation).immediately after ejaculation).

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The geographical The geographical source of HIVsource of HIV

HIV(human immunodeficiency virus)HIV(human immunodeficiency virus) 原本是在原本是在 African green monkey (West African green monkey (West

Africa)Africa) 身體內的身體內的 virus virus 轉入人體。轉入人體。 從西非傳至海地，美國同性戀者渡假地區。從西非傳至海地，美國同性戀者渡假地區。

再經由這些同性戀者，傳入美國。再經由這些同性戀者，傳入美國。 然後，逐漸擴展至全球。然後，逐漸擴展至全球。 無論是同性或異性戀，都可以傳染。無論是同性或異性戀，都可以傳染。

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Essay Essay 20.420.4AIDSAIDS The infectioThe infectio

us agent of Aus agent of AIDS was discIDS was discovered in 198overed in 1984.4.

The virus is cThe virus is called HIV (halled HIV (human immuuman immuno-deficiencno-deficiency virus).y virus).

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HIV HIV 攻擊 攻擊 T-T- 細細胞的過程。胞的過程。

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HIV HIV 攻擊 攻擊 T-T- 細胞的過程。細胞的過程。 The virus attacks the helper T-cell, The virus attacks the helper T-cell,

penetrating the the cell and releasing a penetrating the the cell and releasing a single strand of RNA and an enzyme, single strand of RNA and an enzyme, reverse transcriptase, with it. reverse transcriptase, with it.

The enzyme enables the RNA to make a The enzyme enables the RNA to make a double strand of complementary DNA, double strand of complementary DNA, which then joins the helper T-cell's DNA.which then joins the helper T-cell's DNA.

Finally, there are so few helper T-cells in Finally, there are so few helper T-cells in the blood that no effective immune response the blood that no effective immune response can be mounted against any attack can be mounted against any attack whatsoever.whatsoever.

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AIDS virus seeks out the helper T-cell lymphocytes.AIDS virus seeks out the helper T-cell lymphocytes. Using the various chemical markers on its surface, Using the various chemical markers on its surface,

the AIDS virus binds easily to a receptor on the the AIDS virus binds easily to a receptor on the surface of the helper T-cell.surface of the helper T-cell.

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The HIV injects RNA and the enzyme transcriptase into T-cell.The HIV injects RNA and the enzyme transcriptase into T-cell. The enzyme helps transcribe the invading RNA into DNA.The enzyme helps transcribe the invading RNA into DNA. Once activated, the viral DNA directs the T-cell to make copies Once activated, the viral DNA directs the T-cell to make copies

of the virus. Eventually the host cell dies.of the virus. Eventually the host cell dies.