blueprint of life secondary resources notes

8/16/2019 Blueprint of life secondary resources notes

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Biology: Secondary Resources Summary

BLUEPRINT OF LIFE Sherifa Rachid

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1. Evidence of evolution suggests that the mechanisms ofinheritance, accompanied by selection, allow changes over

many generations

… prepare a case study to show how an environmental change can lead to

changes in a species

PHYSICAL

- Physical changes in the environment cause species to either die out, or

survive and diversify.

e.g.Black peppered moths (Biston Betularia):

- There was variation within the population of peppered moths – there were light

forms and dark forms.

- Prior to the industrial revolution, the majority of the peppered moths were light

coloured as they had the favorable characteristic of camouflaging against the

lichen covered trees. This meant that they were less visible to the birds

(predator) and thus survived, reproduced and passed on the favourable

characteristic of camouflaging to their offspring.

- Post revolution, the pollution caused the black soot to deposit on trees thus

white moths could no longer hide. The darker moths now had the favourable

characteristic of camouflaging & thus survived, reproduced and passed it on

to their offspring.

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- Therefore the population evolved from mainly white to mainly dark near

industrial sites. This is how a change in the environment can affect the

evolution of an organism.

CHEMICAL

- When DDT was first used to kill mosquitoes, low concentrations were

extremely effective. In subsequent sprayings, low concentrations were

ineffective and stronger doses were needed.

- There was variation within the mosquito population in terms of their resistance

to DDT. Some mosquitoes were more resistant than others.

- The few mosquitoes which survived the first spraying had a natural resistance

to DDT hence they survived, reproduced and passed on this favourable

characteristic to their offspring.

- The population evolved from mainly susceptible to mainly resistant due to

selection by DDT in the environment.

COMPETITION

- Long term competition usually results in the elimination of one of the

competing species or the evolution of competing species to occupy different

niches.

e.g.the Flycatcher bird:

- The leaden flycatcher and the restless flycatcher feed on similar insects but in

different ways.

- The leaden flycatcher catches flying insects or collects them from trees.

- The restless flycatcher hovers above the ground, emits a call that disturbs the

insects, then pounces on them.

- Overtime, these different species of flycatcher are thought to have evolved to

occupy slightly different niches due to competition for food.

… observe, analyse and compare the structure of a range of vertebrate

forelimbs

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Humerus

Ulna

ar!al

Phalan"es

Radius

Similar s#ruc#ures #ha# are #he resul# $f descen# fr$m c$mm$n

ances#$rs are called h$m$l$"ies% E%"&

The pattern of limb bones known as a pentadactyl limb is an example of

homologous structures. This pattern is found in all classes of tetrapods (i.e.

from amphibians to mammals). The limb has a single proximal bone

(humerus), two distal bones (radius and ulna), a series of carpals (wrist

bones), followed by five series of metacarpals (palm bones) and phalanges

(digits). Throughout the tetrapods, the fundamental structures of pentadactyl

limbs are the same, indicating that they originated from a common ancestor.

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But it is considered that in the course of evolution, these fundamental

structures have been modified. They have become superficially different and

unrelated structures in order to serve different functions in adaptation to

different environments and modes of life. This phenomenon is clearly shown

in the forelimbs of mammals. For example:

• In #he (hale) #he humerus) radius and ulna is a l$# sh$r#er

and fa##er #han a human*s) +u# #heir ,n"er +$nes are a l$#

l$n"er% This maes #hem ada!#a+le f$r s#eerin" and

main#ainin" e.uili+rium durin" s(immin" (hile (e humans

are m$re ada!#ed #$) sa/) !la/in" 0ide$ "ames (i#h $ur

hands%

• In #he +a#) #he f$relim+s ha0e #urned in#$ (in"s f$r /in" +/

"rea# el$n"a#i$n $f f$ur di"i#s) and #he h$$-lie ,rs# di"i#

remains free f$r han"in" fr$m #rees%

• a#s ha0e small +$nes s!eci,call/ #he !halan"es (i#h

man/ 4$in#s #$ all$( e5i+ili#/ and ease $f m$0emen#6 ac#

as a "$$d sh$c a+s$r+er%

H$(e0er) n$# all similar s#ruc#ures are #he resul# $f c$mm$n

ances#r/% These s#ruc#ures) called anal$"ies) are #he resul# $fada!#a#i$n #$ similar en0ir$nmen#s% F$r e5am!le&

• Bat wings consist of flaps of skin stretched between the bones of the

fingers and arm. Bird wings however, consist of feathers extending

all along the arm. These structural dissimilarities suggest that bird

wings and bat wings were not inherited from a common ancestor

with wings.

• Bird and bat wings are analogous to each other, meaning that they

have separate evolutionary origins, but are superficially similar

because they convergently evolved to serve the same function.

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http://www.newworldencyclopedia.org/entry/Treehttp://www.newworldencyclopedia.org/entry/Tree


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… analyse how advances in technology have changed scientific thinking

about evolutionary relationships

– Previously relationships between organisms were worked out by similarities

in anatomical features.

– New technologies, especially in the field of biochemistry, have increased

knowledge about the relationships between species.

– DNA Hybridisation:

DNA hybridisation is a process by which the DNA of different species can

be compared

The process uses heat (~90-94°C) from a thermal cycler to separate the

double-stranded DNA molecule lengthwise to expose nucleotide bases on

each individual strand (dissociation).

One of these strands of the double helix, is obtained from 2 different

species wished to be compared.

The single strands of the different species are then combined (re-

associating) and form a ‘hybrid” (mixed) DNA molecule, and cooled.

On cooling, the hydrogen bonds re-form in varying degrees, the greater the

number of bonds between the strands, the greater binding of strands, ie a

greater degree of genetic similarity between the two species.

Heat is once again applied, this time to determine how strongly the bases

have combined, higher temperatures are required to separate hybrid

strands that are more strongly combined. Closely related species have a

very similar order of nucleotide bases and so their DNA strands combine

more strongly than species that are distantly related.

– Primate Evolution, an example of evolutionary relationship:

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Primate evolution was previously based on anatomical and physical

features, as the growing scientific advances have been developed, the

classification has changed.

It was previously thought that chimpanzees were more related to gorillas

then humans, this was based on structural anatomy of the hind-limb

“knuckle walking” and the enamel on their teeth, these studies showed

that gorillas and chimpanzees were more closely related to each other

then humans.

Though through the technological advances, in 1970s amino acid

sequencing was used, it was shown that chimpanzees are more closely

related to humans, then they are to gorillas. DNA hybirdisation has been

used and shown humans and chimpanzees have a base difference in their

DNA by (1.6-2.4%).

This has lead to a completely different evolutionary tree, gorillas

chimpanzees and humans were put in the same family , they were in

complete difference families before technological advances, also the

tree shows humans and chimpanzees as two groups diverged most

recently from a common ancestor, whilst gorillas appear to have

diverged slightly earlier.

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analyse information on the historical development of theories of evolution and use

available evidence to assess social and political influences on these

developments

:

lassi,ca#i$n $f "rea# a!s and humans& a #radi#i$nal classi,ca#i$n +ased $ns#ruc#ural ana#$m/ sh$(s #he "rea# a!es "r$u!ed in a famil/ se!ara#e fr$mhumans6 + m$dern al#erna#e classi,ca#i$n #ha# "r$u!s "$rillas) chim!an;ees


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2. Gregor Mendel’s experiments helped advance our knowledge

of the inheritance of charatceristics

… describe an example of hybridisation within a species and explain the

purpose of this hybridisation

- Wheat spread to Europe, Asia, North Africa and China before 1000BC. New

breeds formed when wind carried pollen from wild grasses and fertilized

domesticated plants. Farmers selected the best plant seeds and replanted

them.

- Wheat was farmed in AUS from 1788, but only grew in areas with abundant

rainfall and favourable soil. There was insufficient yield due to poor quality soil,

lack of rainfall and a fungus disease called stem rust.


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- In 1882, William Farrar obtained many favourable varieties of wheat and

hybridized them. E.g:

⇒ Indian wheat was drought tolerant and resistant to some diseases.

⇒ Canadian Fife wheat matured late and had the best milling and baking

qualities.- Farrar hybridised both varieties and then selected the plants that had the

advantages of both parents to produce many hybrids

- Farrar crossed Purple Straw and Yandilla to produce an extremely successful

hybrid, Federation, released in 1902. This had the hardiness of the Indian

variety, a tendency to escape rust diseases and short strong straw that made it

suited to our climate and harvesting methods. It had a high yield and could be

grown in drier areas where fungus diseases were less common.

- Ultimately the purpose of hybrids is to increase the genetic pool of a certain

organism. This increases the likelihood that a desirable plant/animal will be

produced

4. The structure of DNA can be changed and such changes may

be reflected in the phenotype of the affected organism

… outline evidence that lead to Beadle and Tatum’s ‘one gene – one

protein’ hypothesis and explain why this was changed to ‘one gene –

one polypeptide’ hypothesis

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E0idence #ha# lead #$ Beadle and Ta#um>s ?$ne "ene @ $ne !r$#ein>

h/!$#hesis&

- In 1941, Beadle and Tatum began a series of experiments to attempt to

mutate genes on bread mould. (Neurospora)

- The bread mould was irradiated with X-rays to induce mutations.- Each mutated stain lacked the ability to produce particular amino acid or

vitamin.

- If the mould didn’t grow, then it was grown on a variety of media, each

contain\ning a different amino acid. Once the minimal medium was

supplemented with a particular amino acid, the mutant would grow.

- This suggested that the mutants lost the ability to produce particular amino

acids because they lacked particular enzymes.

- To test whether this loss of function had a genetic basis, Beadle and Tatm

crossed the mutant straom with normal bread mould, hence finding that some

of their offsprings shared the mutant phenotype, proving that he inability to

produce the particular amino acid could be inherited

- Beadle and Tatum suggested the ‘one gene-one enzyme’ hypothesis, that is

each biochemical reaction in the cell is controlled by one enzyme and also one

gene

A chan"ed h/!$#hesis&- The enzymes Beadle and Tatum studied were made up of only one

polypeptide.

- Later research showed that, where an enzyme is made up of more that one

polypeptide, a separate gene is involved for each polypeptide.

- Thus, Beadle and Tatum’s was changed to the ‘one gene – one polypeptide’

theory.

… construct a fowchart that shows that changes in DN se!uences

can result in changes in cell activity

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PROESS ORIINAL SECUENE DUTATE BETA LOBIN SECUENE

NA c$de

mRNA c$de

min$ acid c$de

ell ac#i0i#/

P$l/!e!#ide

AT T A A

UA A U U

Thre$nine) !r$line) "lu#amic acid) "lu#amic acid

N$rmal #rans!$r# $f $5/"en

N$rmal "l$+in in haem$"l$+in

AT T T A

UA A A U

Thre$nine) !r$line) 0aline "lu#amic acid

Reduced #rans!$r# $f $5/"en

Du#a#ed "l$+in as $ccurs in sicle cell anaemia

- Sickle cell anaemia is caused by a point mutation where the 17th base of the

haemoglobin gene is changed from A to T.

- This results in the amino acid “glutamic acid” (in the beta chain of

haemoglobin), being replaced by “valine”.

- Hence, the structure and function of RBC’s is altered as they will now have an

abnormal crescent shape.

- This results in a change in cell activity as RBC’s get stuck in capillaries and

thus transport less oxygen to the tissues.

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… Descri"e and analyse the relative wor# o$% &ames 'atson( )rancis

*ric#( +osalind )ran#lin( ,aurice 'il#ins in determining the structure o$

DN and the impact o$ the !uality o$ colla"oration and communicationon their scientic research

- James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins all

played a pivotal role in determining the structure of the DNA molecule. However

it has been publicised that they did not all work together cooperatively and there

is still some debate over who should be accredited with the discovery of the

DNA double helix.

- Watson and Crick both had a passion for science, in particular the DNA

molecule. They began their research together at Cambridge University in

England. They bonded almost straight away and became a formidable research

team. In contrast Rosalind Franklin and Maurice Wilkins were also researching

the structure of DNA. Unlike Watson and Crick these two scientists did not get

along. They had a difficult and argumentative relationship that although they

worked on the same project in the same team, they rarely communicated or

collaborated. Watson and Crick also admitted to having a patronising attitude

towards Franklin. This was largely due to the fact that Rosalind Franklin was a

female in a male dominated area of work. Franklin had few opportunities to

express her ideas and to develop a positive working relationship with Wilkins.

- Watson and Crick worked together as a team. They used the ideas of other

scientists to solve the puzzle that was DNA. Ideas from other scientists that

manipulated Watson and Crick’s ideas included:

- Linus Pauling showed that proteins are arranged in a shape of spring coil.

- A talk by Franklin in 1951 illustrating DNA images produced by X – ray

crystallography initially causing Watson and Crick to produce an inaccurate

model of DNA.

- Erwin Chargaff’s work on nitrogen bases enabled Crick to suggest that these

nitrogen bases were complimentary to one another (A – T, C – G). This was

firstly rejected by Watson until he came up with the idea that these pairs might

be the “rungs of the ladder.”

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- While Watson and Crick were manipulating their ideas surrounding the

structure of DNA, Franklin had discovered from her X – ray diffraction pictures

the double helix nature of DNA in 1953. However Franklin did not announce her

findings. Unknown to Franklin, Wilkins shared these images with Watson and

Crick showing the structure of the DNA molecule. Subsequently Watson and

Crick produced a 3 – D model of the DNA structure as well as a theory

surrounding the DNA double helix.

- In 1962 Watson, Crick and Wilkins were all accredited in determining the

structure of DNA and were awarded the Nobel prize. Ultimately Watson and

Crick are the two main scientists accredited to discovering the DNA structure.

…descri"e a methodology used in cloning

- The methods use in cloning, are different, however the most common is

known as “somatic cell nuclear transfer” or simply "nuclear transfer," requires

two kinds of cell.

- One is a somatic cell which is collected from the animal that is to be cloned

(e.g sheep) The somatic cells contains the complete DNA, or genetic blueprint,

of the animal it came from.

- The other cells obtained is an egg cell which is collected from a female of the

same species (known as an egg donor)

- In the lab, scientists extracts and discards the nucleus of the egg cell (since it

contains the genes of the egg donor)

- The somatic cell is then inserted into the egg cell and the two are fused

together with electricity- The scientist stimulates the egg in order for it to divide by the process of

mitosis. The activated cell is then placed in a culture medium (i.e surrogate)

- The embryo continues to grow and is born as a genetic identical to genetic

donor

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…

identi$y

examples o$ the use o$ transgenic species and use availa"le evidence

to de"ate the ethical issues arising $rom the development and use o$transgenic species

ETHICAL ISSUE FOR AGAINST

Environment and nature - We can produce GM

crops (e.g. Bt crops)

that are resistant to

pests which means less

use of pesticides &

therefore a reduction in

the harmful effects of

the pesticides on the

environments. This also

means less pesticide

resistance.

- Some groups may think it is

wrong to “play God” by

altering the genetic makeup

of organisms.

- Cross pollination could

transfer herbicide resistant

genes from GM crops to

weed.

- Extensive use of crops with

built in pest resistance may

result in increased resistance

of the pests to the toxins.

Financial and social

justice issues

- We can enhance the

quality of crops (e.g.more drought tolerant,

- People in developing

countries can’t afford GMcrops. This widens the

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resistant to pests, have

a higher yield). This is

cost effective as less

money needs to be

spent e.g. on pesticides.

- GM crops with a longer

shelf life (e.g. the gm

tomato), means there’s

less wastage of food –

more money can be

made by the producers

and retailers. The gm

salmon contains the

BGH gene. Producing

larger fish means more

profit and more people

can be fed.

- Any financial gain is

essential as it can be

put back into further

research.

poverty gap even more.

- Single companies can have

the right to own certain genes

and species, not allowing

other companies to access

them even if they may be

beneficial.

Medical and health

issues

- Foods with higher

nutritional value can be

developed to supply

better nutrition to those

in developing countries.

- Reduced use of

pesticides is better for

the consumer’s health.

- Genetic engineering is

used to produce many

human materials (e.g.

blood clotting factors in

transgenic sheep,

insulin in bacteria) for

use in medicine. These

human products

improve health andquality of life.

- Potential long term health

risks of gm products are not

yet known.

- People may have allergic

reactions to foods they could

previously eat if the foods

contain DNA of other

organisms e.g. the presence

of peanut genes in soy

products.

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Animal and human

rights issues

- Gm products may be

used to solve food

shortages in developing

countries, producing a

higher yield at lower

cost.

- Vegetarians may unknowingly

eat food with human DNA

e.g. the transgenic strawberry

contains a gene from salmon.

- Those with religious beliefs

may not be able to eat foods

that they previously ate if

these foods contain genes

from other organisms.

- There have been concerns

about long term effects on the

transgenic organism itself

e.g. mice deliberately

produced to develop cancers

for scientists to study.

The oncomouse has the human

cancer gene and is used in research

programs to search for a cancer

cure. This mouse only lives to about

8 weeks.

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