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8/17/2019 Sains Form 4 Chapter 3
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CHAPTER 3
Heredity
and
Variation
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Human CellsChromosom
es
DNAGenesCharacterist
ics/ traits
Built up of containing
determiningcontaining
containing
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3.1 CELL DIVISION
• Chromosomes, genes and DNA
• Life cycle and cell division –
Mitosis gro!th – Meiosis se"ual reproduction
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,and DNA
Ci# $my
N&CL$&'
CH()M)')M$'*threadli#e structure
*human +eings have - .0pairs
*contain protein and DNA
DNA- Dou+le heli" structure- *Made up of series of
genes
G$N$- 'egment of DNA
*Genetic codes !hichdetermine an organism
characteristics
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!itosis
• De"nition#
A cell division process in !hich aparent cell .original cell1 di$idesinto t%o identi&a' daughter cells.ne! cells1
• O&&(rs in – Human and animal somatic cells
– 2lants tips of roots and shoots
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http://youtube.co/watch?v=nPG6480RQo0http://youtube.co/watch?v=nPG6480RQo0
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Staes o) mitosis
• Chromosomes in the nucleusshorten, thic#en and more
visi+le3
• (eplication of chromosomes
occur3•$ach strand of chromosome iscalled chromatid3
&hromatid
&entromere
n(&'e(s mem*rane
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• 9he nucleus mem+rane forms
again3• 9!o daughter cells are formed3
• $ach daughter cell has the same
num+er of the chromosomes as theparent cell3
• 'pindle :+res emerge3• Chromosomes align themselves in
the centre of the cell3•
9he nucleus mem+rane disappears3
• Chromatids divide and separate to
the opposite ends of the cell3• At the same time the cell starts to
divide3
s+ind'e "*res
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=m
or
Th I t )
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The Im+ortan&e o)!itosis
2roduce ne! cells for
ro%th ? unicellular@ygote to
multicellular organism
Ase(a' re+rod(&tionfor simple organism
li#e amoe+a
Reenerate *odyparts such as li@ard
gro!s a ne! tail
Veetati$ere+rod(&tion such as
rhi@omes, tu+ers,
leaves
2roduce ne! cells forre+'a&in dead&e''s-re+airin
tiss(es
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!eiosis•
De"nition#A process in !hich a nucleus of a parent cell
di$ides into )o(r da(hter &e''s throught!o divisions3
• 9he daughter cells !ill have ha') the n(m*erof chromosomes in parent cell3
• )ccurs in re+rod(&ti$e orans to +rod(&eametes o$(m and s+erms/# – Human and animals testes .male1 and ovary
.female1
– 2lants anthers and ovaries
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http://youtube.co/watch?v=D1_-mQS_FZ0http://youtube.co/watch?v=D1_-mQS_FZ0
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Staes O) !eiosis # !eiosis 1 And !eiosis 0
• Chromosomes in thenucleus shorten, thic#en
and more visi+le3
• Crossing over and
replication process occuron chromatids3
Meosis 1
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• Chromosomes alignthemselves in the centre of the
cell3• 9he nucleus mem+rane
disappears3
• Chromatids separate and
move to the opposite ends ofthe cell3• 9he cell +egins to divide into
t!o3
• 9!o daughter cells areproduced3
• 9he nucleus mem+rane
reforms3
M i 2
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•
9he nucleus mem+rane isformed again3•our daughter cells are formed3• $ach daughter cell has half ofthe num+er of chromosomes in
the parent cell3
• 'pindle :+res emerge3•Chromosomes align themselves
in the centre of the cell3
• 9he nucleus mem+ranedisappears3
•Chromatids divide and separateto the opposite ends of the cell3
• 9he cell starts to divide3
Meosis 2
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http://youtube.co/watch?v=eaf4j19_3Zghttp://youtube.co/watch?v=eaf4j19_3Zg
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!eiosis
Crossino$er
+ro&ess
Inde+endentassortment
o)&hromosom
es(characteristics are separated
during formation of gameteand randomly combined
during fertilization)
3 9oproducegametes
3 9o allo!
variationthrough
C ' i O) !i i
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Con&'(sion O) !itosisAnd !eiosis
Meiosis
ertilisation
Mitosis
Male
.- chromosomes1
emale
.- chromosomes1
'perm0 chromosomes1
)vum.0 chromosomes
ygote
.- chromosomes1
Ba+y.- chromosomes1
C i ! i i A d !it i
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Com+arin !eiosis And !itosisp//youtu+e3co/!atch4v5BaEL;FH@t&
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Simi'arities And Dieren&es2et%een !itosis And !eiosis
SI!ILARITIES
(eplication of DNA
ta#esplace
nvolves
division ofnucleus
andcytoplasm
Celldivisionoccurs
The Dieren&e 2et een !itosis
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The Dieren&e 2et%een !itosisAnd !eiosis
DIFFERENCESMITOSIS MEIOSIS
Replication process
Number of division
Number of daughter
cells produced
Number of
chromosomes indaughter cell
Combination of gene
Occur
One only
Four
Same as in parent cell
Same as parent cell
Occur in the first
division
Two times
Two
Half of parent cell
Different from parent cell
Crossing over processDoes not occur Occur
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.O
INHERITANCEGene
$"ist in pair
Dominant ene
*A gene !hich e"presses
the trait !hen paired !itha dominant or recessive
gene
*Denote as capital letter,eg
T ta''/
Dominant trait
Characteristics controlled
+y dominant genes
Re&essi$e ene
*A gene !hich e"presses thetrait !hen paired !ith a
recessive gene only .in thea+sence of a dominant
gene1
*Denote as small letter, eg t
short/
Re&essi$e trait
Characteristics controlled
+y recessive genes
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Chromosomes are in pair3 )nefrom the father !hile the other
one from the mother3
'ame genesDominant gene andrecessive gene areplaced
opposite to each other
Homologous chromosomes
t T
Eam+'es o) dominant and re&essi$e
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Eam+'es o) dominant and re&essi$etraits
Trait Dominant Re&essi$e
Ear'o*es ree earlo+es Attached earlo+es
To(ne A+ility to roll na+ility to roll
Dim+'es 2resence A+sence
Hair Curly 'traight
Iris&o'o(r
Bro!n Blue
Heiht 9all D!arf
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The !e&hanism O) Trait Inheritan&e
•
Gregory Mendel !as the :rst person!ho discovered the principles ofheredity3
4enoty+e
Phenoty+e
The genetic
information of anorganism
The physicalcharacteristics of an
organism
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!onohy*rid Inheritan&e 2y 4reory !ende'
TT tt
9all .pure +reed1 D!arf .pure +reed1
T T tt
T t tT
9all 9all 9all 9all
9all 9all 9all D!arf
2henotype
Genotype
2henotype Genotype
2henotype
Genotype
Generation
Generation
Gametes
Gametes
Tt Tt Tt Tt
TtTtTT tt
5ey#
Homo6yo(s# *othenes are same
E# TT, ttHetero6yo(s# enesaredierent
E# Tt
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Eer&ise 1
• n the pea plant, the gene for roundseed.(1 is dominant to the gene for!rin#led seed.r13a1 f a homo@ygous round*seeded pea
plant is crossed !ith a homo@ygous!rin#led*seeded plant, !hat !ill +e the
phenotype of plants4+1 f the plants are self*pollinated, !hat!ill +e the genotype and phenotyperatios of the plants4
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RR rr
(ound seed rin#led seed
R R rr
(ound (ound(ound(ound
2arental 2henotype 2arental Genotype
Generation
Gametes
Rr Rr Rr Rr
Hen&e a'' the 1 +'ants ha$e ro(nd seeds.
a1 5ey#R# ro(nd seededr # %rin7'ed
seeded
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+1
R r rR
(ound
(ound
(ound
rin#led
2henotype
Genotype
Generation
Gametes
Rr Rr
RrRrRR rr
notype ratio is 1 RR#0 Rr# 1rr
notype ratio is 3 +'ants %ith ro(nd seeds # 1 +'ant %ith %rin7'ed
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Eer&ise 0
• B represents the dominant gene for+lac# cat, and + represents therecessive gene for a !hite cat3
hat is the phenotype ratio of thenum+er of +lac# cats to the num+erof !hite cats if +lac# fur cat .B+1 is
crossed !ith another +lac# fur cat.B+14
Ans!er
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2 * *2
Blac
#
Blac#Blac# hite
2henotype
Genotype
2arents
Gametes
2* R*
2*2*22 **
henotype ratio is 3 *'a&7 )(r &ats# 1 %hite )(r &at
5ey#R# *'a&7 &atr# %hite &at
Ans!er
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Eersi&e 3
• n the pea plant, the gene for purpleIo!ers .21 is dominant to the genefor !hite Io!ers .p13 A cross
+et!een a hetero6yo(s +ea +'ant%ith +(r+'e 8o%ers and ahomo6yo(s +ea +'ant %ith
%hite 8o%ers is done3hat are the genotypes of theos+rins4
Ans!er
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P + ++
2urpl
e
hite2urpl
e
hite
2henotype
Genotype
2arents
Gametes
P+ ++
++P+P+ ++
Genotype ratio is 0 P+ # 0 ++
5ey#P+# hetero6yo(s ,+(r+'e 8o%er
++# homo6yo(s , %hite8o%er
Ans!er
3 3 SE9 DETER!INATION AND THE
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3.3 SE9 DETER!INATION AND THEOCC:RRENCE O T;INS IN H:!AN 2EIN4S
•
Se &hromosomes the last pair in humanchromosomes
!a'e# pairs of
autosomes and a pair of
ema'e# pairs of
autosomes and a pair of se"
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• Se determination # the se" of +a+y is determined+y the )ather=s s+erm 9>?992a*y *oy>>? 9
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J;;
J; K
J ;
J ;
J;;
J; K
J K
J ;
J;;
J; K
Mother ather
4ametes #
Parents #
s+rins#
Ratio o) da(hter # son is 1#1
There)ore , the &han&e to et da(hter or son is @#@.
Daughter Daughter'on 'on
Th ti O) Id ti ' A d N id ti '
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The ormation O) Identi&a' And NonBidenti&a'T%ins
An ovum is fertilised+y a sperm to form a@ygote3
ygote undergoesmitosis and separates
into t!o to develop intot!o em+ryos3
Genetically identical3
'hare the sameplacenta3
'ame se"3
IDENTICAL
T;INS 9!o dierent ovafertilised +y t!odierent sperms at thesame time3
9!o dierent @ygotesare formed and developinto t!o em+ryos3
Genetically dierent3
$ach has o!nplacenta3
'ame se" or dierent
se"3
NONBIDENTICAL
T;INS
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IDENTICALT;INS
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NONBIDENTICALT;INS
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2:TTT
IDENTICALNONB
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IDENTICALT;INS
IDENTICALT;INS
ygoteundergoes mitosis
9!o
em+ryos
oetusshare thesameplacenta
9!o ovaarefertilise
d
9!odierent@ygotes areformed
9!oseparateem+ryos
$achfoetushas hiso!nplacenta
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• Siamese t%ins – dentical t!ins that are oined at some
parts of the +odies3 – ormed !hen @ygote fails to divide
completely in the course of formation3
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Simi'arities And Dieren&es 2et%een Identi&a' And
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NonBidenti&a' T%insIDENTICAL
T;INS
NONBIDENTICAL
T;INSSimi'arities#
9he t!ins are formed in the uterus3 9!o +a+ies are formed3
)ne
)ne
'ame se"
Kes
'ame / identical
Kes / sharingplacenta
9!o
9!o
'ame or dierentse"
No
Dierent
No / separateplacenta
N(m*er o) s+erms
erti'ised o$(ms+'its into t%o
4eneti& ma7e (+
Sharin o)+'a&enta
Se
N(m*er o) o$a
Dieren&es
y
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ythem4
3 > !:TATION
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3.> !:TATION
• !(tation# the spontaneous changeto the structure of genes orchromosomes
)ccurs in
Somati&-*ody
&e''s.can +e passeddo!n through
mitosis1
4ametes-re+rod(&ti$e &e''s
.inherited1
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T
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Eam+'es O) Chromosome!(tation
• Do%n=s syndrome# an e"tra chromosome
in autosome .< chromosomes1
• 5'ine)e'ter=s syndrome a male !ith
e"tra ; chromosome .;;K1
• T(rner=s syndrome# a female !ith oneless ; chromosome .;)1
• Po'y+'oidy having one or morechromosomes in a set of chromosome
' O) 4 i
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Eam+'es O) 4ene !(tation
• Co'o(r *'indness a mutated gene in the Xchromosome
• Si&7'e &e'' anemia# mutation in gene thatproduces haemoglobin inecient in transportingo"ygen in the +lood
• A'*inism# the gene for sin colour is mutated
una+le to produce +lac# pigment .melanin1
• Haemo+hi'ia# mutation in gene that isimportant for blood!clotting
Eam+'es O) Chromosome
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Eam+'es O) Chromosome!(tation
Do%n=s syndromeAdditiona' chromosome at a(tosome 0
•"hysical retardation•
Thic nec •#lanted eyes•Protuding tounge•Reduced resistance to diseases
5'i ) 't = d
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5'ine)e'ter=s syndrome
A ma'e !ith etra 9
chromosomes .having ;;K1
•$nfertile•%nderde&eloped testes•Narrow shoulder•'nlarged breasts
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T(rner=s syndromeA )ema'e having one 'ess 9chromosome .;)1
•$nfertile•#hort •entally retarded•as no o&aries
•#mall breasts•*olded sin on nec •No menstrual cycle
P ' ' id
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Po'y+'oidy – 9he num+er of chromosomes is
in&reased *y one or more sets.
– More common in plants3
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!(tation
Co'o(r *'indness
!(tant ene .recessive gene1on the 9 chromosome3
•Not able to di+erentiate coloursespecially green and red •ore common in males becausemale has only one Xchromosome
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• Colour Blind
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Colour Blind 9est
A'*inism
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A'*inism
9he ene )or s7in &o'o(r ism(tated .recessive gene1
•%nable to produce melanin(blac pigment)•,hite hair
•"in eyes and pinish sin•#in is sensiti&e to sunlight
Si&7'e &e'' anemia
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Si&7'eB&e'' anemia
!(tation in ene that+rod(&e haemo'o*in
•#icle!cell shaped of red bloodcells•Not e-cient in transporting
oygen•*acing painful crises such aschest pain/
fatigue/ bone pain/•0ellowing of eyes•$nherited from both parents
Haemo+hi'ia
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Haemo+hi'ia
!(tation in &hromosome 9.for +lood clotting1
• a&e problem in blood clotting• ay bleed continuously or fora longer
period• A woman carrier may inheritthe
disease to a son
Ca(ses O) !(tation
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'pontaneouschanges during
cell division
$"posure to
+hysi&a'm(taens &Oradiation, ;*rays,
radioactive radiation
En$ironmenta'&hane# the change oftemperature for a longperiod causes geneticevolution in organism
$"posure to &hemi&a'
m(taens Ben@ene,formaldehyde,nicotine, sodiumnitrite, pesticides
Ca(ses O) !(tation
Ad antaes And Disad antaes
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Ad$antaes And Disad$antaesO) !(tation
*variation di3trait
*more resistantto disease
Advantages
Cause physicaldefects
Causes geneticdiseases
Causes mentaldefects
Disadvantages
.RESEARCH
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RESEARCHON H:!AN LIE
4ene thera+y# to
replace damaged/faultygenes during the foetal
stage4eneti& s&reenin# topredict diseases li#ely
to develop4ene test# to screen
un+orn children fordiseases4eneti& enineerin#
to transfer DNA fromone organism to
anotherH(man enome+roe&t# maps allhuman genes to
determine genes !hichcauses diseases
ie'd o)
!edi&ine
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9o produce plants !hichare resistant to
diseases and infections 9o produce engineeredplants !hich are a*'e
to 'i$e in(n)a$o(ra*'e
conditions
9o produce plants !hichgro! and mat(re )ast
9o produce hiher
yie'ds
9o produce hih(a'ity of crops and
livestoc#
ie'd o)Ari&('t(re
'elective Breeding
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'elective BreedingA process !hich involves
cross breeding and cloning of plants or animals
Ad$antaes
Ne! varieties
9o produce ne!
and high Pualitycrops
More resistant todiseases
Disad$antaes
ne! varieties !ithundesira+le
characteristics
$"ample Co!
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$"ample Co!
is &ross *red %ith
riesian Co% Sahi%a' Co%
!a)ri%a' Co%
*Gro! faster *Bigger in si@e
*More mil# *High resistant to
$"ample 2alm oil
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$"ample 2alm oil
is &ross *red %ith
D(ra Pisi)era
Tenera
*9hic# meso&ar+ and 'are 7enne' #much oil
*Thin she''# easier to e"tract
hineso&ar+
Lare7enne'
Thi&7 meso&ar
Sma''7enne'
Tiss(e C('t(re
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A process of cloning a plant byusing a plant part or single cellin a test tu+e under a controlled
condition
Ad$antaes 9o produce many
copies of thesame plants in ashort time
9o produce plantsanytime !e !ant
'horter
maturation time
No variation
Disad$antaes
Complete !ipe*out of crops if
there is spread ofdiseases
Ste+s o) Tiss(e C('t(re
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Ste+s o) Tiss(e C('t(rea/ E+'ant#
*/ !('ti+'i&ation#
&/ Trans+'antin#
C'onin
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9he process of producing an
organism that is an eactgenetic copy of another
ro&ess#
4eneti&a''y !odi"ed
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yood
*oods from plants and animal!adding genes from anotherorganisms
Ad$antaes#or &ro+s#
enhanced tasteand Puality,
increased yields,matures faster,+etter resistance
to diseases,remain fresh
longer
or 'i$esto&7#increased
resistance toinfections anddiseases, higher
yield of mil#,meat and eggs
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GM2
Disad$antaes o) 4eneti&a''y !odi"ed
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Cause allergies to human+eings
ood and Oranisms#
Mil# of animal may+e unsafe
Anti+iotic*resistant genes inGM organisms may +e pass on
to +acteria dicult to #ill them
Genetic research is e"pensive,poor farmers cannot aord
3.F VARIATION A!ON4 LIVIN4THIN4S
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THIN4SVariation#
9he dierences amongindividuals of the same
species
Contin(o(s $ariation
Dis&ontin(o(s
$ariation
*Characteristics amongindividuals !hich do notsho! distinct dierences
*8uantitative and can +emeasured
*Determined +y genesand can +e inIuenced +yenvironmental factors
*Characteristics amongindividuals !hich sho!distinct dierences
*8ualitative and cannot
+e measured
*Determined +y a singlegene and is notinIuenced +y
environmental factors
Di ti
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Contin(o(s $ariation
Dis&ontin(o(s
$ariation
Height
'#incolour
Lengthof foot
ntelligence
eight
$arlo+es
riscolour
Colour+lindnes
s
9onguerolling
Bloodgroup
a&tors That Ca(se
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Variation
Geneticfactors
Crossin o$er during meiosisgenetic material is e"changed
Random )(sion of male andfemale gametes during
fertilisations
Chromosome and genem(tation creates ne!
phenotypes
Inde+endent assortmentof chromosomes dierent
gametes
$nvironmental factors
S(n'iht e+os(re# !illhave dar#er comple"ion
;ater &'imate,tem+erat(re
+H# the Hydrangea Io!er is+lue in acidic soil and pin# in
al#aline soil
Diet# a person !ho eats alot !ill +e fatter
Im+ortan&e O) Variation
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Im+ortan&e O) Variation
M2)(9ANC$
$nsures the survivalof a species under
changingenvironment
$na+le anyspecies to
occupy a !iderrange of ha+itat
$na+le naturalselection species!ith favoura+le
characteristics !ill+e selected +y
nature
$na+le us todistinguish
individuals ofthe samespecies
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• Discuss the similarities anddierences +et!een continuousvariation and discontinuous variation3
Simi'arities And Dieren&es 2et%eenContin(o(s And Dis&ontin(o(s Variation
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CONTIN:O:SVARIATION
DISCONTIN:O:S VARIATION
Simi'arity#'ho! dierences in characteristics
among individuals of the samespecies
Kes
Not distinct
f it is inIuenced+y environmental
factors cannot +einherited
9!o or moregenes for the
same character8uantitative/ can
+e measured
No
Distinct
Can +e inherited
'ingle gene
8ualitative/cannot +emeasured
In8(en&ed *yen$ironmenta'
)a&torsG
Inheritan&e
No o) ene
Ty+e o) data
Chara&teristi&
Dieren&es
Contin(o(s And Dis&ontin(o(s Variation
3. THE NEED TO ADHERE TO A CODE
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O ETHICS IN 4ENETIC RESEARCH
• Discuss the eects of misusing the#no!ledge of genetics research3
d d f thi QQ
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e need code of ethicsQQ
9he produce of+iological !eapon
anthra" +acteria
GM may have side eectsand endanger human
health,should +e la+elled
Human cloningagainst religion
Manipulation ofhuman genes !hen
carrying out researchon human +eing