pindah silang.ppt
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PINDAH SILANG (CROSSING OVER)
PINDAH SILANG (CROSSING OVER)
Contoh : (1) Pada tan. Ercis (susunan “sis”)Gen-gen terangkai : + (M) = bunga ungu m = bunga merah + (B) = serbuk sari panjang b = serbuk sari bulat
P1 : + + x m b + + m b ungu, serbuksari panjang merah, bulatF1 : + + m b ungu, panjang Test cross : + + (M B) x m b m b m b m b F2 : Kalau Test Cross pada Dihibrid ??
M B
M B
bm
bm
F2 : 192 tan berbunga ungu, serbuk sari panjang 23 tan berbunga ungu, serbuk sari bulat 30 tan berbunga merah, serbuk sari panjang 182 tan berbunga merah, serbuk sari bulat
Gamet-gamet yang tidak mengalami pindah silang : gamet + + (M B) dan gamet m bGamet-gamet yang gen-gennya mengalami pindah
silang : gamet + b (M b) dan gamet m + (m B)
F2 :
Genotif
Fenotif Banyaknya Frekuensi
Tipe
M Bm b
Ungu, panjang
192 (192/427) x 100 %
Parental
M bm b
Ungu, bulat
23 Rekombinan
m Bmb
Merah, panjang
30 Rekombinan
m bm b
Merah, bulat
182 Parental
Prosentase Rekombinasi : 23 + 30 x 100 % = 12,41 % 427 Tipe parentalnya : 100 % - 12,41 % = 87,59
%
(2) Pada tan. Ercis (susunan “trans”)
P : + b x m + + b m +Atau P : M b x m B M b m B
Ungu, bulat merah, panjang
Tentukan gamet, F1 ?
F2 : (hasil uji silang) 14 tan berbunga ungu, serbuk sari panjang
178 tan berbunga ungu, serbuk sari bulat 160 tan berbunga merah, serbuk sari panjang 18 tan berbunga merah, serbuk sari bulat
Gamet-gamet yang tidak mengalami pindah silang : .........
Gamet-gamet yang gen-gennya mengalami pindah silang : ......
F2 :
Berapa prosentase rekombinasi ?
Genotif
Fenotif Banyaknya Frekuensi
Tipe
??? ???
Ringkasan :1. Gen-gen tidak terangkai : a. perkawinan dihibrid (AaBb x AaBb), keturunan 9 :
3 : 3 : 1 b. Uji silang dihibrida (AaBb x aabb), keturunan 1 : 1 :
1 : 12. Gen-gen terangkai sempurna : a. Perkawinan dihibrid, gen-gen terangkai sis (A B x A B), keturunan 3 : 0 : 0 : 1 atau 3 : 1 a b ab b. Perkawinan dihibrid, gen-gen terangkai trans : ( A b x A b ), keturunan 2 : 1 : 1 : 0 atau 2 : 1 : 1 a B a B
3. Gen-gen terangkai tak sempurna a. Uji silang dihibrid, gen terangkai sis .......... b. Uji silang dihibrid, gen terangkai trans
Recombination Occurs Less Frequently Between Closely Linked Genes
Physical crossing over is a normal meiosis event
Crossing-over pertukaran segmen dari kromatid-kromatid bukan non-sister kromatid dari sepasang kromosom homolog
The term used to describe crossing over is recombination
Recombination can occur between any two genes on a chromosome
The farther apart the two genes the more crossing over
Pindah silang dibedakan atas :1.Pindah silang tunggal2.Pindah silang ganda
Pindah silang tunggal
Berapakah NPSnya?
NILAI PINDAH SILANG (NPS)
NPS ADALAH ANGKA YANG MENUNJUKKAN BESARNYA PERSENTASE KOMBINASI BARU YANG DIHASILKAN AKIBAT TERJADINYA PINDAH SILANG
Jawaban
NPS = 16 + 22 x100% = 38 x100%
382+16+22+35 773= 4,92%
Faktor-faktor yang mempengaruhi pindah silang :
1.TEMPERATUR, temperatur kurang atau melebihi temperatur biasa dapat memperbesar kemungkinan pindah silang
2.UMUR, makin tua suatu individu makin kurang mengalami pindah silang
3.ZAT KIMIA tertentu dapat memperbesar kemungkinan terjadinya pindah silang
4.PENYINARAN SINAR X dapat memperbesar kemungkinan pindah silang
5.JARAK ANTAR GEN YANG TERANGKAI, makin jauh letak satu gen dengan gen lainnya, makin besar kemungkinan pindah silang
6.JENIS KELAMIN, umumnya jantan atau betina dapat mengalami pindah silang. Namun pada ulat sutera betina dan Drosophila jantan tidak pernah terjadi pindah silang
PETA KROMOSOM
(CHROMOSOME
MAPPING)
© 2005 Prentice Hall Inc. / A Pearson Education Company / Upper Saddle River, New Jersey 07458
Mapping IMapping is
identifying relationships between genes on chromosomesJust as a road map
shows relationships between towns on highway: fine maps
Two types of mapping: genetic and physical
Mapping II Genetic mapping
Based on differences in recombination frequency between genetic loci: meiosis
Physical mapping Based on actual distances in base pairs
between specific sequences found on the chromosome
Most powerful when genetic and physical mapping are combined
Genetic mapping IBased on recombination frequencies
The further away two points are on a chromosome, the more recombination there is between them
Because recombination frequencies vary along a chromosome, we can obtain a relative position for the loci
Distance between the markers
Genetic mapping IIGenetic mapping requires that a cross be
performed between two related organisms The organism should have phenotypic
differences (contrasting characters like red and white or tall and short etc) resulting from allele differences at two or more loci
The frequency of recombination is determined by counting the F2 progeny with each phenotype
Genetic mapping example IGenes on two
different chromosomesIndependent
assortment during meiosis (Mendel)
No linkageDihybrid ratio
F1
9 : 3 : 3 : 1
F2
P
Genetic mapping example IIGenes very close
together on same chromosomeWill usually end up
together after meiosis
Tightly linked
F1
1 : 2 : 1
F2
P
Genetic mapping example IIIGenes on same
chromosome, but not very close togetherRecombination will
occur Frequency of
recombination proportional to distance between genes
Measured in centiMorgans =cM Recombinants
Non-parental features
One map unit = one centimorgan (cM) = 1% recombination between loci
Membuat Peta Kromosom :Peta Kromosom adalah : gambar skema
sebuah kromosom yang dinyatakan sebagai sebuah garis lurus dimana diperlihatkan lokus setiap gen yang terletak pada kromosom tsb.
Sentromer dari kromosom biasanya dianggap sbg pangkal, maka diberi tanda angka 0
Pada lokus setiap gen dibubuhkan angka yang menunjukkan jarak antara gen itu dengan sentromer atau jarak antara satu gen dengan gen yang lain.
Peta relatif : peta kromosom tanpa menunjukkan letak sentromer
0 p q
26,2
17,713
10
6,2
ab c
Jarak Peta ????
By definition, one map unit is equal to
one percent recombinant gametes or phenotypes
In honor of Morgan, one map unit is also called one centimorgan (cM)
1 mu = 1% = 1 cM
To determine the distance between two genes, divide the number of recombinant gametes by the total number of gametes
Formula :
Number of recombinants x 100% Total Number
Contoh 1 : Coupling Data F1 Gamete Testcross Distribution Gamete Type
pr+ vg+ 1339 Parental
pr+ vg 151 Recombinant
pr vg+ 154 Recombinant
pr vg 1195 Parental
pr vg distance = ((151 +154)/2839)*100% = 10.7 m.u
= 10.7 cM
Contoh 2 : Repulsion Data F1 Gamete Testcross Distribution Gamete Type
pr+ vg+ 157 Recombinant
pr+ vg 965 Parental
pr vg+ 1067 Parental
pr vg 146 Recombinant pr vg distance = ((157 + 146)/2335)*100% = 13.0
cM
Jarak Gen
Coupling : pr vg 10,7 cM
Repulsion : pr vg
13,0 cM
Linkage maps estimate distances between genes.
The closer together two genes are, the more likely they will be inherited together.
Cross-over frequencies are related to distances between genes.The higher the frequency, the further the genes are apart
Linkage maps show the relative locations of genes.
• Cross-over frequencies can be converted into map units.
• Ex: A 5% cross-over frequency equals 5 map units.
– gene A and gene B cross over 6.0 percent of the time
– gene B and gene C cross over 12.5 percent of the time
– gene A and gene C cross over 18.5 percent of the time
Draw a linkage map based on the following cross over percentages:
A – B = 8%B – C = 10%A – C = 2%
Draw a linkage map based on the following cross over percentages:
A – B = 8%B – C = 10%A – C = 2%
8.0 2.0
B A C
8.0 + 2.0 = 10.0
Remember these are estimates; the differences between the two estimates reflect random deviation
Neither estimate is incorrect; repeated experimentation would give a more accurate estimate
Figure 3.18 Genomes 3 (© Garland Science 2007)
cM or centimorgan
1% Recombination = 1 cM
Membuat peta kromosom dengan gen rangkap tiga : Deriving Linkage Distance And Gene Order From Three-Point Crosses
Analyzing three genes allows us to determine gene order as well as linkage distance
Need to create a F1 and follow deviation from a 1:1:1:1:1:1:1:1 ratio What are the expected gametes when three linked genes are
considered?
Analyzing Three-Point Test Cross Data
Genotype Observed
ABC 390
abc 374
AbC 27
aBc 30
ABc 5
abC 8
Abc 81
aBC 85
Total 1000
What are the parental genotypes?
What is the gene order?
What are the linkage distances?
What are the parental genotypes?
The genotypes most frequently found are the parental genotypes
ABC and abc are the parental genotypes
Menentukan urutan gen :Tipe tetua = paling banyak (n.c.o)Tipe crossing over ganda = paling sedikit
(d.c.o) Dua gen pada tipe tetua = dua gen pada
tipe d.co, yang tidak sama terletak di tengah
What is the gene order?
What is the gene order?
* Menentukan susunan gen dengan memperhatikan Tipe Parental dan Tipe DCO
Pada Tipe Parental di-DCO-kan dan dibandingkan dengan hasil DCO pengamatan
The double crossover moves a non-parental allele of the central gene between two parental alleles
Gene C is between genes A and B (gene order = A C B)
Analyzing Three-Point Test Cross Data
Genotype Observed Type of Gamete
ACB 390 Parental
acb 374 Parental
ACb 27 Single-crossover between genes C and B
acB 30 Single-crossover between genes C and B
AcB 5 Double-crossover
aCb 8 Double-crossover
Acb 81 Single-crossover between genes A and C
aCB 85 Single-crossover between genes A and C
Total 1000
What are the linkage distances? Linkage distance equals the sum of the
appropriate single cross plus all double crosses divided by total number of gametes
Formula :Jarak = SCO + DCO x 100%
Jumlah Total
*Jarak A - C = ((81+85+5+8)/1000)*100 = 17.9 cM
*Jarak C - B = ((27+30+5+8)/1000)*100 = 7.0 cM
A C B17,9 cM 7,0 cM
*Jarak A - C = ((81+85+5+8)/1000)*100 = 17.9 cM
*Jarak C - B = ((27+30+5+8)/1000)*100 = 7.0 cM
A C B17,9 cM 7,0 cM
Interference Interference - the reduction in the expected
number of crossovers at two adjacent genetic intervals
Interferensi – interaksi antar pindah silangPindah silang pada tempat tertentu mengurangi
kemungkinan terjadinya pindah silang pada daerah didekatnya.
Pindah silang di daerah I mengurangi terjadinya pindah silang pada daerah II
Mengakibatkan frekuensi pindah silang ganda lebih kecil dari yang diharapkan
coefficient of coincidence (c.o.c.) = ratio of observed to expected double crossovers
Koefisien koinsidensi adalah ukuran dari kekuatan interferensi dan merupakan nisbah antara frekuensi pindah silang ganda yang diamati dan frekuensi pindah silang ganda yang diharapkan
Rumus
atauKK = Banyaknya pindah silang ganda (DCO) yang
sesungguhnya
Banyaknya pindah silang ganda (DCO) yang diharapkan
Interferensi = 1 - KK
Apabila interferensi sempurna (1,0) maka tidak ada pindah silang ganda yang dapat diamati
Apabila semua pindah silang ganda yang diharapkan dapat diamati maka interferensinya nol (0)
Misalnya diketahui data sebagai berikut:
Genotipe gamet Jumlah Fenotipe
Dari F1 heterosigot individu
V Gl Va 235 normal
v gl va 270 mengkilat, steril sebagian, pucat
V gl Va 7 mengkilat
v Gl va 4 steril sebagian, pucat
V gl va 62 mengkilat, steril sebagian
v Gl Va 60 pucat
V Gl va 40 steril sebagian
v gl Va 48 mengkilat, pucat
726
Misalnya :
Diketahui peta kromosom :V Gl Va 18,3 13,6
31,9
SCO-1 (V-Gl) : 18,3%SCO-2 (Gl-Va) : 13,6%Pindah silang ganda yang diharapkan = SCO-1 x
SCO-2 = 0,183 x 0,136 = 0,025 = 2,5%
Pindah silang ganda yang sebenarnya :7+4 = 1,5%726
Sehingga Koefisien Koinsidensinya :KK = 1,5% = 0,6
2,5%
Jadi Interferensinya : I = 1-KK = 1 – 0,6 = 0,4 = 40%
1. In human pedigree below where the male parent does not appear, it is assumed that he is phenotypically normal. Both hemophilia (h) and color blindness (c) are sex linked recessives. In so far as possible, determine the genotype for each invidual in the pedigree ?
I 1 2 2 3 II 1 2 3 4 5 6 7III 1 2 3
= hemophilia = color blind =
hemophilia-colorblind
PR
2. Pada tanaman jagung (Zea mays) dikenal gen-gen yang terangkai yaitu :Bm = tulang daun hijau (normal)bm = tulang daun coklat
Pr = biji kuning (normal) pr = biji merah V = daun hijau (normal) v = daun hijau pucat
Uji silang tanaman trihibrid : Bm Pr V X bm pr v bm pr v bm pr v
Menghasilkan keturunan sebagai berikut :
a.Gambarkan peta kromosom relatif dimana gen-gen iti terangkai ?
b.Tuliskan genotif dari tanaman parental ?c.Berapakan inferensinya ? Apa maknanya ?
Bm pr v bm pr v
57 tanaman
bm pr v 434 tanaman
bm Pr V 60 tanaman
Bm Pr V 441 tanaman
bm Pr v 2 tanaaman
Bm Pr v 1 tanaman
Bm pr V 3 tanaman
bm pr V 2 tanaman
2.