PEWARISAN SIFAT
(HUKUM MENDEL I DAN II)
MENDELIAN INHERITANCE
MENDELIAN INHERITANCE
•Mendel mempelajari pada kacang kapri (Pisumsativum) terutama pada variasi bentuk dan warnaditandai dengan hubungan dominan-resesif.
•Mendel mempelajari sifat-sifat tanaman yangdikendalikan gen pada kromosom berbeda.
•Mendel mempelajari pada tanaman menyerbuksendiri (self pollination).
HASIL PERCOBAAN MENDEL PADA SATU SIFAT MENGARAHPADA DOMINAN SEMPURNA
No
Fenotip parental
F1
F2
1
Round x wrikled seeds
All round
2.96 : 1
2
Yellow x green seeds
All Yellow
3.01 : 1
3
Purple x white petals
All Purple
3.15 : 1
4
Inflated x pinched pods
All inflated
2.95 : 1
5
Green x Yellow pods
All green
2.82 : 1
6
Axial x terminalflowers
All Axial
3.14 : 1
7
Long x short stems
All long
2.84 : 1
LAWS OF INHERITANCELAWS OF INHERITANCE
•Law of Segregation•Law of Segregation
•Law of independent assortment•Law of independent assortment
1. LAW OF SEGREGATION 1. LAW OF SEGREGATION
•The Law of Segregation
•at the time of gamete formation, members of apair of unit characters segregate (separate)from one another and move into differentgametes
•Thus parents like this Tt and Tt make thesegametes
T t T t
CHROMOSOMAL BASIS OF SEGREGATIONCHROMOSOMAL BASIS OF SEGREGATION
•Segregation occurs inmeiosis at MI and then atMII
•As a result, the ova orsperm contributedifferent homologouschromosomes to theprogeny
. LAW OF INDEPENDENTASSORTMENT 2. LAW OF INDEPENDENTASSORTMENT
segregation independently of each other andassort themselves at random •This law states that at the time ofreproduction the members of two or morepairs of unit characters follow the law ofsegregation independently of each other andassort themselves at random into the gametes
MEIOSIS MECHANISMS PRODUCEINDEPENDENT ASSORTMENT
•Meiosis I provides theindependentassortment ofchromosomes andgenes into thegametes.
•The homologs arearranged at random atthe equatorial plane inMetaphase I
•This results in fourdifferent possiblecombinations ofchromosomes andgenes in the gametes,in a 1:1:1:1 ratio:
DOING THE CROSS
•Using these laws we can see how Mendel got the
3 tall to 1 short ratio (3:1) among the peas:
T t T t gametes
Tt X Tt parents
TT Tt Tt tt offspring
Tt X Tt parents
MONOHYBRID CROSS(CROSS WITH ONLY 1 TRAIT)MONOHYBRID CROSS(CROSS WITH ONLY 1 TRAIT)
DIHYBRID CROSSESDIHYBRID CROSSES
•Dihybrid crosses •Dihybrid crosses are made when phenotypes andgenotypes composed of 2 independent alleles areanalyzed.
monohybrid•Process is very similar to monohybrid crosses.
1.Which traits are dominant?
2. Did the phenotypes of the P1 generation affect the F1 or F2 generations?
Dihybrid cross - phenotypes
Analysis of dihybrid cross phenotypes
(forked-line/probability method)
Trait 1
Trait 2
Combined traits
Since yellow and round are dominant,Let G = yellow, g = green, W = round, w = wrinkled.
Dihybrid Cross: P1 cross
Confirm on your own using a Punnett square!
Dihybrid Cross: F1 cross
Dihybrid Cross: Summary
99
33
33
11
Dihybrid Testcross:How to determine the genotype of an individual with2 traits of dominant phenotype
All yellow
All Round
Mixed
A TEST CROSS
•What if you only knowthat you have a black anda brown guinea pig (i.e.you don’t know thegenotype)?
•Do a test cross
•Cross with a known true-breeding recessive brownguinea pig
•Uji silang digunakan untukmengetahui genotipe yangdisilangkan
BACKCROSS
Backcross atau silang balik adalah persilangan antara keturunan pertamadengan salah satu tetua (parents),
Tujuannya untuk memindahkan gen atau sifat tertentu dari salah satutetua.
Tetua yang memberikan sifat tersebut dinamakan “tetua donor”
BACKCROSS (Silang balik)
P ♀ AA X ♂ aa
BC
F1 Aa
aa : tetua donor
AA : penerima
P ♀ AA X ♂ aa
BC
F1 Aa
aa : penerima
AA : tetua donor
Pada silang balik, ada tetua donor dan penerima
BACKCROSS
RECIPROCAL CROSSES (Persilangan Resiprok)
P ♀ hh X ♂ HH
kuning hijau
F1 Hh (hijau)
F2 1 HH (hijau)
2Hh (hijau)
1hh (kuning)
P ♀ HH X ♂ hh
hijau kuning
F1 Hh (hijau)
F2 1 HH (hijau)
2Hh (hijau)
1hh (kuning)
Hasil tidak berbeda
Arti : Gen pengendali warna ada di dalam inti
RUMUSAN UMUM UNTUK JUMLAH GAMET DANTURUNAN DARI n PASANGAN GEN HETEROZIGOT
Jumlahpasangan genheterozigot
Jumlahgenotipegamet
Jumlahfenotipeturunan
Jumlahgenotipeturunan
Jumlahkombinasigamet ygmungkin ada
1
2
2
3
4
2
4
4
9
16
3
8
8
27
64
4
16
16
81
256
n
2n
2n
3n
4n
ISTILAH-ISTILAH
•Alel/alil : pasangan gen yang terletak pada kromosom homolog(gen A alel a atau A ).
•Lokus : posisi gen yang tetap pada kromosom
•Genotip : Konstitusi genetik dari individu, disimbolkan dengan huruf(tidak tampak)
•Fenotip : ekspresi gen yang dapat diamati
•Dominan : produk dari fungsi gen yang menutupi ekspresi alil
•Resesif : produk dari fungsi gen yang tertutupi oleh ekspresi alildominan. Ekspresi gen resesif hanya tampak apabila dalamkeadaan homozigot.
ISTILAH-ISTILAH
•Homozigous : pasangan alil yang sama. Individu disebut homozigot(AA, aa, BB, CC, cc)
•Heterozigous : pasangan alil yg berbeda. Misal Aa, Bb, Ccdinamakan heterozigot.
•F1(Filial 1) : Generasi pertama hasil persilangan dua tetua .
•F2 (Filial 2) : Generasi kedua, turunan dari F1
•Persilangan resiprok : Persilangan dua tetua berbeda yangdilakukan secara bolak balik . Contoh : persilangan 1 ♀A x B ♂,persilangan kedua ♀B x A ♂.
•Silang balik (Backcross): persilangan yang dilakukan antara F1dengan salah satu tetua.
•Uji silang (test cross): persilangan yang dilakukan antara F1 dengantetua homozigot resesif
P
H
E
N
O
T
Y
P
E
V
S
G
E
N
O
T
Y
P
E
•Genotype
The
genetic
makeup
Symbolized
with
letters
Tt
or
TT
•Phenotype
Physical
appearance
of
the
organism
Expression
of
the
trait
Short,
tall,
yellow,
smooth,
etc.
Terima kasih
