Gene Expression and Protein Synthesis

NUKLEOTIDA

STRUKTUR DNA • terdiri dari dua sulur/rantai Polinukleotida yang bersifat Antiparalel (5’P - 3’OH // 3’OH - 5’P) • antar sulur nukleotida berikatan pada basa-N secara Komplementer (A=T) dan (G=C)

Adenin (A) berpasangan dengan Timin (T) dengan dua ikatan hidrogen, dan Guanin (G) berpasangan dengan Citosin (C) dengan tiga ikatan hidrogen

This process is called replication DNA Replication During a cell divides, the DNA strands unwind and separate Each strand makes a new partner by adding the appropriate nucleotides The result is that there are now two double-stranded DNA molecules in the nucleus So that when the cell divides, each nucleus contains identical DNA This process is called replication

Karakteristik DNA sebagai bahan Genetik REPLIKASI DNA Karakteristik DNA sebagai bahan Genetik • Diwariskan • Harus tetap/sama antar generasi DNA harus dapat menggandakan diri (Replikasi) sebelum diwariskan Kemungkinan Pola Replikasi DNA: Semikonservatif Konservatif Dispersif BIO 101/VII/Bahan Genetik

Kemungkinan Pola Replikasi DNA Pola yang benar

The strands separate Each strand builds up its partner PO4 PO4 The strands separate PO4 PO4 Each strand builds up its partner by adding the appropriate nucleotides

Proses Replikasi DNA: Semikonservatif

DNA (Gen) dengan Protein (Enzim) HUBUNGAN ANTARA DNA (Gen) dengan Protein (Enzim) • DNA berada di inti sel (nukleus) dan tidak dijumpai di sitoplasma • Protein yang berperan dalam metabolisme ada di sitoplasma dan tidak ada di inti. Perlu adanya penghubung antara DNA dengan Protein, yaitu molekul yang dijumpai di inti maupun di sitoplasma Penghubung antara DNA dengan Protein adalah RNA

EKSPRESI GEN BIO 101/VII/Bahan Genetik 13

TRANSKRIPSI • Heliks/ulir DNA digunakan sebagai model cetakan, dan enzim RNA Polimerase sebagai katalisator • Sintesis/transkripsi RNA hanya dari salah satu utas DNA (dari utas DNA cetakan , tidak dari utas DNA pendamping) • Sintesis RNA dengan arah 5’P 3’OH (antiparalel dari utas DNA Cetakan)

Gen merupakan fragmen DNA yg Menyandikan protein/enzim. Dalam proses Transkripsi melibatkan RNA polimerase, DNA promotor, dan DNA terminator. BIO 101/VII/Bahan Genetik 15

Transcription 1 (making a mRNA copy of DNA) The part of the DNA molecule (the gene) that the cell wants the information from to make a protein unwinds to expose the bases. Free mRNA nucleotides in the nucleus base pair with one strand of the unwound DNA molecule.

Transcription 2 The mRNA copy is made with the help of RNA polymerase. This enzyme joins up the mRNA nucleotides to make a mRNA strand. This mRNA strand is a complementary copy of the DNA (gene) The mRNA molecule leaves the nucleus via a nuclear pore into the cytoplasm

The sequence of bases in DNA forms the Genetic code 1 19 The sequence of bases in DNA forms the Genetic Code A group of three bases (a triplet) controls the production of a particular amino acid in the cytoplasm of the cell The different amino acids and the order in which they are joined up determines the sort of protein being produced

Tabel Kode Genetik Basa II Basa I Basa III BIO 101/VII/Bahan Genetik 16

Kode Genetik dalam Proses TRANSLASI

PROSES TRANSLASI mRNA Molekul yang terlibat dalam Proses TRANSLASI: Protein Molekul yang terlibat dalam Proses TRANSLASI: • mRNA • tRNA-asam amino • Ribosom (rRNA dan Protein ribosom)

Proses transkripsi yang dilanjutkan dengan translasi BIO 101/VII/Bahan Genetik 19

1. DNA terdiri dari dua sulur/utas polinukleotida Ringkasan 1. DNA terdiri dari dua sulur/utas polinukleotida yang bersifat antiparalel. Antar sulur/utas nukleotida berikatan pada basa N: Ikatan H. 2. Agar dapat diwariskan dari satu generasi ke generasi, DNA harus melakukan replikasi atau penggandaan DNA. 3. Gen merupakan fragmen DNA yang menyandikan protein/enzim. Ekspresi gen meliputi proses transkripsi dan translasi. BIO 101/VII/Bahan Genetik 20

Protein synthesis DNA unwinds mRNA copy is made of one of the DNA strands. mRNA copy moves out of nucleus into cytoplasm. tRNA molecules are activated as their complementary amino acids are attached to them. mRNA copy attaches to the small subunit of the ribosomes in cytoplasm. 6 of the bases in the mRNA are exposed in the ribosome. A tRNA bonds complementarily with the mRNA via its anticodon. A second tRNA bonds with the next three bases of the mRNA, the amino acid joins onto the amino acid of the first tRNA via a peptide bond. The ribosome moves along. The first tRNA leaves the ribosome. A third tRNA brings a third amino acid Eventually a stop codon is reached on the mRNA. The newly synthesised polypeptide leaves the ribosome.

Overview

Summary

tRNA – pick up their specific amino acids from the cytoplasm

Translation - animation

mRNA attaches to small ribosomal subunit

Translation - outline

Translation. mRNA used to make polypeptide chain (protein)

1. First the mRNA attaches itself to a ribosome (to the small subunit). Six bases of the mRNA are exposed. A complementary tRNA molecule with its attached amino acid (methionine) base pairs via its anticodon UAC with the AUG on the mRNA in the first position P. Another tRNA base pairs with the other three mRNA bases in the ribosome at position A. The enzyme peptidyl transferase forms a peptide bond between the two amino acids. The first tRNA (without its amino acid) leaves the ribosome.

Translation 2 The ribosome moves along the mRNA to the next codon (three bases). The second tRNA molecule moves into position P. Another tRNA molecule pairs with the mRNA in position A bringing its amino acid. A growing polypeptide is formed in this way until a stop codon is reached.

End of Translation A stop codon on the mRNA is reached and this signals the ribosome to leave the mRNA. A newly synthesised protein is now complete!

Translation mRNA to Polypeptide

Which amino acid is represented by the codon? what is its anticodon? Contoh UCG Serine AGC 1 GGG … 2 GCU ... 3 AGA 4 AAA 5 CCG 6 CUU 7 UCC 8 UCU 9 GUG 10 GCC

Answer…… Glysine CCC Alanine CGA Arginine UCU Lysin UUU Prolin GGC NO CODON AMINO ACID ANTICODON 1 GGG Glysine CCC 2 GCU Alanine CGA 3 AGA Arginine UCU 4 AAA Lysin UUU 5 CCG Prolin GGC 6 CUU Leusin GAA 7 UCC Serine AGG 8 9 GUG Valine CAC 10 GCC CGG

Rough endoplasmic reticulum

One ribosome from the RER

A ribosome

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