2. Gene to protein The two main processes that link the gene to protein are: RNA transcription and translation. The bridge between DNA and protein synthesis is RNA. The specific sequence of the nucleotides in each gene carries the information for the primary structure of a protein which is the linear order of the 20 possible amino acids.

3. The link between genes & proteins DNA uses RNA to create proteins. In other words, genes provides the basic instructions to make proteins. Thus, proteins are the links between genotype (genes) and phenotype (the way we look). The sequence of nucleotides in DNA is connected with 20 amino acids, therefore, different proteins are created based of type of DNA. Inside the nucleus In the cytoplasm Eukaryotic cells Prokaryotic cells In the cytoplasm

4. During the RNA transcription, a DNA strand provides a template for the synthesis of a complementary RNA strand. Which actually produces a messenger RNA called mRNA. During the RNA translation that occurs in the ribosomes the information is in the sequence of the nucleotides in the mRNA which is used to determine the amino acid sequence of a polypeptide. The basic mechanics of the transcription and the translation are similar in both eukaryotic and prokaryotic cells..

5. In a prokaryote, because the bacteria has no nuclei the two mechanics are coupled and the ribosomes attach to the leading end of the mRNA while the transcription is still in process. In an eukaryotic cell the transcription happens in the nucleus and the translation mainly occurs in the ribosomes in the cytoplasm. There is a molecular command chain in a cell which is : DNA mRNA Protein Transcription translation

6. The link between nucleotides & amino acids In nucleotides, every 3 nitrogenous bases give one amino acid. The triplet is called codon, and every amino acid may be represented by one or more codons. There are special codons that interact with translation process Codon in where the process starts AUG Codons in where the process stops UAA UGA UAG

8. First: the transcription 1. RThe RNA polymerase separates the DNA strands at a suitable point and bonds the RNA nucleotides along the DNA template. RNA polymerase can only add nucleotides to the 3 rd end of the growing polymer just like the DNA polymerase. There are specific points that are marked on the DNA that show when the transcription begins and ends. I, II, and III) RNA polymerase 2 is used to synthesis mRNA. In prokaryotes the bacteria has only one RNA polymerase. But in eukaryotes it has three RNA polymerase ( I, II, and III) RNA polymerase 2 is used to synthesis mRNA. NA polymerase separates the two strands of DNA 2. One of the two DNA strands become the template. 4. RNA nucleotides are bonded to the template by RNA polymerase. The codons along the DNA template are read from 5~>3 as RNA nucleotides are added from the 3’ end. 5. RNA nucleotides addition is based on the base- pair rules (U with A) until it reaches the terminator. 3. A promoter indicates the starting point and has a binding site for RNA polymerase. NOTE THAT Prokaryotes Eukaryotes One RNA polymerase 3 types RNA polymerase ( RNA polymerase II is used to synthase mRNA) 6. pre-mRNA is created & ready to be modified.

10. Pre-mRNA modification in Eukaryotes Two things are added to the pre-mRNA to give mRNA that is ready to leave the nucleus. It is a modified form of guanine (G) that function as: 1.Protection from hydrolytic enzymes. 2.A start point for the translation. 50 to 250 adenine (A) are added to form poly(A) tail that facilitates the export of mRNA from the nucleus.

11. Before the translation.. U should understand carefully CUU The amino acid that goes with the triplet base at mRNA Anticodon base-pair with the complementary codon at mRNA The growing end of the polypeptide chain It’s transcribed in the nucleus and has 3 functions: 1.Pick up its relevant amino acid. 2.Deposit the amino acid at the ribosomes. 3.Return to cytosol to pick up another amino acid The tRNA molecules are transcribed from DNA in the nucleus once it reached the cytoplasm each tRNA is used for 3 functions: 1.Pick up specific amino acids from the cytoplasm 2.Deposit the amino acid in the ribosome 3.Return to the cytoplasm and pick another copy of the same amino acid. The anticodons on some of the tRNA’s recognize more than one codon.

13. Ribosomes Each ribosome has a large subunit and a small subunit which is formed in the nucleolus. They facilitate the coupling of tRNA anticodons with mRNA codons. They are composed of proteins and ribosomal RNA (rRNA) which is the most abundant RNA in the cell.

14. rRNA is transcribed in the nucleus, then it goes to the nucleolus where it binds with ribosomal subunits. The subunits exit the nucleolus to the cytosol and they join to form ribosomes with mRNA attaches to them, Ribosomes have: 1.One binding site for mRNA 2.Tree binding sites for tRNA a.P site: tRNA with the growing polypeptide b.A site: next tRNA c.E site: exit port for tRNA to leave. Multiple ribosomes may trail along the same mRNA, so it can be used to make many copies od polypeptide at the same time.

15. Second: the translation Translation has three stages mRNA attaches to its site. tRNA attaches to A site with the first amino acid (anticodon that binds with mRNA codon) Subunits are joined & tRNA is at P site. mRNA attaches to its site. tRNA attaches to A site with the first amino acid (anticodon that binds with mRNA codon) Subunits are joined & tRNA is at P site. One of the 3 stop codon accurse at A site. (UAG,UAA,UGA ) A release factor binds with the stop codon. The bond between the polypeptide & tRNA is hydrolyzes. This frees the polypeptide and the translation complex disassembles. One of the 3 stop codon accurse at A site. (UAG,UAA,UGA ) A release factor binds with the stop codon. The bond between the polypeptide & tRNA is hydrolyzes. This frees the polypeptide and the translation complex disassembles. Hydrogen bonding is formed between mRNA codon & anticodon by elongation factors. 1. Codon recognition With the help of rRNA molecule, the polypeptide chain in P site is separated from tRNA and moved to A site, it binds with a new amino acid carried by new tRNA. 2. Peptide bond formation Ribosomes move the new tRNA in A site to P site. 3. Translocation of tRNA

16. polyribosomes A ribosome requires less than a minute to translate an average-sized mRNA into a polypeptide A single mRNA is used to make many copies of a polypeptide simultaneously.

17. Mutations Mutations are the changes in the genetic material of a cell or a virus. There are different kinds of mutations, but we are going to study the point mutation. Is the chemical change in only 1 base pair. It may be transmitted to the offspring it happened in cells producing gametes. Types: Base-pair substitution Insertion and deletion X-ray Ultraviolet light Base analogues Distorting double helix Change the pairing properties

18. Point mutation Base-pair substitution Insertion and deletion Silent mutation It’s the switch of one amino acid to another with similar properties ( have no or little impact ) Missense mutation The change in amino acid that leads to another protein. Nonsense mutation Change the amino acid codon to stop codon. This leads to nonfunctional protein. The mutation in which additions or losses of nucleotides. This will make the codon group improperly. This type have a disastrous effect on the resulting protein. And will end in nonsense premature termination This type have a disastrous effect on the resulting protein. And will end in nonsense premature termination

19. Mutagens These are chemical or physical agents that interact with DNA to cause mutations 1. Physical agents: high energy radiation like X-rays and UV light 2. Chemical agents: some mutagens cause chemical changes in the bases that change their pairing properties – others interfere with the replication of the DNA by inserting and distorting the double helix

20. Point mutation and insertions and deletions DNA MUTATION http://www.youtube.com/watch?v=kp0esidDr-c

21. PLZ,OPEN THE VIDEO

22. Protein Synthesis http://www.youtube.com/watch?v=w8FSDQwumTw

23. Protein Synthesis Animation Video http://www.youtube.com/watch?v=Ikq9AcBcohA

24. Translation Animation http://www.youtube.com/watch?v=ZPlnDzkBrpc

26. Q1: Write whether each of the following statements is True (T) or False (F): 1-tRNA carries encoded genetic message from DNA in the nucleus to the ribosomes in the cytoplasm. 2-Missense mutations change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein.. 3-The promoter of a gene is a region at which RNA polymerase attaches and initiate transcription. 4-A genetic codon may code for more than one amino acid. 5- During translation,AUG is a start codon while UAA is a stop codon.

27. Q 2: Choose the correct answer (one answer only): 1-In eukaryotic cells,transcription of RNA occurs in the;- a-Cytoplasm. b-Nucleus. c-Ribosomes. 2. What is the proper order of the following events in the expression of a eukaryotic gene? 1. translation 2. RNA processing 3. transcription 4. modification of protein 1, 2, 3, 4 3, 2, 1, 4 4, 2, 3,1 2,3, 4, 1 3- Translation occurs in the _____. cytoplasm lysosome nucleus mitochondrion 4.During RNA processing a(n) _____ is added to the 5' end of the RNA. 3' untranslated region a long string of adenine nucleotides 5' untranslated region modified guanine nucleotide 5-.Which one of the following statements is true? Each DNA base codes for three amino acids. Each gene codes for three proteins. It takes three genes to code for one protein. Each amino acid in a protein is coded for by three bases in the DNA.

28. 6-The function of tRNA during protein synthesis is to _____. deliver amino acids to their proper site during protein synthesis attach mRNA to the small subunit of the ribosome process mRNA transcribe mRNA 7- The P site of a ribosome does which one of the following? It holds the tRNA that is carrying the next amino acid to be added to the growing polypeptide chain. It holds the growing polypeptide chain. It catalyzes the addition of amino acids to the tRNAs. It recognizes the promoter during transcription initiation. 8- During translation, amino acid chain elongation occurs until _____. no further amino acids are needed by the cell all tRNAs are empty the polypeptide is long enough the ribosome encounters a "stop" codon 9- A geneticist found that a particular mutation had no effect on the polypeptide encoded by the gene. This mutation probably involved _____. deletion of one nucleotide insertion of one nucleotide a nonsense mutation a silent mutation 10. A point mutation in which a single base pair is inserted or deleted from DNA is called a(n) _____. nonsense mutation frame-shift mutation inversion mutation translocation mutation