Replication, Transcription and Translation
Terms in this set (35)
The process of DNA to RNA
3 Differences between DNA and RNA
1. Ribose instead of deoxyribose
2. Single stranded
3. Uracil in replace of thymine
What are RNA molecules mostly involved in?
3 Main Types of RNA molecules
1. Messenger RNA
2. Transfer RNA
3. Ribosomal RNA
In Rna, what does thymine bond with?
What enzyme does transcription require?
Where does RNA polymerase bind to?
TCG GAT ATC GTT CAA
AGC CUA UAG CAA GUU
Molecules Involved in transcription
Why does transcription occur?
To make a protein
Where does transcription occur?
End product of transcription
Process of Transcription
RNA polymerase uses ATP to read the DNA strand and form an mRNA strand in the nucleus
The decoding of an mRNA message into a polypeptide chain (protein)
Where does translation take place?
1. Came from transcription
2.Then leaves the nucleus and enters the cytoplasm and attaches to the rRNA
-Contains a code
-Code is a set of instructions for a specific protein
-Just a ribosome
-Site for protein synthesis
-3 subunits (APE)
-Brings amino acids to the rRNA
-Each has an anticodon at the bottom to compliment one mRNA codon/triplet
What are the four steps of transcription?
What are the molecules involved in translation?
Why does translation occur?
To make a protein
Where does translation occur?
What is the end product of translation?
What molecules are involved in replication?
DNA nucleotides (ATCG)
Why does replication occur?
To carry out mitosis
Where does replication occur?
What is the end product of replication?
Two genetically identical strands
Describe the structure of DNA
DNA is made up of two strands. At one end of each strand there is a phosphate group attached to the carbon atom number 5 of the deoxyribose (this indicates the 5' terminal) and at the other end of each strand is a hydroxyl group attached to the carbon atom number 3 of the deoxyribose (this indicates the 3' terminal). The strands are antiparallel. One strand runs in a 5'-3' direction and the other runs in a 3'-5' direction. Adjacent nucleotides are attached together via a bond between the phosphate group of one nucleotide and the carbon atom number 3 of the deoxyribose of the other nucleotide.
The bases of each strand link together via hydrogen bonds. Adenine and Guanine are purines as they have two rings in their molecular structure. Thymine and Cytosine are pyrimidines as they only have one ring in their molecular structure. A purine will link with a pyrimidine. Adenine and thymine link together by forming two hydrogen bonds while Guanine and cytosine link together by forming 3 hydrogen bonds.
Describe the structure of a nucleosome
Nucleosomes consist of DNA wrapped around eight histone proteins and held together by another histone protein.
Explain the process of transcription in prokaryotes, including the role of the promoter region, RNA polymerase, nucleoside triphosphates and the terminator.
mRNA is produced during transcription. In prokaryotes, RNA polymerase recognises a specific sequence of DNA called the promoter. The promoter basically "tells" the RNA polymerase where to start the transcription process. Transcription is initiated with the binding of RNA polymerase to the promoter site. The RNA polymerase then uncoils the DNA and separates the two strands. One of the strands is used as the template strand for transcription. The RNA polymerase will then use free nucleoside triphosphates to build the mRNA in a 5'→3' direction. These nucleoside triphosphates bond to their complementary base pairs on the template strand. As they bind they become nucleotides by losing two phosphate groups to release energy. Since RNA does not contain thymine, uracil pairs up with adenine instead. RNA polymerase forms covalent bonds between these nucleotides. It moves along the DNA to keep elongating the sequence of mRNA until it reaches a sequence of DNA called the terminator. This sequence of DNA "tells" the RNA polymerase to stop transcription. The RNA polymerase is then released from the DNA and the newly created mRNA separates from the template DNA strand. Finally, the DNA rewinds back to its original double helical structure.
Explain that each tRNA molecule is recognized by a tRNA-activating enzyme that binds a specific amino acid to the tRNA, using ATP for energy.
This enzyme binds a specific amino acid to the tRNA by using ATP as an energy source. The tRNA molecule has a specific structure. It contains double stranded sections (due to base pairing via hydrogen bonds) and loops. It has an anticodon loop which contains the anticodon and two other loops. The nucleotide sequence CCA is found at the 3' end of the tRNA and allows attachment for an amino acid. Each type of tRNA has slightly different chemical properties and three dimensional structure which allows the tRNA-activating enzyme to attach the correct amino acid to the 3' end of the tRNA. There are 20 different tRNA-activating enzymes as there are 20 different amino acids. Each enzyme will attach a specific amino acid to the tRNA which has the matching anticodon for that amino acid. When the amino acid binds to the tRNA molecule a high energy bond is created. The energy from this bond is used later on to bind the amino acids to the growing polypeptide chain during translation.
Explain the process of DNA replication in prokaryotes, including the role of enzymes (helicase, DNA polymerase, RNA primase and DNA ligase), Okazaki fragments and deoxynucleoside triphosphates.
occurs during (S phase of ) interphase/in preparation for mitosis/cell division;
DNA replication is semi-conservative;
unwinding of double helix / separation of strands by helicase (at replication origin);
hydrogen bonds between two strands are broken;
each strand of parent DNA used as template for synthesis;
synthesis continuous on leading strand but not continuous on lagging strand;
leading to formation of Okazaki fragments (on lagging strand);
synthesis occurs in 5 3direction;
RNA primer synthesized on parent DNA using RNA primase;
DNA polymerase III adds the nucleotides (to the 3 end)
added according to complementary base pairing;
adenine pairs with thymine and cytosine pairs with guanine; (Both pairings required. Do not accept letters alone.)
DNA polymerase I removes the RNA primers and replaces them with DNA;
DNA ligase joins Okazaki fragments;
as deoxynucleoside triphosphate joins with growing DNA chain, two phosphates
broken off releasing energy to form bond;
Outline the structure of ribosomes, including protein and RNA composition, large and small subunits, three tRNA binding sites and mRNA binding sites.
They are made up of proteins and ribosomal RNA. They have two subunits, one large the other small. On the surface of the ribosome there are three sites to which tRNA can bind to. However not more than two tRNA molecules can bind to the ribosome at one time. Also there is a site on the surface of the ribosome to which mRNA can bind to.
Explain the process of translation, including ribosomes, polysomes, start codons and stop codons.
consists of initiation, elongation and termination;
mRNA translated in a 5' to 3' direction;
binding of ribosome to mRNA; small sub-unit then large; first / initiator tRNA binds to start codon / to small subunit of ribosome;
AUG is the start codon;
second tRNA binds to ribosome;
large subunit moves down mRNA after a second tRNA binds; amino acid / polypeptide on first tRNA is transferred / bonded to amino acid on second tRNA; peptide bonds between amino acids / peptidyl transferase; requires GTP;
movement of ribosome / small subunit of ribosome down the mRNA;
loss of tRNA and new tRNA binds;
reach a stop codon / termination;
tRNA activating enzymes link correct amino acid to each tRNA;
(activated) tRNA has an anticodon and the corresponding amino acid attached
Compare the structure of DNA and RNA
DNA has deoxyribose, RNA has ribose. For DNA, Thymine is a base for RNA Uracil is the base. DNA is split into two strands RNA has one strand. DNA is Double helix, RNA is a single strand
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