Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Identify the two types of nucleic acids:
100
Helicase
Identify the enzyme responsible for separating DNA:
100
The making of RNA from DNA
What is transcription?
100
Reading the DNA code to make proteins
What is translation?
100
deoxyribonucleic acid
What is the definition for DNA?
200
Adenine, Cytosine, Thymine, Guanine
State the names of the four bases in DNA:
200
Each of the two DNA molecules will have a ‘new’ strand and an ‘old’ strand. DNA replication is __________.
Define ‘semi-conservative’:
200
‘_______’ strand is transcribed, ‘_____’ strand is not transcribed, but it is identically to mRNA except T becomes U.
Distinguish between the ‘anti-sense’ and the ‘sense’ strands of DNA:
200
More than one codon can code for a single amino acid.
What is degenerate?
200
ribosomal RNA (rRNA), transfer RNA (tRNA), and messenger RNA (mRNA)
Identify the three types of RNA
300
Stands must be antiparallel in order for the bases to be facing each other and able to pair. The organic base pair must also have a total of three rings, therefore Adenine and Thymine bind together and Cytosine and Guanine bind together. Adenine and Thymine bind through two hydrogen bonds and Cytosine and Guanine bind through three hydrogen bonds.
Show how the DNA double helix is formed using complementary base pairing and hydrogen bonds:
300
Both strand are identical due to complementary base paring.
Compare and contrast the ‘old’ DNA strand and the ‘new’ DNA strand
300
DNA is shaped as a double helix and RNA is a single strand. The sugar in DNA is deoxyribose and in RNA is ribose. Bases for DNA are A, T, C, and G, and for RNA bases are A, U, C, and G.
Compare the structure of RNA and DNA:
300
A base for the genetic code- composed of three nucleotides, and they code for amino acids.
Define codons:
300
Adds the nucleotide triphosphates, using base paring, to the anti-sense strand. Unwinds and separates DNA, and also rewinds and glues DNA.
What role does RNA polymerase play in transcription?
400
Through covalent bonds and condensation reactions. Phosphate plus sugar plus organic base combine to form a nucleotide and two water molecules. The condensation reaction occurs specifically between the phosphate of one nucleotide and the sugar of another. The sugar and phosphate form the backbone form the nucleic acid
Outline how DNA nucleotides are linked together into a single strand:
400
First the DNA double helix needs to unwind and the two stands need to separate. Free nucleotides ‘floating around’ in the nucleus form complementary pairs with the nucleotides of both the DNA strands. The nucleotides which have formed complementary base pairs with the nucleotides on the old strand now join to each other to form a new strand of DNA. The enzyme ‘DNA polymerase’ is responsible for this process. All these processes result in two identical strands of DNA, each consisting of one ‘old’ and one ‘new’ strand.
Outline the steps and enzymes involved in DNA replication:
400
Transcription takes place in the nucleus. After transcription mRNA leaves the nucleus and enters the cytoplasm.
Show the movement of DNA and RNA during transcription:
400
Every polypeptide chain is coded for by one gene. Hemoglobin contains four polypeptide chains, 2 alpha chains and 2 beta chains. To make hemoglobin therefore requires 2 genes: one for the alpha chains and one for the beta chains.
Discuss the relationship between one gene and one polypeptide:
400
_____ are non-coding sequences that are removed in eukaryotes, ____ are coding sequences that are spliced together.
Differentiate between introns and exons:
500
Construct and label a diagram of the molecular structure of DNA
See drawn image
500
Since every organic base will only fit with one other organic base (complementary base pairing) the ‘new’ strand of DNA will be identical to one from which the ‘old’ strand just separated from. So (theoretically) this process can continue forever without any change to the genetic material. Mistakes, however, do occur and these are called mutations.
Evaluate the effect that complementary base pairing has on the conservation of the base sequence of DNA:
500
Takes place in the nucleus and involves a section of DNA which needs to unzip. Then only one of the two strands of DNA is transcribed (the anti-sense strand) and a complementary RNA strand to this transcribed strand is made. This is called messenger RNA (mRNA) and it has the same sequence of nucleotides, except U instead of T, as the sense strand of DNA (the strand that is NOT transcribed). After transcription, the mRNA leaves the nucleus through the pores in the nuclear envelope and goes into the cytoplasm.
Outline DNA transcription:
500
After the mRNA has reached the cytoplasm, this takes place. In the cytoplasm, ribosomes attach to the mRNA. The ribosome covers an area of three condons on the mRNA. The first tRNA carrying an amino acid will come in and the anti-codon exposed on the tRNA will have complimentary binding with the condon from the mRNA in the A site of the ribosome. The ribosome will move and the first tRNA will be in the P site on the ribosome. The second tRNA with its own anti-condon, and consequently carrying a specific amino acid, will complementary bind to the second codon on the mRNA, filling the A site in the ribosome. The second amino acid will attach to the first (formation of a peptide bond by condensation reaction) and the first amino acid will be release from the first tRNA. The ribosome will move in relation to the mRNA. The first tRNA (without amino acid) is now found in the E site of the ribosome. The second tRNA will be in the P site and the A site is empty. This process continues until a stop condon is reached. The stop condon does not code for an amino acid but terminates this process.
Outline the process of translation leading to polypeptide formation:
500
Transcription of certain genes will produce rRNA or tRNA rather than mRNA. Since neither rRNA or tRNA is translated, these genes do not produce polypeptides.
Explain the exceptions to the ‘one gene-one polypeptide’ hypothesis: