Nucleic Acids Flashcards
What are DNA and
RNA made from?
What do these consist of?
Ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) are
nucleic acids made from nucleotides. A nucleotide has three components:. a phosphate groupe a pentose sugar an organic base
how do purines and pyrimidines differ? which bases are purines and which are pyrmidines? (2, 2) Which are found in RNA and which in DNA?
Punnes hove two carbon rings whilst
pyrimidines only have 1. Adenine and guanine are purines and are found in both DNA and RNA. Cytosine, thymine, and uracil are all pyrimidines, with cytosine and thymine found in DNA, and cytosine and uracil found in RNA
What is RNA? How does it differ from DNA? (4) What are the thee types of RNA and what are each used for?
RNA is a polynucleotide. It is usually single-stranded and much shorter than DNA. The sugar involved is ribose, not deoxyribose. The bases used include adenine, cytosine, guanine and uracil.
There are three types of RNA:1 messenger RNA (mRNA), which carries the code held in the genes to the ribosomes where the code is used to manufacture proteins2 transfer RNA (tRNA), which transports amino acids to the ribosomes3 ribosomal RNA (rRNA), which makes up the ribosome
What is DNA? How do the organic bases in DNA pair up? Why? What pairs to what in terms of bases, and with how many hydrogen bonds? Why are the strands in DNA said to be antiparallel? Why is DNA said to have a double helix? (2)
DNA is also a polynucleotide. The organic bases can pair up - one purine with one pyrimidine. They pair according to their complementary shapes. Adenine always pairs to thymine (or uracil in RNA) using two hydrogen bonds. Cytosine always pairs to guanine using three hydrogen bonds. The two polynucleotide strands lie in opposite directions, which is known as antiparallel. The two single polynucleotide strands are joined together to make a double strand. The whole molecule twists to form a helix, hence the name
‘double helix’.
When is a polynucleotide formed? What are the bonds in polynucleotides called? How can they be formed and how can they be broken? where do the bonds form? What does this result in? (2)
A polynucleotide is formed when nucleotides bind together in a long chain. The bonds are formed by condensation and are called phosphodiester bonds. They can be broken by hydrolysis. These bonds form between the sugar of one nucleotide and the phosphate group of another, making a sugar-phosphate
‘backbone’. This leaves the organic base of each nucleotide sticking out to the side of the chain.
Whata re ADP and ATP? What do they contain? (3) Why does Dna replication occur? Why is DNA double stranded? What are the seven steps of semi-conservative DNA replication?
40e ond AlP are cnoschor ateo nuclegtides. ney contoin a nentose sudar rinose a nitrogenous onse
(adenine) and two or three inorganic phosphates.The replication of DNASemi-conservative DNA
replicationDNA replication occurs in all living organisms in order to copy their NA for biological inheritance.
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process, known as semi-conservative replication, is as follows:1 One double-stranded molecule untwists and the hydrogen bonds between the base pairs break. This is catalysed by the enzyme helicase.2 The two polynucleotide chains separate, exposing the bases.3 Each strand is then used as a template to make two
ne. couo e stronos 4 vew nuc eotoes portone exposed poses on boun stenas, usine melr comolementor shapes to pair correctly.5 Each new chain of nucleotides is bonded together by the enzyme DNA polymerase to form the second half of each DNA molecule.6 The enzyme also checks that the pairing of the bases is correct.7 Each new molecule then twists to form it’s double helix
Why should DNA be replicated precisely? How is precise replication ensured? What is a mutation? What causes them to occur? Which organisms use the. genetic code? What is the genetic code? How many bases code for an amino acid? How many possible amino acids are there? How many possible
comontetions erre-there orthe-coce-to-meke-tnese：
amino acids How is this possible? What is the term for this? Another tnotable thing about the coding for polypeptides? What is a gene? What is the minimum number of genes to form a protein?
MutationsThe precise replication of DNA is essential to ensure that identical copies of the genes are included in every cell of the body. Usually the precise pairing of the bases ensures that two exact copies of the originall DNA molecule are made. However, occasionally an incorrect base may be bonded into place, which is known as a mutation. Mutations are random and spontaneous. The genetic codethe genetic code is universal - all organisms use the same code, It is a sequence of bases. Three consecutive bases (known as triplets) codes for one amino acid. There are 64 possible triplet codes but only 20 amino acids used to make proteins. Some amino acids are coded for by more than one triplet (called degenerate codons). The triplets are non-overlapping. A particular sequence of iplets will code ior one sequence of amino acios. A sequence of amino acids forms one polypeptide. The length of DNA that codes for one polypeptide is called a gene. One gene codes for one polypeptide. This may form a protein. It the protein contains more than one polypeptide (te, it has a quaternary structure), there will be more than one gene used to code for the protein
What are the two stages of polypeptide. synthesis? What happens in each?
The synthesis of polypeptides involves two stages:! Transcription reading the code and producing a messenger molecule to carry the code out to the cytoplasm.2
Translation - converting the code to a sequence of amino acids.
Where is a cell’s genetic code held?
The steps of
transcription? (6)
Ine genetic code Is nela in the nucleus. Ine DNA molecule Is too large to leave ie nucleus, so a smaller messenger molecule Is made called messenger KNA (MRNA). Ine double-strandea DNA molecule is unwound and split by the action of the enzyme RNA polymerase, which breaks the nydrogen donas nolaing the two stranas togeter. Inis exposes the secuence or bases in the gene. The coding strand carries the genetic code and the complementary strand is a non-coaing stana someumes callea the antisense stand or the template strand, whieh is used to bulla a copy or the coding strana called messenger KNA (MRNA). lt nas an laentical sequence or bases to the coalng stana or the gene, except that the thymine is replaced by urach. tach triple of bases on the mRNA is called a codon. The enzyme RNA polymerase joins the bases of the RNA
template and the DNA strands can rejoin to remake the double helix. The mRNA leaves the
nucleus via tne nuclear pores ana enters the cytoplasm.
Which base pairs bond to which?
A is to T (or U in RNA), and G is to C
What is translation?
The seven steps of it?
As each codon enters the ribosome, it is used to position the next amino acid. Amino acids must be activated - they are combined with a specific molecule of transfer RNA (tRNA) that has a specific base triplet called the anticodon. The anticodon of the tRNA is complementary to a codon on the mRNA. ATP is used in this activation process. The amino acids attached to tRNA molecules are aligned with the correct part or the miNA by the complementary paining or the bases in the codon and anucodon. Enzymes bind the amino acids together in a chain by condensation reactions to create a growing polypeptide chain. The tRA molecule is then released to be reused. When the ribosome reaches the end of the mRNA, the complete polypeptide chain is released and folds to form the secondary and tertiary structure of the protein. some proteins need to be activated by cyclc AMP (CAMP, which interacts with the new protein to alter its three dimensional shape. This makes the protein a better shape to fit their complementary molecules.
