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21 Cards in this Set
- Front
- Back
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what is the monomer for a nucleic acid? |
nucleotide |
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what is the structure of a nucleotide? |
a phosphate, five carbon sugar and a nitrogenous base. ( sun on a house with a pool) - formed by condensation reactions and has covalent bonds. - The nitrogenous base is attached at the carbon 1 and the phosphate is at either carbon 3 or 5 |
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what is the difference between the nucleotide in DNA and the one in RNA |
In DNA the the pentose sugar is deoxyribose but in RNA it is ribose |
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what is a phosphorylated nucleotide and what are some examples? |
- when the nucleotide contains more than one phosphate group. eg ATP, ADP |
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What is the structure of ATP and ADP? |
ATP is adenine, ribose and 2 phosphate groups whereas ADP is 2 phosphate groups( di) and AMP is 1 phosphate group ( mono) |
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what is the structure of DNA? |
DNA is a nucleic acid and a polymer as it is made up of many repeating monomeric units. - A strand of DNA consists of 2 polynucleotide strands. these are antiparallel as they run in oposite directions - got nucleotides which has a nitrogenous base( adenine, guanine, cytosine or thymine. - contain a phosphodiester bond ( the covalent bond) which is what is broken down when breaking polynucleotides. - they are long so can carry lots o encoded genetic information |
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which 2 bases are pyrimidines and which are purines? |
adenine and guanine are purines ( 2 rings) cytosine and thymine are pyrimidines (1 ring) Think pyrimidine has a y and so does cytosine and thymine |
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what function do hydrogen bonds have in DNA? |
They form between the two nitrogenous bases in the antiparallel strands. adenine always with thymine ( 2 bonds guanine is always with cytosine ( 1 bond ) - a pyrimidine will always form with purine as this gives stability - hydrogen bonds allow the molecule to unzip |
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What are the differences in how DNA is organised in a eukaryotic cell and a prokaryotic cell? |
Eukaryotic= DNA in nucleus, wound round histones, there is a loop of DNA inside mitochondria and chloroplast. Prokaryotic: DNA is in a loop and within cytoplasm but not in a nucleus. Naked DNA ( not wound round a histone) |
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what are the steps in semi-conservative replication? |
1 the DNA unwinds (gyrase) -4 The enzyme DNA polymerase catylises the addition of these bases in the 5,3 direction using strand as a template. -5 The leading strand is synthesised continuously whereas the lagging strand fragments and is later joined. |
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what happens when the wrong nucleotide is inserted? |
there are enzymes which proof read to edit out incorrect nucleotides |
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In which ways is RNA different to DNA? |
The sugar molecule is ribose the base is urcacil instead of thymine single stranded shorter chain there are 3 forms of RNA |
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What is a gene? |
A sequence of DNA nucleotides that codes for polypeptides |
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What is DNA replication called and why? What happens if DNA mutation occurs? |
Semi-conservative replication as 1 half is new and 1 half is old in a strand. can change the DNA base sequence, meaning an abnormal protein is produced as the sequence of amino acids is different, the protein may function better or worse than the original. |
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what does the genetic code being universal mean? |
in almost all living organisms the same triplet of dna bases codes for the same amino acid |
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why is the genetic code describes as degenerate? |
for most amino acids there is more than one base triplet. This may reduce the effect of point mutations as a change in one base of the triplet could produce another base triplet which still codes for the same amino acid |
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why is the genetic code describes as non-overlapping? |
it is read starting from a fixed point in groups of three bases. If a base is added or deleted it causes a frame shift as every base triplet and there fore the amino acid it codes for is changed |
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What are the 3 main types of RNA? |
mRNA (messenger RNA)tRNA (transfer RNA)rRNA (ribosomal RNA) |
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How are genes made into a length of RNA by transcription? |
- a gene unzips and unwinds - hydrogen bonds between complementary nucleotide bases break - RNA polymerase (enzyme) catalyses the formation of temporary hydrogen bonds between RNA nucleotides and their complementary unpaired DNA bases. on the template strand the nucleotide bases bond to the exposed bases by complementary base pairing. - a length of rna which is complementary to the template strand is produced. ( coding strand - The mrsa then passes out of the nucleus through the nuclear envelope and attaches to a ribosome. |
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Where is transfer RNA made? What shape is it? |
- nucleolus - hairpin - one end is a trio of nucleotides which can attach to an amino acid (specific amino acids) and the other is an anticodon which is complementary to a specific codon of bases on the mrsa. |
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what are the stages in translation (TRNA) |
-TRNA bring the amino acid and find their place when the anticodon binds (temporary H bonds) to the complementary codon on the MRNA. -As the ribosome moves along the length of MRNA, it reads the code and when two amino acids are adjacent the polypertide bond forms -Energy in the form of ATP is needed for polypeptide synthesis. -The amino acid sequence is therefore ultimately determined by the sequence of nucleotide triplets on the length of DNA -After the polypeptide is formed the mrna breaks doWN -the polypeptide is helped by proteins in the cell to fold correctly |
