Nucleic Acids Flashcards
What does DNA stand for?
Deoxyribonucleic acid
Nucleotides…
Form from monomers of nucleic acids
Help regulate many metabolic pathways e.g. By ATP
May be components of many coenzymes
Nucleotides are made from…
Phosphate group (circle) Five carbon sugar (pentagon) Nitrogenous base (square)
What is the structure of DNA?
Double stranded
Polymer made of many nucleotides
Nitrogenous bases; adenine, guanine, cytosine and thymine
Purines and pyrimidines have how many rings?
Purines have two nitrogenous rings
Pyrimidines have one nitrogenous ring
Why does DNA replication need to occur?
Needs to replicate before a cell divides
Occurs during mitosis and meiosis
So when cell divides the two daughter cells will contain correct amount of genetic material
Process of DNA replication
The original DNA molecule has unwound. A reaction that is catalysed by the enzyme Gyrase
The enzyme DNA Helicase causes the two strands of DNA to separate (breaking the hydrogen bonds
Free phosphorylated nucleotides in the nucleoplasm are attracted to their complementary base point (e.g. A-T and C-G)
The strong phosphate backbone is rejoined by DNA polymerase forming two identical strands of DNA
Why is DNA replication called semi conservative?
Half of the original DNA and half new
What is transcription?
The process in which a copy of DNA is made (RNA) and occurs in the nucleus of a cell
Why is RNA made?
DNA that contains genes is too large to leave the nucleus so a copy of that gene called mRNA must be made
Process of transcription
The DNA in the nucleus is unwound
The weak hydrogen bonds between the bases are broken causing the strands to separate
Free RNA nucleotides in the nucleoplasm find their complementary base pair on the DNA (uracil instead of thymine)
Hydrogen bonds form between the RNA nucleotide base and the complementary base on the DNA
RNA polymerase catalyses the formation of the strong phosphodiester bond between the ribose sugar and phosphate groups of adjoining RNA nucleotides
The mRNA is formed
Hydrogen bonds break between the bases on mRNA and the bases on the DNA
The mRNA is ready to make its journey out of the nucleus trough pores and into the cytoplasm
What is translation?
The process in which the mRNA is read and translated into a protein
Where does translation occur?
Ribosomes and involved tRNA (transfer RNA)
Process of translation
The mRNA leaves the nucleus through a nuclear pore and enters the cytoplasm
A ribosome becomes attached to the mRNA
The genetic code on the mRNA is read in groups of 3 letters called codons
tRNA molecules have particularly specific anticodons for each of the 20 amino acids
The complementary anticodon is attracted to the first codon on the mRNA and forms a weak hydrogen bond
The second codon on mRNA also attracts its complementary anticodon on tRNA
A peptide bond is formed between the adjacent amino acids
The first tRNA molecule becomes detached from its amino acid
The ribosome moves along the mRNA molecule
The third tRNA moves in place the anticodon linking with its complementary codon
A peptide bond forms between the two amino acids
A stop is reached
A polypeptide chain has been formed and is released into the cytoplasm
