Nucleic acid Flashcards
Describe structure and function of it in DNA?
Sugar phosphate backbone - strenght
Coiling of DNA - compact
Double helix - each strand serves as template in replication, protection, more stable molecule
Large molecule - large amount of info
Many hydrogen bond - stability, prevents code being disrupted
Specific sequence of bases - provides genetic code
Complementary base pairing - enables info to be replicated accurately
Where is phosphate found on C?
5
What is orientation of nucleotides?
Phosphate is condensed between 3 C and 5 C
What is semic conservative mechanism of DNA replication?
Hydrogen bonds bewteen double strands polypeptide chain is broken by helicase
Each strand act as template
DNA nucleotide would align to template based on specific base pairing
Nucleotides are joined to form polynucleotide chain by DNA polymerase
2 strands are joined by hydrogen bonds
Thus 2 identical strands is produced from original DNA
What is okazaki fragments?
The enzyme DNA polymerase can only add new nucleotides in the 5’ to 3’ direction as it synthesises a complementary strand
As the DNA unwinds, the template strand running in the 3’-5’ direction can be copied in its entirety
As one long length as the two polynucleotide strands separate and produces the leading strand, this is called continuous replication
The strand in the 5’-3’ direction has to be copied in small sections as a new 3’end becomes available
These lagging fragments (Okasaki fragments) need to be joined together at their sugar phosphate backbone to make a continuous polynucleotide strand
This is carried out by DNA ligase. This process is called discontinuous replication
What is ribosomal RNA?
80% of total RNA
rRNA is synthesised in nucleolus
rRNA moves to cytoplasm through nuclear pores and associated with protein forming ribosomes
Ribosomes are site of protein synthesis, and translated into a sequence of amino acid
What is messsenger RNA?
Formed in transcription
Copied from one DNA template
Lenght depends on template gene
Exist for short period in cell
What is transfer RNA?
Smallest RNA
Brings specific amino acid to specific mRNA code
Has clover leaf shape
5 end ends with guanine and 3 end ends with CCA
Anticodon is situated on bottom loop and it is related to amino acid
Expain what is alleles?
Different forms of same gene
Code for very similar polypeptides and are located in the same locus on homologous chromosomes
What is characteristics of bases?
Bases are cytosine, guanine, adenien and thymine (uracil)
Theres 20 amino acids from 64 different codons
Degenerate, different codons coding for same amino acid
Some codons are stop codons, coding for termination at end of polypeptide chain
Non-overlapping, triplets read as separate codons
Describe splicing?
Spliceosome removes the introns and joins the exons together to form mRNA
Describe initiation of transcription?
Ribosome moves along mRNA to start codon and tRNA binds at P site of ribosome with met
tRNA anticodon complementary base pairis with its codon on mRNA
tRNA complementary to second codon aligns at A site
Bond is broken between met and tRNA, energy released forms peptide bond between met and next amino acid
tRNA for met moves away in cytoplasm
tRNA attached with dipeptide moves to P site
Describe elongation in transcription?
Ribosome moves alog to next new codon
New codon is aligned with the A site allowing next tRNA to interact with ribosome
Again when dipeptide is linked to third amino acid, second tRNA moves away
Process continuesalong mRNA strand until all codon have been read and specific polypeptide has been produced
Describe termination in translation?
When a stop codon is reached an enzyme hydrolyses the bond between the polypeptide chain and the last tRNA
The ribosome leaves the mRNA and can reattach at the start again
What is transcription factor?
Molecule stimulating mRNA formation by stimulating RNA polymerase
This prevents transcription
