Nucleic acids structure and Mutations Flashcards
lecture 2
Mention the components of nucleic acid
- Phosphate groups
- Pentose sugar
- A nitrogenous base (purines including Adenine (A) and Guanine (G); and pyrimidines including Cytosine (C), Thiamine (T) and Uracil (U))
- RNA and DNA are two main nucleic acids
Define a nucleoside
A nucleoside a molecule is composed of a purine or pyrimidine base and a ribose or deoxyribose sugar
what is a nucleotide composed of
nucleotide is composed of nucleoside and phosphate group
5 functions of RNA
- Directs translation
- Ribosomal RNA have structural and enzymatic roles.
- Delivery of amino acids
- Participates in posttranscriptional processing
- Carrier of hereditary information in some viruses
Mention the 4 DNA stabilizing forces
- Sugar-phosphate chain conformation
- Base pairing using hydrogen bonds
- Base stacking and hydrophobic interactions
- Ionic interactions
What are the functions of DNA
- directs its own replication
- Direct the transcription of complementary RNA molecules
Define DNA mutation
The genotypic change as compared to the normal sequence
risk factors for DNA mutation
- Exposure to mutagenic agents like UV light, intercalating agents
- Errors in DNA replication and repair
Define polymorphism
Multiple forms of a gene or sequence variants with no obvious effect upon phenotype may be termed
under pont mutations, describe the other minor mtations under it
- Missense – results in a different amino acid
- Nonsense – results in stop codon hence termination of translation of the protein
- Silent - results in the same amino acid
- Transition - a purine replaced by a purine or a pyrimidine by a pyrimidine
- Transversion - a purine replaced by a pyrimidine or vice versa
Mention 2 types of mutations
- Point mutation
- Frameshift muatation
define frameshift mutation
The mutations that cause all of the subsequent three-letter codons to be changed
what does the cenral Dogma of biology states
The usual flow of genetic information is from DNA to mRNA to polypeptide
examples of frameshift mutation
- Deletions: involved loss of one or more nucleotides
- Insertion: involves the addition of one or more nucleotides into a gene
what are the two effects of mutations on proteins
- Loss-of-function: mutations can result in either reduced activity or complete loss of the gene product.
- Gain-of-function: mutations, result in either increased levels of gene expression or the development of a new function(s) of the gene product
Mention 6 enzymes that takes part in DNA replcation
- DNA topoisomerases
- Helicase
- RNA polymerase and primase
- Exonucleases
- Single strand binding proteins (SSBs)
- Ligases
what separates the two standed double helix of the DNA
DNA helicase
results of DNA replication
results in two daughter DNA duplexes that are identical to the original parent molecule
the synthesis of complementary strands occurs in which direction
5′ to 3′ direction
what directs DNA synthesis of a complementary DNA strand
DNA polymerases
where does replication occur
replication bubble
where does replication starts at
replication forks
differentiate the synthesis of leading strand and lagging strad
- The leading strand, is synthesized continuously.
- The lagging strand, is synthesized in Okazaki fragments
What direction does the DnaB protein translocate along the lagging strand template?
The DnaB protein translocates along the lagging strand template in the 5’ – 3’ direction.
