3.1.5 nucleic acids are important information-carrying molecules Flashcards
what is the role of DNA?
to hold genetic information
what is the role of RNA?
to transfer genetic information from DNA to the ribosomes
what are ribosomes formed from?
RNA and proteins
what are the components of a DNA molecule?
deoxyribose, phosphate group and an organic base ( adenine, cytosine, guanine and thymine)
what are the components of an RNA molecule?
ribose, phosphate group and an organic base (adenine, cytosine, guanine and uracil )
how are nucleotides joined and what does it form?
condensation reactions that form phosphodiester bonds
what is the structure of DNA?
double helix
two antiparallel polynucleotide strands
what is the length of RNA in comparison to DNA
RNA is shorter than DNA
what are the 3 types of RNA?
messenger
ribosomal
transfer
what does semi conservative replication of DNA ensure?
genetic continuity between generations of cells
outline the steps involved in semi conservative replication
- before a cell divides the DNA must copy itself
- the enzyme DNA helicase breaks the hydrogen bonds between two polynucleotide strands
- helix unwinds to form 2 strands
- each original strand acts as a template for the synthesis of a new strand
- complementary base pairing means that free floating DNA nucleotides are attracted to their complementary exposed base
- hydrogen bonds reform between bases on the old and new strands
- DNA polymerase catalyses the condensation reaction between the sugar and phosphate groups of adjacent nucleotides
- each new DNA molecule has an original DNA strand and a new one
what was meselson and stahls experiment based on?
all DNA bases contain nitrogen
nitrogen has 2 forms
- lighter nitrogen N14
- heavier nitrogen N15
bacteria will incorporate nitrogen from their growth medium into the new DNA they will make
