DNA and RNA Flashcards
How are nucleotides joined together?
Two mononucleotides are joined between the pentose sugar of one mononucleotide and the phosphate group of the other by a condensation reaction, a phosphodiester bond is formed, water molecule is released and a dinucleotide is formed. If more than two are joined a polynucleotide (nucleic acid) is formed.
Describe the differences between DNA and RNA?
DNA is double stranded and RNA is single stranded.
DNA has the bases adenine, thymine, cytosine and guanine and RNA has the bases adenine, uracil, cytosine and guanine.
DNA contains a deoxyribose sugar and RNA contains a ribose sugar.
DNA is a long molecule compared to RNA which is a short molecule.
Describe the structure of DNA?
DNA is a polymer of nucleotides. Each nucleotide formed from deoxyribose, a phosphate group and an organic nitrogen containing base. Phosphodiester bonds join nucleotides together, the bond forms between the phosphate of one nucleotide and the deoxyribose sugar of another. DNA is a double helix made from two strands held by hydrogen bonds between adenine, thymine and cytosine, guanine (complementary base pairs).
What are the steps in DNA replication (Step 1/4) ?
DNA helicase breaks the hydrogen bonds between the complementary base pairs. This causes the DNA to unwind and the double helix separates into two strands.
What are the steps in DNA replication (Step 2/4) ?
Both strands act as a template and free DNA nucleotides are attracted to exposed bases to which they bind using complementary base pairing. Adenine with thymine and guanine with cytosine.
What are the steps in DNA replication (Step 3/4) ?
DNA polymerase then joins adjacent nucleotides on the new strand together by catalysing a condensation reaction that causes the formation of phosphodiester bonds between the deoxyribose sugar of one nucleotide and the phosphate group of another.
What are the steps in DNA replication (Step 4/4) ?
Each of the new molecules contains one parental strand and one new strand. This is known as semi-conservative DNA replication.
How is DNA suited to its function-Strong covalent bonds?
The stronger covalent bonds create the sugar phosphate backbone are on the outside of the double helix structure and the weaker hydrogen bonds are protected on the inside, so the DNA is stable and strong.
How is DNA suited to its function-It is a large molecule?
This means that DNA can store lots of genetic information.
How is DNA suited to its function- DNA has a coiled helix structure?
The shape means that it is compact and can therefore store lots of DNA in a small space.
How is DNA suited to its function-Complementary base pairing?
The base pairing, Adenine with thymine and guanine with cytosine, means that replication is accurate forming identical copies.
How is DNA suited to its function-What the base sequence codes for?
The base sequence codes for the order of amino acids in proteins, which allows the information to be stored.
How is DNA suited to its function-It is double stranded?
It allows both strands to act as templates, this means that replication can act semi-conservatively.
How is DNA suited to its function-Has weak hydrogen bonds?
The weak hydrogen bonds allow the helix to be easily unzipped, this allows for DNA to be replicated.
How is DNA suited to its function-The large number of hydrogen bonds?
The large number of hydrogen bonds between bases join the two DNA strands together, this means that the DNA structure is stable.