DNA and RNA structure Flashcards
what does DNA stand for?
deoxyribonucleic acid
where is DNA found?
in the nucleus
what is the function of DNA?
contains genetic info and codes for amino acid sequence.
where and how is DNA read?
in the ribosomes - needs to be converted to mRNA to leave the nucleus as DNA is charged/polar and too big too leave.
what are ribosomes made of?
RNA and proteins.
what are the similarities between RNA and DNA?
both have nitrogenous bases - adenine, guanine, cytosine.
both have pentose sugar.
both have phosphate groups.
both are polymers of nucleotides.
what are the differences between RNA and DNA?
RNA is single stranded whereas DNA is double stranded.
RNA has a ribose sugar whereas DNA has a deoxyribose sugar.
RNA has uracil whereas DNA has thymine - (organic bases)
which bases make up purines?
A - adenine
G - guanine
how many rings do purines have?
2 rings
which bases make up pyrimidines?
T - thymine
U - uracil
C - cytosine
how many rings do pyrimidines have?
1 ring
what is the function of RNA?
transfers genetic information from DNA to ribosomes.
describe how nucleotides join together to from polynucleotides.
via a condensation reaction between phosphate group and deoxyribose forming phosphodiester bonds, losing water.
what is the difference between DNA nucleotide and RNA nucleotide.
DNA - pentose deoxyribose sugar and thymine base.
RNA - pentose ribose sugar and uracil base.
describe the structure of DNA.
- its a polymer of nucleotides.
- each nucleotide is formed from a deoxyribose sugar, a phosphate group and a nitrogenous base.
- nucleotides are joined by phosphodiester bonds.
- two polynucleotide chains are joined by hydrogen bonds.
- its a double helix.
describe the structure of RNA.
- its a polymer of nucleotides.
- each nucleotide is formed from a ribose sugar, a phosphate group and a nitrogenous base.
- bases are uracil, adenine, cytosine and guanine.
nucleotides are joined by phosphodiester bonds. - its single stranded.
suggest how the structure of DNA relates to its function.
- double helix (two strands) acts as templates for semi-conservative replication.
- hydrogen bonds between bases are weak, so strands can be separated for replication.
- long molecule, so it stores lots of genetic information.
- double helix with a sugar phosphate backbone, which protects bases.
describe the process of semi-conservative DNA replication.
- DNA helicase unwinds double stranded DNA, breaking the hydrogen bonds and leaving two template strands.
- DNA polymerase binds at the 5’ end of the template strand of DNA.
- free DNA nucleotides, complementary to the template strand, join together by DNA polymerase in a condensation reaction, forming phosphodiester bonds.
EXTRA: - the leading strand can be copied from start to finish in one entire section.
- the lagging strand has to be copied in sections as the double stranded DNA is being unwound.
using knowledge of enzyme action, suggest why DNA polymerase moves in opposite directions along DNA strands.
DNA has anti-parallel strands so the shapes of nucleotides on the two ends are different.
DNA polymerase is an enzyme with a specific shaped active site, so can only bind to substrate with complementary shape.
