Structure of RNA and DNA pt2 Flashcards
(18 cards)
Suggest how the structure of DNA relates to its functions (7)
● Two strands → both can act as templates for semi-conservative replication
● Hydrogen bonds between bases are weak → strands can be separated for replication
● Complementary base pairing → accurate replication
● Many hydrogen bonds between bases → stable / strong molecule
● Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
● Long molecule → store lots of genetic information (that codes for polypeptides)
● Double helix (coiled) → compact
Why did many scientists initially doubt that DNA carried the genetic code
DNA was relatively simple- Chemically simple molecules with few components
What are the three types of RNA
mRNA-Messenger
tRNA-Transfer
rRNA-Ribosomal
What is mRNA
- A copy of a gene from DNA
- Created in the nucleus
What is the function of mRNA (messenger)
To carry a copy of the genetic code of one gene to a ribosome in the cytoplasm
Why is the function of mRNA important
DNA is too large to leave the nucleus and would be at risk of being damaged by enzymes —-> therefore destroying the genetic code permanently
Why is mRNA short
It is the length of one gene so it can therefore leave the nucleus
Why is mRNA short lived
It is only needed temporarily to help create a protein —> therefore by the time an enzyme breaks it down it would have already carried out its function
Where is tRNA found and What is the structure of tRNA (4)
- Found in the cytoplasm
- Single stranded
- Folded to create a shape that looks like a clover leaf that is held in place by H bonds
What is the function of tRNA
To attach to one of the 20 amino acids and transfer this amino acid to the ribosome to create the polypeptide chain
Explain the specificity of a tRNA molecule
-Specific amino acids attach to specific tRNA molecules
- This is determined by 3 bases found on the tRNA which are complimentary to the 3 bases on mRNA
How are mRNA and tRNA similar(codon-anticodon)
The three bases found in the tRNA are complimemtary to mRNA and these are called anti codon
(anticodon of tRNA is opposite of that of codon e.g. ANticodon= CGG and codon= GCC)
Describe the structure of mRNA (5)
- Polymer of nucleotides
- Each nucelotide formed from ribose, a phosphate group and a nitrogen base containing organic base
- Bases are Uracil Adenine Cytosine Guanine
- Phosphodiester bonds join adjacent nucelotides
- Single helix
Describe the structure of DNA (6)
● Polymer of nucleotides (polynucleotide)
● Each nucleotide formed from
deoxyribose, a phosphate group and a
nitrogen-containing organic base
● Phosphodiester bonds join adjacent
nucleotides
● 2 polynucleotide chains held together by
hydrogen bonds
● Between specific complementary base
pairs - adenine / thymine and
cytosine / guanine
● Double helix
Compare and contrast the structure of DNA and mRNA (5) (diff between polymers)
- DNA Pentose sugar is deoxyribose whereas in mRNA the pentose sugar is ribose
- DNA has the base thymine whereas in mRNA the base has no thymine but has Uracil instead
- DNA is double stranded whilst mRNA is single stranded
- DNA is longer (more nucelotides) mRNA is shorter (less nucelotides)
- DNA has hydrogen bonding mRNA does not
Describe the differences between a DNA nucleotide and an RNA nucleotide (diff between monomers)
-DNA nucleotide
-Pentose sugar is deoxyribose
-Base can be thymine
RNA nucleotide:
-Pentose sugar is ribose
-Base can be uracil
What is a codon and is mRNA single or double stranded
Single stranded
Three bases in a gene that code for specific amino acids
What is the function of RNA
To copy and transfer the genetic code from the DNA in the nucleus to the ribosomes
