Structure Of DNA And RNA Flashcards
What does DNA stand for?
- deoxyribonucleic acid
What does DNA do?
- codes for the sequence of amino acids in the primary structure of a protein, which in turn determines the final 3D structure and function of a protein
What is the shape of a DNA polymer?
- double helix
What is the monomer that makes up DNA?
- nucleotide
What is a nucleotide made up of?
- deoxyribose or ribose (Pentose sugar)
- nitrogenous base
- phosphate group
What are nucleic acids made up of?
- nucleotides
What are the two types of nucleic acids?
- Deoxyribonucleic acid
- Ribonucleic acid
What are the nitrogenous bases for DNA?
- adenine
- thymine
- cytosine
- guanine
What are the nitrogenous bases for RNA?
- adenine
- uracil
- cytosine
- guanine
What is the polymer of these nucleotides called?
- polynucleotide
How are polynucleotides formed?
- condensation reactions between deoxyribose sugar and the phosphate group
- creates a phosphodiester bond which are strong covalent bonds and help ensure that genetic code is not broken down
What are phosphodiester bonds?
- strong covalent bonds which help ensure genetic code is not broken down
What is a property of a polynucleotide?
- sugar phosphate backbone
What is a sugar phosphate backbone?
- strong covalent bonds between the sugar and phosphate groups that hold the polymer together
What is the DNA polymer pairs joined together by?
- hydrogen bonds between the bases
How is the double helix structure created?
- DNA polymer pairs joined together by hydrogen bonds between the complementary base pairs
- cytosine can only bond with guanine and adenine can only bond with thymine
- adenine and thymine form two hydrogen bonds whereas cytosine and guanine can form three hydrogen bonds
- important to help maintain the order of the genetic code when DNA replicates
How is a why is complementary base pairing important?
- help maintain the order of the genetic code when DNA replicates
Draw a nucleotide
Draw deoxyribonucleic acid
DNA structure
- stable structure
- double stranded molecule
- weak hydrogen bonds
- large molecule
- complementary base pairing
DNA function of stable structure
- due to sugar phosphate backbone and the double helix
DNA function of double strand
- so replication can occur using one strand as a template
DNA function weak hydrogen bonds
- for easy unzipping of the two strands in a double helix during replication
DNA function large molecule
- due to double helix coils and twist around proteins in eukaryotic cells called histones and enables to condense and coil tightly to fit information in small space
- carry lots of information
DNA function complementary base pairing
- allows identical copies to be made
Which nitrogenous bases are pyramidines?
- thymine and cytosine
Which nitrogenous bases are purines?
- adenine and guanine
Describe the structure of purines
- two ring structure
Describe the structure of pyrimidine
- one ring structure
Why on a diagram of a nucleic acid are the purines in a bigger box?
- due to their two ring structure
What is RNA?
- a polymer of a nucleotide formed of a ribose, nitrogenous base and a phosphate group
What is the function of RNA?
- Copy and transfer the genetic code from DNA in the nucleus to the ribosomes
- some RNA is combined with proteins to create ribosomes
Difference between RNA and DNA
- DNA contains deoxyribose sugar whereas RNA contains ribose sugar
- DNA contains nitrogenous bases: adenine, thymine, cytosine and guanine whereas RNA contains the nitrogenous bases: adenine, uracil, cytosine and guanine
- DNA is double stranded whereas RNA is single stranded
- DNA is more stable and long lasting whereas RNA is less stable and breaks up quickly
- DNA is found in the nucleus in eukaryotes and RNA is found in the cytoplasm in eukaryotes
- there is only one variety of DNA whereas there are three varieties of RNA
What are the three varieties of RNA?
- ribosomal
- transfer
- messenger
What is a messenger RNA?
- copy of a gene from DNA
Where is mRNA created?
- in the nucleus
What is the function of mRNA?
- leaves nucleus to carry copy of the genetic code of one gene to a ribosome in the cytoplasm
Why is mRNA used to carry genetic code instead of DNA?
- DNA too large to leave nucleus and would be at risk of being damaged by enzymes, destroying the genetic code permanently
- mRNA is much shorter as it is only length of one gene and can leave nucleus
What are the features of mRNA?
- short
- short lived
- single stranded
Why is mRNA short?
- only length of one gene and can leave nucleus
Why is mRNA short lived?
- only needed temporarily to help create a protein so by the time the enzymes break it down it has already carried out its function
Why is mRNA single stranded?
- codes for a specific amino acid
What are the three bases in mRNA called?
- codons
Where is tRNA found?
- cytoplasm
What are the structures of tRNA?
- single stranded
- contain amino acid attachment site
- folded in a cloverleaf shape
- contain anticodon
What is the cloverleaf shape of tRNA held in place by?
- hydrogen bonds
What is the function of tRNA?
- attach to one of the twenty amino acids and transfer this amino acid to the ribosome to create a polypeptide chain
What are the specific amino acids attached to specific tRNA molecules determined by?
- three bases found on the tRNA (anticodons) which are complementary to the three bases on mRNA
What are anticodons?
- three bases found in tRNA which attaches to complementary bases on mRNA
What is ribosomal RNA?
- type of RNA that makes up the bulk of ribosomes
What is the structure of a ribosome?
- small subunit (30s)
- large subunit (50s)
- forms a 70s ribosome
Differences between DNA and RNA monomers?
- DNA contains thymine whereas RNA contains uracil
- DNA contains Pentose sugar deoxyribose whereas RNA contains Pentose sugar ribose
Differences between DNA and RNA polymers
- DNA is larger as it contains entire genome whereas RNA is shorter as it is the length of only one gene
- DNA is double stranded whereas RNA is single stranded
What stops RNA forming a double helix?
- extra oxygen in ribose
Gene
- sequence of DNA nucleotide bases of DNA that codes for a particular polypeptide. Polypeptides are the chains of amino acids which fold up into a protein.
Describe the structure of DNA
- polymer of nucleotides
- each nucleotide formed from deoxyribose a phosphate group and a nitrogenous base
- phosphodiester bonds between nucleotides
- double helix/ 2 strands held by hydrogen bonds
- hydrogen bonds and complementary base pairing between adenine, thymine, cytosine and guanine
Relate the structure of DNA to its function
- Sugar-phosphate (backbone) / double stranded / helix so provides strength / stability
/ protects bases / protects hydrogen bonds; - Long / large molecule so can store lots of information;
- Helix / coiled so compact;
Accept: can store in a small amount of space for ‘compact’ - Base sequence allows information to be stored / base sequence codes for amino acids / protein;
Accept: base sequence allows transcription - Double stranded so replication can occur semi-conservatively / strands can act as templates / complementary base pairing / A-T and G-C so accurate replication / identical copies can be made;
- (Weak) hydrogen bonds for replication / unzipping / strand separation / many hydrogen bonds so stable / strong;
