Nucleotides and Nucleic acid Flashcards
Who discovered the DNA helix structure and who received the credit?
Rosalind Franklin used X-ray diffraction to identify the structure of DNA
James Watson and Francis Crick too the findings and shared them to get credit
What is a nucelotide?
A monomer of nucleic acid that is made of a nitrogenous base, a phosphate group and a pentose sugar
What type of sugar is found in DNA and RNA?
DNA uses a deoxyribose sugar
RNA uses a ribose sugar
How do polynucleotides form?
A condensation forms an ester bond between an oxygen on the phosphate group and carbon 3 on the hydroxy group (named pentose sugar)
Name the 5 nitrogenous bases and their 2 types
Purine- Adenine, guanine
Pyrimidine- Thymine, cytosine, uracil
What bases are used for DNA and RNA?
DNA- Adenine, Guanine, Thymine, Cytosine
RNA- Adenine, Guanine, Uracil, Cytosine
How many bonds are formed between the DNA strands and what bond are they?
Hydrogen bonds are formed
Between Adenine and Thymine 2 bonds are formed
Between Guanine and Cytosine 3 bonds are formed
What is uracil?
It is the nitrogenous base that replaces Thymine in the RNA during transcription and translation
Define and explain the term anti-parallel
Anti-parallel refers to a double helix having opposite facing strands(one goes up and the other goes down)
This is needed to happen in order for complementary base pairing to occur and creates the double helix structure
How often does the DNA chain twist?
Every 10 nucleotides which is approximately 0.34nm and helps create the double helix
Describe the process for DNA replication
1)The semi-conservative replication of DNA occurs in the nucleus,
2)The double helix is unwound by the enzyme gyrase,
3)The hydrogen bonds are broken by the enzyme DNA helicase,
3)Each strand acts as a template to allow for free DNA nucleotides within the nucleus to align with the exposed nucleotides on the strand,
4)Complementary base pairing occurs which leads to 2 hydrogen bonds forming between A and T and 3 hydrogen bonds forming between G and C,
5)Phosphodiester bonds form between the oxygen in the phosphate group of one nucleotide and carbon 3 of the deoxyribose sugar above using the enzyme DNA polymerase,
6)This creates the sugar-phosphate backbones which gives the DNA its structure,
7)The whole process results in 2 identical strands of DNA that each contain half new DNA and half original DNA
Why is it called ‘semi-conservative’ DNA replication?
It is known as semi-conservative because semi means half and after the process half of the original DNA has been conserved in the strand but the other half is new
Where else does semi-conservative replication take place?
Bacteria- The nucleoid and plasmids
Chloroplasts and mitochondria- Their plasmids undergo semi-conservative replication
Explain what protein synthesis is
The production of a chain of amino acids from a gene through the transcription of a gene into a strand of mRNA and the translation of the mRNA strand into a polypeptide chain
Describe the process for protein synthesis and secretion
1) An mRNA copy of the gene is made in the nucleus and then levs the nucleus through a nuclear pore,
2) The mRNA attaches to a ribosome which reads the gene and then assembles the protein,
3) Molecules of the protein are pinched off in vesicles and move towards the golgi apparatus and then fuse with it,
4) The golgi apparatus processes and packages the molecules which are then pinched off in vesicles and move to the cell surface membrane,
5) The vesicle fuses with the membrane which then opens and releases molecules
How does RNA differ from DNA?
RNA uses ribose as opposed to deoxyribose,
RNA uses the base uracil as opposed to thymine,
RNA has single stranded polynucleotides as opposed to double stranded,
RNA exists in the three form mRNA, rRNA and tRNA as opposed to DNA which is singular
Describe messenger RNA (mRNA)
It is a copy of a DNA template strand
It has 3 adjacent codons which are nucleotides that code for amino acids,
It is used in transcription and translation
It is made in the nucleolus and moves to a ribosome as a template for protein synthesis
Describe ribosomal RNA (rRNA)
A complex molecule that accounts for half the mass of a ribosome,
Forces tRNA and mRNA process and translate genes into proteins
It is used in the process of translation
Describe transfer RNA (tRNA)
Small and single stranded
It has a binding site for a specific amino acid
It has an unpaired triplet of bases called an anticodon
It carries an amino acid to a ribosome where they are bonded together to form a polypeptide
Define and describe the process of transcription
Transcription is the process of an mRNA making a copy of a gene
1) The gene to be transcribed unwinds via the enzyme gyrase,
2) The hydrogen bonds are then broken by the enzyme helicase,
3) One DNA strand acts as a template to allow free RNA nucleotides to bind to the complementary bases,
4) Hydrogen bonds then form with 3 forming between G and C, 2 forming between U-A and A-T because uracil replaces thymine as a base in RNA
5) RNA polymerase then catalyses the formation of phosphodiester bonds (covalent) between the nucleotides,
6) The bonds attach from the phosphate group of one nucleotide to carbon 3 of the pentose sugar of another,
7) The mRNA is complementary to the template strand but not identical,
8) The mRNA is then released from the DNA and leaves the nucleus through a nuclear pore to the ribosome
Define and describe the process of translation
needs work
Translation is the process of an mRNA being converted into a chain of amino acids on a ribosome
1) mRNA bonds to a ribosome where a tRNA attaches and its anticodon binds to the first codon on the mRNA through complementary base pairing,
2) The tRNA is carrying a specific amino acid,
3) The 2nd tRNA then bonds to the 2nd exposed codon with its anticodon (there is room for two codons to attach at once),
4) A peptide bond then forms between the 2 amino acids,
5) mRNA moves along the ribosome,
6) A 3rd tRNA brings another amino acid as the first tRNA leaves to collect another amino acid,
7) The process continues until a stop codon is reached
What are the three key characteristics of the genetic code?
It is:
Universal- All living organisms use the same code
Degenerate- For most amino acids there is more than one base triplet
Non-overlapping- It is read starting from a fixed point in groups of three
What is the structure of ATP?
A nitrogenous base of Adenine is attached to a ribose sugar which is attached to three phosphate groups
What is the structure of ADP?
A nitrogenous base of Adenine is attached to a ribose sugar which is attached to two phosphate groups
How is ADP formed?
An ATP molecule undergoes a hydrolysis reaction which results in the formation of ADP and Pi (phosphate group)
This process also releases energy and occurs during respiration
