L9 - Nucleic Acids Flashcards
Where do organisms store protein structure information?
In macromolecules known as nucleic acids
Where is information passed to?
Information is passed onto daughter cells during cell division
What do nucleic acids serve as?
Storage units for our unique hereditary information
What does DNA stand for?
Deoxyribonucleic Acid
Describe DNA.
- Basic hereditary material
- Stored in the nucleus
- Contains information necessary to synthesise proteins
What does RNA stand for?
Ribonucleic Acid
Describe RNA.
- Exists in several forms
- Translates information found in DNA
- Directs the production of proteins in the cytoplasm
What are both DNA and RNA?
Polymers of nucleotides; also known as polynucleotides or nucleic acids.
What 3 components are nucleotides made up of?
- Sugar (Ribose / 2-Deoxyribose)
- Nitrogenous Base
- Phosphate Group(s)
Name the 5 possible nitrogenous bases.
- Adenine
- Cytosine
- Guanine
- Thymine
- Uracil
As per nomenclature, what is a nitrogenous base called?
Nucleobase
As per nomenclature, what is a Nucleobase + Sugar called?
Nucleoside
As per nomenclature, what is a Nucleoside + Phosphate called?
Nucleotide
Can nucleotides be cyclic?
Yes
How does a nucleobase attach to a sugar?
With a β-N-glycosidic link
What 2 types can nucleobases be?
- Pyrimidines
- Purines
What is a pyrimidine?
A heterocyclic organic compound consisting of a pyrimidine ring.
Name the 3 pyrimidine bases.
- Cytosine (C)
- Uracil (U)
- Thymine (T)
What is a purine?
A heterocyclic organic compound consisting of a pyrimidine ring fused to an imidazole ring.
Name the 2 purine bases.
- Adenine (A)
- Guanine (G)
Name 2 multiphosphorylated nucleotides.
- ATP
- GTP
What is NAD+?
A co-enzyme in cellular reactions.
What is NADP+?
The phosphorylated form of NAD+.
What do NAD+ and NADP+ do?
- Act as electron acceptors (oxidising agents)
- Are involved in cellular respiration
How can cyclic AMP be produced?
By the adenylate cyclase enzyme.
What is cyclic AMP (cAMP)?
An important cell signalling molecule.
How is energy released? Provide 3 equations in your explanation.
Adenosine triphosphate (ATP) can be dephosphorylated to release energy.
ATP ⇌ ADP + P
ADP ⇌ AMP + P
ATP ⇌ ADP + PP (Pyrophosphate)
Describe GTP.
- Guanine Triphosphate is similar to ATP
- Important in protein synthesis and cell signalling
Describe the structure of DNA.
- Polymer made from nucleotides
- Phosphate on one nucleotide covalently links (phosphodiester bond) to the 2-deoxy ribose sugar on the next nucleotide forming a strong = sugar-phosphate back bone
- Nitrogenous bases protrude from each sugar unit
- 2 DNA strands twist around each other, forming a double helix
What is significant about 2 DNA strands that form a double helix?
2 single DNA strands are complementary to each other in terms of their orientation and their nitrogenous bases
Who discovered the structure of DNA, and when?
- Watson and Crick
- 1953
Describe 2 features of complementary DNA strands.
- Read 5’ to 3’
- Complementary strands have asymmetric ends
What is the base-pair rule?
Hydrogen bonds between bases follow the base-pair rule:
- A binds to T (2 hydrogen bonds)
- C binds to G (3 hydrogen bonds)
What is a gene?
A section of DNA which carries the instructions for making proteins.
What does the order of bases determine?
The order of amino acids in a protein (Genetic Code).
What do the proteins determine?
Cell structure, function and identity.
What is significant about DNA replication?
DNA can replicate the genetic code to pass genetic information onto daughter cells.
(Semi-Conservative Replication of DNA)
How many chromosomes are in a cell’s nucleus?
46 chromosomes
Describe the organisation of DNA in the cell.
Millions of base pairs in a DNA molecule make up genes on the chromosomes in the nucleus.
1) DNA Helix
2) Histones
3) Nucleosomes
4) Chromatin
5) Chromosome
What is a karotype?
The number and appearance of chromosomes in the nucleus of a eukaryotic cell.
Describe the relationship between DNA and RNA.
- DNA serves as the template for the synthesis of the polynucleotide RNA
- Information contained in the DNA is preserved in the RNA
Describe the 3 differences between DNA and RNA.
- Ribose sugar replaces deoxyribose sugar in RNA
- RNA is single stranded, while DNA is double stranded
- Uracil (U) replaces Thymine (T) in RNA
Describe the 3 types of RNA.
- Messenger RNA (mRNA): Converts the genetic information in DNA into a template that can be used to construct a protein molecule
- Transfer RNA (tRNA): Helps to transport amino acids that build the polypeptide chain of a protein
- Ribosomal RNA (rRNA): With ribosomal proteins, rRNA makes up the ribosomes, which are organelles that translate the mRNA
Describe the structure of a tRNA molecule.
- 3 hairpin loops that form the shape of a three-leafed clover
- One of these hairpin loops contains a sequence called the anticodon, which can recognize and decode an mRNA codon
- Each tRNA has its corresponding amino acid attached to its end
What does the central dogma state?
- “Once (sequential) information has been passed into a protein, it cannot get out again.” (Crick, 1958)
- “The central dogma states that the information in nucleic acids can be perpetuated or transferred, but the transfer of information into the protein is irreversible.” (B. Lewin, 2004)
Describe the uses of DNA.
- DNA testing for forensic use: Forensic DNA ‘fingerprint’ analysis
- DNA for medical uses: DNA sequencing, somatic gene therapy
- DNA for genetic engineering: Genetic engineering to make/change proteins, insulin synthesis
- Gene editing using CRISPR