S1-L9: Nucleic Acids Flashcards
Explain what nucleic acids are
- organism store protein structure information in macromolecules known as nucleic acids
- ->this info passed onto daughter cells during cell division
- nucleic acids serve as storage units for our unique hereditary info
What does DNA stand for and describe it
- DNA is deoxyribonucleic acid
- basic hereditary material in nucleus
- contains info necessary to make proteins
Similarly, what does RNA stand for and describe it
- RNA is ribonucleic acid
- exists in several forms
- translates info found in DNA
- directs protein production in cytoplasm
State what is common between DNA & RNA
-both polymers of nucleotides also known as polynucleotides or nucleic acids
What is the basic structure of nucleotides?
- nucleotides made up of 3 building blocks
- ->sugar (ribose OR 2-deoxy ribose)
- ->nitrogenous base
- ->phosphate group(s)
What is each of the following composed of and outline some key features:
1-Nucleobase
2-Nucleoside
3-Nucleotide
1-is nitrogenous base 2-nucleobase + sugar 3-nucleoside + phosphate -normally named after nucleobase -additional phosphate may be present- nucleotide diphosphate/ nucleotide triphosphate -nucleotide can be cyclic
Describe a nucleobase (refer to figure 2)
- attach to sugar with B-N-glyosidic link to form nucleoside
- adenosine formed from nucleobases adenine + sugar ribose
- nucleobases can be either pyrimidines OR purines
What are pyrimidine nucleobases? (figure 3)
-heterocyclic organic compounds consisting of pyrimidine ring
Define a purine (figure 4)
-heterocyclic organic compound consisting of pyrimidine ring infused to an imidazole ring
State the common nucleotides which contain ribose
- multiphosphorylated nucleotides (figure 5)
- DNA (in deoxy form) figure 6
- ->other forms exist too (figure 7)
- NAD+ (figure 8)
- cAMP (figure 9)
Describe NAD+
1-NAD+: co-enzyme in cellular reactions
- NADP+ is phosphorylated form
- act as e- acceptor (oxidising agent)
- involved in cellular respiration
Similarly describe cAMP
- Cyclic AMP can be produced by adenylate cyclase
- cAMP important in cell signalling molecule
How may adenosine triphosphate be changed to release energy? (figure 10)
- adensoine triphosphate (ATP) can be dephosphorylated to release energy:
- ATP ADP + P
- ADP AMP + P
- ATP
What is Guanosine triphosphate (GTP)?
- it similar to ATP
- important in protein synthesis AND cell signalling
Structure of common nucleotides
- purines
- ->adenine/ guanine
- pyrimidines
- ->cytosine/ uracil/ thymine
- nucleoside–>nucleoside monophosphate etc
- figure 11 shows all of the common nucleotides
Outline and describe the structure of of a single strand of DNA (figure 12 gives a visual representation)
- DNA polymer made of nucleotides
- phosphate on one nucleotide covalently links (phosphodiester bond) t o2-deoxy ribose sugar on next nucleotide
- ->forms strand (sugar phosphate backbone)
- nitrogenous bases protrude from each sugar unit
Explain what DNA is and how it forms (figure 13)
- 2 strands twist around each other- to form double helix
- 2 single DNA strands complementary to each other in terms of orientation AND their nitrogenous base
- structure discovered by Watson & Crick 1953
What is the interaction between anti-parallel strands in DNA?
- DNA strands are anti-parallel–> read 5’ to 3’ (figure 14)
- complementary strands have asymmetric ends
- H bonds form between bases which follow base pair rulings (figure 15):
- ->A-T (2 H bonds)
- ->G-C (3 H bonds)
Explain what genes are and their function
- portions of DNA
- genes carry instructions for making proteins
What does the order of bases determine?
-determines order of amino acids in protein (genetic code)
What do proteins determine?
-determine cell structure/function AND identity
How may genetic info be passed on?
-DNA able to replicate genetic code to pass genetic info on to daughter cells
Outline the way DNA is organised in a cell
-cell–>nucleus–>contains 46 chromosomes–>tightly packed DNA (associated with histone proteins)–>DNA organised in double helix–>DNA determined by sequence of DNA
Define the term Karyotype (figure 17)
- number and appearance of chromosomes in nucleus of eukaryotic cell
- Karyotype: (22+X OR Y)=23
Describe RNA (refer to 4 diagrams in figure 18)
- RNA similar to DNA except:
- ->ribose sugar replaces deoxyribose
- ->ribose single-stranded
- ->uracil (U) replaces thymine (T)
What is the function of RNA?
- RNA serves as template for polynucleotide RNA synthesis
- information contained in DNA preserved in the RNA
Outline each of the following types of RNA:
1-Messenger RNA (mRNA) (figure 19)
2-Transfer RNA (tRNA) (figure 20)
3-Ribosomal RNA (rRNA)
1-converts genetic info in DNA into template which used to construct a protein molecule
2-helps transport amino acids which build polypeptide chain of proteins
3-with ribosomal proteins, rRNA makes up ribosomes-the organelles which translate the mRNA
How does it all fit together?
- transcription and translation occurs involving all the different features discussed before (involving):
- tRNA/mRNA/rRNA
- figure 21 shows a visual representation
What did Lewin state about the Central Dogma? (figure 22)
- central dogma states that info in nucleic acid can continue indefinitely OR be transferred
- ->but transfer of information into protein is irreversible
Similarly what did Crick say about the Central Dogma? (figure 22)
-once sequential information has been passed into protein it cannot get out again
What is the use of DNA in forensic biology? (figure 23)
- DNA testing for forensic use
- ->forensic DNA “fingerprint analysis”
How is DNA used in medicine? (figure 24)
-for medical use–>DNA sequencing AND somatic gene therapy
Outline the use of DNA in genetic engineering (figure 25)
- DNA used in genetic engineering to make OR change proteins
- ->like insulin
What is gene editing using CRISPR (family of DNA sequences found in genomes of prokaryotic organisms like bacteria/ archaea) ?
- changing single nucleotide genome
- ->deletion in certain places and then insertion of DNA
- ->good as very specific
- reach targeted genome editing
- figure 26 gives a visual representation of the process
