A1.2: Nucleic Acids Flashcards
State the two primary functions of nucleic acids.
- Pass information between generations
- Code for protein production
State the two types of nucleic acids used in cells.
- DNA; Deoxyribonucleic acid
- RNA; Ribonucleic acid
Outline the meaning and implication of DNA being the genetic material of all living organisms.
DNA carries all the genetic information of all living organisms through generations
State why RNA viruses do not falsify the claim that all living things use DNA as the genetic material.
Viruses are not considered living organisms as they are not made of cells
List the three components of a nucleotide.
- Pentose sugar (Ribose/Deoxyribose)
- Nitrogenous base
- Phosphate group
Identify and label the carbons of a pentose sugar.
- starts at 0 from the top and increases sequentially in a clockwork direction
Draw the basic structure of a single nucleotide (using circle, pentagon and rectangle).
- 1C in pentagon connects nitrogenous base
- 5C in pentagon connects phosphate group
Define “backbone” as related to nucleic acid structure.
DNA and RNA have a backbone of repeating phosphate and sugar formed when nucleotides combine in a condensation reaction
Explain how nucleotides connect to form a nucleic acid polymer.
- A covalent bond forms between the phosphate group attached to the 5′ C of one deoxyribose sugar and the –OH group attached to the 3′ C of another sugar, releasing one molecule of water with the use of energy.
State the names of the nitrogenous bases found in DNA and RNA.
DNA:
- Thymine
- Adenine
- Cytosine
- Guanine
RNA:
- Uracil
- Adenine
- Cytosine
- Guanine
State a similarity and a difference between the nitrogenous bases.
Similarity:
- All contain Nitrogen atoms
Difference:
- Different molecular structures
Outline how the sequence of bases in a nucleic acid serves as a ‘code.’
- The order of different types of nucleotides arranged in DNA or RNA serves as a code for storing genetic info in all living organisms
Define gene.
A gene is a specific sequence of nitrogenous bases in DNA nucleotides that code for the making of a protein
Describe the condensation reaction that forms a polymer of RNA from RNA nucleotides.
- The 3’ C of the ribose sugar in one nucleotide links with phosphate group on the 5’ C of the ribose sugar in another nucleotide
- H is lost from the 3’ C (OH) and OH is lost from Phosphate group thus, forming H2O
Identify the monomer and polymer of an RNA molecule.
Monomer:
- Nucleotides
Polymer:
- RNA chain
Draw a short section of an RNA polymer (using circle, pentagon and rectangle)
- Pentose sugar is Ribose
- Same position of nitrogenous base and phosphate group
Describe the structure of a DNA double helix.
- two sugar-phosphate backbones hydrogen bond between the nitrogenous bases to create a double helix
Outline the complementary base pairing rule, including the type and number of bonds between bases.
- Only certain bases between RNA and DNA strand or within a DNA strand can match as a result of their structure and ability to create H bonds
- A = T (or U); Connected with 2 H bonds
- G = C; Connected with 3 H bonds
Define antiparallel in relation to DNA structure.
- Two different strands of the DNA double helix run in opposite directions; at each end, one strand is 5’ and the other is 3’
Compare and contrast the structures of DNA and RNA.
- both are nucleic acids
DNA:
- made of 2 strand of nucleotides connected in the middle at the bases via H bonds
- contains the bases: adenine, thymine, cytosine, guanine
- contains a deoxyribose sugar (H on 2C)
RNA:
- made of only 1 strand of nucleotides
- contains the bases: adenine, uracil, cytosine, guanine
- contains a ribose sugar (OH on 2C)
Compare and contrast the functions of DNA and RNA.
DNA:
- Pass information between generations of cels
- Codes for making RNA during transcription
RNA:
- Codes for making proteins during translation (mRNA, tRNA and rRNA involved)
Compare and contrast the location of DNA and RNA in prokaryotic and eukaryotic cells.
DNA (Eukaryotic):
- located in the nucleus
- due to endosymbiosis, can also be found in chloroplasts and mitochondria
DNA (Prokaryotic):
- Nucleoid
- Plasmids
RNA (Eukaryotic):
- made in the nucleus during transcription and transported to the cytoplasm for translation
RNA (Prokaryotic):
- Cytoplasm
Outline the role of complementary base pairing in maintaining the DNA sequence during DNA replication.
- enzyme DNA Polymerase III builds a new strand by reading the DNA template and adding the complementary DNA nucleotide
- Thus, replication builds 2 identical DNA molecules
Outline the role of complementary base pairing in transmitting the genetic code in transcription and translation.
- enzyme RNA Polymerase builds an RNA strand by reading the DNA template and adding the complementary RNA nucleotide
Outline why there is a limitless diversity of DNA base sequences.
- DNA has 4 different bases (4^x where x is the # of bases); storing information can be done based on all the possible combinations that can be made from this sequence (4^4, 4^20, etc)
- DNA molecules don’t take up much space making the possible combination count for long strands seem limitless
Define universal in relation to the genetic code.
All living organisms use DNA as their genetic code
Outline why conservation of the genetic code across all forms of life is evidence of common ancestry.
This means that the genetic code was carried by the LUCA of all life and has been passed over time to all its descendants
Identify and label the 5’ and 3’ ends on a diagram of DNA.
- 5’ end is the open phosphate group
- 3’ end is the open sugar
Identify and label the 5’ and 3’ ends of the daughter DNA strands on a diagram of the DNA replication fork.
- top strand; 5’ to 3’ (continuous)
- bottom strand 5’ to 3’ (discontinuous)
Outline the impact of DNA directionality on DNA replication.
Dictate the structure of both DNA and RNA
Identify and label the 5’ and 3’ ends of RNA on a diagram of the transcription bubble.
- Open phosphate group (5’ C)
- Open sugar (3’ C)
Outline the impact of DNA directionality on transcription.
Ribosome is attached to the 5’ end of an mRNA and moves TO the 3’ end; translation is 5’ to 3’
Identify and label the 5’ and 3’ ends of mRNA on a diagram the ribosome bound to mRNA.
left to right (5’ to 3’)
Outline the impact of RNA directionality on transcription.
- Enzymes of transcription, RNA polymerase, can only add nucleotides to the 3’ end of a growing polymer of RNA nucleotides
- 5’ phosphate end is ADDED TO the 3’ ribose end of the growing RNA strand; transcription is 5’ to 3’
Compare and contrast the structures of purines and pyrimidines.
Purines:
- 2 ring structure
- Adenine and Guanine
Pyrimidines:
- 1 ring structure
- Cytosine and Thymine and Uracil
State the type of bonds formed in DNA between a purine and a pyrimidine
H bonds
Given a diagram of DNA, identify the four bases of DNA based on purine or pyrimidine and the number of hydrogen bonds.
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State two consequences of purine-to-pyrimidine bonding on the structure of DNA.
- promotes DNA stability
- have a consistent diameter throughout the entire molecule
Describe the structure of eukaryotic DNA and associated histone proteins during interphase (chromatin).
- DNA wraps around the histone
Draw and label the structure of a nucleosome, including the H1 protein, the octamer core proteins, linker DNA and two wraps of DNA.
- 4 circles in a square composition; this is the octamer core proteins or of histones
- DNA coils around the octamer of histones
- H1 protein is a vertical line next to octamer where the two ends of the DNA coil go through
Identify nucleosome structures using molecular visualization software.
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Outline the mechanism of histone-DNA association.
Due to the Phosphate groups in nucleotides, DNA is negatively charged and binds tightly to histone proteins using electromagnetic attraction
State the experimental question being tested in the Hershey and Chase experiment.
whether it was protein or DNA that acted as the genetic material that entered the bacteria
Outline the procedure of the Hershey and Chase experiment.
Determining whether proteins are the genetic material:
- Bacteriophage that had radioactive S on protein coat outside of the virus (as proteins contain S and not P)
Determining whether nucleic acids are the genetic material:
- Bacteriophage that had radioactive P on protein coat outside of the virus (as DNA contains P and not S)
The resulting infected bacteria populations were blended and centrifuged; heavier bacteria cell on the bottom (pellet), and lighter the virus components (supernatant)
Explain how the results of the Hershey and Chase experiment supported the notion of nucleic acids as the genetic material.
- More radioactive S was in the lighter supernatant
- More radioactive P was in the heavier pellet
Thus, this supported the idea that DNA was the genetic material as it had transferred into the bacteria cells evident by the radioactive P
Outline the use of radioisotopes as research tools.
Radioisotopes can be used as markers of certain elements on, for instance, bacteriophage to be tracked
Explain the role of falsifiability in determining the structure and function of DNA.
Falsify:
- To prove wrong
It’s now understood that;
- DNA has a double helix made of 2 anti-parallel strands of nucleotides linked by hydrogen bonding between complementary base pairs
Describe implications of Chargaff’s data that showed a 1:1 ratio of purine to pyrimidine in a sample of DNA.
- Distribution of bases was not equal 25%; Adenine and Thymine shared similar percentages of abundance same with Cytosine and Guanine
- This falsified the tetranucleotide hypothesis
State the function of histone proteins
- Packages DNA into nucleosomes through coiling
importance of nucleosomes in DNA supercoiling?
To fit the length of DNA into the nucleus
