A1.2 Nucleic Acids Flashcards
DNA and RNA full names (A1.2.1)
Deoxyribonucleic acid
Ribonucleic acid
What are nucleic acids? (A1.2.1)
Very large molecules, made from subunits called nucleotides which link to form a polymer.
RNA + DNA
What is genetic material(/hereditary information)?(A1.2.1)
A store of information. If copied, can be passed from cell to cell and also from parent to offspring.
DNA is the genetic material of all living organisms.
Components of a nucleotide (A1.2.2)
Pentose sugar - 5 carbons
Phosphate group - acidic + neg. charged part
Base - Contains nitrogen
What does the sugar–phosphate “backbone” do? (A1.2.3)
The sugar–phosphate backbone links nucleotides into a chain, preserving the base sequence, by forming covalent bonds between the phosphate group of one nucleotide and the pentose of the next.
What role do the bases play in forming the genetic code? (A1.2.4)
Genetic information is stored in sequences of bases, encoded in a universal genetic code shared by all organisms.
Nucleic acids as polymers formed by condensation of nucleotide monomers (A1.2.5)
OH of phosphorus + pentose used. -> One group combined w/ H from the other, producing H2O.
Remaining O forms new covalent bond, linking nucleotides.
DNA structure (A1.2.6)
Double helix made of two antiparallel strands of nucleotides, linked by hydrogen bonding between complementary base pairs.
Why is it important that DNA strands run antiparallel? (A1.2.6)
One strand ends with the phosphate group of the terminal nucleotide while the other strand ends with a deoxyribose. This allows bases to form hydrogen bonds.
Differences between DNA and RNA (A1.2.7)
DNA double stranded, RNA single stranded.
Uracil is present instead of thymine in RNA.
Pentose sugar DNA = deoxyribose. RNA = ribose. Deoxyribose -> one fewer oxygen (no O on C2).
Role of complementary base pairing in allowing genetic information to be replicated (A1.2.8)
Strands separate. Original strands = templates.
Newly synthesized strand has same base sequence as other template strand.
Semi-conservative replication: one DNA molecule -> two identical DNA molecule.
Role of complementary base pairing in allowing genetic information to be expressed (A1.2.8)
A gene contains the instructions for a specific function. When this information influences the cell, it is called gene expression.
The first step of gene expression is transcription, where the base sequence of the gene is copied from one template strand using complementary base pairing.
Conservation of the genetic code across all life forms as evidence of universal common ancestry (A1.2.10)
Groups of three bases = codons -> have meanings in the code. 64 different codons. Genetic code universal w/ minor exceptions.
Most codons code particular amino acid. 1 signals protein synthesis start, 3 signal stop.
Directionality of DNA and RNA (A1.2.11)
The unlinked pentose sugar at one end is the 3′ terminal, with the 3′ carbon available for linking. The unlinked phosphate at the other end is the 5′ terminal, attached to the 5′ carbon of a pentose sugar
Directionality of DNA on replication (A1.2.11)
5′ to 3′ -> nucleotides added to 3′ end of growing polymer. 5′ phosphate of free nucleotide links to sugar at 3′ end of growing polymer.
One strand, 5′ to 3′ assembly moves same direction as overall process of replication. The other it moves opposite.
Directionality of DNA and RNA on transcription (A1.2.11)
5′ to 3′ -> nucleotides added to the 3′ end of the growing polymer.
Directionality of RNA on translation (A1.2.11)
The rRNA, responsible for translation, moves along the RNA molecule toward the 3′ end.
5’ to 3’
Purine-to-pyrimidine bonding (A1.2.12)
Adenine + guanine = purine bases (2 rings of atoms)
Cytosine + thymine = pyrimidine (1 ring)
Purine-to-pyrimidine bonding as a component of DNA helix stability (A1.2.12)
Each base pair has 1 purine and pyrimidine.
Two base pairs are equally width + require same distance between the two backbones -> helps make the structure of DNA stable + allows any sequence of bases in genes.
Structure of a nucleosome (A1.2.13)
Nucleosome core = 8 histone proteins (2x4) makes a disc-shaped structure.
DNA wound approx. 2x around core + short linker DNA between adjacent nucleo.
H1 reinforces binding + can help package chromos. when nucleus prepairs to divide.
Evidence from the Hershey–Chase experiment for DNA as the genetic material (A1.2.14)
Viruses contained proteins with radioactive 35S and others that contained DNA with radioactive 32P.
Used blender to separate the non-genetic component of the virus. Then centrifuge -> bacteriophages + bacteria separate through density -> concentrates cells in a pellet.
Measure radioactivity in the pellet and the supernatant.
