DNA + Protein Synthesis Flashcards
What is the structure of a nucleotide?
A nucleotide consists of a pentose sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, guanine).
What is the difference between RNA and DNA?
- RNA has a hydroxyl group at the 2nd position on the ribose sugar, making it easier to hydrolyze and act as a transport molecule.
- RNA is single-stranded.
- RNA does not contain thymine; it contains uracil, a non-methylated form of thymine, which is an energy-expensive process to form.
What are purines?
Purines are nitrogenous bases with double rings, such as adenine and guanine.
What are pyrimidines?
Pyrimidines are nitrogenous bases with single rings, such as thymine, cytosine, and uracil.
How are nucleotides joined together in DNA and RNA?
Nucleotides are joined by condensation reactions to form phosphodiester bonds, creating the sugar-phosphate backbone between the sugar and phosphate groups.
What is the structure of DNA?
DNA consists of two antiparallel polynucleotide chains held together by hydrogen bonds between complementary base pairs (A-T, C-G). Each strand has a 3’ end and a 5’ end, depending on how the ribose sugar is attached to the next nucleotide. DNA forms a double helix structure.
What is the structure of RNA?
RNA is single-stranded with nitrogenous bases pointing outward from the sugar-phosphate backbone. It includes mRNA, tRNA (has a specific anticodon which binds to a complementary codon on mRNA and amino acids also bind to this molecule), and rRNA.
What is semi-conservative replication?
In semi-conservative replication, the new DNA molecule contains one strand of the original DNA and one newly replicated strand. This ensures genetic continuity and that new cells inherit all genes from parent cells meaning it is important for the regular replacement and growth of cells.
Why is semi-conservative replication important?
It ensures genetic continuity, guarantees that new cells inherit all genes from parent cells, and allows for regular replacement and growth of cells.
What is the process of semi-conservative DNA replication?
- Helicase unwinds the double helix and separates the strands by breaking hydrogen bonds between bases
- Single polynucleotide strands act as templates for new strands, attracting free nucleotides to exposed DNA bases through complementary base pairing.
- Free nucleotides (nucleoside triphosphates) are activated by extra phosphate, align with the template strand, and DNA polymerase cleaves off the extra phosphate to form the sugar-phosphate backbone by using energy from this process.
- DNA polymerase synthesizes the leading strand from 3’ to 5’. On the lagging strand, DNA is synthesized in fragments (Okazaki fragments) from 5’ to 3’, which are joined by DNA ligase through condensation reactions.
- The old and new strands join together to form the new DNA molecule, which coils automatically due to weak hydrogen bonds.
What does the experiment with isotopes Nitrogen-15 and Nitrogen-14 prove?
The experiment showed that when bacterial DNA is replicated in Nitrogen-15 and then in Nitrogen-14 for one cycle, the DNA settles in the middle of a centrifuge, proving that replication is semi-conservative.
How is DNA precipitated?
DNA can be precipitated using the Marmar preparation method, which involves lysing cells, disrupting the nuclear membrane to release DNA, using enzymes to denature histones, and then precipitating DNA using an organic solvent like ethanol.
Where is DNA located in the cell and how is it structured?
DNA is located in the nucleus and is associated with histones, forming a dense network of chromatin in chromosomes. The ends of chromosomes are capped by telomeres.
What is transcription and where does it occur?
Transcription occurs in the nucleus, where helicase breaks hydrogen bonds between the DNA strands. The exposed gene is transcribed from the template strand into a complementary mRNA strand by free RNA nucleotides, with the RNA polymerase forming the sugar-phosphate backbone.
What happens after transcription of mRNA?
Once transcription is complete, the hydrogen bonds between the mRNA and the original DNA strand break, and the DNA rewinds. The mRNA then leaves the nucleus through a nuclear pore.
