Chapter 11 Flashcards
What are the two important cellular functions of DNA?
- It is the genetic material passed from parent to offspring
- It serves as the information to direct and regulate the construction of the proteins necessary for the cell to perform all of its functions
What is the central dogma?
A theory that states that DNA organized into genes specifies the sequence of mRNA which specifies the amino acid sequence of proteins.
What does it mean to say that DNA replication is semiconservative?
Each DNA molecule has one parental strand of DNA and one newly synthesized strand.
How does replication start in bacteria?
The initiation of replication occurs at the origin of replication, where supercoiled DNA is unwound by topoisomerase II, made single stranded by helicase breaking the hydrogen bonds.
What happens during elongation?
RNA primer provides a free 3’-OH group to which DNA polymerase III can add DNA nucleotides.
What happens during elongation?
The leading strand (3’ to 5’ outside to inside) of DNA is synthesized continuously from a single primer. The lagging strand (5’ to 3’ inside to out) is synthesized discontinuously in short Okazaki fragments, each requiring its own primer. The RNA primers are removed and replaced with DNA nucleotides by bacterial DNA polymerase I, and DNA ligase seals the gaps.
What happens in termination?
Involves the resolution of circular DNA concatemers by topoisomerase IV to release the two copies of the circular chromosome.
How does replication in eukaryotes differ from that in prokaryotes?
Eukaryotes typically have multiple linear chromosomes, each with multiple origins of replication. Overall, replication in eukaryotes is similar to that in prokaryotes.
What are telomeres?
A region of repetitive DNA sequences at the end of a chromosome that protects them.
What is telomerase?
It extends telomeres, preventing their degradation, in some cell types.
What happens during transcription?
The information encoded in DNA is used to make RNA.
What does RNA polymerase do?
RNA polymerase adds nucleotides one by one to the 3’-OH group of the growing nucleotide chain.
How does initiation of transcription work?
The initiation of transcription begins at a promoter, a DNA sequence onto which the transcription machinery binds and initiates transcription.
Initiation.
How does elongation during transcription work?
As elongation proceeds, the DNA is continuously unwound ahead of the core enzyme and rewound behind it.
How does termination during transcription work?
Once a gene is transcribed, the bacterial polymerase must dissociate from the DNA template and liberate the newly made RNA.
