final Flashcards
(30 cards)
Who discovered DNA and when?
Friedrich Miescher in 1869.
What is a genome?
An organism’s entire genetic information, primarily composed of DNA (or RNA in some viruses).
State the Central Dogma of Molecular Biology.
DNA → RNA → Protein. It describes how genetic information flows from DNA to RNA via transcription, and from RNA to protein via translation.
What are nucleic acids polymers of?
Nucleotides (they are also called polynucleotides).
What are the three main components of a nucleotide?
A five-carbon sugar, one or more phosphate groups, and a nitrogenous base.
Name the major pyrimidine bases found in nucleic acids.
Uracil (U), Thymine (T), and Cytosine (C).
Name the major purine bases found in nucleic acids.
Adenine (A) and Guanine (G).
What is a nucleoside?
A ribose or deoxyribose sugar linked to a heterocyclic base (without the phosphate group).
How are deoxyribonucleotide residues linked together in a DNA strand?
By 3’–5’ phosphodiester bonds.
Describe the specific base pairing rules in DNA.
Adenine (A) pairs with Thymine (T) via two hydrogen bonds, and Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.
What does “antiparallel” mean in the context of DNA strands?
The two polynucleotide strands in a DNA double helix run in opposite orientations; one strand runs 5’ to 3’, and the complementary strand runs 3’ to 5’.
What is B-DNA, and list two of its key features.
B-DNA is the common, most prevalent form of DNA found in living cells. Features include: it’s a right-handed helix, has about 10.4 base pairs per turn, and possesses major and minor grooves.
What is DNA denaturation?
The complete unwinding and separation of the double-stranded DNA into two single strands, typically caused by increasing heat or exposure to certain chemicals.
What is the melting point (Tm) of DNA?
The specific temperature at which half of the double-stranded DNA molecules in a sample have become single-stranded due to denaturation.
How does the G-C content of DNA affect its melting temperature (Tm)?
DNA with a higher G-C content has a higher melting temperature because G-C base pairs are stabilized by three hydrogen bonds, whereas A-T pairs only have two, making G-C bonds stronger.
What is chromatin?
The complex of DNA and proteins (primarily histones) that packages DNA within the nucleus of eukaryotic cells.
What is a nucleosome?
The basic unit of chromatin, consisting of approximately 200 base pairs of DNA wrapped around an octamer of eight histone proteins (two each of H2A, H2B, H3, and H4).
Name the three main types of RNA molecules and their primary functions.
Messenger RNA (mRNA) - carries genetic information from DNA to ribosomes for protein synthesis; Ribosomal RNA (rRNA) - forms the structural and catalytic core of ribosomes; Transfer RNA (tRNA) - carries specific amino acids to the ribosome during protein synthesis.
Define transcription.
The process by which the genetic information stored in a segment of DNA is copied into an RNA molecule.
Where do transcription and translation occur in eukaryotes versus prokaryotes?
In eukaryotes, transcription occurs in the nucleus, and translation occurs in the cytoplasm. In prokaryotes, both transcription and translation occur in the cytoplasm.
What enzyme is responsible for catalyzing DNA-directed RNA synthesis (transcription)?
RNA polymerase.
What is an operon, and in which type of cell is it typically found?
An operon is a unit where multiple genes are under the control of a single promoter and are transcribed together into a single mRNA molecule. They are typically found only in prokaryotes (e.g., the lac operon).
List two major post-transcriptional modifications that occur in eukaryotic mRNA.
Splicing (removal of introns and rejoining of exons), 5’ capping (addition of a 7-methylguanosine cap to the 5’ end), and 3’ polyadenylation (addition of a poly-A tail to the 3’ end). (Any two are sufficient).
Differentiate between exons and introns.
Exons are the DNA sequences that contain the coding information for proteins, while introns are non-coding DNA sequences that are removed from the pre-mRNA during splicing.
