DNA Structure Flashcards
What are the building blocks of nucleic acids?
Nucleotides
Nucleotides are formed of phosphates, ribose/deoxyribose, and nitrogenous bases.
What is a polymer of nucleotides called?
Nucleic acids
What is the structure of Deoxyribonucleic Acid (DNA)?
Usually a double helix made up of two chains of deoxyribonucleotides
What is Ribonucleic Acid (RNA) typically composed of?
Usually a single-stranded chain of ribonucleotides
List the core bases found in DNA.
- Guanine (G)
- Cytosine (C)
- Adenine (A)
- Thymine (T)
List the core bases found in RNA.
- Guanine (G)
- Cytosine (C)
- Adenine (A)
- Uracil (U)
What type of bond connects each nucleotide in nucleic acids?
Phosphodiester bonds
What are the free ends of a nucleic acid chain called?
- Free 5’ end
- Free 3’ end
True or False: DNA is double-stranded while RNA is mostly single-stranded.
True
Which base pairing is stronger in DNA, G:C or A:T?
G:C bonding is stronger than A:T
GC = 3 hydrogen bonds
AT = 2 hydrogen bonds
What structural feature helps form the DNA double helix?
Complementary hydrogen bonds
Reinforced by the sugar phosphat ebackbone and complementary bases.
What is the approximate length of genomic DNA in a mammalian genome?
~2 meters long
What is the diameter of the nucleus in which DNA is packaged?
6-10 microns
What protein is genomic DNA packaged around?
Histones
How many types of histone sub-units are critical for the histone octamer?
4 types
What is the composition of a histone octamer?
- 2x Histone H2A
- 2x Histone H2B
- 2x Histone H3
- 2x Histone H4
How many base pairs of DNA are wrapped around the histone octamer?
147 bp
What is formed when DNA wraps around histones?
Nucleosome
What is the range of linker DNA between nucleosomes?
~10-80 bp
What histone binds to each nucleosome?
H1 histone
What structure is formed by multiple stacked nucleosomes?
30 nm fibre (or solenoid fibre)
What term is used to refer to the nucleosomes made of DNA and histones?
Chromatin
What is the final condensed structure of chromatin called?
Chromosomes
How does the condensed nature of chromatin impact gene expression?
It is variable and impacts gene expression.
What are the effects of additions of methyl groups and acyl groups to histones?
Impact chromatin and gene expression
These modifications can influence the accessibility of DNA for transcription and other processes.
What diseases are targeted for drug development in relation to DNA packaging?
Parasites like Fasciola hepatica and cancer
This highlights the importance of DNA packaging mechanisms in both health and disease.
What is the cancer incidence rate in male dogs?
99.3 per 100,000
This statistic provides insight into the prevalence of cancer in canine populations.
What is the cancer incidence rate in female dogs?
272.1 per 100,000
This indicates a significantly higher incidence of cancer in female dogs compared to males.
Why is DNA replication necessary?
To produce more cells and offspring
DNA replication is essential for growth, development, and reproduction.
What is the most important enzyme in DNA replication?
DNA polymerase
DNA polymerase synthesizes new DNA strands during replication.
In which direction does DNA replication occur?
From 5’ to 3’ end
This directional nature is crucial for the fidelity of DNA replication.
What initiates DNA replication?
Origin of replication
This is the specific location on the DNA where replication begins.
What is the function of helicases?
Aid in the unwinding of DNA at replication forks
Unwinding is necessary to allow access to the DNA strands for replication.
What is the role of primase in DNA replication?
Synthesizes short RNA sequences called primers
Primers are essential for initiating DNA synthesis.
What is the role of DNA gyrase?
Prevents supercoiling during DNA replication
This enzyme is crucial for maintaining the structure of DNA as it replicates.
What distinguishes prokaryotic DNA gyrase from eukaryotic topoisomerases?
Quinolones target bacterial DNA gyrases
This difference is exploited in antibiotic treatments.
What is PCR?
An amplification technique of DNA
PCR is widely used in various applications, including diagnostics and research.
List the main components required for PCR.
- Template DNA
- Free dNTPs (dATP, dGTP, dCTP, dTTP)
- 2 specific primers (18-25 bases long)
- Taq polymerase
- Buffer
Each component plays a vital role in the PCR process.
What is the first step in the PCR process?
Heat DNA to 94°C to separate the strands (denature)
Denaturation is necessary to allow the primers to anneal to the single-stranded DNA.
What happens during the annealing step of PCR?
Cool DNA to ~60°C to allow primers to anneal
This step ensures that primers bind specifically to the target DNA sequences.
What is the temperature for DNA polymerization during PCR?
72°C
This is the optimal temperature for Taq polymerase activity.
How does PCR help in veterinary diagnostics?
Used to determine infections (species, strain, etc.)
PCR provides a rapid and specific method for identifying pathogens.
What is the purpose of running a PCR mix on an agarose gel?
To separate by size and visualize the presence/absence of DNA
Gel electrophoresis allows for the analysis of PCR products.
