DNA Replication (unit 16) Flashcards
(25 cards)
What is the primary genetic material in organisms?
DNA
DNA is the molecule responsible for heredity and genetic information in living organisms.
Who first demonstrated that genes are located on chromosomes?
T. H. Morgan
Morgan’s work helped establish the relationship between genes and chromosomes.
What phenomenon describes the change in genotype and phenotype due to assimilation of foreign DNA?
Transformation
This term was introduced by Frederick Griffith in his experiments with bacteria.
What did Frederick Griffith study to discover the role of DNA?
Bacteria and viruses that infect them
Griffith’s experiments involved pathogenic and harmless strains of bacteria.
What type of viruses infect bacteria?
Bacteriophages (or phages)
These viruses are significant tools in molecular genetics research.
What did Hershey and Chase demonstrate about phages?
DNA is the genetic material of the phage known as T2
Their experiments showed that only DNA enters E. coli during infection.
What are the four nitrogenous bases found in DNA?
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
These bases pair specifically in the DNA structure.
What are Chargaff’s rules?
- Base composition of DNA varies between species
- In any species, the number of A and T bases is equal, and the number of G and C bases is equal
These rules reflect the specific pairing of DNA bases.
What technique did Franklin and Wilkins use to study the structure of DNA?
X-ray crystallography
This technique allowed them to produce images of the DNA molecule.
What is the structural shape of DNA as determined by Watson and Crick?
Double helix
The double helix structure is crucial for understanding DNA’s function in heredity.
What is the semiconservative model of DNA replication?
Each daughter molecule has one old strand and one newly made strand
This model was supported by Meselson and Stahl’s experiments.
What initiates DNA replication?
Origins of replication
These are specific sites where the DNA strands are separated.
What are replication forks?
Y-shaped regions where parental DNA strands are unwound
They are crucial for the replication process.
What is the role of helicases in DNA replication?
Untwist the double helix at the replication forks
Helicases are essential for separating the DNA strands.
What is the function of DNA polymerases?
Catalyze the synthesis of new DNA strands
They require a primer and a template strand to add nucleotides.
What are Okazaki fragments?
Segments of the lagging strand synthesized during DNA replication
They are joined together by DNA ligase.
What is mismatch repair?
Repair enzymes replace incorrectly paired nucleotides
This process helps maintain DNA integrity.
What are telomeres?
Special nucleotide sequences at the ends of eukaryotic chromosomes
They help postpone the erosion of essential genes during replication.
What enzyme catalyzes the lengthening of telomeres in germ cells?
Telomerase
This enzyme is important for maintaining chromosome length in reproductive cells.
What is chromatin?
DNA combined with proteins in eukaryotic cells
Chromatin plays a key role in gene regulation and packaging DNA.
What are histones?
Proteins responsible for the main level of DNA packing
They form nucleosomes, which are fundamental units of chromatin structure.
What is euchromatin?
Loosely packed chromatin during interphase
This form of chromatin is accessible for gene expression.
What is heterochromatin?
Highly condensed chromatin that is not actively expressed
It is typically found at centromeres and telomeres.
What happens to chromatin during mitosis?
It condenses into short, thick metaphase chromosomes
This organization is crucial for proper chromosome segregation.
