What is DNA?
DNA is the molecule that carries genetic information in living organisms.
DNA stands for deoxyribonucleic acid.
What is a nucleotide?
A nucleotide is the basic building block of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.
Nucleotides are linked together to form the DNA or RNA strand.
What are purines?
Purines are a type of nitrogenous base found in nucleotides, specifically adenine (A) and guanine (G).
Purines have a double-ring structure.
What are pyrimidines?
Pyrimidines are a type of nitrogenous base found in nucleotides, specifically cytosine (C), thymine (T), and uracil (U).
Pyrimidines have a single-ring structure.
What is a gene?
A gene is a segment of DNA that contains the instructions for building a specific protein or set of proteins.
Genes are the functional units of heredity.
What is a genome?
A genome is the complete set of genetic material in an organism, including all of its genes.
The human genome contains approximately 20,000-25,000 genes.
What are sister chromatids?
Sister chromatids are identical copies of a chromosome that are joined together by a common centromere.
They are formed during DNA replication.
What is RNA?
RNA, or ribonucleic acid, is a molecule that plays a crucial role in the synthesis of proteins and can also serve as genetic material in some viruses.
RNA is typically single-stranded.
What are histones?
Histones are proteins that help package and organize DNA into structural units called nucleosomes.
Histones play a key role in gene regulation.
What is helicase?
Helicase is an enzyme that unwinds the DNA double helix during DNA replication.
This process is essential for allowing the replication machinery to access the DNA strands.
What does semiconservative replication mean?
Semiconservative replication is the process by which DNA is replicated in such a way that each new DNA molecule contains one original strand and one newly synthesized strand.
This method ensures genetic continuity.
What is cytokinesis?
Cytokinesis is the process that divides the cytoplasm of a parental cell into two daughter cells after mitosis.
It usually occurs simultaneously with telophase.
What are the base pairing rules of DNA?
The base pairing rules state that adenine pairs with thymine and cytosine pairs with guanine.
These rules are critical for the structure of DNA.
What are the differences between DNA and RNA?
Differences include:
* DNA is double-stranded; RNA is single-stranded
* DNA contains thymine; RNA contains uracil
* DNA has deoxyribose sugar; RNA has ribose sugar.
These differences affect their functions in the cell.
What are the steps of DNA replication?
The steps include:
* Unwinding the DNA double helix by helicase
* Synthesizing new strands by DNA polymerase
* Joining Okazaki fragments on the lagging strand.
Each step is crucial for accurate DNA duplication.
What are the phases of the cell cycle?
The phases include:
* G1 phase: cell growth
* S phase: DNA synthesis
* G2 phase: preparation for mitosis
* M phase: mitosis and cytokinesis.
These phases ensure proper cell division and function.
What are the phases of mitosis?
The phases include:
* Prophase: chromatin condenses into chromosomes
* Metaphase: chromosomes align at the cell’s equator
* Anaphase: sister chromatids separate
* Telophase: nuclear membranes reform.
Mitosis is critical for cell division and growth.
What things trigger a cell to divide?
Triggers include:
* Growth factors
* Nutrient availability
* Cell size.
These factors signal the cell to enter the cell cycle.
What things inhibit a cell from dividing?
Inhibitors include:
* Lack of nutrients
* Contact inhibition
* DNA damage.
These factors prevent uncontrolled cell division.
