The word “gene” was coined by geneticist Wilhelm Johannsen in 1909 to simply describe what parents passed to their offspring. The detailed structure of DNA associated with genes was discovered much later.
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Definitions [6]
Define the following term:
Gene
Genes are specific sequences of nucleotides on a chromosome that encode particular proteins which are expressed in the form of some particular feature of the body. They are the units of heredity which are transferred from parents to offspring and are responsible for some specific characteristics of the offspring.
Definition: Genome
GENOME is the full complement of DNA (including all genes and the intergenic regions) of an organism.
Definition: Genes
Genes are specific sequences of nucleotides on a chromosome, that encode particular proteins which are expressed in the form of some particular feature of the body.
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GENES are the specific parts (DNA segments) of a chromosome, which determine the hereditary characteristics.
Definition: Genetics
Genetics is the study of heredity i.e. transmission of body features (both similarities and differences) from parents to offspring and the laws relating to such transmission.
Definition: Monohybrid Experiments
Mendel's first experiments were with the varieties of garden pea that differed in only one visible character. These are known as monohybrid experiments.
Definition: Mutation
Mutation is a sudden change in one or more genes, or in the number or in the structure of chromosomes.
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Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism.
Key Points
Key Points: Molecular Structure of DNA
1. DNA structure was first studied by Rosalind Franklin (1953); later explained by Watson and Crick, who proposed the double helix model (Nobel Prize, 1962).
2. DNA is a macromolecule made of two complementary strands twisted into a double helix.
3. Each strand is made up of nucleotides, which include phosphate, sugar (pentose), and a nitrogenous base.
4. There are four nitrogenous bases:
- Adenine (A) pairs with Thymine (T) (2 hydrogen bonds)
- Guanine (G) pairs with Cytosine (C) (3 hydrogen bonds)
5. The two strands form a ladder-like structure, with bases as rungs and sugar-phosphate as the backbone.
