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Nature of the gene and the genome
Introduction: The evolution of the concept of gene
The concept of gene has evolved significantly throughout the history of biology.
Initially, they were considered hereditary factors that passed from generation to generation, but the
advancement of knowledge led to the discovery that these factors resided in the chromosomes
and were made up of DNA.
The genome, understood as the total set of genetic information of a species, contains all the genes
necessary for the construction and functioning of an organism.
Over the past few decades, whole-genome sequencing has made it possible to compare human evolution
with other organisms, such as the chimpanzee, our closest living relative. This has made it possible to
reconstruct the genetic trajectory of human evolution, identifying regions of the genome that
have undergone duplications, losses, or adaptive changes due to natural selection.
10.1 Concept of Gene as a Unit of Inheritance
The study of inheritance began with the experiments of Gregor Mendel in the 19th century.
Mendel worked with peas, identifying patterns of trait transmission across generations. His fundamental
principles include:
1. Inheritance factors (genes): Each organism has two copies of a gene, one of each
progenitor.
2. Dominance and recessiveness: Some alleles can mask the expression of others.
3. Segregation: Alleles separate to form gametes.
4. Independent permutation: The transmission of one allele does not affect that of another.
These principles were later confirmed with the discovery of chromosomes, identifying them as the
physical carriers of genes.
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10.2 Chromosomes: Physical Carriers of Genes
The discovery of chromosomes in the 19th century was crucial to understanding the physical basis of inheritance. It
was identified that nuclear material, organized into chromosomes, is divided equally among daughter cells during
mitosis. This confirmed that chromosomes contain genetic information necessary for cell development and function.
Key advances include:
Observation of the fertilization process, where the male and female gametes contribute equivalent
chromosomes.
Discovery of homologous chromosomes, similar pairs inherited from each parent.
Chromosomal theory of inheritance, postulated by Walter Sutton, who related chromosomal segregation
to Mendelian principles.
Experiments on Drosophila melanogaster (fruit fly) conducted by Thomas Morgan confirmed the existence of
linkage groups, showing that genes located on the same chromosome are inherited together. However,
crossing over, a process in which homologous chromosomes exchange segments, allowing for
genetic recombination, was identified .
10.3 Chemical Nature of the Gene
DNA is the genetic material that makes up genes. Its structure was elucidated by James Watson and Francis Crick in
1953, based on X-ray diffraction data obtained by Rosalind Franklin. The double helix model revealed the
following principles:
Nitrogenous bases (adenine, thymine, guanine and cytosine) that form complementary pairs.
Antiparallel chains, with a sugar-phosphate backbone.
Supercoiling, a DNA compaction mechanism, regulated by topoisomerases.
10.4 Structure of the Genome
Nature of the gene and the genome
Introduction: The evolution of the concept of gene
The concept of gene has evolved significantly throughout the history of biology.
Initially, they were considered hereditary factors that passed from generation to generation, but the
advancement of knowledge led to the discovery that these factors resided in the chromosomes
and were made up of DNA.
The genome, understood as the total set of genetic information of a species, contains all the genes
necessary for the construction and functioning of an organism.
Over the past few decades, whole-genome sequencing has made it possible to compare human evolution
with other organisms, such as the chimpanzee, our closest living relative. This has made it possible to
reconstruct the genetic trajectory of human evolution, identifying regions of the genome that
have undergone duplications, losses, or adaptive changes due to natural selection.
10.1 Concept of Gene as a Unit of Inheritance
The study of inheritance began with the experiments of Gregor Mendel in the 19th century.
Mendel worked with peas, identifying patterns of trait transmission across generations. His fundamental
principles include:
1. Inheritance factors (genes): Each organism has two copies of a gene, one of each
progenitor.
2. Dominance and recessiveness: Some alleles can mask the expression of others.
3. Segregation: Alleles separate to form gametes.
4. Independent permutation: The transmission of one allele does not affect that of another.
These principles were later confirmed with the discovery of chromosomes, identifying them as the
physical carriers of genes.
, Machine Translated by Google
10.2 Chromosomes: Physical Carriers of Genes
The discovery of chromosomes in the 19th century was crucial to understanding the physical basis of inheritance. It
was identified that nuclear material, organized into chromosomes, is divided equally among daughter cells during
mitosis. This confirmed that chromosomes contain genetic information necessary for cell development and function.
Key advances include:
Observation of the fertilization process, where the male and female gametes contribute equivalent
chromosomes.
Discovery of homologous chromosomes, similar pairs inherited from each parent.
Chromosomal theory of inheritance, postulated by Walter Sutton, who related chromosomal segregation
to Mendelian principles.
Experiments on Drosophila melanogaster (fruit fly) conducted by Thomas Morgan confirmed the existence of
linkage groups, showing that genes located on the same chromosome are inherited together. However,
crossing over, a process in which homologous chromosomes exchange segments, allowing for
genetic recombination, was identified .
10.3 Chemical Nature of the Gene
DNA is the genetic material that makes up genes. Its structure was elucidated by James Watson and Francis Crick in
1953, based on X-ray diffraction data obtained by Rosalind Franklin. The double helix model revealed the
following principles:
Nitrogenous bases (adenine, thymine, guanine and cytosine) that form complementary pairs.
Antiparallel chains, with a sugar-phosphate backbone.
Supercoiling, a DNA compaction mechanism, regulated by topoisomerases.
10.4 Structure of the Genome
