Molecular Biology, Genetics, and Genomes

Molecular Biology

• Study of biology at the molecular level.
• Concerned with essential cellular macromolecules like DNA, RNA, and proteins.
• Focuses on the biological pathways between these molecules (replication, transcription, translation).
• Overall biological process involves DNA replicating, DNA to RNA via transcription, and RNA to proteins via translation.

Genetics

• Science focused on the mode of genetic material transmission from one generation to the next.

Genome

• Total genetic material in the nucleus.
• Includes both gene and non-gene coding regions.

Gene

• A unit of hereditary information.
• Sequence of DNA nucleotides that determines a specific phenotypic trait directly or indirectly.

Genotype and Phenotype

• An organism's genetic makeup is its genotype.
• Phenotype is the traits of an organism which are expressed (morphology).

Autosomes

• Chromosomes that are not involved in sex determination.
• Present in pairs in somatic cells.
• Present singly in gametes.

Homologous Chromosomes

• Chromosomes that occur in pairs.
• Have similar morphology (length, centromere position, banding pattern).
• Each member of a pair originates from one parent.
• Contains the same gene loci.
• They meet and segregate during meiosis.

Chromosome Number

• Haploid (1n) refers to a cell having one set of chromosomes only, human gametes are an example.
• Diploid (2n) refers to a cell having two sets of chromosomes, human somatic cells are an example.
• Polyploid (>2n) refers to a cell having more than two sets of chromosomes, example is plant cells.
• Aneuploid is a diploid cell having one or two extra chromosomes and is related to syndromes.

Somatic vs Germ Line Cells

• Somatic cell: any biological cell forming the body of an organism (tissue).
• Germ line cell: the cell at early stages of embryonic development (gametes and zygote).

Alleles

• One of the alternative forms of a gene.
• Occupies a corresponding locus on homologous chromosomes.

Homozygous vs Hemizygous

• Homozygous alleles: the state of an organism possessing two identical alleles on one or more loci.
• Hemizygous: the state of an organism possessing only one allele (usually on sex chromosomes).

Heterozygous

• Heterozygous alleles: the state of an organism possessing different alleles at one or more loci.

Allele Expression

• Dominant allele: can express itself over another allele (PRODUCE PROTEIN).
• Recessive allele: cannot express itself when a dominant allele is present (ABSENCE OF PROTEIN).

Codominance

• Both alleles of a pair are fully expressed in the heterozygous state (ABO system).
• Leads to the production of two different proteins.

Wild Type vs Mutant

• Wild type: an individual has a normal phenotype (most common phenotype).
• Mutant: an individual with a phenotype that differs from the normal phenotype due to gene mutation which can become recessive or give abnormal protein).

Tumors and Cancer

• Mutagen: an agent (physical, chemical, biological) that causes mutation.
• Carcinogen: a mutagen, if the mutation occurs to genes that control cell division and ends up with a tumor.
• Benign tumors have localized cells.
• Malignant tumor : if the cells can move to different sites (metastasis equates to cancer).
• Not all benign tumors are friendly, depends on location.