Genetics VI

Sexual Reproduction

The process of creating and maintaining genetic diversity through the combination of genetic material from two parents.

Asexual Reproduction

A type of reproduction that does not involve the fusion of gametes and often results in offspring that are genetic clones of the parent.

Heterogametic Sex

The sex that has two different sex chromosomes (e.g., XY in mammals).

Homogametic Sex

The sex that has two of the same sex chromosomes (e.g., XX in mammals).

SRY Gene

The Sex Determining Region of the Y chromosome responsible for male sex determination.

Sex Determination

The biological process by which the development of sexual characteristics is directed and established, including the formation of either male or female patterns.

Sexual Differentiation

The subsequent development of the sexual characteristics and structures following sex determination.

Klinefelter Syndrome

A genetic condition in males caused by an extra X chromosome (XXY), leading to characteristics such as infertility.

Turner Syndrome

A genetic condition in females characterized by the absence of one X chromosome (X0), which may result in infertility.

Androgens

Hormones that play a role in male traits and reproductive activity, with testosterone being a primary example.

Estrogens

Hormones that play a role in female traits and reproductive activity, with estradiol being a primary example.

Disorders of Sexual Development (DSDs)

Conditions caused by mutations in genes related to sex determination and steroid hormone synthesis, leading to reproductive and sexual development issues.

Indifferent Gonad

The embryonic structure from which either testes or ovaries develop, characterized by the lack of distinct male or female features until sex determination.

Genital Ridge

The embryonic structure that will develop into the indifferent gonad and contains somatic gonadal precursor cells.

Testosterone

A steroid hormone produced primarily in males that drives the development of male reproductive tissues and secondary sexual characteristics.

Estradiol and Progesterone

Steroid hormones produced primarily in females that drive the development of female reproductive tissues and secondary sexual characteristics.

Wolffian Duct

The embryonic duct that develops into male reproductive structures (vas deferens) in the presence of testosterone.

Mullerian Duct

The embryonic duct that develops into female reproductive structures (oviduct) in the absence of testosterone.

Cholesterol

A type of lipid that serves as a precursor for the biosynthesis of steroid hormones.

Transcription Factor

A protein that binds to specific DNA sequences, regulating the expression of nearby genes.

Sex-specific Gonads

Gonads (ovaries or testes) that produce sex-specific hormones and influence sexual differentiation and reproductive development.

Brief history of banana cultivation

Bananas have been cultivated for thousands of years, originating in Southeast Asia. Modern cultivars are primarily clones, resulting from vegetative propagation, leading to genetic uniformity among commercial banana plants.

Panama disease

A devastating fungal disease caused by the pathogen Fusarium oxysporum f.sp. cubense, impacting banana crops, especially the Cavendish variety, due to their genetic homogeneity.

Genetic identity and infectious disease susceptibility

The genetic identity of host species increases vulnerability to diseases, as pathogens can easily adapt to a uniform genetic makeup. In contrast, genetic diversity enhances resilience against infectious diseases.

Red Queen Hypothesis

The Red Queen Hypothesis posits that organisms must constantly evolve to survive in a changing environment and to keep up with co-evolving pathogens and predators, likened to running in place to stay in the same place.

Pathogen evolution compared to hosts

Pathogens can evolve more quickly than their hosts due to their shorter generation times and higher mutation rates, leading to rapid adaptation. Examples of human pathogens that have evolved include strains of influenza and antibiotic-resistant bacteria.