Introduction to Heredity and Mendelian Genetics

Introduction to Heredity

• Heredity is the passing of traits from parents to offspring.
• These traits are determined by genes, which are segments of DNA.
• Genes hold the instructions for creating proteins which code for different traits.
• This process is fundamental to biological diversity and evolution.

Mendelian Genetics

• Gregor Mendel's experiments with pea plants established the basic principles of heredity.
• His findings led to the understanding of dominant and recessive alleles.
• Dominant alleles express their trait even when paired with a recessive allele.
• Recessive alleles only express their trait when paired with another recessive allele.
• Mendel's work demonstrated patterns of inheritance within families.
• These patterns help predict the likelihood of specific traits within offspring.

Chromosomes and Genes

• Chromosomes are structures within cells containing genetic material (DNA).
• Chromosomes carry genes in a linear arrangement.
• Humans have 23 pairs of chromosomes, one set inherited from each parent.
• Autosomes are non-sex chromosomes and are numbered 1-22.
• Sex chromosomes determine the sex of an individual (XX for female, XY for male).

Gene Expression

• Genes influence traits but do not directly create them.
• Gene expression is the process by which information encoded in a gene is used to synthesize a functional gene product (protein).
• This process is highly complex and regulated at several levels within a cell.
• Environmental factors can also influence gene expression.

Genetic Variation

• Genetic variation exists within populations due to differences in alleles.
• This variation is crucial for natural selection and adaptation to changing environments.
• Mutations are changes in DNA sequence and can introduce new alleles.
• Genetic recombination during meiosis further shuffles existing alleles.
• A variety of sources of genetic variation are constantly at play.

Patterns of Inheritance

• Inheritance patterns can be observed in pedigrees which track phenotypes within generations of a family.
• Autosomal dominant disorders affect individuals with one or more dominant alleles.
• Autosomal recessive disorders require two copies of the recessive allele to affect individuals.
• Sex-linked inheritance patterns like hemophilia affect one or more of the sex chromosomes.
• Complex patterns of inheritance involve interactions between multiple genes.

Modern Genetic Techniques

• Modern genetic techniques allow for the analysis of entire genomes.
• DNA sequencing reveals the order of bases within an organism's DNA.
• Genetic testing can identify genetic variations associated with specific diseases.
• This knowledge can guide personalized treatment strategies.

Genetic Disorders

• Genetic disorders are caused by mutations in genes.
• Genetic testing plays a crucial role in identifying these disorders.
• Many types of genetic disorders may include: cystic fibrosis, sickle-cell anemia, Huntington's disease.
• These disorders can have a wide range of effects and severity.
• Genetic counseling can provide support and information regarding these disorders.

Applications of Heredity

• Understanding heredity is crucial for agricultural sciences (e.g. selective breeding for livestock).
• Modern medicine utilizes heredity principles and genetic engineering to treat and cure diseases, including CRISPR-Cas9 gene editing technology.