Introduction to Heredity and Mendelian Genetics

Study Notes

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 carry the instructions for building and maintaining an organism.
The process of passing genetic information from one generation to the next is central to all life forms.

Mendelian Genetics

Gregor Mendel, through his experiments with pea plants, established the basic principles of heredity.
Mendel's Laws describe how traits are inherited.
The Law of Segregation states that each parent contributes one allele for a trait to their offspring.
The Law of Independent Assortment states that different traits are inherited independently of each other.
Alleles are different forms of a gene.
Dominant alleles mask the expression of recessive alleles when both are present.
Genotype refers to the genetic makeup of an organism.
Phenotype refers to the observable physical traits of an organism.

Types of Inheritance

Monohybrid cross: A cross between parents that differ in only one trait.
Dihybrid cross: A cross between parents that differ in two traits.
Incomplete dominance: neither allele is completely dominant over the other, with the heterozygote expressing an intermediate phenotype (e.g., red and white flowers producing pink flowers).
Codominance: both alleles are expressed equally in the heterozygote (e.g., AB blood type).
Multiple alleles: A gene can have more than two alleles (e.g., human blood type).
Polygenic inheritance: several genes influence a single trait (e.g., human height).
Sex-linked inheritance: genes located on the sex chromosomes (e.g., color blindness).
Sex-limited traits are traits that are present in both sexes but are expressed only in one (e.g., milk production in mammals).
Sex-influenced traits are traits whose expression differs in males and females.

Chromosomes and Genes

Chromosomes are thread-like structures found in the nucleus of cells.
Humans have 23 pairs of chromosomes.
Chromosomes are made up of DNA.
Genes are located on specific positions (loci) on chromosomes.

Gene Mutations

Mutations are changes in the DNA sequence of a gene.
Mutations can be caused by errors during DNA replication or by environmental factors (mutagens).
Mutations can be beneficial, neutral, or harmful, depending on their effect on the organism.

Genetic Disorders

Genetic disorders are caused by mutations in genes.
Some common genetic disorders include cystic fibrosis, sickle cell anemia, and Huntington's disease.
These disorders can affect various aspects of health, from physical function to development.
Genetic counseling can help families understand, assess, and cope with the risk of genetic disorders.

DNA Structure & Function

DNA is a double helix shaped molecule.
The backbone of DNA is composed of sugar and phosphate molecules.
The rungs of the DNA ladder are composed of nitrogenous bases paired together (A with T and G with C).
DNA carries the genetic instructions for building proteins, and all cells and biological processes.
RNA is a single-stranded nucleic acid that plays a crucial role in protein synthesis.

Description

Explore the fundamental concepts of heredity, including the principles established by Gregor Mendel. This quiz covers key terms such as alleles, genotype, and phenotype, as well as the Laws of Segregation and Independent Assortment. Test your knowledge on how genetic traits are passed from parents to offspring.