Genetics: Homozygous and Heterozygous Genotypes

Genotype and Gene Expression

• An organism homozygous at a given locus has two copies of the same allele (e.g., 'BB' and 'bb' are both homozygous genotypes)
• An organism heterozygous at a given locus has two different alleles (e.g., 'Bb' is a heterozygous genotype)
• A dominant trait is expressed in a heterozygous state
• A recessive trait is not expressed in a heterozygous state

Genetic Engineering

• Genetic engineering involves altering an organism's genome using a vector (e.g., plasmid, bacterial chromosome, or virus) to transfer a gene into a host organism
• Plasmids are naturally found in bacteria and are good vectors for transferring DNA into bacteria
• Recombinant DNA is DNA that has sequences from multiple species
• Genetic engineering can produce transgenic organisms (organisms with DNA from different species) and genetically modified organisms (organisms with altered DNA, not necessarily from another species)
• Uses of genetic engineering include agriculture, medicine, research, and commercial applications
• Genetic engineering is controversial due to ethical and environmental concerns

Plasmids

• A plasmid is a small circular DNA molecule separate from the chromosome of a host cell
• Plasmids replicate independently inside a host cell and can be used as cloning vectors
• Construction of plasmids involves using restriction enzymes at restriction sites
• Plasmids have an origin of replication, a selectable marker, and a region for inserting foreign DNA
• Plasmids can be used for gene therapy, creating disease models, protein production, and cloning
• Examples of plasmids include the virulence plasmid in Escherichia coli and Salmonella enterica

Animal Body Plans

• Animal body plans help with the study, classification, and differentiation of animals in evolutionary and developmental biology
• Features that distinguish animal body plans include body symmetry, body cavities, tissues, mouths, and the locations of structures
• Body symmetry can be radial (animal's halves look the same no matter how it's split) or bilateral (animal's halves mirror each other)
• Examples of body plans include coelom, pseudocoelom, and the development of mouth and anus

Kingdom Animalia

• All animals in Kingdom Animalia are multicellular heterotrophs without a cell wall
• Animals can be classified as vertebrates (with a backbone) or invertebrates (without a backbone)
• Vertebrates include fish, amphibians, reptiles, birds, and mammals
• Invertebrates are divided into over 30 phyla and 1.3 million species, with unique features such as digestive chambers instead of complete digestive tracts

Types of Worms

• There are three main types of worms: flatworms, roundworms, and segmented worms
• Flatworms are typically flat in appearance and have one opening in their digestive system
• Roundworms are more rounded in shape and have two openings in their digestive system
• Segmented worms have a segmented body with organ structures in each segment
• Examples of worms include tapeworms, hookworms, and earthworms
• Some worms are parasitic and can infect other organisms, taking nutrients and negatively impacting the host

Learn about the different genotypes in genetics, including homozygous and heterozygous genotypes. Understand the concepts of dominant and recessive traits in organisms.