Unit 3: Variation and Mutation

Mutation

A change to a person’s nucleotide sequence, which causes a change in their DNA and possibly their proteins.

Genetic Variation

The diversity of alleles and phenotypes within a population, which allows specific species to adapt to environments.

Sexual Reproduction

The process by which offspring are produced from two parents.

Asexual Reproduction

The process by which offspring are produced from just one parent, resulting in the offspring being genetically identical to the parent.

Point Mutation

A change to a single DNA letter (nucleotide).

Missense Mutation

A mutation that changes one nucleotide to another, causing a change in the resulting protein.

Nonsense Mutation

A mutation that makes a premature “STOP” codon, resulting in a protein that isn’t finished or non-functional.

Silent Mutation

Codes for the same amino acid as before. There are no effective results.

Frameshift Mutations

Mutations that shift the 'reading frame' of the genetic code, changing every amino acid that follows after the mutation.

Insertion Mutation

Insertion of another nucleotide, resulting in any codons after the mutation to be shifted by one nucleotide.

Deletion Mutation

Deletion of a nucleotide, resulting in any codons after shifting left as one nucleotide is lost.

Universal Genetic Code

All living organisms read genes in the same way, allowing the same gene expression and translation of the genetic code.

Germline Mutation

Mutations that happen in the sex cells and can be passed onto offspring.

Somatic Mutation

Mutations that happen anywhere except the sex cells, meaning they will not be passed on.

Alleles

Different versions or forms of the same genes.

Dominant Allele

An allele that is expressed if an organism only has one copy (e.g. Bb, BB).

Recessive Allele

An allele only expressed if an organism has two copies (e.g., bb). Its trait is hidden if the dominant allele is present.

Karyogram

A diagram to show a human’s complete set of chromosomes, totaling 23 pairs.

Homologous Chromosomes

A pair of chromosomes that are almost identical in size, code, and shape.

Meiosis

A type of cell division that reduces the chromosome number by half to produce haploid gametes (sperm and egg) for sexual reproduction.

Mitosis

The process of cell division for growth and repair, where one parent divides to produce two genetically identical daughter cells.

Chromosomes

Thread-like structures located in the nucleus made of DNA and proteins; they contain the specific genes passed from parents to offspring.