Biology - Year 9: DNA, Evolution & Heredity

DNA

A long molecule in the nucleus of a cell that contains all of the genetic information for a living organism.

Chromosomes

Thread-like structures located in the nucleus of animal and plant cells, which are made up of proteins and DNA containing hundreds of genes, all connected together.

DNA structure

Contains the base pairs Adenine, Guanin, Cytokine and Thymine, where each base is also attached to a sugar molecule called a nucleotide, in a double helix structure.

Proteins

Large complex molecules that have critical functions in the body, made up of amino acids which are attached to each other in long chains. They are critical for the function, structure and regelation of the body tissues and organs.

Amino acids

They are molecules that combine to form protein and are the building blocks of life as they help the body to function: Grow, repair, organ function, break down, etc.

Essential amino acids

Can't be made by the body, you need to get them from food. There are a total of 9.

Non-essential amino acids

Our bodies can make them.

Conditional amino acids

Usually not essential unless ill/stressed.

Genes

Segments of DNA found in almost every cell's nucleus, containing instructions for making proteins for the cell.

Mitosis

Cell division in which the nucleus divides into nuclei containing the same number of chromosomes.

Meiosis

The special type of cell division that results in cells with half the normal number of chromosomes.

Mutations

A change in the cells genetic material (in genes or chromosomes) due to errors in DNA replications, exposure to UV or just random. They may be transmitted to the nest generations if it occurs in the sex life, which can either benefit the species or harm them.

Allele

Different versions of a gene due to mutations. Can be different versions (like eye color).

Heredity

Passing of traits from parents to offspring.

Genotype

Genetic information an organism has. (UNCHANGING)

Phenotype

Total observable characteristics, including behaviour. (CHANGES)

Dominant allele

Allele which controls the characteristic. You only need one of these present among the chromosomes for it to be "expressed". (AA or Aa)

Recessive allele

Allele whose characteristics which only show up when it is present on both chromosomes. (aa)

Homozygous

Two alleles that are the same (AA or aa)

Heterozygous

Two alleles that are different. (Aa)

Evolution

The change in the physical characteristics (phenotype) of a species over several generations and relies on the process of natural selection.

Germline mutation

Variation in the germ cells (cells that become egg and sperm cell), which is passed to the offspring.

Silent mutations

Are not noticeable but can be passed to the offspring.

Substitution mutations

Wrong bases matched (nitrogen bases).

Deletion mutation

A base is removed (nitrogen base).

Insertion mutation

Extra base/bases are added inside the DNA.

Natural selection

The spreading of a trait due to its usefulness in a natural environment.

Artificial selection

The spreading of a trait due to human involvement, like controlled breeding.

Lamarckism

An idea that when an organism strives to overcome a challenge, new features develop.

Darwinism

The idea that species change and evolve over time due to environmental and genetical factors.