Cells

The base that combines with thymine to form a base pair

A version of a gene An organism gets two alleles of each gene – one from its mother and one from its father.

A small molecule that joins with others to form proteins Amino acids are the building blocks of proteins, which are the building blocks of cells.

A stage of cell division in which the chromosomes separate Anaphase is when the chromosomes separate and are pulled away from each other to opposite sides of the cell.

Part of a DNA molecule that comes in four types: A, C, G and T Bases join together in pairs to form the ‘rungs’ of the DNA molecule.

Two bases joined together Base pairs form in only two combinations: AT or G-C. These are the letters that make up the genetic code.

The repeated process of cell growth and division During most of the cell cycle, a cell grows and performs its function. This ends when the cell divides by mitosis

The splitting of a cell to form new cells Cell division allows organisms to grow, repair damage and reproduce. There are two types: mitosis and meiosis.

A DNA molecule that condenses during cell division Most human cells contain 46 chromosomes but sex cells only contain 23 chromosomes.

The swapping of genes between chromosomes in a homologous pair Crossing over only occurs in meiosis, during prophase I. It increases the genetic variety of the sex cells produced.

The base that combines with guanine to form a base pair Cytosine is one of the four letters that make up the genetic code in humans and other living things.

Any new cell formed by cell division Each daughter cell has its own nucleus and set of DNA.

A molecule that contains genetic information DNA, or deoxyribonucleic acid, is a very large molecule that contains instructions for building proteins.

A version of a gene that is expressed even when only one copy is present A dominant allele is represented by an uppercase letter. Yy or YY will result in the appearance of the Y trait.

A feature that appears when at least one allele is present Dominant traits include freckles, dimples and the ability to roll your tongue.

A structure consisting of two chains twisted around each other The DNA molecule has a double helix structure. The ‘rungs’ connecting the two chains are base pairs.

The joining of an egg and a sperm to form a new organism Fertilization combines DNA from the mother and father so the child gets half of its chromosomes from each parent.

A unit of genetic information A gene is a section of a DNA molecule that provides instructions for building a specific protein.

Members of a family that are born and live at about the same time Traits are passed down from one generation to the next by the transfer of DNA from parents to children.

A pair of alleles that influence the appearance of a particular trait A genotype is represented by two letters. An organism’s genotype determines which traits it acquires – its phenotype.

The base that combines with cytosine to form a base pair Guanine is one of the four letters that make up the genetic code in humans and other living things.

A genotype in which the two alleles are different A heterozygous genotype consists of one dominant allele and one recessive allele – Yy.

Two chromosomes that contain versions of the same genes One chromosome in a homologous pair is inherited from the mother and the other from the father.

A genotype in which the two alleles are the same A homozygous genotype consists of either two dominant alleles – YY – or two recessive alleles – yy.