Biology IGCSE: Inheritance (Key Terms)

Mitosis

A type of cell division where one diploid cell divides to produce two genetically identical diploid daughter cells

Meiosis

A type of cell division that produces four genetically different daughter cells, called gametes (sex cells), from a single parent cell

Diploid

A cell that contains two complete sets of chromosomes (2n)

Haploid

A cell with a single set of chromosomes (n)

Prophase

The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus disappears.

Metaphase

Chromosomes and their copies line up in the middle of the cell.

Anaphase

Chromosomes and their copies are pulled to different ends of the cell.

Telophase

New membranes form around the chromosomes at each end of the cell.

Chromosomes

A long, coiled molecule of DNA that contains genetic information in the form of genes

Alleles

A different version of the same gene

Gametes

A sex cell that contains half the number of chromosomes of a normal body cell (haploid)

Zygote

The first cell formed when a male gamete (sperm) and a female gamete (egg) fuse during fertilization

DNA (Deoxyribonucleic acid)

A double-stranded polymer that forms a double helix, carrying the genetic code for an organism's characteristics

Deoxyribose

The five-carbon (pentose) sugar component of DNA (deoxyribonucleic acid)

Ribose

A pentose sugar (a simple sugar with five carbon atoms) that forms part of the backbone of ribonucleic acid (RNA).

Gene

A section of DNA on a chromosome that codes for a protein

Human Genome

The complete set of genetic material for a human, containing all of the DNA that makes up the 23 pairs of chromosomes in a typical body cell

Nucleotide

A molecule that is the basic building block of DNA, consisting of three parts: a sugar, a phosphate group, and one of four different nitrogenous bases (A, T, C, or G)

Nucleic Acid

A large molecule, like DNA or RNA, that is essential for all living organisms because it carries the genetic information needed to make proteins

mRNA

A single-stranded RNA molecule that carries a copy of the genetic code for a specific gene from the DNA in the nucleus to the ribosomes in the cytoplasm

Transcription

The process where the genetic information from a segment of DNA is copied into a complementary molecule of messenger RNA (mRNA)

Translation

The process, occurring in the cytoplasm at the ribosomes, where the genetic information carried by a messenger RNA (mRNA) molecule is used to synthesise a specific sequence of amino acids, which then fold into a protein

RNA polymerase

The enzyme that binds to the non-coding region in front of a gene and synthesises a complementary single-stranded messenger RNA (mRNA) molecule from a DNA template strand during the process of transcription

tRNA

A small RNA molecule that acts as an adapter in protein synthesis, carrying specific amino acids to the ribosome to be assembled into a polypeptide chain

Codon

A sequence of three bases on a messenger RNA (mRNA) molecule that codes for a specific amino acid or signals the end of protein synthesis

Anticodon

A sequence of three unpaired bases on a transfer RNA (tRNA) molecule that is complementary to a specific three-base sequence, or codon, on a messenger RNA (mRNA) molecule.

Polypeptide chain

A linear sequence of many amino acids joined together by peptide bonds.

Homozygous

An individual that has two identical alleles for a specific gene.

Heterozygous

An organism that has two different alleles for a particular gene

Phenotype

The observable characteristics of an organism, such as eye colour or height

Genotype

The specific combination of alleles an individual has for a particular gene, which determines their phenotype