Genetics - NCEA level 1

Cell

The basic structural and functional unit of all organisms

Nucleus

The part of the cell containing genetic material (DNA) responsible for growth and reproduction

Chromosomes

Threadlike structures made of DNA found in the nucleus.

Homologous pair

A matched pair of chromosomes, one from each parent, that are identical in size, shape and the position of the genes on them.

Gametes

A sex cell such as an egg or sperm or pollen, containing half the normal number of chromosomes.

Sperm

Male sex cell in animals with half the normal number of chromosomes.

Ova/egg

The female sex cell with half of the DNA.

Somatic cell

Any cell in a multicellular organism except for the sex cells

DNA

A long polymer found in the nucleus of a cell shaped like a double helix. Makes up chromosomes which contain the genetic information used in the development and functioning of an organism.

Genes

A sequence of bases on the DNA that codes for a protein, which determines a certain characteristic.

Allele

Alternate forms of a gene containing a slightly different base sequence on the DNA.

Nucleotide

The repeating units that make up DNA, consists of a sugar, a phosphate group, and a base

Adenine

The DNA base that pairs with (T) thymine

Thymine

The DNA base that pairs with (A) adenine

Cytosine

The DNA base that pairs with (G) guanine

Guanine

The DNA base that pairs with (C) cytosine

Amino acids

The building blocks of proteins

Proteins

Important molecules for life. They can be used to build the body, to control the reactions inside the cell, used for transport, to make muscles work and many other things.

Traits

A physical characteristic controlled by the genes and can be passed on to offspring.

Mutation

A change in a DNA base sequence which forms a new allele and can cause a change in physical characteristics or phenotype.

Mitosis

Cell division used for growth and repair. The cell divides to form two genetically identical cells.

Meiosis

Cell division to produce sex cells or gametes. A cell divides to form four cells each containing the haploid number of chromosomes, each genetically different due to random assortment of chromosomes.

Sexual reproduction

Form of reproduction common in most animals and plants as it allows variation needed for adaptation. Involves the fusing of two gametes.

Asexual reproduction

A type of reproduction that does not involve gametes. A single individual produces offspring that are genetically identical to the parent.

Fertilisation

Where two gametes (ova and sperm or pollen and ovule) successfuly join together to form a zygote.

Zygote

A fertilised egg.

Genetic variation

Differences among individuals in the composition of their genes. The main causes for this are mutation and sexual reproduction.

Natural selection

Process by which individuals that are better suited to their environment survive and reproduce passing on their successful alleles to their offspring.

Somatic mutation

A mutation that occurs in the body cells, cannot be inherited

Mutation in sex cells

Causes the mutation to be inheritable

Phenotype

The physical expression of the genotype

Genotype

A combination of alleles for a particular gene or characteristic.

Homozygous

A genotype with two identical alleles for a particular trait.

Heterozygous

A genotype with two different alleles for a particular trait

Pure breeding

Describes an organism whose genotype is homozygous for a specific trait and will always produce offspring that have the same phenotype for that trait.

Dominant allele

An allele whose trait is always expressed when there are two different alleles in the genotype. It masks or hides the other allele.

Recessive allele

An allele whose trait will be expressed only if two recessive alleles are present in the genotype. It will be masked in the presence of one dominant allele.

Punnett square

A chart that shows all the possible combinations of alleles that can result from a genetic cross