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NCEA L1 Genetic Variation - AS 1.9


A base (A) that is found in DNA, only bonds with Thymine (T) and this pairing forms part of the rungs of DNA


One of a number of possible forms of a gene. Each characteristic has two alleles

Amino acids

building blocks of proteins - there are 20 different kinds


Found in plant flowers and carries pollen - the male gamete of plants

Asexual reproduction

Reproduction of identical offspring from a single parent. No gametes are involved (e.g fission in bacteria, spores)


Any chromosomes found in a cell other than sex chromosomes


One of four chemicals which make up the 'rungs' of DNA. A, T, C, G

Base pair

The two bases making up each 'rung' of DNA: either A-T, or C-G


The variation in species within an ecosystem


The structural and functional unit of all living things

Cell division

The formation of two or more daughter cells from one origional cell


Thread-like structures bearing genes that are found in the nucleus of a cell. Visible during the prophase of cell division


A distinctive inherited feature of an organism


A process that produces identical genetic individuals


A sequence of three nucleotides found on a DNA strand


A base that is found in DNA. Cytosine (C) will only bond with Guanine (G)


Deoxyribonucleic acid. A molecule found in the nucleus of cells which codes for an individuals genetic makeup.

DNA replication

The process whereby DNA makes an exact copy of itself.


An allele that controls the phenotype regardless of what the other allele is.

Double helix

A term used to describe the structure of DNA, a spiral-ladder shaped molecule


Are proteins that act as biological catalyst in living organisms. They control the rate of reactions


The fusion (joining) of a male and a female gamete to form a zygote


A sex cell: Ovum and sperm in animals or ovule and pollen grain in plants. A cell that has to join with another gamete to form a zygote before further development can occur


A length of DNA carrying the code for one feature


The study of how living organisms inherit features from one generation to another.

Genetic code

The genetic information held in the DNA

Genetic diversity

The variation in the genetic code within a species, population, or ecosystem


The combination of two alleles that an organism has for a particular gene


A base that is found in DNA. Guanine (G) will only bond with Cytosine (C) and this pairing forms part of the 'rungs' of DNA.


Having two different alleles for a particular gene; not true breeding


Having two identical alleles for a particular gene; breeds true when crossed with genetically identical organisms


The passing on of traits from generation to generation through the genetic code


Photograph of individual chromosomes of a cell arranged in pairs and showing their number, size and shape


The type of cell division which produces sex cells/gametes. In animals occurs in ovaries/testes. Process where diploid nucleus divides TWICE to produce four haploid, genetically different nuclei


The type of cell division which produces two identicial daughter cells from one parent cell


Two or more atoms chemically bonded together, e.g. CO2 or O2


A random change in the genetic code of an individual


A molecule containing a sugar-phosphate-base, found in DNA. Nuceotide bases pair to form DNA


New individuals formed by either asexual or sexual reproduction.


An individual that is able to grow and reproduce, etc. (MRS GREN)


The female organ that produces female gametes - eggs. Eggs are used in sexual reproduction in both plants and animals

Pedigree chart

A chart which shows how genes are inherited


The characteristics of an organism produced by a particular genotype.


Molecules that contain amino acids. They are found in all living organisms. There are many different types and all have important roles in living systems.


The male gamete of plants

Punnet square

A diagram used to predict the phenotype and genotype ratios of offspring by showing how alleles combine together during fertilisation

Pure breeding

Organisms homozygous for a trait


An allele which is only expressed in the offspring if the dominant allele is absent

Selective breeding

A process that is used to breed for specific required traits

Semi-conservative replication

DNA replication by 'unzipping' a DNA molecule followed by pairing up of nucleotides to produce two new DNA molecules each with one origional and one newly synthesised strand of DNA

Sex Chromosome

A chromosome that determines the sex of the individual

Sexual reproduction

Form of reproduction involving the fusion of two gametes from two parents. Produces a variation in the offspring


The male organ that produces male gametes - sperm. Sperm are used in sexual reproduction in animals


A base that is found in DNA. T will only bond with A.


A feature whose appearance is determined by genes


The difference between individuals


A fertilised egg. A single cell containing chromosomes from male and female gametes at the time/point of fertilisation

Test cross

Used to find out the genotype of an individual. We cross the 'unknown' with a homozygous recessive and observe phenotypes of offspring.

Genotype and Phenotype ratio

Using the punnet square we write down the number/4 and % of individuals showing particular genotypes and phenotypes. i.e Genotype 2 BB: 2 Bb. Phenotype (100%) All Brown Eyed.

How is variation introduced in Meiosis?

Introduced through 1) independant assortment (each chromosome is organised into gametes independantly of each other chromosome), 2) Crossing over (homologous chromosomes - one from mum, one from dad - can switch genetic information creating chromsomes with new arrangment of genes) 3) Mutations - DNA can replicate with some errors 4) Fertilision - gametes produced in Meiosis come together to produce new/novel combinations.

Homologous Chromosomes

Pair of chromosomes (same length, gene positions), i.e Chromosome #3, one comes from Mum, one from Dad.

Independant assortment

Each chromosome is organised into gametes independantly of each other chromosome

Crossing over/Recombination

This is when homologous chromosomes (one from mum, one from dad)can switch genetic information when they line up during cell division, this creates chromosomes with different arrangment of genes to parent chromosomes.


Can be either somatic (in body cells) or gametic (in gametes). Only Gametic mutations are passed on. This creates variation in a population. Natural selection acts on these new traits.

Explain what Natural Selection is and how it leads to evolution

More individuals are born than can survive. There is natural VARIATION in populations (not all the same). Some are BETTER SUITED to environment than others. Individuals COMPETE for resources. Those that are better suited produce MORE OFFSPRING. There genes are represented in greater proportion. Environment can change. This leads to gradual CHANGES (evolution) sometimes new species are formed.

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