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NCEA L1 Genetic Variation - AS 1.9

Adenine

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

Allele

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

Anther

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)

Autosomes

Any chromosomes found in a cell other than sex chromosomes

Base

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

Biodiversity

The variation in species within an ecosystem

Cell

The structural and functional unit of all living things

Cell division

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

Chromosome

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

Characteristic

A distinctive inherited feature of an organism

Cloning

A process that produces identical genetic individuals

Codon

A sequence of three nucleotides found on a DNA strand

Cytosine

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

DNA

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.

Dominant

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

Enzymes

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

Fertilisation

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

Gamete

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

Gene

A length of DNA carrying the code for one feature

Genetics

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

Genotype

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

Guanine

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.

Heterozygous

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

Homozygous

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

Inheritance

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

Karyotype

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

Meiosis

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

Mitosis

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

Molecule

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

Mutation

A random change in the genetic code of an individual

Nucleotide

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

Offspring

New individuals formed by either asexual or sexual reproduction.

Organism

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

Ovaries

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

Phenotype

The characteristics of an organism produced by a particular genotype.

Proteins

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.

Pollen

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

Recessive

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

Testes

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

Thymine

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

Trait

A feature whose appearance is determined by genes

Variation

The difference between individuals

Zygote

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.

Mutations

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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