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65 terms

Genetic Variation

NCEA L1 Genetic Variation - AS 1.9
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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/trait
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/Characteristic
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.