Biology – Genetics
allele
Form of a gene. Each characteristic has two alleles.
recessive
trait that will only appear in the phenotype if organism inherits two of them; covered up by the dominant gene
gamete
sex cell; sperm or egg
adenine
A base thats found in DNA. It will only bond with Thymine.
amino acid
Building blocks of protein
asexual reproduction
Reproduction of identical offspring from a single parent. No gametes involved
autosomes
Any chromosome other than the sex chromosomes.
base
One of four chemicals which make up the ‘rungs’ of DNA; A;T;C;G
base-pair
Two bases making 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
chromosome
Thread-like structures bearing genes that are found in the nucleus of a cell
characteristic
A distinctive inherited feature of organism
cloning
A process that produces identical genetic individuals
cytosine
A base pair found in DNA. It will only bond with Guanine.
DNA
Deoxyribonucleic acid. A molecule found in the nucleus of cells which provides an individuals genetic code
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 shape
fertilization
The fusion of a male and female gamete to form a zygote
gamete
A sex cell. Ovum (egg) in females or sperm in males. Ovule and pollen in plants.
gene
A length of DNA carrying the code for one feature
genetic code
the genetic information held in DNA
genotype
The combination of two alleles that an organism has for a particular gene.
guanine
A base that is found in DNA. It will only bond with cytosine
heterozygous
Having two different alleles for a particular gene; not true breeding
homozygous
Having two identical alleles for a particular gene; true or pure breeding
inheritance
the passing on of traits from generation to generation through the genetic code.
karotype
photograph of individual chromosomes of a cell arranged in pairs and showing their number, size and shape
meiosis
The type of cell division that produces gametes. Occurs in the ovaries or testes in animals.
mitosis
The type of cell division which produces identical daughter cells from one parent cell.
mutation
A change in sequence of bases in the genetic code which is transmitted to subsequent generations
nucleotide
A molecule containing a sugar-phosphate-base, found in DNA. These 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
ovaries
The female organ that produces female gametes.
pedigree chart
A chart which shows how genes are inherited
phenotype
The characteristics of an organism produced by a particular genetype
proteins
Molecules that contain amino acids.
pollen
The male gametes of plants
Punnett square
A diagram used to predict the phenotype and genotype ratios of offspring.
pure-breeding
Organisms that are homozygous for a trait.
recessive
An allele which is only expressed in the offspring if the dominant allele is missing
selective breeding
A process that is used to breed for specific required traits
semi-conservative replication
DNA replication which involving the DNA unzipping and pairing up with new matching nucleotides forming two new DNA molecules.
sex chromosome
A chromosome that determines the sex of the individual
sexual reproduction
Reproduction involving the fusion of two gametes. Produces variation in offspring
testes
The male organ that produces gametes
thymine
A base that is found in DNA. It will only bond with adenine.
trait
A feature whose appearance is determined by genes
triplet
A sequence of three nucleotides found on a DNA strand
variation
the difference between individuals
zygote
A fertilised egg. A single cell containing chromosomes from male and female gametes at the point of fertilisation.