Learn the meanings of the keywords in this topic.
allele – An alternative form of a gene.
asexual reproduction – The production of offspring from a single parent by mitosis. The offspring are clones of the parent.
chromosome – Structures that contain the DNA of an organism and are found in the nucleus.
cystic fibrosis – A disorder of cell membranes caused by a recessive allele.
DNA – A polymer that is made up of two strands that form a double helix.
dominant – An allele that is always expressed, even if only one copy is present.
fertilisation – The fusion of male and female gametes.
gamete – Sperm cell and egg cell in animals; pollen and egg cell in plants.
gene – A small section of DNA that codes for a specific protein.
genome – The entire genetic material of an organism.
genotype – The combination of alleles.
heterozygous – A genotype that has two different
alleles – one dominant and one recessive.
homozygous – A genotype that has two of the same alleles. Either two dominant alleles or two recessive alleles.
meiosis – The two-stage process of cell division that reduces the chromosome number of the daughter
embryo screening – Genetic tests carried out on an embryo to see whether it carries a faulty allele.
evolution – A change in the inherited characteristics of a population over time through a process of natural selection.
evolutionary tree – A method used to show how scientists believe organisms are related.
extinction – The permanent loss of all members of a species.
fossils – The remains of organisms from millions of years ago which are found in rocks.
genetic engineering – The process by which scientists manipulate and change the genotype of an organism.
natural selection – The process by which organisms that are better suited to an environment are more likely to survive and reproduce.
selective breeding – Humans selecting animals or plants, that have a required characteristic, for breeding.
speciation – The process by which two species evolve from a single original species by natural selection. The two populations have become so different that they can no longer interbreed to produce fertile offspring.
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