keywords Flashcards
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 that is caused be 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 cells 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 rescessive
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 cells. It makes gametes for sexual reproduction.
mutation
a change in DNA
phenotype
the characteristic expressed because of the combination of alleles
polydactyly
having extra fingers or toes, It is caused by a dominant allele
recessive
an allele that is only expressed if two copies of it are present
sexual reproduction
the production of offspring by combing genetic information from the gametes of two parents. Leads to variation in the offspring
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 to
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
variation
differences in characteristics of individuals in a population
biodiversity
the variety of living organisms
