Biology 16-17 Flashcards
(20 cards)
How chromosomes are made
Of DNA, which contains genetic information in the form of genes
Define an allele
An alternative form of a gene
Define a gene
A length of DNA that codes for a protein
Describe the inheritance of sex in humans
XX and XY chromosomes
Describe inheritance
The transmission of genetic information from generation to generation
Describe genotype
The genetic make-up of an organism and in terms of the alleles present
Describe phenotype
The observable features of an organism
Describe homozygous
Having two identical alleles of a particular gene
Two identical homozygous individuals that breed together will be …
Pure-breeding
Describe heterozygous
Having two different alleles of a particular gene
Heterozygous individual will …
Not be pure-breeding
Describe a dominant allele
An allele that is expressed if it is present in the genotype
Describe a recessive allele
An allele that is only expressed when there is no dominant allele of the gene present in the genotype
Describe variation
Differences between individuals of the same species
Continuous variation results in a …
Range of phenotypes between two extremes
Discontinuous variation results
in a …
Limited number of phenotypes with no
intermediates
Describe mutation
A genetic change
Mutation is the way in which …
New alleles are formed
Describe natural selection (3/5)
Genetic variation within populations
Production of many offspring
Struggle for survival, including competition for resources
A greater chance of reproduction by individuals that are better adapted to the environment than others
These individuals passing on their alleles
to the next generation
Describe selective breeding (3)
Selection by humans of individuals with desirable features
Crossing these individuals to produce the next generation
Selection of offspring showing the desirable features
