Inheritance Flashcards
Definition of gene
A section of a molecule of DNA that codes for a specific protein
Definition of alleles
Alleles are different versions of a particular gene.
Definition of phenotype
The observable characteristics of an organism.
Definition of genotype
The combination of alleles that control each characteristic.
Definition of dominant
A dominant allele is always expressed, even if only one copy is expressed
Definition of recessive
A recessive allele is only expressed is two copies are present (therefore no dominant allele present)
Definition of homozygous
When the 2 alleles of a gene are the same
Definition of heterozygous
When the 2 alleles of a gene are different
Definition of codominance
When both alleles within a genotype are expressed in the phenotype of an individual
What are the 2 main types of variation?
Continuous and discontinuous variation
Define continuous variation
A characteristic that changes gradually over a range of values e.g. height
Define discontinuous variation
A characteristic with only a limited range of possible values
Why do people have a wide range of heights but have a specific blood group?
Height is continuous.
Height is polygenic and depends on the combination of many genes.
Blood group is discontinuous
Blood group is monogenic
Define polygenic
A characteristic, such as height or skin colour, that is influenced by two or more genes
Pair of chromosomes for men
XY
Pair of chromosomes for women
XX
Definition of mutation
A rare, random change in genetic material that can be inherited
Variation can be … or …. or both
Genetic or environmental
Define polygenic characteristics
Polygenic characteristics have phenotypes that can show a wide range of combinations of features.
Give reasons why children from the same parents all look different from each other
Different environmental effects
Multiple genes determine appearance
Different combinations of alleles
From different eggs/sperm
