Cell division, inheritance and genetics Flashcards
Define the term inheritance
Inheritance is the passage of hereditary traits from one generation to another
Define the term Genetics
Genetics is the branch of biology that deals with inheritance
Define the term Genotype
Genotype if the genetic makeup of an individual E.g. Pp
Define phenotype
Phenotype if the physical characteristics determined by the genotype and the environment E.g. brown hair, blue eyes
Define the term mutation
A mutation is a permanent, heritable change in a gene that causes it to have a different effect than it has previously
Define the term “Autosome”
A normal chromosome that is not a sex chromosome: in humans, one of the 22 oher pairs
Define X-linked (sex) chromosomes
a chromosomes concerned in determining the sex of a person
Explain what is meant by dominant and recessive alleles
- dominant alleles is an allele that is always expressed, or evident, in a person. it does this by overriding the influence of the corresponding allele on the other homologous chromosomes E.g. Pp a dominant allele can show up and a homozygous (PP) or heterozygous (Pp)
- recessive alleles is an allele that is completely hidden or masked by the presence of a dominant allele. A recessive allele is only expressed when no dominant allele is present E.g. pp (homozygous recessive)
Explain Autosomal dominant dominant genetic conditions and give an example of a condition
- Pp
- caused by mutation of a single gene on a chromosome
- one heterozygous parent will have a 50% chance o having a child with the disease
- E.g. huntington’s disease
Explain Autosomal recessive genetic conditions and give an example of a condition
- pp
- caused by mutation of two gene pairs on a chromosome
- E.g. cystic fibrosis
Explain X-linked recessive genetic conditions and give an example of a condition
- caused by a mutation on the X chromosome
- more common in men as have only one X chromosome
- E.g. colorblindness and hemophilia
Define multiple allele inheritance and give on example of a genetic trait carried by this type of inheritance
- Three or more alternative forms of a gene (allele) that can occupy the same ocous.
- However, only two of the alleles can be present in a single organism. For example, the ABO system of blood groups is controlled by three alleles, only two of which are present in an individual
Define complex inheritance and give one example of a genetic trait carried by this type of inheritance
- Most inherited traits are not controlled by one gene but by:
- the combined effects of two or more genes or
- combined effects of many genes and environmental factors E.g. skin colour, hair colour, height, body weight, build and metabolism rate.
Explain why many X-linked conditions primarily affect males
- genes for X-linked traits appear on X chromosomes, bu many of them are absent from Y chromosomes.
- primarily affect males because there are no counterbalancing dominant genes on the Y chromosomes
Explain the term Trisomy and give an example
- a Trisomy is a type of polysomy in which there are three instances of the particular chromosome, instead of the normal two.
(2n+1) has an extra chromosome (trisomy) - E.g. downs syndrome
