6.1.2~Patterns of inheritance

Define interspecific variation?

• The difference between different species

Define intraspecific variation?

• the difference between individuals of the same species

Define continuous variation?

• Where individuals in a population vary within range and there are no distinct categories

  • e.g. height

Define discontinuous variation?

• where there are two or more distinct categories and each individual falls into only one of these categories

  e.g. blood group A, B, AB, O

Define alllele?

• a different version of a gene

Define genotype?

• the alleles an organism has

Define phenotype?

• the observable characteristics alleles produce

Define polygenic?

• controlled by many genes( continuous variation)

Define monogenic?

• controlled by one gene(discontinuous)

Define etiolation?

• where plants grow abnormally long and spindly because they are not getting enough light

Define chlorosis ?

• Where plants do not produce enough chlorophyll due to lack of magnesium

State the 4 ways how sexual reproduction can lead to genetic variation within a species?

• Crossing over

• independent assortment

• Random fertilisation

• Meiosis

Define crossing over?

• Where chromatids twist around each other and swap alleles, they then contain the Sam evened but different alleles

Define independent assortment of chromosomes?

• Chromosomes align on the metaphase plate randomly during metaphase

• One from each pair passes into a daughter cell

Define random fertilisation?

• any sperm can fertilise any egg

Define gene?

• a sequence of nucleotide bases that code for a probe

Define dominant?

• an allele that is always expressed if present

Define homozygous?

• where both alleles are the same

Define heterozygous?

• where both alleles are different

Define locus?

• where on the chromosome the alleles are

Define carrier?

• a person carrying an allele which is not expressed in the phenotype but can be passed on to the offspring

Define codominat?

• allles that are both expressed in the phenotype as they are equally dominant

Define autosomal linkage?

• Genes which are linked and found on one of the pairs of chromosomes

Define epistasis?

• where 1 gene masks or suppresses the expression of another

What is your blood group determined by?

• the immunoglobulin gene which codes for the production of different antigens present on the surface of different red blood cells

State the 3 alleles of the immunoglobulin gene?

• IA- results in the production of antigen A

• IB- results in the production of antigen B

• IO- result in the production of neither antigen

State wether the alleles produce by immunoglobulin are dominant or recessive?

• IA= codminant

• IB= codominant

• IO= recessive

How many pairs of chromosomes do humans have?

• 23 pairs

Define sex linked genes?

• genes carried on the sex chromosomes

What are dihybrid crosses used to show?

• the inheritance of 2 different characteristics caused by 2 genes located on different pairs of the homologous chromosome