Variation Flashcards
What is a gene?
-DNA segment that codes for a single polypeptide or protein
What are the 2 types of phenotypic variation?
-continuous + discontinuous
What is continuous variation?
-no categories
-quantitive
-controlled by lots of genes
-influenced by environment
What is discontinuous variation?
-categories
-qualitative
-controlled by few genes
-unaffected by environment
How does reproduction cause phenotype variation?
-chromosome level - DNA crossing
-gamete level - independent assortment
What is meiosis?
-production of haploid gametes
-genetically different cells
How is genetic variation achieved?
-crossing over of chromatids
-independent assortment
What is an allele?
-alternative form of a gene
What is loci/locus’s?
-position on chromosome where an allele is found
What is phenotype?
-observable characteristics
What is genotype?
-genetic makeup of an organism
What is homozygous?
-2 identical copies of the same allele
What is heterozygous?
-2 different alleles code for the same characteristics
What is codominance?
-both alleles contribute to the phenotype
What is homologous?
-pair of chromosomes with same gene loci
2 factors influencing continuous variation?
- Environment
- Genes
Example of discontinuous variation
-humans having 4 possible blood groups
How does genetic variation occur in species?
-sexual reproduction = random fertilisation
-independent assortment
-crossing over between homologous chromosomes
-can be mutations in DNA
-natural selection leads to changes in allele frequency
How could mutations be spread throughout a bacterial population?
-vertical transmission = parent to daughter cells
-conjugation = transfer of plasmids between bacteria
