Chapter 2- patterns of inheritance Flashcards
Continuous variation
when individuals in a population vary within a range with no distinct categories. e.g humans can be any height and dogs can have any fur length.
Discontinuous variation
two or more distinct categories and each individual falls into one of them, there are no intermediates. e.g human blood type or the colour of violets.
What is an allele?
different versions of the same genes.
How does meiosis lead to variation?
Sexual production leads to variation in genotypes within a species. Meiosis makes gametes with a unique assortment of alleles through crossing over and independent assortment of chromosomes. The random fusion of gametes during fertilisation also increases genetic variation of offspring.
What is Etiolation?
where plants grow abnormally long and spindly because they aren’t getting enough light.
What is chlorosis?
when plants don’t produce enough chlorophyll and turn yellow.
What is phenotypic variation caused by?
Genotypic and/ or environmental factors. phenotypic variation influenced by both is often continuous.
What is a gene?
sequence of bases on DNA molecule that codes for a polypeptide which results in a phenotype e.g eye colour.
What is a genotype?
The alleles an organism has
What is a phenotype?
The observable characteristics of an organism that an allele produces e.g eye colour.
What is a dominant allele?
An allele who’s characteristic appears in the phenotype, even when there’s only one copy. They are shown with a capital letter.
What is a recessive allele?
An allele who’s characteristic only appears in the phenotype when 2 copies are present. They are shown with a lower case letter.
What is co dominance?
Alleles that are both expressed in the phenotype- neither one is recessive. e.g alleles for haemoglobin.
What is a locus?
The fixed position of a gene on a chromosome. Alleles of a gene are found at the same locus on a chromosome in a pair.
What is a homozygote?
An organism that carries two copies of the same allele, e.g BB or bb
