Chapter 9 Inheritance Flashcards
Define gene
A sequence of DNA that codes for a polypeptide and which occupies a locus on a chromosome
Define alleles
A variant nucleotide sequence for a particular gene at a given locus, which codes for an altered Phenotype
What does homozygous mean?
When the allele for a particular gene are the same for both parents
What does heterozygous mean?
When the alleles for a particular gene from both parents are different.
What is a genotype?
All the alleles an individual contains
Define Phenotype
The way in which allies are expressed determined by both the genes and environment
What does it mean when an allele is dominant?
The allele is always expressed when it is present
What does it mean when an allele is recessive?
When the allele is only expressed when it is homozygous and not expressed in the presence of a dominant allele
What is a test cross,back cross?
Cross between an individual with the Phenotype of the dominant characteristic , but unknown genotype with an individual that is homozygous recessive for the gene in question.
If individuals produced in the cross are displaying recessive traits, the parents genotype is heterozygous.
What is co-dominance?
Both alleles in a heterozygote are expressed individually, as a result, the heterozygote has a combination of characteristics. For example, blood groups follow the ABO system, but A and B and can be co-dominant to form the blood group AB
What is incomplete dominance?
The Phenotype of heterozygotes are intermediate between the two parental phenotypes, rather than both being expressed. For example, carnations can have red or white flowers, pink carnations show incomplete dominance as neither allele for red or white is shown as they are incomplete dominant.
