XABY02 GENETICS Flashcards
What is a genotype?
the genetic constitution of an organism, for a particular gene refers to alleles present
What is a phenotype?
appearance of a characteristic due to expression of genotype and its interaction with the environment
What is an allele?
different forms of the same gene
What is a locus?
position of gene on chromosome, alleles occupy same locus on each pair of homologous chromosomes
What is a dominant allele?
an allele always expressed in the phenotype
What is a recessive allele?
an allele only expressed when genotype is homozygous recessive
What does homozygous mean?
both alleles in the genotype being the same
What does heterozygous mean?
both alleles in genotype differing
What is codominance?
both alleles expressed in the phenotype
What is multiple allelism?
more than 2 alleles of a particular gene, however only two alleles present in the genotype
What is a sex-linked gene?
a gene carried on only one type of sex chromosome (usually X chromosome)
What is autosomal gene linkage?
genes that are present on the same chromosome at different loci, usually inherited together
What are 2 examples of sex linked conditions?
- colour blindness
2. haemophilia
Why are males more at risk of a sex-linked condition than females?
- males only require one recessive allele to have the condition as they only have one X chromosome
- females require two recessive alleles to have the condition as they have two X chromosomes
- females can be heterozygous (carriers) but males cannot
