Topic 7: Inheritance Flashcards
In a dihybrid cross, what ratio would you expect to see in the offspring if both parents were heterozygous for both genes?
9:3:3:1
Give two reasons why you may not observe the above ratio you would expect.
1) Autosomal linkage
2) Crossing over in meiosis
Which statistic could you use to see if there is a difference between the expected phenotype frequencies and the frequencies of the phenotypes actually observed?
Chi-squared
Define gene pool
All the alleles of all the genes in a population at a particular time
Define allele frequency
The proportion of each allele for a gene in a gene pool
What are the two formulae for the Hardy-Weinberg principle?
Colour blindness is caused by a recessive allele found only on the X chromosome. If a non colour-blind male reproduces with a female carrier of the allele, what is the probability their children will be colour-blind?
25% chance of colour blind child
Define genotype
genetic constitution of an organism
Define phenotype
expression of genes and its interaction with the environment
Define homozygous
pair of homologous chromosomes carrying same alleles for a single gene
Define heterozygous
pair of homologous chromosomes carrying two different alleles for a single genes
Define recessive allele
allele only expressed if no dominant allele is present
Define dominant allele
an allele that will always be expressed in the phenotype
define codominant
both alleles are equally dominant and are both expressed in the phenotype
Define multiple alleles
more than two alleles for a single gene
