7.1 Inheritance Flashcards
(13 cards)
define Genotype
The genetic constitution of an organism
define Phenotype
The expression of the genetic constitution (genotype) and its interaction with the environment
What are the 3 things that alleles may be
Dominant, Recessive or Codominant
What is Co-Dominance
When both alleles can be expressed in the phenotype of an organism at the same time
When writing the genotype for codominance the gene is symbolised as the capital letter and the alleles are represented by different superscript letters.
How can a test cross be used to deduce the genotype of an unknown individual that is expressing a dominant phenotype?
The individual in question can be crossed with an individual that is expressing the recessive phenotype
The resulting phenotypes of the offspring provide sufficient information to suggest the genotype of the unknown individual
If there are any offspring expressing the recessive phenotype then the unknown individual must have a heterozygous genotype (because if they were homozygous dominant, then no % of offsprings would be homozygous recessive or express the recessive phenotype– FF x ff = 100% Ff)
What is Sex-linkage?
Sex linkage refers to a trait which is coded for by a gene on a sex chromosome, in mammals these are the X and Y chromosomes. As males are XY and females XX, alleles on these chromosomes have different probabilities to be expressed in the phenotype between the sexes.
What is autosomal linkage
This occurs on the autosomes (any chromosome that isn’t a sex chromosome)
Two or more genes on the same chromosome do not assort independently during meiosis
These genes are linked and they stay together in the original parental combination
What does a monohybrid cross look at?
Looks at how the alleles for a single gene are passed on from one generation to the next
What does a dihybrid cross look at?
Looks at how the alleles of two genes transfer across generations
What are the steps to working out a Mono/Dihybrid cross ?
1)Parent phenotype
2)Parent genotype
3)Parent gametes
4)Cross punnet square with gametes
5)Phenotypic ratio of offspring
What is Epistasis? Give an Overview
When two genes on different chromosomes affect the same feature
The whole combination of alleles from the different genes dictates the phenotype
Which statistical test determines whether or not there is a SIGNIFICANT DIFFERENCE between the OBSERVED and EXPECTED results in an experiment + its formula
Chi-squared test : chisquared = the sum of ((O-E)^2 / E in which O- observed value
E- expected value
Give an overview of the Chi-squared test
If the difference between results is statistically significant this suggests the presence of a factor that isn’t being accounted for
E.g. linkage between genes
When a difference is not significant, any differences that are observed can be said to be due to chance alone
The chi-squared test is carried out when the data is categorical, i.e. falls into distinct groups
