Topic 31-31: Chromosomal Inheritance Flashcards
What are linked genes, recombinant types and parental types?
Linked Genes: genes that are on the same chromosome and they violate the law of Independent assortment.
Recombinant Types: Genes that have been crossed over. Contain non-parental phenotypes.
Parental Types: Offspring that match one of the parental phenotypes.
If you crossed a double heterozygous individual with a double homozygous recessive, what phenotypic ratio would you expect if the traits are inherited independently? How woud this differ if the traits were linked?
What is a recombination frequency? How is an experiment set up to calculate it?
Recombination Frequency: The recombination frequency is observed for any two genes on different chromosomes. (#of recombinants)/(total#of offspring) x 100
An experiment set up to calculate the distance between two genes, a test cross is carried out and the percentage of recombinants are assessed to calculate the recombination.
How does recombination frequency relate to distance on the chromosome? What is a map unit?
Recombination frequency gives the relative position of genes in relation to one another.
1% recombination = 1cM or map unit. Map unit is the distance between genes on a chromosome.
Describe nondisjunction. What is the result of non-disjunction?
Nondisjunction is an error that occurs in either Meiosis 1 or Meiosis 2.
Nondisjunction in Meiosis 1: Homologous chromosomes failt to seperate. This leads to two haploid cells with extra chromosomes and 2 haploid cells with less number of chromosomes.
Nondisjunction in Meiosis 2: Sister chromatids can fail to seperate. This results in two normal n haploid cells. Also in one cell lacking chromosomes and one cell with extra chromosomes.
Define trisomy and monosomy and provide examples from class.
Trisomy: Is the error of having three copies of one chromosome. (Down Syndrome)
Monosomy: Only one copy of one chromosome. (Monosomy X) (Turner Syndrome)
Why are monosomies of the autosomes, and most trisomies, not observed in humans?
Most trisomies and monosomies in autosomes are not observed in humans because it does not bring many phenotypes. Many humans do not know unless a test is taken.
