Lecture 10 Flashcards
What is a translocation?
Movement of genetic material between nonhomologous chromosomes and between the same chromosome
What are the two types of translocation?
Reciprocal and nonreciprocal
What are the effects of translocations?
Can result in genes that were on different chromosomes becoming linked, Can result in a gene becoming regulated by a new set of regulators , the break caused by the translocation may occur within a gene disrupting its function, can cause abnormal meiotic configurations with only 50% of gametes being viable
What are the three ways in which translocated chromosomes can segregate during meiosis?
Alternate segregation where normal and translocated chromosomes segregate and produces viable gametes
Adjacent segregation 1 and 2 (rare) where chromosomes segregate so that one normal chromosome and one translocated chromosome goes into each cell for meiosis II and the resulting gametes are non-viable
What is pseudolinkage with regards to translocated chromosomes?
Genes on translocated chromosomes act as if linked as recombinants carry unbalanced genomes making them non viable so only those with the parental type survive
What is a robertsonian translocation?
When the short arm of one acrocentric chromosome is exchanged for the long arm of another lading to the formation of two metacentric chromosomes one which is large and one which is small
This smaller chromosome is often lost as it will fail to segregate
Is the cause of a small number of downs syndrome cases where the long arm of chromosome 21 is linked to chromosome 14 as a carrier of this will have approx. 1/3 of their children having downs syndrome
What is the difference between euploidy and aneuploidy?
Euploidy is a change in the number of chromosome sets while aneuploidy is a change in the number of individual chromosomes
What is polyploidy?
Organisms that have more than two sets of chromosomes, this is more common in plants than in animals, there is often a relationship between genome size and organism size (Likely due to a corresponding relationship between genome and cell volume)
What is the difference between autopolyploids and allopolyploids?
Autopolyploids arise from multiple chromosome sets from the same species while allopolyploids have chromosomes sets from different species
How can colchicine be used to induce polyploidy?
It can prevent spindle formation resulting in a failure of the chromatids to migrate after the splitting of the centromere
What are the genetic consequences of polyploidy?
Uneven polyploids are sterile
Even polyploids are less fertile as univalents, trivalents etc may form
Polyploids increase the number of allelic combinations resulting in greater diversity and the ability to have mutations occur without deleterious effects
