changes in chromosome structure

• • Chromosomal Deletion: sections of DNA are removed and not replaced→ reduction in the number of genes in a chromosome. Caused by exposure to high heat, viruses or radiation
• What is chromosomal insertion (duplication)?

  DNA portion is duplicated
• • Chromosomal inversion: section of DNA removed, turned around 10 degrees and reinserted in the chromosome, bases are in reverse order. May range in size from a few hundred bases to 5 megabases in size. E.g haemophilia A
• How does chromosomal insertion affect the number of genes?

  It increases the number of genes on the chromosome
• What determines the phenotypic effect of a mutation in DNA?

  The position of duplication and number of repeats
• • Translocation: A section of DNA is moved from one chromosome to a nonhomologous chromosome→ may lead to gene fusion where the translocated region joins 2 normally separated genes. 
• How does the size of the insertion affect individuals?

  It affects individuals similarly to altering chromosome number
• What role do the number of repeats play in phenotypic effects?

  They may or may not have a phenotypic effect
• What is the term for variations in copy number of DNA sequences?

  Copy number variations
• What happens when the number of repeats exceeds a certain threshold?

  It may have a phenotypic effect
• • Chromosomal insertion: a section of a chromosome breaks off and attaches to a different chromosome
• • Polyploidy: more than two copies of every chromosome, e.g. an organism has three copies of every chromosome. caused by errors during meiosis or mitosis. more common in plants than animals because they can reproduce asexually via vegetative propagation