Variations In Chromosome Structure 34-38 Flashcards
What does 1 or more breaks in the chromosome do (possibly by unequal recombination)?
- free ends of DNA unstable
—-> can be degraded by exonuclease
—-> can bond with other free ends (sometimes telomeres)
What is a Deletion?
-loss of segment
-break, then degredation
What is Intercalary Deletion?
What is Terminal Deletion?
ABC.DEFG —> ABC.DG
ABD.DEFG —> ABC.DE
What happens if you delete dominant allele?
What happens if gene dosage occurs?
What happens during meiosis prophase I?
expression of recessive allele
haploinsufficiency
looped out structure
What is a Duplication?
-2 copies of chromosomal segment
What is Tandem Duplication?
What is Reverse Tandem Duplication?
What is Displaced Duplication?
ABC.DEFG —> ABCBC.DEFG
ABC.DEFG —> ABC.DEFFEG
ABC.DEFG —> ABC.DEFGBC
What causes phenotypic changes in Duplication?
-gene dosage effects
-break in the middle destroys function
-looped structure during meiosis prophase I (loop in mutant only)
What is an Inversion?
-chromosomal segment turns around
What is a Paracentric Inversion?
What is a Pericentric Inversion?
ABC.DEFG —> ABC.DGFE
ABC.DEFG —> ABD.CEFG
AB.CDEFGH —> AEDC.BFGH
What causes phenotypic changes in Inversions?
-gene expression altered —> position effect
-break in the middle destroys function
-inversion loop during meiosis prophase I
-Hets for gametes usually have gamete issues
What is crossing over in Inversions?
-abnormal gametes
–> dicentric + acentric if PARA
–> duplicates + deletion if PERI
What is Translocation?
-movement of DNA between non-homologous chromosomes
What are Reciprocal Translocations?
What are Simple Translocations?
ABC.DEFG
HI.JK
—>
ABC.DEK
HI.JFG
ABC.DEFG
HI.JK
—>
A.DEFG
HBCI.JK
What causes phenotype changes in Translocations?
-gene expression may be altered –> position effect
-break in the middle of gene destroys function
-can lead to deletions
What type of deletions can Translocations cause?
unbalanced - DNA deleted after break & before translocation
balanced - no DNA deleted after break & before translation (normal phenotype likely)