L9 Flashcards
how do chromosome mutations occur
due to change in chromosome number and structure
what are the four main types of structural mutation
deletion, inversion, duplication and translocations
what are deletions
are the result of a loss of a chromosome segment and when homozygous are usually really lethal
What are duplications
are the result of the addition of an extra copy of a chromosome region
true or false, both duplications and deletions are rare in nature
true, especially in diploid organism
what are inversions
involves two breaks in the chromosome and a 180 degrees turn, ligated once more into the same chromosome it broke off from; relatively common
what are the two types of inversion
paracentric and pericentric
what is paracentric inversion
includes the centromere during an inversion
what is pericentric
do not include the centromere during an inversion
why chromosome mutations important (5)
- allow us to understand how genes work together in the genome
- provide insights into meiosis and chromosome architecture
- have proven useful tools for genomic manipulation
- cause of some genetic diseases in humans
- have revealed insights into evolutionary processes
what are structural mutations
involve novel sequence rearrangements within one or more DNA molecules
true or false, changes in the number of chromosomes are not associated with the alterations in the DNA molecules
true
true or false, both changes in the chromosome number and chromosome structure can occur spontaneously and can also be induced by both chemical and physical mutagens
true
true or false, double stranded breaks are lethal unless repaired
true; repair mechanisms in cell correct double stranded breaks by joining broken ends together; if the ends of two different chromosome ends are joined then chromosomal rearrangement can occur
true or false, only DNA molecules with a centromere and two telomeres will survive meiosis
true
what is non allelic homologous recombination ( can produce the 4 types of structural mutation)
In organisms with repeat DNA sequences within one chromosome or on different chromosomes non homologous crossing over can occur; if repeats pair that are not on the same position on homologs, crossing over can produce rearrangements
what is a deletion
- simply the loss of part of a chromosome; the process of deletion usually requires two chromosomal breaks to cut out of the intervening segment (the segment will be lost because it does not have a centromere)
what are the two places of deletion
terminal or interstitial
what is a terminal deletion
deletion at the end of a chromosome
what is interstitial deletion
within a chromosome arm; occurs after two breaks occur and the ends rejoin
what does the magnitude of deletion on the chromosome depend on
size of the fragment deleted
what are the two types of deletion
intragenic and multigenic
what is intragenic deletion
intragenic deletion is a small deletion within a gene that inactivates the gene
what is multigenic deletion
multigenic deletion involves several or many genes and their consequences are more severe
what does a deletion heterozygote chromosome form
forms a loop
true or false, if multigenic deletion is made homozygous by inbreeding the consequence is always lethal
true
true or false, multigenic deletions never revert back to the wild type
true
how does pseudodominance occur
when deletions allow for the expression of phenotypes carried as recessive alleles
what is a duplication
a duplication is a mutation with an extra copy of a chromosome region
true or false, duplication is an effective mechanism for increasing the number of copies of genes and also the genome size
true
how does positional effect affect a Drosophila fly
Occasionally a fly carries three copies of the duplication on its X chromosome (double bar) the eye is extremely reduced; due to its eyes having a reduced number of facets
how does the Bar mutation result
results from a small duplication on the X chromosome
true or false, the Bar mutation is inherited as an incomplete or partial dominant X linked trait
true
what is a inversion
Inversions involve two chromosome breaks in the same chromosome, the region is flipped and re-inserted
why are individuals with inversions usually look normal
this is because inversions do not change the amount of genetic information of the individual
what is an inversion heterozygote
cells containing one normal and one chromosome carrying the inversion
how is an inversion loop formed
in meiosis one chromosome twists at the ends of the inversions so that it can pair with the untwisted homolog
how are dicentric bridges and acentric fragment formed
in paracentric inversion crossing over within the inversion loop causes a dicentric bridge and an acentric fragment to form
what happens in pericentric inversions crossing over in inversion loop
can result in duplications and deletions
what is the result of paracentric inversion crossing over
we will result in our two starting products
true or false, inversions appear to act as cross over suppressors
true; due to resulting non viable gametes which make it seem as if no crossing over has occurred
true or false, inversions can lead to the creation of super genes
true; this is because those genes are locked together because cross over cannot break them up; those genes will remain in inversion
