L9

Question 1

how do chromosome mutations occur

Answer 1

due to change in chromosome number and structure

Question 2

what are the four main types of structural mutation

Answer 2

deletion, inversion, duplication and translocations

Question 3

what are deletions

Answer 3

are the result of a loss of a chromosome segment and when homozygous are usually really lethal

Question 4

What are duplications

Answer 4

are the result of the addition of an extra copy of a chromosome region

Question 5

true or false, both duplications and deletions are rare in nature

Answer 5

true, especially in diploid organism

Question 6

what are inversions

Answer 6

involves two breaks in the chromosome and a 180 degrees turn, ligated once more into the same chromosome it broke off from; relatively common

Question 7

what are the two types of inversion

Answer 7

paracentric and pericentric

Question 8

what is paracentric inversion

Answer 8

includes the centromere during an inversion

Question 9

what is pericentric

Answer 9

do not include the centromere during an inversion

Question 10

why chromosome mutations important (5)

Answer 10

• 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

Question 11

what are structural mutations

Answer 11

involve novel sequence rearrangements within one or more DNA molecules

Question 12

true or false, changes in the number of chromosomes are not associated with the alterations in the DNA molecules

Answer 12

true

Question 13

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

Answer 13

true

Question 14

true or false, double stranded breaks are lethal unless repaired

Answer 14

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

Question 15

true or false, only DNA molecules with a centromere and two telomeres will survive meiosis

Answer 15

true

Question 16

what is non allelic homologous recombination ( can produce the 4 types of structural mutation)

Answer 16

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

Question 17

what is a deletion

Answer 17

• 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)

Question 18

what are the two places of deletion

Answer 18

terminal or interstitial

Question 19

what is a terminal deletion

Answer 19

deletion at the end of a chromosome

Question 20

what is interstitial deletion

Answer 20

within a chromosome arm; occurs after two breaks occur and the ends rejoin

Question 21

what does the magnitude of deletion on the chromosome depend on

Answer 21

size of the fragment deleted

Question 22

what are the two types of deletion

Answer 22

intragenic and multigenic

Question 23

what is intragenic deletion

Answer 23

intragenic deletion is a small deletion within a gene that inactivates the gene

Question 24

what is multigenic deletion

Answer 24

multigenic deletion involves several or many genes and their consequences are more severe

Question 25

what does a deletion heterozygote chromosome form

Answer 25

forms a loop

Question 26

true or false, if multigenic deletion is made homozygous by inbreeding the consequence is always lethal

Answer 26

true

Question 27

true or false, multigenic deletions never revert back to the wild type

Answer 27

true

Question 28

how does pseudodominance occur

Answer 28

when deletions allow for the expression of phenotypes carried as recessive alleles

Question 29

what is a duplication

Answer 29

a duplication is a mutation with an extra copy of a chromosome region

Question 30

true or false, duplication is an effective mechanism for increasing the number of copies of genes and also the genome size

Answer 30

true

Question 31

how does positional effect affect a Drosophila fly

Answer 31

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

Question 32

how does the Bar mutation result

Answer 32

results from a small duplication on the X chromosome

Question 33

true or false, the Bar mutation is inherited as an incomplete or partial dominant X linked trait

Answer 33

true

Question 34

what is a inversion

Answer 34

Inversions involve two chromosome breaks in the same chromosome, the region is flipped and re-inserted

Question 35

why are individuals with inversions usually look normal

Answer 35

this is because inversions do not change the amount of genetic information of the individual

Question 36

what is an inversion heterozygote

Answer 36

cells containing one normal and one chromosome carrying the inversion

Question 37

how is an inversion loop formed

Answer 37

in meiosis one chromosome twists at the ends of the inversions so that it can pair with the untwisted homolog

Question 38

how are dicentric bridges and acentric fragment formed

Answer 38

in paracentric inversion crossing over within the inversion loop causes a dicentric bridge and an acentric fragment to form

Question 39

what happens in pericentric inversions crossing over in inversion loop

Answer 39

can result in duplications and deletions

Question 40

what is the result of paracentric inversion crossing over

Answer 40

we will result in our two starting products

Question 41

true or false, inversions appear to act as cross over suppressors

Answer 41

true; due to resulting non viable gametes which make it seem as if no crossing over has occurred

Question 42

true or false, inversions can lead to the creation of super genes

Answer 42

true; this is because those genes are locked together because cross over cannot break them up; those genes will remain in inversion