Chapter 8: Chromosome Variation Flashcards
What is duplicated in chromosome duplication?
a segment of the chromosome
What is a developmental process that often requires the interaction of many genes?
gene dosage problems
What is development affected by in chromosome duplication?
relative amounts of gene products
What is a chromosome inversion?
a segment of the chromosome is turned 180 and is dependent on the involvement of the centromere
Paracentric Inversion
do not include centromere
Pericentric inversion
includes centromere
Do individual homozygous inversions cause problems during meiosis?
no problems will arise
Do individual heterozygous inversions cause problems during meiosis?
yes, paracentric and pericentric inversions produce some abnormal gametes after crossing over
What happens in a chromosome deletion?
a segment of the chromosome is deleted
How are large deletions of a chromsome easily detected?
during pairing, the normal part of the chromsome loops out
What are some effects of a chromsome deletion?
-imbalances in gene product
-expression of a normally recessive gene
-haploinsuffincinacy
What happens in a translocation?
a segment of a chromsome moves from one chromosome or to another place on the same chromosome
Nonreciprocal translocation
one chromsome to another without equal exchange
Reciprocal translocation
chromosome movement with exchange
Philidelphia chromosome
found in chronic myelogenous leukemia
What is the impact of translocation?
position effect and break occured in gene
Robertsonian translocation
the short arm of one acrocentric chromosome is exchanged with the long arm of another which creates a large metacentric chromsome and a fragment that is often lost
What is an increase or decrease in the number of individual chromsomes?
aneuploidy
What causes variations in copy number?
aneuploidy
What causes aneuploidy?
-deletion of centromere
-robertosonian translocation
-nondisjunction during meiosis and mitosis
Nullisomy
loss of both members of a homologous pair of chromosomes
Monosomy
loss of a single chromosome
Trisomy
gain of a single chromosome
Tetrasomy
gain of 2 homologous chromosomes
What is primary down syndrome caused by?
75% random nondisjunction in egg formation
What is familial down syndrome caused by?
robertsonian translocation between chromosomes 14 and 21
What is the prescence of more than 2 sets of chromosomes?
polyploidy
What is significant in polyploidy?
increase in cell size and larger plant attributes
Autopolyploidy
from single species
What is the mechanisim of autopolyploidy?
-Mitosis: Replication→seperation of chromstids→Nondisjucntion without cell division→ autotetraploid
-Meiosis: Replication→ non-disjunction→ 2n gametes are produced→ fertilization→fusion with a 1n gamete to produce an autotriploid
Allopolyploidy
from two species
What is the mechanisim for allopolyploidy?
Hybridization between 2 diploid species occurs which produces a hybrid with 6 nonhomologous chromosomes that do not pair or segregare properly→resulting in nonviable gametes→Doubling of chromosomes produces an allotetraploid→chromsome pairing and segregation are noraml, producing balanced gametes
