chromosome variation Flashcards
aneuploidy
2n+1 =7
Types of rearrangement
duplication
Deletion
Inversion
Translocation
dupliocation arises from — between synapsed chromosomes in meoisis
unequal crossing over
effect of duplication
increased gene dosage
nw genes with distinct gene products
effect of deletion
pseudominance
imbalance in gene product
paracentric means
inversions do not include centromere
pericentric means
inversion includes centromere
effect of inversion in individual homozygous
no problems arise in meoisis
effect of imversion in individuals heterozygous
homologous sequences align only if two chromosomes from an inversion loop
abnormal gametes form if recombination is in inverted regions
a single crossover within paracentric inversion leads to
abnormal recombination gametes
effect single crossover in paracentric inversion
suppress recombination in inverted region
types of translocations
- Non reciprocal
reciprocal
robertsonian translocation
example of disease causing reciprocal translocation
burkitt lymphoma
what is burkitt lymphoma
cancer of B cells, which are lymphocytes making antibodies
c-MYC stimulates
cell division
translocation of B-cells does what
puts c-MYC behind immunoglobin gene leading to high expression of c-MYC
high expression of c-MYC leads to
cell division out of control
describe robertsonian translocation
when the short arm of one acrocentric centrosome is exchanged for the long arm of another
leading to a large metacentric chromosmes
and a fragment taht often fails to segegrate and is losy
causes of aneuploidy
robertsonian translocation
deletion of centromere during mitosis and meiosis
nondisjunction during meiosis and mitosis
trisomy 21 results in
down syndrome
which down syndrome has 75% random nondisjunction in egg formartion
primary down syndrome
which down syndrome is robertsonian translocation between chromosome 14 and 21
familial down syndrome
when does nondisjunction occur
meiosis I or II, mitosis if sister chromatids fails to seperate
non disjunction give rise to
variation in chromosmal number
loss of both members of a homologous pair of chromosmes
nullisomy, 2n-2
loss of a single chromosome
monosomy, 2n-1
gain of a single chromosome
2n+1, trisomy
gainof two homologous chromosomes
tetrasony, 2n+_2
if a parent who is a 14-21 translocation carrier mates with a normal person, what is teh pheinotypes of offspring
2/3 will have normal phenotype including translocation carrier
1/3 will have down syndrome, others die
explain aneuploidy and maternal age
older mothers are more likely to give birth toi a child with down syndrome
significance of polyploidy
increase in cell size
larger plant attributes
Evolution
many crop plantys are polyploid
how many nuclei does skeletal muscle have
multiple nuclei
when do myoblasts fuse
as muscle cells form
what is disjunction
paired homologs fail to disjoin during segregation
