Ch. 8 Flashcards
Aneuploids
alters the number of chromosomes
chromosome rearrangements (provide the types)
alter the chromosome structure; duplication, deletion, inversion, translocation
Polyploids
one or more additional sets of chromosomes (some plants, tumors)
non-disjunction
failure of homologous chromosomes or sister chromatids to segregate properly
Correct gene dosage means…
the proper number and kind of chromosomes are required for proper development
Monosomy
loss of one member of the homologous pair; almost always lethal
Trisomy
one additional member of an homologous pair; almost always lethal
When there is nondisjunction in meiosis I, how many gametes are abnormal
4
Nondisjunction in meiosis II
2 normal gametes, 2 abnormal gametes
nondisjunction occurs in
anaphase- problem in separation
Trisomy 13
Patau Syndrome; extreme malformation of organ systems
trisomy 18
Edward syndrome; slow growth and multiple abnormalities
Trisomy 21
Down syndrome; characteristic facial features and wide range of cognitive impairment
Which is more damaging- imbalance in sex chromosomes or imbalance in autosomes?
imbalance in autosomes
Random X-inactivation
only 1 X is in an active state; all others are inactive and condensed into Barr bodies
Barr Body
small, darkly staining body in interphase cells of normal female
Klinefelter syndrome
XXY; poor beard growth, breast development, and under-developed testes
Turner Syndrome
X0; characteristic facial features, web of skin, constriction of aorta, poor breast development, under-developed ovaries
changing the copy number of a gene can result in…
unbalanced gene dosage
duplication
a mutation in which part of the chromosome has been doubled
human segmental duplications make up how much of the human genome
about 4%
Deletion
the loss of a chromosome segment (the impact of a deleted region depends on what was deleted)
If the centromere is deleted
no segregation during mitosis or meiosis; gets lost
Inversions
The order of alleles change (a chromosome segment is inverted)
paracentric inversion
does not include the centromere
Pericentric inversion
includes the centromere
translocations
movement of genetic material between NON-homologous chromosomes or the same chromosome
reciprocal translocations
reciprocal exchange of segments between 2 non-homologous chromosomes
What are 2 examples of a reciprocal translocation?
Burkitt’s Lymphoma and Philadelphia chromosome
Robertsonian Translocation
occurs between the short arm of an acrocentric chromosome and the long arm of another; generates a metacentric chromosome with 2 long arms and another chromosome with 2 very short arms
Uniparental Disomy
both homologs from one parent
What are examples of uniparental disomy
Angelman Syndrome and Prader-Willi Syndrome
Why is it a problem to have both homologs from one parent?
homozygosity for any detrimental alleles; imprinting
solving nondisjunction problems:
if we have one X^something at the end it is from
the opposite parent
so X^aY crossed with X^- X^-
which gives X^a which would be nondis in mother but we can’t determine meiosis 1 or 2
in a nondisjunction problem what if we have both alleles from that parents at the end
there was nondisjunction in that parent
if it has both of their alleles= meiosis 1
if it has one of their alleles replicated= meiosis 2
