module 11 Flashcards
Genomes are ___________?
dynamic
What is a failed chromosome and/or sister chromatid segregation during cell division called?
Nondisjunction
What occurs when an
organism carries one or more
complete extra sets of
chromosomes?
Most common in _______
polyploids may be __________
or ______________
Polyploidy
plants
autopolyploid
allopolyploids
Extra chromosomes from within
same species
tetraploid ex:
triploid ex:
Autoployploids
- peanuts
- bananas
Three mechanisms lead to autopolyploidy
▪ multiple fertilizations (sexual)
▪ meiotic nondisjunction (sexual)
▪ mitotic nondisjunction (asexual)
______________is thought to be
the most common form of
polyploidy in plants
diploid ex:
tetraploid ex:
alloployploid
einkorn wheat
emmer wheat
Two species of goatsbeard, Tragopogon miscellus and T.
mirus, have arisen multiple times in the past 80 years
through hybridization of other Tragopogon species.
Following hybridization, the genome doubled, resulting in
the new, fertile species. These speciation events are an
example of:
a) autopolyploidy
b) allopolyploidy
c) euploidy
d) aneuploidy
e) all the above
Banding pattern during metaphase:
more condensed = ?
less condensed = ?
Banding pattern during metaphase:
more condensed = ?
less condensed = ?
________ _____ provides consistent banding
patterns across human chromosomes.
lower resolution
finer resolution
Giemsa staining
Organisms with one normal and
one terminally deleted
chromosome are called what?
▪ Example?
- terminal deletion on what chromosome?
partial deletion heterozygotes
human cri-du-chat
syndrome
▪ terminal deletion on chromosome 5
Define interstitial deletion
loss of an internal portion of a chromosome
Wagr syndrome, Series of conditions
caused by deletion on
chromosome 11, is what type of deletion?
Interstitial (internal) deletion
Define WAGR syndrome
W=Wilms tumor
A=aniridia
G=genitourinary abnormalities
R=mental retardation
Occasionally an unequal crossover takes
place where?
what does this cause?
between two homologs
partial duplication on one homolog and
partial deletion on the other
What syndrome with a deletion on chromosome 7 is an example of unequal crossover?
Williams-Beuren syndrome
chromosome _____________: reattachment
in the wrong orientation
▪ chromosome ____________: reattachment
to a nonhomologous chromosome
these two things can result from?
inversion
translocation
chromosome breakage
what is Chromosome Translocation
Attachment of all or parts of
non-homologous chromosomes
differing by ONE extra or ONE fewer
chromosome than normal (sometimes a few)
_____________ = three of a particular chromosome
___________= one of a particular chromosome
Define Euploidy
Aneuploidy
trisomy
monosomy
differ by ONE OR MORE entire sets of chromosomes (triploid, tetraploid)
what are translocation heterozygotes
one normal copy and one translocated copy of each chromosome
Three Types of Translocations
1.arise when a piece of one chromosome is translocated to a non-homolog and there is no
reciprocal event
- Reciprocal balanced translocations:
- also called chromosome fusions, involve fusion of two nonhomologous chromosomes
- unbalanced translocations
- occur when pieces of two non-homologs
switch places - Robertsonian translocations
ANEUPLOIDY
Either sex chromosomes or ____________
▪ Severe _______ ____________(e.g., Down’s syndrome = trisomy
of chromosome 21)
▪ Do Plants or animals tolerate aneuploidy better?
Problems arising from aneuploidy are typically due to?
autosomes
genetic imbalance
Plants tolerate aneuploidy better than animals
altered gene dosage
what are the consequences of translocations during meiosis?
partially homologous chromosomes can synapse
during meiosis for reciprocal balanced
translocations, this leads to formation of a tetravalent
complex
What is the leading cause of congenital birth defects and miscarriages?
T/F Estimated 1 in every 170 live births is at least partially aneuploid
aneuploidy
TRUE
DNA sequences that can move around the genome. Enzyme-driven process called transposition
-make up large portion of genome in many species
Transposable genetic elements (TEs)
If two pairs of chromosomes fuse by Robertsonian
translocation, the number of chromosomes drops to what?
2n − 2
Transposable Genetic Elements Move
throughout the Genome and can disrupt gene function via?
insertional inactivation
Transposable elements typically share a similar general structure, which
may include:
- _______ ____ repeats: (not part of element)
- __________ _______ repeats (part of element)
- central region with ______ or more genes
- flanking direct repeats
- terminal inverted
- one
During gamete formation in an adult male, a nondisjunction
event occurs during anaphase of meiosis II.
As a result, _____ gamete(s) resulting from this meiosis will
carry an aneuploidy.
a) 1
b) 2
c) 3
d) 4
e) none of the
_______________ can develop from mitotic nondisjunction early in embryogenesis.
Mosaicism
25–30% of Turner
syndrome cases
occur in mosaic
females
mix of 2n=45 XO,
2n=46 XX (and
2N=47 XXX cells)
T/F
TRUE
Transposition mechanism
Staggered cut at the insertion site
generated by transposase (or
integrase)
individuals with both male
and female characteristics
gynandromorphs
Class I TEs: 1. ____________
▪ 2.________________ (replicative) transposition
▪ TE transcribed into RNA, reverse-transcribed to 3.______ for insertion
- __________ in copy number, can disrupt gene function
▪ examples: LINEs, SINEs
- retrotransposons
- ‘copy and paste’ transposition
- DNA
- expansion
Class 1.___ TEs: DNA transposons
2.___________ (non-replicative) transposition
no RNA intermediate, TE is cut out and re-inserted in
another location
no expansion in copy number, can disrupt
3. ______ function
▪ examples: Ds and Ac elements in maize
- Class II
- ‘cut and paste’ transposition
- gene function
which elements can move by themselves?
▪ example: LINEs
▪ which elements require other TEs for transposition?
▪ example: SINEs
autonomous
non-autonomous
Most bacterial transposons are what class?
DNA transposons (Class II)
1.________ transposons (aka insertion sequences)
▪ transposase gene and terminal inverted repeats
- ______________ transposons
▪ two flanking insertion sequences and one or more additional genes
▪ often carry antibiotic resistance gene
- simple transposons
- composite transposons
Simple transposons (insertion sequences) are found in ?
bacteria, archaea, viruses and plasmids
what transposons are up to ~10,000 bp, with flanking insertion sequences?
Bacterial composite transposons
T or F Eukaryotes carry ONLY class I and not class II transposable elements
FALSE, Eukaryotes carry both class I and class II transposable elements
Retrotransposons (Class I transposable elements) are
composed of what, are found in what and are replicative?
composed of DNA, are found in eukaryotes
How is RNA copied back into DNA?
reverse transcriptase
LINEs and SINEs make up
roughly ___% and ___% of the
human genome, respectively
roughly 20% and 10%
- Retrotransposons are related
to ? - gene(s) carried on retrotransposons are often flanked by what?
- retroviruses
- long terminal repeats
(LTRs)
wild-type C allele results in purple kernels
▪ mutant c1 allele produces yellow kernels
▪ closely linked genes produce
plump/wrinkled (Sh/sh) and shiny/waxy
(Wx/wx) kernels
Class II elements
Activator element (Ac)
often leads to
chromosome breakage
at Ds gene
- Ac element (activator)
contains transposase
gene, ‘activates’
transposition of Ds gene - loss of Wx, Sh and C
results in
colorless/shrunken/waxy
phenotype
- insertion of Ds
(dissociation) gene
disrupts C gene - Ac-activated excision of
Ds from C is a
reversion mutation
▪ C allele restored, purple
color results
Many duplicate copies
eventually lose some or
all function
▪ referred to as
pseudogenes
‘neo-functionalization’ =
new function
▪ ‘sub-functionalization’ =
division of function
