CYTOGEN 3RD TRINAL Flashcards
- diff varieties of chromosomes
VARIATION
- division of normal chromosome
structure
MUTATION
- Change in the sequence structure of genetic
material
MUTATION
2 TYPES OF MUTAGENS
- PHYSICAL MUTAGENS
- CHEMICAL MUTAGENS
e.g., X-rays, UV rays
Physical Mutagens
- leads to cancer
e.g., mustard gas, nicotine, benzene
Chemical Mutagens
ORIGIN OF MUTATION
1) HEREDITARY/GERMLINE MUTATION
2) ACQUIRED/SOMATIC MUTATION
- runs in the family
- de-novo mutation = new (no previous
history, first time to experience)
HEREDITARY/GERMLINE MUTATION
- occurs in body cells
- Not hereditary
- e.g., cancer
ACQUIRED/SOMATIC MUTATION
TYPES OF MUTATION
On basis of HOW
- SPONTANEOUS
- INDUCED -
TYPES OF MUTATION
On basis of HOW that naturally occurs (internal
factors)
SPONTANEOUS
TYPES OF MUTATION
On basis of HOW is an external factors (mutagens)
——>Euploidy (tri, tetra, so on)
INDUCED
TYPES OF MUTATION
On basis of WHERE
- DNA or gene mutation-
- Chromosomal aberration -
TYPES OF MUTATION
On basis of WHERE that changes in
structure/number
Chromosomal aberration
TYPES OF MUTATION
On basis of WHERE that is a point mutation
DNA or gene mutation
causative agent of mutation
mutagens
2 copies of each chromosome
somatic non sex cells
composed of first 22 copies of chromosome
diploid organism
sex cells,
one copy of each chromosome (gametes)
last chromosome (X,Y)
haploid
- equational division takes place in
somatic cells
mitosis
process of mitosis
interphase
prophase
metaphase
anaphase
telophase
last step in the process of mitosis and is a divison of 2 new cells
cytokenesis
- normal chromosome
-No. of sets of chromosomes in a biological
cell.
PLOIDY
- abnormal chromosome
- is the state of a cell or organism having an
integral multiple of monoploid number
EUPLOIDY
- Refers to number of basic chromosome sets
PLOIDY
- A diploid has ____ sets where as a hexaploidy
has ____ sets
2
6
The basic chromosome number x, also
called the ____________ is the number
of different chromosomes that make up a
single complete set
monoploid number
gene containing chromosomes that are
multiple of basic single set
EUPLOIDY
the variation in the chromosome number that
occurs due to increase or decrease of full
set of chromosomes
EUPLOIDY
the condition of an organism having
complete set of chromosomes or multiples of
the basic set is euploidy and the cell is said
to be euploid
EUPLOIDY
is lethal in most animal species, but
often tolerated in plants, where it has played
a role in specification and diversification
euploidy
same species/ same individual
autoploidy
same species/different individual
allploidy
- This is a condition where the chromosome
number is not an exact multiple of the
normal diploid number, with either fewer or
more than the normal number of
chromosomes in the cell
ANEUPLOIDY
- can result when either round of meiotic division lacks cytokinesis, or when meiotic
nondisjunction occurs for all chromosomes
-did not separate
Monoploidy and polyploidy
A gamete with 2 sets of chromosomes fused
with a normal gamete produces a
triploid (3N) zygote
Complete nondisjunction at meiosis produce
____________ with the normal chromosomes, and ________________
½ gametes
½ with no chromosome
Fusion of 2 gametes that each have 2 sets of
chromosomes produces a
tetraploid (4N) zygote
can result from mitotic nondisjunction of complete chromosome sets
Polyploidy of somatic cells
An individual that contains ½ the normal
number of chromosomes is a ____________
and exhibits ___________
monoploid
monoploidy
Some species such as bee, ants and male
bees are normally _____________ because they
developed from unfertilized eggs.
Consequently, these individuals will be
sterile
monoploid
are very rare in nature because
recessive lethal mutations become
unmasked, and thus they die before they are
detected
Monoploids
These alleles normally are not a problem in
diploids because their effects are masked by
dominant alleles in the genome
MONOPLOIDY
- Occurs in cells and organisms when there
are more than 2 homologous sets of
chromosomes - Very common in plants
POLYPLOIDY
- polyploids as a result of
duplications in the SAME species
AUTOPOLYPLOIDS
- polyploid formed by the
hybridization BETWEEN TWO species.
ALLOPLOIDS
A ___________________. is derived from
hybridization from two or more diploid species
with chromosome doubling following the
hybridization
typica allopolyploid spp.
A human cell has ________chromosomes, which is an integral multiple of the monoploid number, 23
46
> MONOSOMY (2n-1)
NULLISOMY (2n-2)
HYPOPLOIDY
> TRISOMY (2n+1)
TETRASOMY (2n+2)
HYPERPLOIDY
- second most common condition
- there are 45 chromosomes in each cell of the body instead of the usual 46
Monosomy
- most common condition
- this means they have 47 chromosomes instead of 46.
ex. down syndrome
Trisomy
are abnormal structural and numerical changes
Chromosomal changes
- Chromosomal changes are abnormal
structural and numerical changes - They are also called chromosomal mutations
chromosomal aberrations
Gross structural changes of chromosomes are
called
structural aberrations or
chromosome re-arrangements
Numerical changes are called
ploidy changes or numerical aberrations
are chromosomes involve in the gain, loss or relocation of chromosome
segments and genes
Structural changes
STRUCTURAL CHANGES are
o Intrachromosomal aberrations
(homosomal aberration)
o Interchromosomal aberrations
Chromosomal aberration are of 4 basic types
- Deficiency or deletion
- Duplication
- Inversion
- Translocation
▪ Loss of a chromosome segment, together
with the genes contains in it
DEFICIENCY OR DELETION
- loss of a terminal segment, with a single break in the chromosomes
- end part
Terminal deletion
- loss of an intercalary segment, with 2 breaks
- center
Intercalary deletion
- a segment is lost from both the chromosomes of a homologous pair
Homozygous deletion
- a segment is lot only from 1 of the 2 homologues
Heterozygous deletion
involves the loss of genes so they
have deleterious effect on organisms
Deletion
If the lost genes are crucial for viability,
___________________________ may result
sterile gametes or nonfunctional somatic
cells
- deletion of long arm of chromosome 21
- 9 part is lost
Granulocytic leukemia
- heterozygous deletion in the short arm of chromosome 5
Cri-du-chat syndrome
is the doubling or repetition of
chromosome segment during chromosome
__________
Duplication
a set of genes gets doubles
or repeated
Duplication
The extra set of genes in duplication is generally called
“repeat”
3 types of duplication
- Tandem Duplication
- Reverse Tandem Duplication
- Displaced duplication
- the extra segment and the parent segment are next to each other and have the same order of genes
- repeated
Tandem Duplication
- the extra segment lies next to parent segment with reversed gene sequence
- nagbaliktad
Reverse Tandem Duplication
- the duplicate segment lies some distance away from the parent segment
- away
Displaced duplication
are more frequent and less
deleterious than deletions
Duplications
are believed to be important
raw materials of organic evolution
Duplications
affect the regulation of
gene activity and there by causes
phenotypic alterations which in turn
promotes speciation and evolution
Large duplications
- the reversal of the linear order of
a chromosome segment and its gene
sequence
Inversion
Believed to be occur in intercalary
segments-
intercalary inversion
involves the breakage of a chromosome segment an its subsequent re-insertion into the same location in a reversed orientation
Intercalary inversion
in this case 2 breaks occur in a
chromosome-
inversion points
- the rotation (180)
and reinsertion of an acentric segment
paracentric inversion
- the rotation (180)
and reinsertion of a centric segment
pericentric inversion
paracentric inversion is of two types
(i) Intraradial or homobranchial
inversion
(ii) Interradial or heterobranchial
inversion
- single inversion in one arm
Intraradial or homobranchial
inversion
- 2 inversions 1 in each arm
Interradial or heterobranchial
inversion
inversion that does not include centromere
paracentric inversion
inversion that includes centromere
pericentric inversion
- only 1 segment is inverted
Single inversions
- more than 1 segment
would be inverted
Complex inversions
- both the homologues are inverted
Homozygous inversion
- 2 homologue is un-inverted and its companion is inverted
heterozygous inversion
COMPLEX INVERSIONS
- Independent inversions
- Direct tandem inversions
- Reversed tandem inversions
- Included inversions
- Overlapping inversions
- Inversions occur in diff. regions of the
chromosome and they are separated from
1 another by un-inverted (normal) segment
independent inversions
- There are 2 or more inverted segments
which are directly adjacent to each other,
i.e., the inverted regions are not separated
by normal regions
Direct tandem inversions
- The 2 inverted segments are adjancent to
each other but their positions are mutually
interchanged i.e., g. the first segment lies
in place of the 2nd an vice versa
Reversed tandem inversions
- 1 inversion is confined with another
inversion, i.e., a segment within an inverted
segment is inverted again; as a result, the
2nd inverted segment possesses the normal
gene sequence for the concerned segment
Included inversions
- Such inversions have a common segment,
i.e., a part of an inverted chromosome
segment is inverted again together with an
adjacent segment which was not included
in the 1st inverted segment
Overlapping inversions
- Helps to retain the original gene combination
by reducing the crossing over frequency
INVERSION
enhances the position effect & there
by produces phenotypic changes
Inversion
causes chromosome polymorphism
with in a population leading to karyotype
evolution
Inversion
produces balanced gene complexes
(super genes) though reduction of crossing
over, which in turn confers greater biological
fitness and adaptability & increases the
evolutionary potentiality.
Inversion
is the re-organization of chromosomes through the transfer or change
in position of chromosome segments without
gain or loss of genes.
Translocation
– change in position of
a segment within a chromosome, either from
one arm to the other or from one location to
another in the same arm.
Intrachromosomal Translocation
(Chromosomal shift)
Intrachromosomal Translocation
(Chromosomal shift) –
o Intraradial
o Extraradial –
o Interchromosomal Translocation
o Transpositional Translocation
o Reciprocal Translocation
– translocation from one
location to another in the same arm
Intraradial
– translocation from one arm
to the other.
Extraradial
–Transfer of a segment from one
chromosome to other.
Interchromosomal Translocation
– one way transfer of a chromosome segment from one portion to another in the same
chromosome.
Transpositional Translocation
– mutual exchange of segments between two
chromosomes.
Reciprocal Translocation
– Mutual exchange between homologous chromosomes
Fraternal Translocation
– Mutual exchange
between non-homologous chromosomes
External Translocation
–intercalary incorporation of a chromosome
segment by transposition.
Intercalation or Insertional translocation
– Exchanged segments are
asymmetrical, produces a dicentric & an
acentric chromosome
Asymmetrical or Aneucentric
Translocation
–Exchanged segments are symmetrical,
produces two monocentric chromosomes.
Symmetrical or Eucentric Translocation
a segment from the orange (donor) chromosome is transferred to the purple (recipient) chromosome without any reciprocal
exchange.
insertional translocation
- Translocation which involves the transfer of a
whole chromosome arm.
WHOLE ARM TRANSLOCATION
– Two breaks in two acrocentric chromosomes. One break is in the short arm of a chromosome and the other one is in the long arm of the other chromosome. Their subsequent fusion results in a metacentric chromosome.
Centric Fusion
– It is the reverse process in
which a metacentric chromosome and a sub
metacentric chromosome give rise to two
acrocentric chromosomes.
Dissociation
– It is the end-to-end fusion
between an acrocentric chromosome and a
metacentric chromosome with the loss of a
centric segment. It produces a double length
acrocentric chromosome.
Tandem fusion
change the linkage relationships of the genes involved in the affected segments
Translocations & Inversions
results in unusual linkage,
reduced meiotic recombination, low
viability of chromosomes, familial patterns
of trisomy
Translocation
is an unbranched
structural abnormality in which the arms of
the chromosome are mirror images of
each other
ISOCHROMOSOME
is a structural rearranged chromosome generated either by a rearrangement involving two or more chromosomes or by multiple
aberrations within a single chromosome
derivative chromosome
- is a chromosome whose arms are fused together to form a ring
- A structurally abnormal chromosome in
which the end of ach chromosome arm
has been lost and the broken arms have
been reunited to form a ring.
ring chromosome
