Chromosomes Flashcards
(157 cards)
1
Q
Is the highly condensed form of DNA
Wrapped into NUCLEOSOMES and CHROMATIN FIBER
Condensed during Metaphase into familiar shape
Humans have 22 autosomal pairs and one pair of sex chromosomes
Rod-shaped, filamentous bodies present in the nucleus, which become visible during cell division
Carriers of the gene or unit of heredity
Not visible in active nucleus due to their high water content, but clearly seen during cell division
Were first described by Strausberger in 1875
First used by Waldeyer in 1888
A
Chromosome
2
Q
Chromosomes is wrapped into?
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Nucleosomes and Chromatin Fiber
3
Q
Chromosomes condensed during?
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Metaphase
4
Q
Chromosomes were first described by who?
A
Strausberger in 1875
5
Q
The term ‘Chromosome’ was first used by ….
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Weldeyer in 1888
6
Q
Chromo means….
A
Colour
7
Q
Soma means…….
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Body
8
Q
Presence of a whle sets of chromosomes is called…
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Eeuploidy
9
Q
when a change in the chromosome number does not involve entire set of chromosomes, but only a few f the chromosomes is…
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Aneuploidy
10
Q
Gametes normally contain only one set of chromosome — this number is called __________..
A
Haploid
11
Q
Each ______ has been packed into a MITOTIC CHROMOSOME that is 10,000-fold shorter than its extended length.
A
DNA Molecule
12
Q
____ cells usually two sets of chromosome
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Somatic Cell
13
Q
what are the symbols of the ff:
Diploid
Triploid
Tetraploid
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Diploid - 2n
Triploid - 3n
Tetraploid - 4n
14
Q
Chromosome size -
In contrast to other cell organelles, the size of chromosomes shows a remarkable variation depending upon the _____________.
A
stages of cell division
15
Q
Chromosome Size
_________________: chromosome are longest and thinnest
A
Interphase
16
Q
Chromosome Size
______________: there is progressive decrease in their length accompanied with an increase in thickness
A
Prophase
17
Q
Chromosome Size
______________: chromosomes are smallest
A
Anaphase
18
Q
Chromosome Size
______________: Chromosomes are the most easily observed and studied during metaphase when they are very thick, quite short and well spread in the cell.
A
Metaphase
19
Q
Chromosomes can be distinguished by “___________” - using DNA hybridization + fluorescent probes
A
Painting
20
Q
Types of Chromosomes
A
Autosomes and Sex chromosomes
21
Q
- Paired chromosomes with same length, shape, centromere location and genes
- any chromosomes other than a sex chromosome
-determine size, color, hair of a body.
A
Autosomes
22
Q
Members of a pair chromosomes that differ between males and females
A
Sex chromosomes
23
Q
Chromosome Parts
A
Heterochromatin
Euchromatin
Telomeres
Centromeres
p arm
q arm
24
Q
- more condensed
- silenced genes(Methylated)
- Gene poor( High AT content)
- stains darker
A
Heterochromatin
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- Less condensed
- Gene expressing
- Gene rich(higher GC content)
- stains lighter
Euchromatin
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- chromosome tips
- repeats
Act as sort biological clock
Being whittled down at each Mitosis
Telomeres
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- Middle
- highly condensed
- Also repetitive sequence
- Region where spindle fibers attach
- Pulling chromatids apart during Mitosis
Centromeres
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the smaller of the two arms
p arm
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the longer of the two arms
q arm
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How's band numbered?
Bands are numbered from centromere to outward
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Chromosome Types
1. Telocentric
2. Acrocentric
3. Submetacentric
4. Metacentric
*divided based on the position of the centromere
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no p arm; centromere in on end
Telocentric
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very small p arm; centromere is very near end
Acrocentric
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p arm just a little smaller than q arm; centromere in middle
Submetacentric
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p and q arms are exactly the same length; centromere in exact middle of chromosome
Metacentric
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__________ chromosomes are not genetically identical. They can have different alleles of genes
Homologous chromosomes
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are genetically identical
Sister chromatids
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Sister chromatids are generally identical
- form as cells go throughS PHASE(replication)
- attached to each other by centromere until ANAPHASEof MITOSIS
- Once separated each is again referred to as CHROMOSOME
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Study of chromosomes and chromosomal abnormalities
Cytogenetics
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Picture of an individual's chromosomes in Metaphase, spread out on a slide
Study Karyotypes
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3 copies of single chromosome (47)
Trisomy
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1 copy of a single chromosome (45)
Monosomy
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3N
Triploidy
44
Tetraploidy
4N
45
Structural Chromosomal Aberations
- deletion
- duplication
- translocation(involves 2 chromoses)
- inversion
- isochromosome
- ring chromosome
46
complete extra set of chromosomes:
- three of every chromosome
- cannot survive to birth
Polyploidy
47
Missing or extra of one chromosome:
- Monosomy -- missing one
- Trisomy -- extra one
- only trisomy 13, 18 and 21 are viable
Aneuploidy
48
Trisomy that are viable
Trisomy 13, 18, and 21
49
- when nondisjunction occurs in both the mother and the father's gametes
- causing two copies of one chromosome to come only from one parent
- "Two bodies, one parent" bodies are chromosomes
- incredible rare event
- more often nondisjunction leads to either monosomy or trisomy
Uniparental Disomy
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- large part of one chromosome has been lost during mitosis
- vary in size - larger is more severe
Deletion
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- Large part of one chromosome has been duplicated on same chromosome
- vary in size -- larger is more severe
Duplication
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Two Translocations
1. Robertsonian Translocation
2. Reciprocal Translocation
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Non-homologues chromosomes have exchanged pieces(crossed over)
Translocations
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- Two q arms of two different chromosomes come together
- two p arms are lost entirely
Robertsonian Translocation
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- Two different chromosomes exchange parts
- since all parts are still present -- often normal
Reciprocal Translocation
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One part of chromosomes has been flipped around in opposite direction
- again, individual may be normal
- unless Its breakpoints are in MIDDLE of a gene
- or unless its affects CENTROMERES
inversion
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- Have two identical arms
- two p's or two q's and not the other
Isochromosomes
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- Telomeres are lost or don't function
- so one end of chromosome attaches to other end forming a ring
- cannot undergo mitosis successfully
Ring chromosomes
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Causes of chromosomal disorders
Ionising radiation, autoimmunity, virus infections and chemical toxins in the pathogens of certain disorders.
60
- Unequal division of chromosomes during Meiosis
- Can happen to either sperm or oocyte
- form one gamete with two copies of same chromosome
- other gamete with zero copies of that chromosome
- different outcomes if happens at first or second stage of Meiosis
Non-disjunction
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True or False.
Non-disjunction part 1 is the dangerous compared to part 2.
True
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Numerical Chromosomal Aberrations
- Klinefelter's syndrome(male)
- Jacob's syndrome(male)
- Trisomy X syndrome
- Turner syndrome(female)
- Patau's Syndrome(trisomy 13)
- Down Syndrome(Trisomy 21)
- Edward Syndrome(Trisomy 18)
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Structural Chromosomal Aberrations
- Cri-du-chat syndrome
- aniridia-wilms tumor syndrome
- thirteen q deletion syndrome
- prader-willi syndrome
- eighteen q deletion syndrome
- burkitt lymphoma
- cat-eye syndrome
- four-ring syndrome
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Trisomy 13 was first observed by_____________, the chromosomal nature of the disease was ascertained by ____________.
Thomas Bartholin in 1657; Dr. Klaus in 1960.
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Down syndrome was name after ___________, the british physician who described the syndrome in 1866.
John Langdon Down
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Trisomy 18 was named after ____________, wo first described the syndrome in 1960
John H. Edward
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Polyploidy
Extra chromosome sets
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Anueploidy
An extra missing chromosome
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Monosomy
one chromosome absent
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trisomy
one chromosome extra
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deletion
part of chromosome missing
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duplication
part of a chromosome present twic
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translocation
two chromosomes join arms or exchange parts
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Inversion
segment of chromosome reversed
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Isochromosome
a chromosome with identical arms
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Ring chromosome
a chromosome that forms a ring due to deletions in telomeres which cause ends to adhere
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Is one of the techniques that allows us to diagnose several thousand possible genetic diseases in humans
refers to the use of microscope to examine the size, shape and number of chromosomes in a sample of body cells.
Karyotyping
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can cause problems with a person's growth, development and body functions.
Extra, missing or abnormal positions of chromosome pieces
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the number and visual appearance of the chromosomes in the nucleus of a cell is called....
karyotype
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is recommended as a routine diagnostic procedure for number of indications
Chromosome analysis
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when is chromosome analysis indicated?
1. Problems noted during early growth/development
2. Stillbirths and neonatal deaths
3. Fertility problems
4.Pregnancy in women 35 years or older at time of delivery
5. family history
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Two categories of chromosome abnormalities
Numerical and Structural
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Cells Used for chromosomal Analysis
- Any cell with a nucleus
- Lymphocytes
- skin cells
- Tumor cells
- Amniotic Cells
- Chorionic villi
- Rare fetal cells from maternal blood
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collects fetal cells for chromosomal and biochemical studies. Generally performed in the 16th week
Amniocentesis
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refers to the application of spectral imaging to the simultaneous visualization of all human chromosomes in different colors.
is a laboratory technique that allows scientists to visualize all of the human chromosomes a one time by "painting" each pair of chromosomes in different fluorescent color
Spectral karyotyping
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Combining two techniques in 1996, the SKY technique was developed by _____ et al
Schrock
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Principle of SKY
1. Chromosome painting is a technique of drawing and ENTIRE IMAGE of chromosome by using FLUORESCENT SIGNALS
2. Multicolor fluorescence is a technique of drawing images of SEVERAL hybridization signals with different florescent dyes.
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Karyotyping is also called as....
Chromosome analysis
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allows scientists to view the full set of human chromosomes in black and white, a technique that is useful for observing the number, size and shape of the chromosomes.
Traditional karyotyping
90
it is disruption in the normal chromosomal content of the cell.
it brings about a change in the genetic character of the individual(Chromosomal mutation)
Chromosomal Aberration
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Two types of Chromosomal Aberration
Numerical aberration and structural aberration
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alteration of genes or gene sequence influenced only one chromosome
Intra chromosomal
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alteration of genes or gene sequence influenced involve at least two chromosomes
Inter chromosomal
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Intrachromosomal; Deletion, Duplication and Inversion
Inter chromosomal; ______________
Translocation
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Intrachromosomal; _______________
Inter chromosomal; Translocation
Deletion, Duplication and Inversion
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cytogeneticist use three main features to identify and clasify chromosomes;
1. Location of the centromere
2. Size
3. Banding patterns
* all seen in a karyotype and important in identifying chromosomal aberrations
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two primary ways in which the structure of chromosomes can be altered
1. the total amount of genetic information in the chromosome can change(Deficiencies/Deletion and Duplication)
2. The genetic material remains the same but is rearrange(inversion and translocation)
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Types of structural aberrations
Deletion
Duplication
Inversion
Translocation
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The loss of chromosomal segment
Deletion
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The repetition of a chromosomal segment compared to the normal parent chromosome
Duplication
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a change in the direction of part of the genetic material along a single chromosome
Inversion
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A segment of one chromosome becomes attached to a different chromosome
Translocation
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ABCDEFGHI>>> (abcdhi)
part of the chromosome has been removed
Deletion
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ABCDEFGHI>>>ABCDEFDEFGHI
part of the chromosome is duplicated
Duplication
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ABCDEFGHI>>> ABCFEDGHI
Part of the chromosome has been re-inserted in reverse order
Inversion
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ABCDEFGHI:UVWXYZ>>> ABCDEFXYZ:UVWGHI
parts of two non-homologous chromosomes are joined
translocation
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it also known as DEFICIENCY, these involves the loss of a segment or loss of a portion of the chromosome
occurs when a break in the chromosome at any one point results in the tearing away of a part of chromosome
Deletion
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Two types of Deletion
Terminal Deletion and Intercalary Deletion
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A break occurs in a chromosome a little away from one end and a segment comes out.
ex. if a chromosome has gene loci 1234 in one of its arm and portion 24 will be deleted, it wil become 12
Terminal Deletion
110
A segment comes out of the middle due to breaks at two points in chromosome
ex. in a chromosome with a gene loci 1234 in one of its arm, there will be two nicks: one between 3 and 4 and the other between 1 and 2 resulting segment in one of its arm would be 14.
Interstitial/ Intercalary Deletion
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The phenotypic consequences of deletion depends on the
1. Size of the deletion
2. chromosomal material deleted
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Deletions are detrimental is they have a _____
phenotypic effect
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a segment of the chromosome containing several gene loci duplicate itself
occur at the tip of in the middle of the chromosome
it affects a single chromosome
Duplication
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Different types of Duplication
tandem; reverse
tandem; terminal
tandem; displaced
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the duplicated segment is attached to the chromosome in the same locus and in the same sequence
ABCBCDEFGH
Tandem
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the duplicated part will attach itself to the chromosome at the same locus but in reverse sequence
ABCCBDEFGH
Reverse tandem
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the duplicated segment is located in the tip of the chromosome
ABABCDEFGH
Terminal Tandem
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the duplicated segment attach to the same chromosome but in different locus other than its original position
RSTBCUVW
Displaced Duplication
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Displaced Duplication
*if the segments retains the sequence, it is called ____________.
DISPLACED TANDEM
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Displaced Duplication
*if it is in reverse sequence it is called __________
DISPLACED REVERSE TANDEM
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when displaced duplication occurs in the same arm
homobrachial displacement
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when the displaced duplication occurs in a different arm
hetero displacement
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Effects of Duplication
- Formation of gene families
- Bar eyes locus in Drosophila melanogaster
- Mental disorders
- evolutionary consequence
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a chromosomal duplication is usually caused by abnormal events during ____________.
Recombination
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a kind of intra chromosomal aberration where there is an alteration int he normal sequence of genes.
involves two breaks in the chromosome, with a segment separated from it, then it joins back the chromosome in a reverse sequence
no change in the quality and quantity of genes
maybe detrimental to the organism in rare cases
ABCDEFG>>> AEDCBFG
Inversion
126
Two types of Inversion
Paracentric Inversion
Pericentric Inversion
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Centromere lies outside inverted region, thus it does not alter the morphological shape of the chromosome
Paracentric Inversion
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Pericentric Inversion
the centromere lies within inverted region which results to the change in the appearance of the chromosome
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Effects of inversion
repositioning of protooncogenes in inverted chromosomes can active oncogenes and disrupt normal regulation of the cell cycle causing various forms of tumors and leukemias
chromosome rearrangements can contribute to the transformation of normal cell into a cancerous cell
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Involves a change in the location of chromosome segment
like inversion no gene is lost or gained
Translocation
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Types of Translocation
Intrachromosomal
Interchromosomal
Reciprocal
Non-reciprocal
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A(BC)EDFGH>>>ADEF(BC)GB
Nonreciprocal Intrachromosomal
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A(BC)DEFGH>>>MNOPQRS
Non-interchromosomal translocation
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(AB)CDEFGH;(MNO)PQR>>> (MNO)CDEFGH;ABPQR
Reciprocal interchromosomal
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two non-homologous chromosomes exchange genetic material
it leads to a rearrangement of the genetic material, not a change in the total amount
usually without phenotypic consequences
then can result in position effect(few cases)
Reciprocal translocation /Balanced Translocation
136
involves at the extreme end of two non-homologous acrocentric chromosomes
the short ends are lost, long ends fuse
Robertsonian translocations
137
Other effects of translocation
cancer
infertility
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Causes of chromosomal aberration
- non-disjunction during anaphase
- misalign cross over
- chromosome breaks
- loss, gain or rearrangement of chromosomes
- maternal age
- environmental risks factors(radiation, smoking, alcohol consumption, drugs, oral contraceptives)
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abnormality in chromosomal number and structure
aberration
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one of the alternative forms of a gene
allele
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a mutation affecting large region of chromosome or an entire chromosome thereby affecting many genes
chromosomal mutation
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a felt duplicating body in the nucleus of the cell that is made up DNA and protein
chromosome
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a disease characterized by uncontrolled cell division
cancer
144
chromosome segment is lost
depletion
145
chromosome segment is duplicated
duplication
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the genetic makeup of an individual, including all genes on both sets of chromosomes in diploid cell
genotype
147
an individual having two different alleles for specific trait
heterozygote
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two identical alleles for specific trait
homozygote
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chromosome segment breaks off and reinserts in inverted sequence
Inversion
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a change proto-oncogene that promotes uncontrolled cell division and growth
oncogene
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the physical appearance of an organism controlled by its genes interacting with the environment
phenotype
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a gene involve in stimulating normal growth and division of cells in controlled manner
protooncogene
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a set of medical symptoms which tend to occur together
syndrome
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a segment of one chromosome is transferred to another chromosome
translocation
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deletion sydromes
Prader-willi syndrome
cri-du-chat syndrome
william syndrome
jacobsen
156
translocation syndrome
Philadelphia syndrome
familial down's syndrome
Burkitt lymphoma
different types of cancer
157
Duplication syndromes
cat's eye syndrome
bat eye in fruit fly
bar eye mutation
formation of gene families
beckwith-wiedemann s.
charcot-marie syndrome
