LESSON 1: CHROMOSOMAL STRUCTURE & MUTATION Flashcards
the largest (246 million nucleotide bp)
Chromosome 1
the smallest (48 million nucleotide bp)
Chromosome 2
is a trait or group of traits resulting from the transcription and translation of these genes.
Phenotype
is the DNA nucleotide sequence responsible for a phenotype.
Genotype
3 CATEGORIES OF DNA MUTATION
Gene Mutations
Chromosome Mutations
Genome Mutations
affect single genes and are often, but not always, small changes in the DNA sequence.
Gene Mutations
affect the structures of entire chromosomes; the movement of large chromosomal regions either within the same chromosome or to another chromosome.
Chromosome Mutations
changes in the number of chromosomes
Genome Mutations
a cell or cell population with a normal complement of chromosomes.
Euploid
mostly observed as increased numbers of chromosomes or when there are more than two copies of one or more chromosomes.
Aneuploid
a phenomenon that a gene inserted or moved into a different chromosomal location may be expressed differently than it was in its original position
Position effect
a disease resulting from aneuploidy, where there are three copies or trisomy of chromosome 21
Down syndrome
eight histone proteins
two each of H2a, H2b, H3, and H4
Nucleosomes are visible by:
electron microscopy
is the state of compaction of the DNA double helix that affects gene activity.
Chromosome topology
is less available for RNA transcription.
Highly compacted DNA
closed chromatin, or ____
heterochromatin
open chromatin, or euchromatin____
euchromatin
is the site of attachment of the chromosome to the spindle apparatus.
centromere
CLASSIFICATION OF CHROMOSOMES
Metacentric
Submetacentric
Acrocentric & Telocentric
arms are approximately equal in length
Metacentric
one arm is longer than the other
Submetacentric
one arm is extremely small or missing
Acrocentric & Telocentric
are considered acrocentric but may be classified as subtelocentric.
Chromosomes 13 to 15, 21, and 22
cytological stains used to visualize chromosomes.
Feulgen, Wright, and hematoxylin
region specific staining of chromosomes by the use of silver nitrate to stain specifically the constricted regions, or stalks on the acrocentric chromosomes.
Nucleolar organizing region (NOR) staining
stains chromosomes to detect mycoplasmal contamination in cell cultures; binds to the surface grooves of dsDNA and fluoresces blue under ultraviolet (UV) light (353- nm wavelength); also used to visualize chromosomes as well as whole nuclei
4′,6-diamidino-2-phenylindole (DAPI)
give particularly intense staining of the human Y chromosome and are used to distinguish the Y chromosome in interphase nuclei.
Q bands
stained by chemical dye (Giemsa) similar to those seen in Q banding; also produced by Feulgen staining after treatment with DNase I.
G banding
pattern produced by harsher treatment of chromosomes (87°C for 10 min, then cooling to 70°C) before Giemsa staining which can also be visualized after staining with acridine orange.
R banding
Alkali treatment of chromosomes results in centromere staining
C banding
the “quiet” or poorly transcribed sequences along the chromosomes that are also present around centromeres.
heterochromatin
which is relatively rich in gene activity, may not be stained as much as heterochromatin in C banding.
euchromatin
Genetic Mapping: ‘CARBS’
Chromosome Number, Chromosome Arm, Region, Band, Sub-band
complete set of chromosomes in a cell.
karyotype
is the direct observation of metaphase chromosome structure by arranging metaphase chromosomes according to size.
Karyotyping
translocation results in no gain nor loss of chromosomal material, therefore, without phenotypic effects.
Balanced translocations
occur when chromosomes are not properly assorted during meiosis affecting the phenotype of offspring
Unbalanced translocations
involves the movement of the long arm of an acrocentric chromosome to the centromere of another acrocentric chromosome. (e.g. t(9;22) translocation known as Philadelphia chromosome)
Robertsonian translocation
translocation in Chronic Myelogenous Leukemia 2
t(8;21)
translocation in Follicular Lymphoma
t(14;18)
translocation in Acute Promyelocytic Leukemia.
t(15;17)
is a gain of chromosomal material. The inserted sequences arise from duplication of particular regions within the affected chromosome or from fragments of other chromosomes
Insertion
result from excision, flipping, and reconnecting chromosomal material within the same chromosome.
Inversions
include the centromere in the inverted region,
Pericentric inversions
involve sequences within one arm of the chromosome.
paracentric inversions
is a metacentric chromosome that results from the transverse splitting of the centromere during cell division.
Isochromosome
causes two long arms or two short arms to separate into daughter cells instead of normal chromosomes with one long arm and one short arm.
Transverse splitting
results from the deletion of genetic regions from the ends of the chromosome and a joining of the ends to form a ring.
Ring chromosome
consists of translocated or otherwise rearranged parts from two or more unidentified chromosomes joined to a normal chromosome.
Derivative chromosome
normal karyotype is ____ in a female
46,XX
normal karyotype is ____ in a male
46,XY
karyotype showing 46,XX,del(7)(q13) denotes a ___ in the long arm (q) of chromosome 7 at region 1, band 3.
deletion
karyotype showing 46,XY,t(5;17)(p13.3;p13) denotes a___ between the short arms p of chromosomes 5 and 17 and region 1, band 3, sub-band 3, and region 1, band 3, respectively.
translocation
karyotype showing 47,XX + 21 is the karyotype of a female with ___ resulting from an extra chromosome
Down syndrome
is caused by an extra X chromosome in males, for example, 47,XXY.
Klinefelter syndrome
+
Gain
-
Loss
del
Deletion
der
Derivative of Chromosomes
dup
Duplication
ins
Insertion
inv
Inversion
i,iso
isochromosome
mat
Maternal Origin
pat
Paternal Origin
r
Ring Chromosome
t
Translocation
tel
Telomere (end of chromosome arm)
