Cyto Flashcards
Hybrid science which attempts to correlate cellular events, especially those of the chromosomes, with genetic phenomena
Cytogenetics
Cytogenetics is the combination of?
Cytology and Genetics
Steps of the cell cycle
G1 -> S -> G2 -> M
G1 - Prepare to Grow 10H
S - Replication 9H
G2 - Prepares to divide 4H
M - Mitosis/Meiosis 1H
Which steps of the cell cycle is considered Interphase?
G1, S, G2
Step in the M-phase that consists of:
- Condensation of chromosomes
- Each chromosome is already doubled
Prophase (1/2)
Step in the M-phase that consists of:
- Mitotic Spindle Formation (Microtubules become spindles)
- Centromeres located at polar ends of cell
Metaphase
Point of attachment for centromeres and spindles
Kinetochore
Step in the M-phase that consists of:
- Pulling apart due to progressive shortening of spindles
- Separation of chromosomes
Anaphase (1/2)
Once chromosomes are separated, they are now considered ______________. (2 words)
Sister Chromatids
Step in the M-phase that consists of:
- Formation of Nuclear Envelope
Telophase (hehe mb)
Differentiate Meiosis I and Meiosis II
Meiosis I - Reductional Division (Ploidy decreases)
Meiosis II - Equational Division (Ploidy stays the same)
Generalized Parts of Chromosome (3)
P arm - shorter arm
Q arm - longer arm
Centromere
consists of a p and q arm
Chromatid
DNA-protein structures found at each end of a chromosome
Protect the genome from degradation
Telomere
Black bands
Gene-poor
Not actively transcribing
In interphase they are condensed and tightly packed
Made up of repeated satellite DNA
Can silence euchromatic gene expression
30-nm fiber
Heterochromatin
Also called the Primary (1°ry) constriction
Region where kinetochore proteins are located
Binds two sister chromatids together
Made up of repeated α-satellite DNA
Centromere
White band
Actively transcribing
More open/loosely packed
Allow recruitment of RNA polymerase complexes and gene regulatory proteins to initiate transcription
Made up of nucleosomes
11-nm Fiber
Euchromatin
Any narrowing or constricted point in the chromosome other than the centromere
Site of Nucleolar Organizer Region (NOR)
18S and 28S ribosomal genes that synthesize rRNA for ribosomes
Forms a satellite at the distal end of the chromosome
Stalk/ 2°ry constriction
A part of the chromosome that is separated from the rest via a secondary constriction
Used as markers in research
Satellite
Types of Chromosomes based on Number and what does it mean
Monad - only one sister chromatid
Dyad - two sister chromatids
Tetrad
- Four sister chromatids
- Two homologs during synapsis pairing
Types of chromosomes based on the number of centromeres and define.
Univalent - Only one centromere; monad or dyad
Bivalent - two centromeres; only tetrad
Types based on locations of centromeres
Metacentric
Submetacentric
Acrocentric
Telocentric
Type of chromosome where both arms are equal in length
Metacentric
Type of chromosome where one arm is slightly longer than the other
Submetacentric
Type of chromosome where one arm is significantly longer than the other
Acrocentric
Type of chromosome where the centromere is located at the telomeres
Telocentric
T/F Prophase 1 in meiosis is less elaborate than in Mitosis
F, Prophase 1 in meiosis actually has 5 stages and is more elaborate
5 stages in Prophase 1
Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis
Stage in Prophase where chromosomes become visible
Leptotene
Stage in Prophase where Chromosomes start to pair
Zygotene
Stage in Prophase where crossing over takes place
Pachytene
Stage in Prophase where Homologous chromosomes start to move away
Diplotene
Stage in Prophase where Chromosomes condense to their greatest extent; nucleolus disappears, fragments of nuclear envelope disperse
Diakinesis
Point of contact between two homologous chromosomes for recombination
Chiasma
Differentiate mitosis and meiosis
Mitosis:
- One division
- 2 daughters
- genetic identical
- same # of chromosomes in parents and daughter
- Occur in somatic cells
- Occur throughout life cycle
- Used for growth, repair, and asexual reproduction
Meiosis:
- Two divisions
- 4 daughters
- recombinant DNA
- Haploid product
- Occurs in gametes
- Limited occurance
- Used for genetic diversity
DNA where proteins of the spindle fibers bind
Centromeric DNA
DNA where ends of chromosomes that form hairpin loops to facilitate DNA replication
Telomeric DNA
T/F Ends of chromosomes stay the same length at each division.
F, ends of the chromosomes get shorter every time the cells divide,
because part of the bases are used to template off of themselves
Ribozyme that makes telomeres longer
Contains a necessary piece of RNA which serves as the template for synthesizing the new strand
Some cancer cells have overexpressed ___________ that make cancer cells live “forever”
Telomerase
Formed during Pachytene stage of Prophase I between two (2) homologs
Resembles a zipper
Made of central and lateral elements
Synaptonemal Complex
Two types of specialized chromosomes
Polytene Chromosomes and Lampbrush Chromosomes
Giant chromosomes found in larval stages of Dipteran insects
Found in
Salivary glands, Midgut, Malpighian tubules
Formed by repeated chromosome synthesis without cell division
“Puffs” - actively transcribed regions
Polytene Chromosomes
Appearance similar to the brushes used to clean street lamps
Isolated from the diplotene stage of prophase I of meiosis in most animals, particularly in amphibians
Lampbrush Chromosomes
Lampbrush chromosomes consist of
Chromomere - Condensed area that is repeated along main axis
Lateral loops - Extended less coiled dna emanating from chromomeres
Give the ploidy levels:
Spermatogonium (x)
Spermatocyte (y)
spermatids (z)
sperm cells (w)
Spermatogonium (2n)
Spermatocyte (2n)
spermatids (n)
sperm cells (n)
Cells that induce spermatocyte to undergo meiosis
Sertoli Cells
What is the ploidy level of U, V, W, X, Y, and Z
Oogonium (W)
Primary oocytes (X)
[Meiosis I halted]
[Puberty, Meiosis I resumes]
Secondary oocyte (Y)
1st Polar Body (Z)
[Meiosis II halted]
[Fertilization commences; Meiosis II resumes]
Ovum (U), 2nd polar body (V)
Oogonium (2n)
Primary oocytes (2n)
[Meiosis I halted]
[Puberty, Meiosis I resumes]
Secondary oocyte (n)
1st Polar Body (n)
[Meiosis II halted]
[Fertilization commences; Meiosis II resumes]
Ovum (n), 2nd polar body (n)
As long as Meiosis I has not continued, 2n
When are human chromosomes usually observed for sex determination, why?
During Metaphase because it is during metaphase that they are most condensed
T/F Chromosome number does not vary among species and bears little relation to the complexity of the organism
F, It varies tremendously among species
T/F The nucleus of each somatic cell contains a fixed number of chromosomes that is characteristic of a particular species
T
Non-sex chromosomes
Autosomes
Chromosomal Systems of Sex determination
X-Y
X-0
Z-W
Haplo-Diplo
Common in mammals
Female is default gender
___-Chromosome contains factors triggering male development
X-Y System
Y-Chromosomes
Systemof sex determination wherein Males produce gametes with either an X chromosome or with no sex chromosome
X-0 System
Common in birds
Default gender is male
___ Chromosome triggers female development
Also present in bees and moths
Z-W System
Peculiar to Hymenoptera
Can develop from unfertilized or fertilized egg, this determines if they are male or female
Haplo-Diplo System
Added Context:
If there is only one copy of the gene, because the animal is haploid, then the
animal develops as a male.
If there are two copies (representing two chromosomes) and they differ in
their DNA sequences, then the animal is female.
Dosage Compensation Mechanism for X-Linked Genes in Mammals
- Random inactivation of one of the X chromosomes
- Expressed as a BARR body
X-Chromosome Inactivation
Condensed and (mostly) inactivated X chromosome (Xi)
Lyonization/ heterochromatization of one chromosome leaves one transcriptionally active X, equalizing gene dose between the sexes
Characterized by:
- High levels of DNA methylation
- Low levels of histone acetylation
- Generally random
- Generally irreversible
BARR Body
How to calculate Number of Barr bodies?
n-1, where n=number of X chromosomes
- Region in the X chromosome crucial for inactivation
- Contains genes that code for non-translated RNA sequences that are involved in X chromosome inactivation
X Inactivation Center (XIC)
Mechanisms of X inactivation (2)
Xist and Tsix genes
Encodes an X inactive specific transcript RNA that binds to a specific site on one of the X chromosomes
Xist gene (X-Inactivated Specific Transcript)
Overlaps with the Xist gene but is complementary or opposite to it
Believed to be an antagonist of the Xist gene in that X chromosomes lacking this gene are inactivated more easily and quickly
Tsix gene
X and Y chromosome pairing during prophase I is facilitated by:
Pseudoautosomal Regions
- Characteristics of pseudoautosomal regions:
- present as homologous copies in X and Y chromosomes
- they are not inactivated in the X chromosome
- crossing-over takes place in X and Y in male cells
- genes in this region are not linked to either X or Y chromosome
- Found in placental and marsupial mammals
- Intronless
- Code for the transcription factor protein for male sex determination
- member of the high mobility group (HMG)-box family of DNA-binding protein
Sex-determining region of the Y (SRY)
Syndrome caused by:
- translocation of part of the SRY region to the X chromosome
- 4-5 individuals in 100,000
- With small testis and varying degrees of gynecomastia
- XX Male Syndrome (de la Chapelle syndrome)
Two main changes observed in chromosomal aberrations
Numerical and Structural changes
Types of Numerical Aberrations
- Too many or too few
Aneuploidy
Euploidy
Types of Structural Aberrations
- Total # same, structure change lang
Deletion
Duplication
Inversion
Translocation
2 main methods of detection
Karyotyping
FISH
- Cytological technique that demonstrates chromosomal aberrations
- Makes use of cultured cells at late prophase or metaphase
- Chromosomes are arranged from largest to smallest and according to
centromere location - Chromosomes are identified based on the banding patterns revealed
by stains
Karyotyping
Types of Karyotyping Banding (5)
- G-banding
- Q-banding
- C-banding
- T-banding
- R-banding
- Giemsa Stain
- alternating dark and light bands
G-Banding
- Quinacrine stain
- fluorescent
Q- Banding
- Giemsa
- centromere focused
C-Banding
- Acridine orange
- telomere focused
T-Banding
- Giemsa stain
- Reverse of G banding
R-Banding
Karyotyping method wherein:
- Sampling fetal cells shed into the amniotic fluid
*Used on fetuses at 15-16 weeks of gestation
Amniocentesis
Karyotyping method wherein:
*Uses cells from the chorionic villi, whose chromosomes match those of the fetus because they all descend from the fertilized ovum
*Used on fetuses at 10 weeks of gestation
Chorionic Villus Sampling
Karyotyping method wherein:
- Makes use of fetal cells separated from the mother’s blood stream
- A device called fluorescence-activated cell sorter (FACS) separates fetal cells by identifying surface characteristics that differ from those on the mother’s cells
- Safer than the other two techniques because it reduces the risk of a miscarriage while fetal cells are being sampled
Fetal Cell Sampling
- Rapid technique to identify the different chromosomes
- Does not require cell culturing
- Makes use of DNA probes that are complementary to DNA sequences found only on one chromosome type
- Probes are attached to molecules that fluoresce when illuminated
Lumalangoy (Swims in english)
Fluorescent In-Situ Hybridization (FISH)
Shows a karyotype where each chromosome type is fluoresced by a unique color
Chromosome Painting
Change in chromosome number involving whole sets of chromosomes
Euploidy
Change in chromosome number involving single whole chromosomes
Aneuploidy
Euploids whose chromosome number is more than the diploid condition by multiples of the haploid (n) chromosome number
Polyploids
produced when cytokinesis is interfered either during mitosis or meiosis
Mitosis:
- Chromosomes remain dyads
- Failure of separation of sister chromatids
Meiosis:
- Gametes produced are unreduced
- Failure of separation of homologous chromosomes
Polyploids
T/F Viable polyploids are common in animals because self-fertilization of unreduced gametes can commonly take place
F, Rare in animals because self fertilization rarely occurs
T/F Polyploidy is more common in plants
T
T/F Tetraploids (4N) are usually fertile because chromosome pairing is possible during meiosis
T
T/F Tetraploids are usually less fit than their diploid counterparts
F, more fit
Induces polyploidy in plants by preventing spindle fiber formation
Colchicine
Self-fertilization of unreduced gametes
Autotetraploidy
Sterile hybrids from different species double their chromosomes so as to undergo regular meiosis
Allotetraploidy
- Change in chromosome number involving single whole chromosomes
- The chromosome number is not an exact multiple of the haploid number of the species
- Results in non-disjunction of one or more homologous chromosome pairs either during meiosis I or meiosis II
Aneuploidy
Aneuploidy in humans related to their Sex chromosomes (4)
- Turner Syndrome (45, X0)
- Metafemale Syndrome (47, XXX)
- Klinefelter Syndrome (47, XXY)
- Jacobs Syndrome (47, XYY)
Aneuploidy in humans related to their Autosomes
- Down Syndrome (Trisomy 21)
- Edward Syndrome (Trisomy 18)
- Patau Syndrome (Trisomy 13)
- Warkany Syndrome (Trisomy 8)
- Women lacking an X chromosome
- 1 in 2000 females
- Short, stocky
- Flat-chested
- With folds of skin at the back of the neck (50% of affected individuals)
- Wide-set nipples
- Has undeveloped ovaries
- Verbal IQ normal
- Performance IQ lower than average
- Sterile
- Not correlated with age of the mother
Turner Syndrome (45, X)
- 1 in 1000 females
- Phenotypically female
- Rarely mentally retarded, although they may be less intelligent than their siblings
- Mental IQ reduces as the number of X chromosomes increases
- Irregular menstrual cycle
- May be tall or short
- Others are flat-chested
- May be fertile, although may produce eggs with two X chromosomes
- Incidence of offspring increases with maternal age
- Non-disjunction of X chromosomes in aging oocytes
Metafemale Syndrome (47, XXX)
- 1 in 500 males
- With female-like breast development (Gynecomastia)
- However, it only occurs in 25% of those with 47 XXY
- With rudimentary testis
- With long arms and legs
- Large hands and feet
- No pubic or facial hair
- Usually sterile
- Slow to learn, but not mentally retarded
- Mental retardation sets in as more X chromosomes are added
- Incidence also increases with maternal age (mid to late 30’s)
- Klinefelter Syndrome (47,XXY)
- 1 in 1000 males
- Studied 197 inmates in Carstairs, a high-security mental hospital in Scotland
- 7 out of 12 men with unusual chromosomes had an extra Y
- attributed to “congenital criminals” due to these patients’ violent or aggressive behavior
- no clear correlation between extra Y and aggressive behavior
- great height
- acne
- speech and reading problems
- may be mentally retarded
- Jacobs Syndrome (47, XYY)
- 1 in 800 to 1000 births
- Patients resembled people of Mongolian heritage
- Poor muscle tone
- Flat face
- Eyes slant upward
- Abnormally shaped ears
- Single deep crease across palms
- Joints extremely flexible
- Underdeveloped fifth fingers
- With epicanthal folds (skin folds at inner corners of the eyes)
- Gap between first and second toes
- Large tongue
- People affected with this syndrome has increased risk of getting affected with Alzheimer’s disease beyond 40 years old
- Down Syndrome (Trisomy 21)
- 1 in 6000 individuals
- heart defects
- displaced liver
- growth retardation
- oddly clenched fists
- narrow and flat skull
- abnormally shaped and low-set ears
- small mouth and face
- unusual or absent fingerprints
- short large toes
- “rocker-bottom” feet
- 90% of newborns do not survive the first 6 months
Edward Syndrome (Trisomy 18)
- 1 in 15000 individuals
- fusion of the eyes during development, forming one large eye-like structure in the center of the face (CYCLOPIA)
- malformed nose
- cleft lip/palate present
- extra fingers or toes may appear
- some with extra spleen
- abnormal liver structure
- rotated intestines
- abnormal pancreas
- more than 80% die during the first month
- some survive up to adulthood, but they do not progress developmentally beyond the
six-month level
Patau Syndrome (Trisomy 13)
- Maternal meiotic errors
- Nondisjunction of chromosome in the egg of the mother
- causes severe defects on the
developing fetus and is almost
always perinatal lethal - accounts for 0.8% of pregnancy
losses - 1 in 25,000 to 1 in 50,000
- Prominent forehead
- Deep set eyes
- Hypertelorism with broad nasal root
- Thick everted lips
- Prominent ears
- Camptodactyly
- Deep plantar and palmar creases
- Wilms tumors
- Myelodysplasia
- Myeloid leukemia
- Complete Warkany Syndrome (Trisomy 8)
Complete is different from Mosaic (T8MS)
- 1 in 2500 – 1 in 5000
- occurs when only a portion of these cells contains three copies of chromosome 8, while others contain the usual two copies of that chromosome
- hydronephrosis (swelling of kidney), cryptorchidism (undescended testes),
- Mosaic Warkany Syndrome (T8MS/Trisomy 8 Mosaic Syndrome)
Structural aberration where in there is loss of a chromosomal portion or segment
Deletion
Structural aberration where in there is repetition of a portion or segment
Duplication
Structural aberration where in there is switching a chromosomal portion or segment within the same chromosome
Inversion
Inversion that does not involve the centromere
Paracentric inversion
Inversion that involve the centromere
Pericentric inversion
Structural aberration where in transfer of a chromosomal portion or segment to another non-homologous chromosome
Translocation
Translocation where in no net genetic material is gained or lost
Reciprocal transloction
Translocation where in some genetic material is gained or lost
Non-reciprocal translocation
Translocation where in it occurs between two acrocentric chromosomes
Robertsonian translocation
- Affected individuals have a high-pitched cry similar to the mewing of a cat
- Low birth weight
- Poor muscle tone
- Small head
- Impaired language skills
- Mentally retarded
- Rarely survives to teens
Cri du chat (5p-)
5p- = Deletion in the p arm of chrom 5
- deletion of segments q11 and q12 in chromosome 15
- affected chromosome from the father
- mentally retarded, obese
- eats uncontrollably
- small hands and feet
- does not develop signs of puberty
- Poor muscle tone, resulting in floppy infants
- Can be treated with growth hormones
Prader Willi Syndrome (15q-) or PWS
15q- = deletion in the q arm of chromosome 15
deletion in the region including the SNRPN gene (encodes a component of the mRNA splicing system)
- deletion of same segments in chromosome 15 as in PWS
- affected chromosome from the mother
- Developmental delay
- Speech impairment
- Movement or balance disorder
- Frequent laughter or smiling
- Easily excitable
- Frequent flapping of arms
- Jerky movements
- Also known as the happy puppet syndrome
- Angelman syndrome (15q-)
15q- = deletion in the q arm of chromosome 15
deletion in a gene of the Ubiquitin Pathway (UBE3A)
- Still with 3 copies of chromosome 21s
- Extra 21 is attached to Group D chromosome (14 or 15)
- With 46 chromosomes
- Phenotypically identical with trisomy Down
- Inherited from translocation carrier
Translocation/Familial Down Syndrome
- Associated with reciprocal translocation between chromosomes 9 and 11
- Leads to disruption of the DIBD 1 gene in chromosome 11
- People exhibit manic episodes sometimes with extreme depressive episodes
- Bipolar Affective Disorder (Manic Depression)
- Chromosomes with identical arms
- Formed when, during anaphase,
the centromeres part in the
wrong plane - Result in loss of some genes and
duplication of other genes - May be genetically or
environmentally induced
Isochromes
- Abnormal fusion of two fragments from nonhomologous chromosomes, each with a centromere
Dicentric Chromosomes
- Occur when the ends of a chromosome are broken and the subsequent new ends fuse to form a ring
Ring Chromosomes
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