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