Chromosome Theory of Inheritance ch 3&4 Flashcards
What are the 2 means of cell division?
Mitosis and Meiosis
What is mitosis
Mitosis is the nuclear cell division that generates two daughter cells.
- Chromosome number maintained
Mitosis Vs Meiosis. In which cells mitosis/meiosis occur?
Which cells undergo mitosis/meiosis?
What is Meiosis?
Meiosis is the nuclear cell division that generates gametes (egg and sperm) and results in 4 daughter cells
Diploid meaning? In which cells occur?
Diploid - is a cell that contains 2 complete sets (copies) of chromosomes, one from each parent. Most body cells (somatic cells) are diploid (2n).
Haploid means?
Haploid - is a cell that has a half of the set (one copy) of unpaired chromosomes.
Meiosis —> haploid (n) gametes –half chromosome number
How zygote is formed?
Two gametes fuse during fertilization to form a zygote. (2n)
Drosophila VS humans (number of diploid and haploid cells)
In Drosophila, 2n=8 - diploid cells , n=4 - haploid cells (gametes)
In humans , 2n=46 - diploid cells (46 chromosomes) and n=23 - haploid cells
(23 chromosomes in each of the gamete)
Chromosomes can be classified by centromere position. What are they?
> metacentric, submetacentric, acrocentric, and telocentric
Sister chromatids definition
Sister chromatids are identical copies of a replicated chromosome
What are the homologous chromosomes (homologs)?
Homologs contain the same set of genes, but can have different alleles for some genes
Nonhomologs chromosomes definition
Nonhomologs carry completely unrelated sets of genes
What is Karyotype?
Karyotype: Micrograph of stained chromosomes arranged in homologous pairs
Difference between sex chromosomes and autosomes.
The key difference between autosomes (22 pairs) and sex chromosomes (1 pair) is that the autosomes contain genes that are responsible for the determination of somatic characteristics while the sex chromosomes contain genes that determine sex and sex-related characteristics of an organism.
The primary determinant of maleness is a single gene called??
SRY gene
What are the phases (stages) of meiosis I?
Prophase I, Metaphase I, Anaphase I, Telophase I and
Interkinesis - (not actual stage)
What are the phases (stages) of meiosis II?
Prophase II, Metaphase II, Anaphase II, Telophase II and (Cytokinesis - division of cytoplasm, which ends with 4 non-identical haploid cells)
What is interphase?
Interphase is the phase of the cell cycle in which a typical cell spends most of its life prior to cell division. It’s the normal state of the cell.
(growth, metabolism, function)
What are the phases (stages) of the cell cycle (interphase)?
Describe the brief function of each.
1) G1 Phase, 2) S Phase, 3) G2 Phase,
4) M (Mitosis or Meiosis) phase - nucleus and cell divides
Late in G1, all cells follow one of two paths:
- they withdraw from cell cycle and become dormant in G0
2. they become committed to DNA synthesis, cell cycle.
What is G0 phase?
G0 - viable and metabolically active, but NO proliferation (no division)
What is chromatid
A chromatid is one half of a replicated (duplicated) chromosome
in preparation for cell division
Centromere meaning and function?
It’s the highly constricted region of the DNA (a specialized structure
on the chromosome), which serves as
the point of attachment of the kinetochore proteins.
Kinetochore?
It’s the protein unit (mixture of DNA and proteins), that provide the attachment points (black dots - kinetochores) for spindle fibers in the chromosome
What is Mitotic Spindle?
The mitotic spindle is a structure that forms during cell division and separates replicated (duplicated) chromosomes.
How mitotic spindle is formed?
It’s formed from microtubule organizing centers
MTOC’s) at centrosomes (2 centrioles lay at right angles to each other
Microtubules definition
They are basically fibers that help to move the chromosomes during cell division.
Centrosome vs Centrioles
Centrosome are 2 pair of centrioles that lay at right angles to each other. The units of centrioles together are called the centrosome
Centrioles are the actual mictrotubules (each of them, 2 total)
What are the 3 types of microtubules in animal cell mitotic spindle?
- aster- outward from centriole to membrane (on top)
- polar-between the 2 poles (long yellow microtubules)
- kinetochore (green microtubules, allow for the connection to the chromosomes)
What are the phases (stages) of mitosis?
Interphase, Prophase, (Prometaphase), Metaphase, Anaphase, Telophase
What happens during Prophase of Mitotic cell division?
a. Nuclear envelope breaks down
b. Chromosomes become visible.
c. Sister chromatids are connected at the centromere
What happens during Prometaphase of Mitotic cell division?
a. Chromosomes are clearly double structures
b. Centrioles reach opposite poles, which form centrosomes
c. Spindle fibers form and attach to centromeres and kinetochore proteins
What happens during Metaphase of Mitotic cell division?
Chromosomes align on metaphase (equatorial) plate
What happens during Anaphase of Mitotic cell division?
a. Removal of cohesin proteins causes centromeres to separate
b. Kinetochore microtubules shorten and pull separated sister chromatids
to opposite poles (characteristic V shape)
What happens during Telophase of Mitotic cell division?
a. Spindle fibers disappear
b. Centrioles return to normal positioning
c. Uncoiling of chromosomes (become decondensed)
d. Reformation of nuclear envelope (new nuclei appear
in each of the new dividing cell)
Checkpoints function. Which checkpoints do we have?
A variety of checkpoints ensure that the cell is able to move from
one phase to another in the cell cycle.
They are G1 checkpoint, G2 checkpoint, M checkpoint
What is CDK-cyclin complex?
CDKs (cyclin-dependent kinases) only function when associated with Cyclins, which form CDK-cyclin complex.
Cyclin-dependent kinases function
a. act as master control molecules
b. advance the cell from one stage of the cell cycle to next
Meiotic cell division produces?
Haploid gametes from germ cells
1 (parent cell) : 4 (daughter cells) cell division
Meiosis I VS Meiosis II
Meiosis I is a reductional division
Meiosis II is an equational division
When DNA synthesis occurs in meiosis?
DNA synthesis occurs before the beginning of meiosis I,
but does not occur again before meiosis II
What is the division of Meiosis?
Chromosomes duplicate once; nuclei divide twice
• Meiosis I reduces the chromosomes from 2n to n.
What happens in Prophase I in Leptotene substage during Meiosis I?
Chromatin condenses into very thin chromosomes
What happens in Prophase I in Zygotene substage during Meiosis I?
Homolog search and recognition. Synapsis begins (homologous chromosomes pair with each other)
What happens in Prophase I in Pachytene substage
during Meiosis I?
Tetrads form (between homologous chromosomes). Crossing over occurs, genetic exchange between nonsister chromatids of a homologous pair (one chromosome from each parent).
What happens in Prophase I in Diplotene substage during Meiosis I?
Chiasma (chiasmata pl) remains (section that results from crossing over)
- Tetrad begins to pull apart slightly
What happens in Prophase I in Diakinesis substage during Meiosis I?
What happens in Metaphase I during Meiosis I?
Independent assortment of nonhomologs (chromosomes are exchanged between each other independently).
Chromosomes align on metaphase (equatorial) plate
What happens in Anaphase I during Meiosis I?
homologs chromosomes move to opposite sides (One half of each tetrad
to each pole)
What happens in Telophase I during Meiosis I?
The nuclear envelope is formed. Each daughter cell (2) contains 2 chromosomes.
Cytokinesis (division of cytoplasm - fluid of cell) separates the daughter cells.
What happens in Interkinesis I during Meiosis I?
It’s similar to interphase. But, no chromosomal duplication takes place.
What happens in Prophase II during Meiosis II?
What happens in Metaphase II during Meiosis II?
What happens in Anaphase II during Meiosis II?
What happens in Telophase II during Meiosis II?
Telophase II- one member of each pair of homologous chromosomes
at each pole. Each cell contains 2 chromosomes (n - haploid), so that the number of chromosomes was reduced in twice from 4 chromosomes (2n)
to 2 chromosomes (n).
What happens in Cytokinesis during Meiosis II?
Cytokinesis, ends with 4 non-identical haploid cells
Chromosome number abnormalities occurs due to?
Non-disjunction (Homologous chromosomes fail to separate)
