Mitosis and Meiosis Flashcards
Where is the centromere located in metacentric chromosomes?
Middle
Where is the centromere located in a submetacentric chromosome?
between the middle and the end
Where is the centromere located in an acrocentric chromosome?
Close to the end
Where is the centromere located in a telocentric chromosome?
At the end
What is happening in the G1 phase (interphase)?
Active gene expression and normal cell activity. Preparation for DNA synthesis.
What happens in S phase (interphase)?
DNA replication and chromosome duplication.
What is happening in G2 phase (interphase)?
Preparation for cell division.
Describe G0 phase?
Terminal differentiation and arrest of cell division.
Cell is specialized and will eventually undergo apoptosis.
Describe prophase (M phase).
Chromosomes condense
Paired centrosomes begin moving towards poles
Nucleolus disappears
Describe metaphase (M phase).
Condensed chromosomes line up at metaphase plate. Each sister chromatid connected at kinetochore by by centrosomes.
Mitotic spindle is complete
Describe anaphase (M phase).
Daughter chromosomes pulled to opposite poles of the cell.
Describe telophase and cytokinesis (M phase).
Nuclear envelope reassembles
chromosomes decondense
cytokinesis divides cytoplasm via cleavage furrow created by contractile ring.
What is a bivalent?
2 homologs that have synapsed
What is a tetrad?
4 part structure of 2 homologous chromosomes, each with 2 sister chromatids.
What is a dyad?
a pair of homologous chromosomes or sister chromatids after nondisjunction in anaphase I or II
What is crossing over?
This is when genetic material is exchanged between two of the sister chromatids.
This happens at the chiasmata after synapsis.
Which phases of meiosis contributes to genetic diversity?
Prophase 1 - crossing over
Metaphase 1 - random alignment at metaphase plate
What cells perform mitosis and what cells undergo meiosis?
Somatic - mitosis
germ-line - meiosis
State the cells of spermatogenesis from earliest to latest stage. Label them haploid or diploid. If division occurs state what phase of meiosis it is.
Spermatogonium (germ-line cell) 2n
– growth maturation
Primary spermatocyte 2n
–meiosis I
2 Secondary spermatocytes n
–meiosis II
4 spermatids n
– differentiation
Spermatozoa
What is the calculation for possibilities of random alignment?
2^n
n = # of pairs of chromosomes
(2^n)^2 for sperm and egg combinations
State the cells of oogenesis from earliest to latest stage and label them haploid or diploid.
Oogonium 2n
— growth and maturation
Primary oocyte 2n
— Arrest at prophase I till puberty
– meiosis I
1 Secondary oocyte (most of cytoplasm) n and small first polar body (degrades) n
— secondary oocyte arrests at metaphase II until fertilization
– Meiosis II
1 Ootid (most of cytoplasm) n and 1 second polar body (degrades) n
– differentiation
1 Ovum n
