EXAM 4 - Chapter 14, Meiosis Flashcards
The Karyotype is
a pictorial representation of all the chromosomes of an organism or a cell
Diploid cells
have two copies of each chromosome, one inherited from each parent (duplicated)
Meiosis is…mitosis is…
meiosis - specific way used to sexually replicate
mitosis - used to grow and replace cells
Chromosomes can be duplicated AND come in pairs so…
each chromosome is duplicated (X) and then similar ones form a pair (X X)
Homologous chromosomes are
2 copies of each chromosomes pair (so you have 2 duplicated chromosomes) (X X)
Haploid cells
have one copy of each chromosome, resulting from meiosis
Essentially, in meiosis,
you are going from one cell of 46 duplicated chromosomes to 4 cells with 23 unduplicated chromosomes
The first meiotic divison…
reduces the chromosome number from diploid to haploid, so meaning going from 46 duplicated in one cell to 23 unduplicated in 2 cells
During Prophase I
- as chromosomes begin to condense, SYNAPSIS OCCURS (different than mitosis)
- Disappearance of nucleolus
- Centrosomes move to opposite nuclear poles
- Disintegration of nuclear membrane into vesicles
- Spindle fibers form
Synapsis is when…
- homologous chromosomes pair up (physically) and form bivalents (two duplicated chromosomes)
- Chiasmata form - exchange between nonsister chromatids
Chiasmata is when
chromosomes break off peices of same size and exchange information , type of genetic recombination
Synaptonemal complex includes…
enzymes which cut non-sister chromatids and connect the “wrong” ends to recombine the homologous chromosomes
Just glues them together and swaps them
Genetic Recombination is…
the added genetic variation produced by “shuffling” the genes (allows microevolution)
Independent Assortment of chromosomes also…
increases genetic recombination
this is just another way, happens in meiosis
Metaphase I…
bivalents are moved to the metaphase plate
mitosis similar, but now its homologous pairs lined up (2 duplicated chromosomes side by side)
Anaphase I…
Homologous chromosomes are separated
After genetic recombination, each have each others DNA, so then the pair of duplicated chromosomes are separated, one whole duplicated chromosome going to opposite ends
Telophase I…
concurrent with cytokinesis
cytokinesis forms 2 haploid cells
started with 6 total duplicated chromosomes in nucleus, now have 2 nuclei with 3 duplicated chromosomes each
Second meiotic division is…
similar to mitosis, but different
“sister” chromatids are separated
Between meiosis I and II is…
interkinesis
During interkinesis…
DNA replication does NOT occur
Prophase II
Miotic spindle forms, connecting sister chromatids
All things that happens in other prophase still happens
Metaphase II…
Individual duplicated chromosomes are lined up at the metaphase plate
If you look at cell and know that total diploid pairs, difference in meiosis 2 from mitosis is half the number of pairs are getting separated
Anaphase II
Sister chromatids are separated to opposite poles
In meiosis 1, you are halving number of chromosomes, in meiosis 2, you are making chromosomes haploid
Telophase II…
Cytokinesis occurs concurrent with telophase, forming 4 haploid cells (with unduplicated chromosomes)
