Meiosis Flashcards
What is meiosis?
making gametes
What are gamets?
egg and sperm ( s*x cells)
What is asexual reproduction?
binary fission, budding, and regeneration are used by plants and animals to reproduce asexually through mitosis. Produces IDENTICAL copies of paretn cell.
- faster
- doesn’t need a partner
are …
advantages of asexual reproduction
- all ALIKE
- species can’t change and adopt
-one disease can wipe out a whole popultation
are…
disadvantages of asexual reproduction
What is sexual reproduction?
combines genetic material from 2 parents ( sperm and egg) so offspring are genetically different from paretn
- allows for variation in population
- allow species to adopt to canges in environment
are…
advantages of sexual reproduciton
What is another word for body cells?
somatic cells
Body cells ( somatic cells) have ____ copies of each chromosome= diploid ( 2n) ( one from mom and one from dad)
2 copies
All sperm and egg cells are
haploid(1n)
s*x cells have only ___ copy of each chromosome
one copy
- makes 2 cells genetically identical to parent cell and to each other
0 used by organisms to increase size of organism, repair inguries, repalce worn out cells
mitosis creates diploid body cells
- makes 4 cells genetically different from paretn cell and from each other
- used for sexual reproduction
meiosis creates haploid sex cell
What are the two steps Meiosis takes place in?
1) Meiosis I : IPMAT
2) PMAT
DNA replicates creating hmologous chromosomes
interphase I
- Homologous chromosomes pair up = synapsis
- this group of FOUR (4) chromatids is called a =tetrad
Prophase I
Homologous chromosomes pair up
synapsis
This group of FOUR (4) chromatids is called a
tetrad
- exchange of DNA between homoglous pairs
-allows for rearranging of DNA in different combinations - after crossin gover, chromatid arms are NOT identical anymore
crossing over
tetrads line up in the middle
metaphase 1
tetrads pull apart to opposite ends of the cell
anaphase 1
cell separates into 2 new cells
telophase 1
No interphase II which means chromosomes are NOT copied again
Meiosis II
2 cells begin meiosis II
Prophase II
Chromosomes line up in the middle of the cell
Metaphase II
Chomarids are pulled to opposite ends of the cel
Anaphase II
The 2 cells divide to form 4 genetically different cells (gametes )
Telophase II / cytokinesis
End result of meiosis
- 4 new cells
- half number of chromosomes ad parent cell ( haploid )
- humans 23 chromosomes
Spermatogenesis
Making mature sperm
- spermatogenesis
- mature and grow flagella
- 4 sperms
Male
Oogenesis
Making a mature egg
- oogenesis
- produced :1 “good “ egg and 3 polar bodies
- cytoplasm divides unevenly ; polar bodies degenerate ( die )
Female
Why make only one “good egg “
- sperm donated mostly DNA
- most of the cell parts and nutrients needed for baby come from egg !