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49 terms

Meiosis-Biology

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Do chromosomes replicate or double before meiosis?
replicate
How many divisions occur in meiosis?
2
How many divisions occur in mitosis?
1
What is another name for meiosis?
reduction
What is the original cell that divides by meiosis called?
diploid (2n)
How many daughter cells can be produced by meiosis?
4
How many daughter cells can be produced by mitosis?
2
What is the chromosome number of the daughter cells produced by meiosis?
half the number of the chromosomes as the original cells
What are the daughter cells called that are produced by meiosis?
gametes
What are the 2 types of meiosis?
meiosis 1, meiosis 2
Where does spermatogenesis occur?
testes
Where does oogenesis occur?
ovaries
After one division, how many chromosomes are in the cells? Are they double or single stranded?
23, double
Is meiosis sexual or asexual reproduction?
sexual
Are eggs and sperm haploid or diploid?
haploid
What process joins the egg and sperm to restore the original chromosome number of the organism?
fertilization
What has the same genes and the same alleles?
sister chromatids
When a sperm fertilizes an egg, a new 2n cell forms called what?
zygote (it is diploid)
What are homologs?
pairs of sister chromatids that have the same genes, but may have different alleles
What reduces the chromosome number by half?
division in meiosis
What restores the chromosome number?
fertalization
In Meiosis 1 what separates?
homologs
In Meiosis 2 what separates?
sister chromatids
What 2 things occur in Early Prophase 1?
1. homologs pair, 2. crossing over occurs
What 3 things happen in Late Prophase 1?
1. chromosomes condense, 2. spindles form, 3. nuclear envelope fragments
What is a tetrad?
homologus chromosomes combine to form a tetrad
What is synapsis?
the process in propase 1 that forms tetrads
Once tetrads form, what happens to the homologus chromosomes?
pieces of chromosomes or genes are exchanged (cross-over each other)
What does crossing-over result in?
genetic recombination in the offspring
What happens during Metaphase 1?
homologus pairs of chromosomes align along the equator of the cell
What 2 things happen in Anaphase 1?
1. homologs separate and move to opposite poles, 2. sister chromatids remain attached at their centromeres
What 3 things happen in Telophase 1?
1. nuclear envelope reassembles, 2. spindle disappears, 3. cytokinesis divides cell into two
At the beginning of Meiosis II, each cell has how many homologs of each chromosome?
only 1 is present
Sister chromatids carry _________ genetic information
identical
Name the stages of Meiosis II
Prophase II, Metaphase II, Anaphase II, Telophase II
What happens in Prophase II?
nuclear envelope fragments; spindles form
The gametes at the end of Meiosis 2 will have how many copies of a gene for a trait?
Meiosis 2 produces gametes with one copy of each chromosome and thus one copy of each gene
Where are the sister chromatids in Metaphase 2?
chromosomes align along the equator of the cell/ separate and move to opposite poles
Name 4 things that occur in Telophase II
1. nuclear envelope assembles, 2. chromosomes decondense, 3. spindle disappears, 4. cytokinesis divides cell into two
Meiosis results in how many haploid cells?
4
How many copies of each chromosome does each gamete have in meiosis?
1
How many alleles does each gene have in different combinations?
1
Immature sperm cells are called what?
spermatids
Approximately how many sperm do men produce each day?
250 million
Name 4 cells produced by oogenesis
3 polar bodies and 1 egg
What are immature eggs?
oocyte
How often do females produce an ooctye?
one oocyte matures into an ovum (egg) every 28 days
What age does producing of an oocyte occur?
puberty
What happens to the polar bodies that oogenesis produces?
it dies