reduction (cell) division
A term for “meiosis”
doubled homologous chromosomes move away from the equator towards the centrioles but centromeres DO NOT split
Anaphase 1
centromeres split so single stranded chromosomes are pulled back towards the centrioles/poles
Anaphase 2
prophase 2
begins with a pair of haploid cells, each containing a single set of chromosomes, each with its fraternal
polar bodies
cells produced in females that do NOT participate in reproduction
prophase 1 of meiosis
chromosomes form tetrads during what phase
portions of sister chromatids on a pair of homolgous chromosomes will break off & trade locations; usually happens in prophase 1 (tetrad in synapsis)
Crossing Over
2N, contains two sets of homologous chromosomes
describe a diploid cell
During anaphase 2
the paired chromatids separate
during meiosis 2
homologous chromosomes separate into two sister chomatids
4 cells are formed; 1 cell is functional
For Females: Number of cells formed; Number of functional cells
4 cells are formed; 4 cells are functional
For Males: Number of cells formed; Number of functional cells
sex cells; egg and sperm
Gametes are considered
eggs
haploid gametes produced in females are
sperm
Haploid gametes produced in males are
cells that contain 1 full set of unpaired chromosomes
Haploid means
anaphase 1
homologous chromosomes migrate to opposite poles in dividing the cell in what phase
a tetrad is formed when each chromosome pairs with its corresponding homologous chromosome; 2 chromosomes ‘tied’ together
How does a tetrad form in prophase I of meiosis
4
how many chromatids are in a tetrad
12
how many chromosomes are found in each gamete of the dogfish shark if there are 24 chromosomes in a body cell
polar bodies receive less cytoplasm due to unequal cytokinesis; cell furrow does not form along equator; instead it forms off-center
Why do or how do polar bodies receive less cytoplasm?
6
if an organisms diploid number is 12, its haploid number is what
interphase
in gamete production, the DNA in the chromosomes are replicated during which phase
metaphase 2
in what phase doe non-identical (fraternal) sister chromosomes line up in the center of the dividing cell
they have the same number of chromosomes
in what ways are human sperm and human eggs similar
type of cell division that cuts in half the number of chromsomes while the body is producing gametes
Meiosis
doubled chromosomes meet in the middle with their homologous partner; each doubled chromosome faces own pole
Metaphase 1
doubled chromosomes meet in the middle at the equator WITHOUT their partner; chromatids face own pole
Metaphase 2
IPMATPMAT; I-P1-M1-A1-T1-P2-M2-A2-T2
Name all stages of meiosis in order
primary oocyte (diploid cell with 46 chromosomes)
name of cell that begins oogenesis
primary spermatocyte (diploid cell with 46 chromosomes)
name of cell that begins spermatogenesis
metaphase 1 is the phase that determines this
Name the stage that ultimately determines which chromosomes end up in gametes
Before fertilization, each egg or sperm will have 23 unpaired chromosomes
Number of chromosomes in gametes
formation of eggs (ova); occurs in ovaries helps maintain cytoplasm is the ovum
oogenesis
oogenesis
1 of the 4 will mature into the ovum (egg)
the name of the cells that are formed at the end of oogenesis
ootids
the unfertilized egg; haploid; ovum is singular; ova is more than one
ovum or ova
the smaller-sized cells formed during oogenesis due to unequal cytokinesis; normal nucleus but less cytoplasm
polar bodies
nuclear membrane breaks down as spindle forms; chromosomes are doubled & with their homologous partner
Prophase 1
the names of the haploid cells that are formed at the end of telophase 1 and begin prophase 2 in oogenesis
secondary oocyte & first polar body
formation of sperm; occurs in testes
spermatogenesis
doubled homologous chromosomes arrive at poles; nuclear membranes reform as spindle breaks down; cell furrow forms; cytokinesis occurs
Telophase 1
single-stranded chromosomes arrive at opposite poles; nuclear membrane reforms as spindle breaks down; cell furrow forms so cytokinesis can occur
Telophase 2
one homologous pair of chromosomes because 4 chromatid strands are close together, side by side
tetrad (tetrad in synapsis)
two times; one parent cell divides 2 times to produce 4 cells
The number of times cytokinesis occurs during meiosis
homologous chromosomes
the paired mom and dad chromosomes (homologs) are referred to as what
4 cells-haploid
unlike mitosis, meiosis results in the formation of (in males)
meiosis 1 and Meiosis 2
what are the two distinct division of meiosis
begin with a diploid cell
what do mitosis and meiosis have in common
variation among species
what does “crossing over” ensure
that each of the chromosomes that came from the male parent has a corrosponding chromosome from the female parent
what does it mean when two sets of chromosomes are homologous
4 haploid cells at the end of meiosis
what does the diploid cell that enters meiosis become
a change from diploid to haploid
what happens in a germ cell during gamete formation
They die and get reabsorbed
What happens to polar bodies?
prophase I, Metaphase I, anaphase I, telophase I, prophase II, metaphase II
when do homologous chromosomes separate
When homologous chromosomes in tetrads exchange portions of their chromatids, alleles are exchanged between the homologous chromosomes to produce new combinations of alleles.
what results from the process of crossing -over during prophase I
Gametes are haploid so that upon fertilization the zygote will be diploid; the diploid number will be restored since each gamete is haploid
Why are gametes haploid?
polar bodies receive less cytoplam to make sure the cell that will eventually mature into the ovum has enough cytoplasm & nutrients to survive & support a new living organism
Why do polar bodies have less cytoplasm?
The number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
why is meiosis described as a process of reduction division
16
if an organisms diploid number is 32, how many chromosomes at the end of Meiosis 1
15-the haploid number
if an organisms diploid number is 30, how many chromosomes (in each cell) at the end of Meiosis 2
What half the chromosomes are regular body cell
Gametes have
2
There are—-rounds of cell division and meiosis
The chromosomes to the correct diploid number
Fertilization returns
Crossing over ;pic
When homologous chromosomes traveled opposite sides of the cell
What actually reduces chromosome numbers in meiosis
tetrads pic
Anaphase 2
Sister chromatids are separated in this phase
metaphase 2 meiosis pic
anaphase 2 meiosis pic
telophase meiosis pic
Diploid numbers 16
Haploid number is 8
Meiosis
Gametes are made by
Tetrads are first made
prophase 1 of meiosis
Once
Replication of chromosomes occurs- How many times in meiosis
2N – diploid number of chromosomes
Body cells have—-chromosomes
4 different kinds of gametes-
Meiosis generically produces
Prophase 1
Stage B is
Anaphase 1
Stage C is
Metaphase 2
Stage e is
Anaphase 2
Stage f is
A tetrad
In stage a —you can see
Male spermatogenesis
This is a picture of– focus on stage G
4=2n
In this picture are the diploid number for this cell is
2 =n
the haploid number for these cells is (in this image)
