Meiosis
homologous chromosomes
a pair of chromosomes that are the same size, same shape and same information
they have the same types of genes in the same place and same centromere location
tetrad
a pair of homologous chromosomes that move as a unit
sister chromatids
two halves of a chromosome attached with a centromere
diploid
a cell that contains both sets of homologous chromosomes
(2n)
Haploid
a cell that only contains only a single set of chromosomes
gametes
haploid sex cells produced by meiosis
zygote
fusion of haploid sperm cells and egg to make a diploid cell
genes
recipes for making proteins
humans have ____
23 pairs or matching chromosomes
karyotype
a chart that shows all the chromosomes in one human somatic cell
somatic cell
body cell (zygote)
meiosis makes
gametes (sperm and egg haploid cells)
23rd pair of chromosomes are called ____
sex chromosomes
male sex chromosomes
XY
female sex chromosomes
XX
chromosomes 1-22 are called _____
Autosomes
Allele is a ___
a type of gene
interphase
G1 S and G2 has occurred
DNA as Chromatin
Prophase 1
Homologous chromosomes pair up and form a tetrad
crossing over occurs
diploid -> 2N
Crossing over leads to
genetic variation
exchanging genetic information
Metaphase 1
paired homologous chromosomes line up across the middle of the cell
(diploid 2N)
Anaphase 1
spindle fibers pull each homologous chromosomes towards the ends of the cell
tetrads are gone
diploid (2N)
Telophase 1
nuclear envelope forms around each cluster of chromosomes in telophase
diploid
cytokinesis
cytoplasm divides and forms 2 new daughter cells.
haploid
Meiosis 2 - there are now ____ daughters cells going through meiosis
there are now 2 cells going through meiosis
NO INTERPHASE
Prophase 2
chromosomes with sister chromatids
haploid (1N)
Metaphase 2
chromosomes line up across the middle of the cell (linear one by one)
haploid
Anaphase 2
sister chromatids are pulled to opposite ends of the cell
haploid
Telophase 2
nuclear envelope is forming around each of chromatids
haploid
cytokinesis
cytoplasm divides and results in 4 unique haploid daughter cells
Gametes to Zygotes
male
haploid cell sperm (23)
gametes to zygotes
females
haploid cell egg (23)
gametes to zygotes
fertilization
sperm fuses with an egg (23+23)
three sexual sources of genetic variation
1) crossing over (prophase 1 - random)
2) independent assortment (metaphase 1)
3) metaphase 2 (which side the chromatids get pulled too)
3 reasons why cells must divide
1) reproduction
2) growth
3) healing and repair
G1
1st growth phase
performs cellular function and is active
many cells stay in this phase and they don't divide (G0) examples are nerve cells and stems of plants
(check point 1)
At the end of mitosis the daughter cells are ___
identical
at what point during meiosis does the number of chromosomes become halved
at the end of meiosis 1 (after telophase/cytokinesis)
how many paternal cells (father)
how many maternal cells (mother)
23 each (46 in total)
at the end of telophase 1 there are ____ daughter cells
2
at the end of telophase 2 ____ daughter cells
4