Lab 10 Mitosis and Meiosis

Why does sexual reproduction leads to enormous potential for variation between individuals?

1.) the various mix of material and paternal chromosomes that can occur in each gamete 2.) crossing over (where homologous chromosomes exchange DNA during prophase of meiosis 1) 3.) mutations 4.) random fertilization (whereby only one of the many possible male gametes fuses with only one of the possile feamle gametes)

If a parent cell has 100 chromosomes how many chromosomes will each daughter cell have after mitosis how many will there be?

100 it will always be exactly like the parents after mitosis.

In your modeling of meiosis using pipe cleaners, how many chromosomes of each type (i.e. shape- straight or bent) and color (paternal or maternal-white or colored) are present in the parent cell?

2 paternal (green) 2 maternal (orange) 2 bent and 2 straight

In which stage were the least cells found? (mitosis)

Anaphase

What appears in Telophase for plants and animal cells?

Animals: Cleavage Furrow Plants: Cell Plate

What happens in Telaphase in mitosis?

Cell division and reorganization of the contents of the 2 daughter cells begins. A cell plate appears as a fine line across the center of the parent cell in plants (the new cell wall). In animal cells, a cleavage furrow develops from the outside of the cell inward. These structures will divide the parent cell into two daughter cells, each with an identical set of chromosomes and roughly half the cytoplasm. As telophase progresses, the nuclei,begin to reorganize and the chromosomes become indistinct and form compact clusters. The individual chromosomes are no longer oriented along the spindle. By late telophase, new nuclear membranes have been formed around the clusters, Telophase ends when the nucleus assumes the characteristics of interphase the mitotic division is completed.

Why does sexual reprodcution (meiosis) cause double the amount of chromosomes?

Due to the fact that two different sex cells are getting together therefore doubling their chromosome number.

What happens in Metaphase 2?

Each duplicated chromatid ( a pair of sister chromatids) in each cell attaches to a spindle fiber by its centromere and aligns at the equator of the cell. they are in a single file line and are in longer in homologous pairs.

What is each sex cell called and how does it change during fertilization? And how does the indivudal gamete cell differ from from the parent cell?

Each sex cell is called a gamete and each gamete ends with half(n) of the number of chromosomes of the parent's cell (2n). The gametes contain only one of each type of chromosome whereas the parent organism contains two copies of each type of chromosome. When two haploid (n) gametes fuse during fertilization, the diploid (2n) state is returned and the resulting cell (called a zygote) carry genetic information contributed for broth parents.

What is Interphase in Meiosis?

It is the part of the cell cycle (only 10% of cell cycle) note: the nuclear eneveolpe and nucleous is still intact in this phase.

If many cells are found in a particular phase what does that tell you about the length of time a cell spends in that phase? (for both types of cell division)

It tells us that, that phase is very vital for the cell process.

What are the stages of Meiosis 1?

Prophase 1 Metaphase 1 Anaphase 1 Telophase 1

What are the stages of Meiosis 2?

Prophase 2 Metaphase 2 Anaphase 2 Telophase 2

What stage of mitosis (prohase, metaphase, anaphase, or telophase) was the longest?

Prophase is the longest

what are the 4 stages of mitosis?

Prophase, Metaphase, Anaphase, Telaphase.

What happens Metaphase 1

The 4 paired and replicated homologous chromosomes (tetrads) line up along the equator of the cell. The centromere of one chromosome (half of the tetrads) attaches to microtubules originating from only one pole of the cell. The other chromosome of the tetrad attaches to a microtubule from the other pole. It does not matter the color of each tetrad faces which pole because all possibilities are equally likely and the chromosomes assort randomly. (this is referred to as independent assortment) The tetrads still remain together in this phase. The chromosomes are NOT lined up in a perfect single file line.

What happens in Anaphase 2?

The centromere splits thereby allowing the TWO SISTER CHROMATIDS of each chromosome to move to opposite poles. Each FORMER CHROMATID now had its own centromere and is referred to as a CHROMOSOME.

what happens in Metaphase in mitosis?

The chromosomes are arranged near the center of the cell (the metaphase plate) once each of the chromosomes is attached to spindle fibers for each pole. The centromeres are in a line across the middle of the cell however, the ends of the chromosomes(telomeres) are not typically lined up so neatly. The order in which the chromosomes line up in is random.

What happens in Prophase in mitosis?

The chromosomes begin to condense and appear as tangled threads. Later, as the threads become more district, the nuclear membrane disappears and the chromosomes spread out and become shorter and thicker. Each chromosome can be seen to be composed of two identical strands (chromatids) joined together at one spot the centromere. During prophase, small thread-like spindle fibers (microtubules) from two opposite poles of the cell (near the centrioles in an animal cell, plants lack centrioles). Some spindle fibers are attached to the centromere(the little things that attaches the two sister chromatids) of the chromosomes and provide the machinery for the movement of the chromosomes.

What do we do inorder to decrease the number of chromosomes so we can have a constant number fo chromosomes in an organsisums life?

This balancing of chromosome number occurs by a process called meiosis. During the process of meiosis the chromosome number is reduced from the diploid(2n) to the haploid (n) amount in a series of two divisions.

How does the number, color and shape of chromosomes in each new nucleus of your gametes compare to the contents of you parent cell?

Thye have a combination of paternal and maternal and holds the chromosomes. they are all different.

What happens in Telophase 1?

Two daughter cells form, each with HALF THE NUMBER OF DIFFERENT CHROMOSOMES, but each chromosome still has TWO CHROMATIDS. You should now have two cells that each contains one doubled straight chromosome and one doubled bent chromosome. You cannot have a cell with 2 doubled straight or 2 double bent chromosomes. Nuclear envelope reforms. DNA is partitioned into each daughter cell. These are now haploid. They will have half the number of chromosomes compared to parents.

What happens in Anaphase 1?

Unlike mitosis, the centromeres of the chromosomes do not split in meiosis 1. Instead, the tetrads separate as the two homologous chromosomes (still consisting of two sister chromatids) move away from the other and towards opposite poles of the cell and the spindle fibers shorten. this is a key difference between meiosis and mitosis and this process is called "reduction division" At this point, you will see that the two daughters cells are haploid (n). Although they have 2 types of chromosomes (straight and bent), they only contain one color and therefore only one version (either the maternal or paternal copy) of each type of chromosome.

What happens in Telophase 2?

You should have 4 haploid cells. Each cell should now contain ONE of both chromosome types (one straight and one bent). The color of each chromosome in each cell will depend on how the chromosomes were aligned at the cell equator during metaphase 1. You should now see 4 genetically different sex cells are possible. One cell could have both maternal chromosomes. Note that one round meiotic division gives two of the four possible chromosome combinations.

What happens in Prophase 2?

a new spindle forms in each cell and the nuclear envelope breaks down.The chromosomes are still associated by centromere, NO CROSSING OVER IN THIS PHASE! (and that's it)

What is interphase referred to as in mitosis?

business as usually 90% of the cell cycle happens here.

In which stage were most cells found? (mitosis)

interphase

What happens in Anaphase in mitosis?

the chromatids separate and begin to migrate towards each pole. As soon as they are no longer physically attached to each other, the two chromatids are called chromosomes. As the chromosomes are pulled apart tey become temporarily V-shaped with a sharp end chromosome or the centromere pointed towards the outside of the cell. By late anaphase, the two separate groups of chromosomes are aggregated at opposite poles and have started to lose their short, thick shake (begin to uncoil)

What happens in Prophase 1?

the nuclear membrane breaks down and a spindle of microtubules forms between opposite poles of the cell. The chromosomes condense into visible structures, and homologous chromosomes line up along their length in a process called synapsis or paring. the 4 chromatids that comprise each pair of the two homologous chromosomes form a tetrad (or group of four). At this stage, the adjacent chromatids of the homologous pair (NOT sister chromatids) can intertwine, break and exchange DNA in a process called "crossing over" (swapping DNA between maternal and paternal chromatids).

What are Homologous Chromosomes?

two chromosomes in a diploid cell that possess genes that control the same traits (e.g. eye color, blood type..) One of the two chromosomes was contributed from the male parent and one from the female parent.

what is a tetrad?

two duplicated homologous chromosomes (the tetrad job is synapsing and crossing over)