Ch. 8 and 9 Study guide

G1 phase

(first gap) The cell makes a variety of proteins that are needed for DNA replication, and begins to grow

What are the two goals of meiosis

-Produce haploid gametes -increase genetic diversity -ensure chromosome number doesn't double for each generation

What are the causes of genetic variation in sexual reproduction

-crossing over (meiosis) -random alignment of chromosomes in metaphase I (meiosis) -variations of traits in both parents -random fertilization

What is a haploid cell

A cell containing one set of chromosome's (n) -ex: gametes

What is a diploid cell

A cell containing two homologous pair of chromosome's (2n)

What are sex chromosomes

A chromosome that determines whether an individual is male or female. These are non homologous pair of chromosomes

What is a zygote

A fertilized egg

What are homologous chromosomes

A pair of chromosomes in a diploid cell that are the same size, shape, and carry the same genetic information, but may carry different alleles (blue or brown eyes)

Define Karotype

A photo of an individual's full set of chromosomes, in order

Cleavage furrow

A shallow indentation in the cell furrow

Prophase II for meiosis

A spindle forms and moves the chromosomes toward the middle of the cell

What is binary fission

A type of asexual reproduction in prokaryotic cells where a single cell copies and divides into two genetically identical cells -ex: bacteria

Meiosis

A type of cell division that produces haploid gamete in diploid organisms. Two haploid gametes may combine by fertilization to restore the diploid state in the zygote

Metaphase

All the miotic spindles are fully formed with its poles at the opposite ends of the cell. The chromosomes line up in the middle of the cell, and the spindle fibers connect to the centromere's of the sister chromatids.

Define crossing over

An exchange of genetic information between non sister chromatids (chromosomes break off and reattach). This produces genetic information which is necessary for natural selection for evolution

Compare and contrast asexual and sexual reproduction

Asexual and Sexual reproduction: Sexual reproduction: -Requires two parents -by meiosis, gametes are produced -In a zygote, chromosomes contain a unique combination of genes Similarities: -Produces cells -Both are forms of reproduction -Chromatids separate in both forms of reproduction Asexual reproduction: -Requires only one parent -Creates genetically identical offspring -"copy and divide" -Mitosis (eukaryotic cells) -Binary Fission (prokaryotic cells) -Creates diploid cells

Prophase

During prophase, Chromosomes become more coiled and can be viewed under a light microscope.The nucleolus also disappears during this phase. In the cytoplasm, the mitotic spindle, consisting of microtubules and other proteins, forms between the two pairs of centrioles as they migrate to opposite poles of the cell. The nuclear envelope disappears at the end of prophase. This signals the beginning of the substage called prometaphase.

Interphase for Meoisis

During this interphase, chromosomes duplicate. At the end of interphase, each chromosome consists of two genetically identical sister chromatids attached by the centromere. The centrosome also has duplicated by the end of interphase

S phase

During this phase, all of the chromosomes are replicated. Because of this, each chromosome now consists of two sister chromatids. The the amount of DNA in the cell has effectively doubled. (2n=4)

What is fertilization

Gametes come together to restore the diploid state of chromosomes in each gamete

What would happen, if there was no meiosis

If meosis did not exist each generation would have twice as mauch genetic material as the generation before.

Prophase I for meiosis

In early prophase I, the chromatin coils up so that individual chromosomes are visible under a microscope. During synapsis, homologous chromosome's (each composed of tow sister chromatids) come together as pairs consisting of two four chromatids called a tetrad. In a process called crossing over, homologous chromosomes share segments. Crossing over rearranges genetic information because the versions of some genes differ from those on its homolog. Chromosomes condense further, and the centrosomes move away from each other, and a spindle forms between them. The nuclear membrane breaks into fragments and the chromosome tetrads captured by the spindle move towards the middle of the cell

What is the difference between mitosis and meiosis II

Meiosis begins with the haploid cell

Which form of reproduction allow a zygote to become a multicellular organism

Mitosis

Telophase II for meiosis

Nuclei form at the poles of the cell, and cytokinesis occurs at the same time. This crates four daughter cells, each with a haploid number of (single) chromosomes

Prometaphase

Prometaphase is the second phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. During prometaphase, the physical barrier that encloses the nucleus, called the nuclear envelope, breaks down. The breakdown of the nuclear envelope frees the sister chromatids from the nucleus, which is necessary for separating the nuclear material into two cells.

What are the differences and similarities between mitosis and meiosis

Similarities: -Chromosomes duplicate only once during the S phase of interphase. -Both are types of cell division Mitosis: -involves one division of the nucleus accompanied by cytokinesis -produces two identical diploid cells -metaphase: individual chromosomes are lined up in the middle of the cell -anaphase: individual chromosomes separate, and so do the sister chromatids Meiosis: -has two nuclear and cytoplasmic divisions -produces four haploid cells -in metaphase I tetrads are aligned in the middle of the cell -in anaphase II pairs of homolgous chromosomes separate, but the sister chromatids stay together -crossing over occurs -ensures genetic diversity

Telophase

The cell elongation that started in anaphase continues. Daughter nuclei appear at the two poles of the cell as the nuclear envelopes form around the chromosomes. By the end telophase, the chromatin fiber of each chromosome uncoils and spindle fibers disappear. The equal division of one nucleus into two genetically identical daughter nuclei is now finished.

G2 phase

The cell synthesizes a variety of proteins, including most microtubules (the proteins that are required during mitosis) are produced during G2. The cell continues to grow more as it completes preparations for cell division

Anaphase II for meiosis

The centromere's of sister chromatids separate and the sister chromatids of each pair are now individual daughter chromosomes that move towards the opposite sides of the cell

Telophase I for meiosis

The chromosmes arrive ate the poles of the cell. When the chromsosmes finsihs their journey, each side of the cell has a haploid chromosome set even though each chromosome still consists of two sister chromatids

Metaphase I meiosis

The chromosome tetrads line up in the middle of the cell. In each tetrad the homologous chromosomes are held together by the site of crossing over. The spindles attached to the chromosmes come from opposite sides of the cell. With this arrangement the homologous chromosomes of each tetrad are rady to move toward opposite poles of the cell

Metaphase II for meiosis

The chromosomes move toward the center of the cell

Define Meiosis

The division of a single diploid nucleus into 4 haploid daughter cells. Meiosis and cytokinesis produce haploid gametes from diploid cells

Cytokinesis

The division of the cytoplasm usually occurs along with telophase, with two daughter cells completely separating soon after the end of mitosis. In animals, a cleavage furrow forms and the cell pinches into two.

Anaphase I meiosis

The homologous chromosome's of each tetrad move to the opposite sides of the cell. However in contrast to the mitosis, the sister chromatids making up each double chromosome remain attached at their centromere's. Only the tetrad's split up

Interphase

The phase in which the cell is not actually dividing and in preparation for dividing This is where the cell spends most time in

Anaphase

Two centromere's of each chromosome pops apart separating the sister chromatids. Once they are separated each sister chromatid is considered a daughter chromosome. Proteins "walk" the daughter chromosomes (centromere first) to the opposite poles of the cell. When this happens the spindle fibers attached to the chromosomes shorten. However, the spindle fibers not attached to the chromosomes lengthen. The poles move further apart, elongating the cell. This stage is over when the chromosomes have reached the two poles of the cell.

Cytokinesis I

Two haploid daughter cells are formed