Bio Meiosis Test

Number of divisions in mitosis

1

Number of divisions in meiosis

2

Haploid (N)

A cell that possess a single set of unpaired chromosomes i.e. 23 chromosomes in humans...sex cells such as sperm and egg are haploid (half normal amount of chromosomes)

Diploid (2N)

A cell that possesses two sets of identical chromosomes (half from each parent) i.e. 46 chromosomes in humans

Meiosis I

Homologous chromosomes pair closely and exchange hereditary material and includes the steps: Early and Late Prophase (I), Metaphase (I), Anaphase (I) and Telophase (I) producing two haploid cells (it is the first of two meiotic divisions)

Examples of Non-disjunction

In autosomes: Trisomy 21 (Down Syndrome) Trisomy 13 (Patau Syndrome) Trisomy 18 (Edwards Syndrome) In sex chromosomes: XXY (Klinefelter Syndrome) XYY Monosomy X (Turner Syndrome) Trisomy X (XXX)

Where does meiosis take place and why?

In the sex organs, to sex cells, so that genetically unique offspring are produced when the sex cell is fertilized, to ensure genetic diversity

How chromosomes segregate (separate) and the numbers of chromosomes in each daughter cell in Mitosis?

Line up over equator of nucleus Goes from 2n chromosomes to two cells with 2n chromatids each

Steps of mitosis

Steps include: Prophase- chromosomes become visible, paired chromatids and nuclear envelope disappear Metaphase- chromosomes align along the equator of the cell and attach to the spindle fibers Anaphase- chromosomes move away from each other to opposite poles of the spindle Telophase- chromatids/chromosomes move to opposite ends of the cell and 2 nuclei are formed Does not include: Cytokinesis-division of the cytoplasm There only requires to be one division to produce a finalized 2 daughter cells from a mother cell, however the process can be repeated over and over again (asexual reproduction)

Where does mitosis take place and why?

Somatic cells, to replace dead cells with new ones that perform an identical function, and to grow and develop, as well as to reproduce in some simple organisms such as bacteria

Difference between Spermatogenesis and Oogenesis

Spermatogenesis in males, Oogenesis in females. Spermatogenesis produces four sperm cells, oogenesis produces one functional egg cell. Spermatogenesis occurs constantly throughout a man's life, starting from puberty, while oogenesis only occurs once a month in females from puberty until menopause.

Metastasis

Spread of cancer

Steps of Meiosis

Steps include: Prophase I: The chromosomes condense, and the nuclear envelope breaks down. crossing-over (Synapsis) occurs. Metaphase I: Pairs of homologous chromosomes (tetrads) move to the equator of the cell. Anaphase I: Homologous chromosomes move to the opposite poles of the cell, pulled by spindle fibers. Telophase I: Chromosomes gather at the poles of the cells Prophase II: A new spindle forms around the chromosomes. Metaphase II: Chromosomes line up at the equator. Anaphase II: Sister chromatids separate at the centromeres. chromatids move to the opposite poles of the cells. Telophase II: A nuclear envelope forms around each set of chromosomes Does not include Cytokinesis: the cytoplasm divides.

Oogenesis

The process by eggs become fertile in females. This is split into two processes, Meiosis I and II. After Meiosis I, there are two haploid cells, but one takes up over 90% of the cytoplasm. The other is a polar body. After Meiosis II, there are four cells, but only one is a functional egg cell. The rest are useless polar bodies. NO INTERPHASE BETWEEN STAGES Meiosis II:

Spermatogenesis

The process by which sperm is formed in males. This is split into two processes, Meiosis I and II. NO INTERPHASE BETWEEN STAGES Results in 4 sperm cells

Recombination

The rearrangement of genetic material, especially by crossing over in chromosomes or by the artificial joining of DNA segments

Meiosis II

The second of two meiotic divisions which is very similar to mitosis. Each haploid cell is divided into two daughter cells and includes the four stages of Prophase (II), Metaphase (II), Anaphase (II) and Telophase (II).

Homologous

chromosomes which pair in meiosis are homologous chromosomes and are relatively identical in size, shape and genes they contain (but they could have different forms of the allele. Two homologous chromosomes form a pair (ex. a human has 46 chromosomes, or 23 homologous chromosome pairs)

Meiosis

sexual reduction division where after 2 successful divisions you produce 4 haploid sex cells (product is haploid cells)

Chiasma

site of crossing over of genes during synapsis

Centromere

the part of a chromosome that links sister chromatids

Kinetochore

the part outside of the centromere that spindle fibers attach to

Oncogene

A gene that causes cancer

Protooncogene

A gene with the potential to cause cancer

Gametes

A mature sperm or egg cell ready for fertilization

Tetrad (also known as bivalent)

A pair of homologous chromosomes (or 4 homologous chromatids) that are attached to each other.

Somatic cells or Autosomes

Any cell in an organism other than the reproductive cells

Carcinogen

Anything that causes cancer (sunlight, radiation, tobacco, alcohol, etc)

Difference in alignment of chromosomes between mitosis and meiosis

Mitosis lines up individually in a row over equator of cell Meiosis lines up in tetrads over equator

Chromatid

One of two strands of DNA joined together by a centromere in a duplicated chromosome, or the single strand when the chromosome is not duplicated

Karyotype

Picture of chromosomes taken by freezing cell cycle during metaphase by using the chemical colchicine.

Crossing Over

Reshuffling of the genes on a chromosome that occurs during meiosis as a result of the separation and rejoining of DNA segments within homologous chromosomes (occurs after synapsis joins them together) Occurs during Prophase I

How chromosomes segregate (separate) and the numbers of chromosomes in each daughter cell in Meiosis?

Tetrads line up over metaphase plate In Meiosis, the amount of chromosomes goes from 2n chromosomes to 2 cells with n chromosomes to 4 cells with n chromatids.

Non-disjunction

The failure of chromosomes to separate from one another during meiosis and mitosis, resulting in an extra or missing chromosome. There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis.

Synapsis

The joining of homologous chromosomes during prophase I (Does not include crossing over)

Sister Chromatids

The two identical halves of a duplicated chromosome, joined by the centromere in the middle

Homologous Chromosomes

Two alike chromosomes (In homologous chromosomes there are four chromatids, 2 from each parent) that possess the same genes and share the same shape and size.

Difference between chromatids and chromosomes

When a chromosome duplicates itself, the two identical parts are called chromatids. When the chromosome is not duplicated, it is just called a chromosome

Polyploid

a cell that contains more than 2 sets of homologous chromosomes

Zygote

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum, eventually develops into offspring

Chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. Can be singular in one long strand, or duplicated with two strands that form an X shape

Mitosis

asexual cell division that results in two identical daughter cells containing the same number and kind of chromosomes as the parent nucleus (the product is diploid somatic cells = 2N)