Term
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Definition
A sperm and an egg unite to form a new individual.
Two haploid gametes fuse and a full complement of chromosomes are restored.
The cell that results from fertilization is:
–Diploid (2n)
–Called a zygote
[image] |
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Term
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Definition
Is nuclear division that precedes the formation of gametes.
Results in a halving of chromosome number
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Term
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Definition
The number and types of chromosomes present in an organism. |
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Term
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Definition
All chromosomes besides Sex Chromosomes
Humans have 46 chromosomes
1 pair of sex chromosomes
22 pairs of autosomes |
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Term
Homologous chromosomes (Homologs) |
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Definition
Chromosomes of the same type
Carry the same genes in the same locations but each one may contain different alleles |
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Term
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Definition
| Different versions of a specific gene |
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Term
| Homologous Chromosomes (Image) |
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Definition
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Term
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Definition
The number of distinct types of chromosomes present
Organisms with just one of each type of chromosome.
In most plants and animals the four daughter cells are haploid.
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Term
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Definition
The number of each type of chromosomes present |
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Term
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Definition
Organisms with two of each type of chromosome.
–One paternal (father) chromosome
–One maternal (mother) chromosome
The products of meiosis are haploid
Just before meiosis begins, each chromosome in the diploid (2n) parent cell is replicated
In most plants and animals the original cell is diploid
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Term
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Definition
| Organisms with three or more versions of each type of chromosome. |
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Term
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Definition
Homologous replicated chromosomes that are joined together during prophase I and metaphase I of Meiosis
[image] |
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Term
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Definition
-two identical sister chromatids
-attached at the centromere
[image]
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Term
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Definition
1. Diploid (2n) parent cell produces two haploid (n) daughter cells.
2. Homologs separate and go to different daughter cells.
3. Each chromosome consists of two identical sister chromatids
[image]
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Term
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Definition
1. Sister chromatids of each chromosome separate go to different daughter cells.
2. Four haploid daughter cells are produced.
3. They also have one of each type of chromosome
but now the chromosomes are unreplicated.
[image] |
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Term
| Meiosis I & II summary (image) |
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Definition
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Term
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Definition
The outcome of meiosis is a reduction in chromosome number. |
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Term
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Definition
In animals, 4 haploid daughter cells from Meiosis become gametes |
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Term
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Definition
The homolog pairs come together in a pairing process called synapsis
The structure that results from synapsis is called a tetrad, consisting of two homolog
The chromatids of the homologs are called non-sister chromatids
[image] |
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Term
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Definition
The non-sister chromatids begin to separate
Exchange or crossing over between homologous non-sister chromatids
Chiasmata are formed during this stage |
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Term
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Definition
Tetrads line up at the metaphase plate.
[image] |
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Term
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Definition
The paired homologs separate
Begin to migrate to opposite ends of the cell
[image] |
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Term
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Definition
The homologs finish migrating to the poles of the cell
Then the cell divides in the process of cytokinesis.
[image] |
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Term
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Definition
One chromosome of each homologous pair is distributed to a different daughter cell.
The daughter cells of Meiosis I are
-Haploid
-Still in the form of sister chromatids |
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Term
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Definition
The spindle apparatus forms
One spindle fiber attaches to the centromere of each sister chromatid
[image] |
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Term
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Definition
Replicated chromosomes line up at the metaphase plate.
[image] |
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Term
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Definition
Sister chromatids separate
The resulting daughter chromosomes begin moving to opposite sides of the cell
[image] |
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Term
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Definition
Chromosomes arrive at opposite sides of the cell
A nuclear envelope forms around each haploid set of chromosomes
Each cell undergoes cytokinesis.
[image] |
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Term
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Definition
Results in four haploid cells
Each has one of each type of chromosome
One diploid cell with replicated chromosomes = four haploid cells with unreplicated chromosomes
[image] |
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Term
| Differences between Meiosis and Mitosis |
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Definition
–Homologs pair in meiosis
–Homologs do not pair in mitosis
Homologs pair in Prophase I of Meiosis I
Meiosis I resultes in a reduction division |
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Term
| Summary table of Mitosis and Meiosis |
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Definition
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Term
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Definition
Chromosomal segments are swapped between adjacent homologs.
The non-sister chromatids from each homolog get physically broken at the same point and are attached to each other.
Segments of maternal and paternal chromosomes are swapped.
[image] |
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Term
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Definition
Clones that are genetically identical to one another and to the parent. |
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Term
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Definition
Fusion of gametes
A chromosome makeup different from that of one another and from that of either parent |
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Term
| Genetic recombination (Crossing Over) |
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Definition
Increases the genetic variability of gametes produced by meiosis.
New combinations of alleles on the same chromosome.
Combinations that did not exist in each parent
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Term
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Definition
Where gametes from the same individual combine
Even Self-Fertilization leads to genetically variable offspring |
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Term
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Definition
In many sexually reproducing species, gametes from different individuals combine to form offspring.
Increases the genetic diversity of the offspring because chromosomes from two different parents are combined |
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Term
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Definition
If both homologs or both sister chromatids move to the same pole of the parent cell
The resulting gametes will contain an abnormal set of chromosomes
[image]
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Term
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Definition
Those with too few or too many chromosomes
Do not survive to produce viable offspring
**Mistakes in meiosis are the leading cause of spontaneous abortion |
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Term
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Definition
Two gametes will have an extra copy of a chromosome
Example: Down syndrome - Caused by an extra copy of chromosome 21.
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Term
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Definition
| Two gametes will lack that chromosome |
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Term
| Changing-Environment Hypothesis |
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Definition
Offspring that are genetically different from their parents (Sexual) are more likely to survive and produce offspring if the environment changes
genetically identical offspring (Asexual) are less likely to survive and produce offspring if the environment changes
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Term
| Testing the Changing-Environment Hypothesis |
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Definition
| If a new disease comes through the population, genetically different species are more likely to survive and create offspringthat can survive it. While Asexual beings are unable to adapt. |
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