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Meiosis
Meiosis, Ploidy Levels, Sources of Variation
27
Biology
9th Grade
03/24/2012

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Term
Ploidy Levels
Definition
The number of sets of chromosomes in a cell
Term
Haploid
Definition
One set of chromosomes, as in reproductive cells of gametes: egg and sperm
Term
Diploid
Definition
Two sets of chromosomes, as in the body cells of most plants and animals
Term
Triploid
Definition
Three sets of chromosomes, as in some plants, like bananas
Term
Tetraploid
Definition
Four sets of chromosomes, as in some plant species, especially plants with big, showy flowers
Term
Meiosis
Definition
Reduction division; we reduce the number of chromosomes from diploid to haploid
Term
Somatic cells
Definition
Non-reproductive or body cells, usually diploid
Term
Gametes
Definition
Reproductive cells; egg or ova and sperm; they're haploid
Term
Meiosis I
Definition
The first round of division in meiosis
Term
What is the result of Meiosis I?
Definition
We reduce the number of chromosomes from diploid to haploid
Term
Homologous chromosomes
Definition
Chromosomes that are the same size, the same shape and they contain the same chromosomes in the same order
Term
Where do you get your homologous chromosomes from?
Definition
They exist in pairs: you get one from mom and one from dad
Term
Karyotype
Definition
A picture of the all the chromosomes in a cell
Term
Synapsis
Definition
The pairing up of homologous chromosomes during Prophase I of meiosis
Term
Crossing over
Definition
The exchange of genetic material between non-sister chromatids during synapsis of Prophase I of meiosis
Term
Metaphase I
Definition
The paired homologous chromosomes line up in the middle of the cell IN PAIRS
Term
Anaphase I
Definition
The homologous chromosomes separate during Anaphase I, but the centromeres do not split.
Term
What is the result of Meiosis I
Definition
The chromosomes number is reduced from diploid to haploid, crossing over has occurred
Term
Meiosis II
Definition
The second round of division in meiosis, it proceeds just like mitosis; it separates the sister chromatids during Anaphase II
Term
What are the products of Meiosis?
Definition
Four haploid cells
Term
Interkinesis
Definition
A pause between Meiosis I and Meiosis II, DNA is NOT copied; it can be very short or very long, depending on the species of organism
Term
What are the three sources of variation in gamete formation?
Definition
Independent assortment, crossing over, random fertilization
Term
What is independent assortment
Definition
The orientation of the homologous pairs during Metaphase I can be either left-right or right-left; each chromosome pair will separate or assort independent from the others
Term
How many different kinds of gametes can a human make?
Definition
223 or over 8 million
Term
What is random fertilization
Definition
Any possible egg can be fertilized by any possible sperm; so 8 million x 8 million means each person is one out of 64 million possible combinations
Term
Zygote
Definition
The product of fertilization; the result of the fusion of an egg and a sperm
Term
Syngamy
Definition
Another word for fertilization
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