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30 Cards in this Set

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1st division of meiosis
separates homologous pairs
reduction division
the usually first division of meiosis in which chromosome reduction occurs
interphase 1
the interval between the end of one mitotic or meiotic division and the beginning of another
prophase
the initial stage of mitosis and of the mitotic division of meiosis characterized by the condensation of chromosomes consisting of two chromatids, disappearance of the nucleolus and nuclear membrane, and formation of mitotic spindle
metaphase
the stage of mitosis and meiosis in which the chromosomes become arranged in the equatorial plane of the spindle
anaphase
the stage of mitosis and meiosis in which the chromosomes move toward the poles of the spindle
telophase
the final stage of mitosis and of the second division of meiosis in which the spindle disappears and the nuclear envelope reforms around each set of chromosomes
tetrad
group or arrangement of four: as a : a group of four cells produced by the successive divisions of a mother cell or tetrad of spores
synapsis
the association of homologous chromosomes that is characteristic of the first meiotic prophase
independent assortment
formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes by the passage according to the laws of probability of one of each diploid pair of homologous chromosomes into each gamete independently of each other pair
2nd division of meiosis
separates sister chromatids
telophase 2
the final stage in the first division of meiosis that may be missing in some organisms and is characterized by the gathering at opposite poles of the cell of half the original number of chromosomes including one from each homologous pair
Mendelian Inheritance
inheritance of characters specifically transmitted by genes in accord with Mendel's law -- called also particulate inheritance
metaphase 1
In metaphase I the tetrads are again arranged across the center by the movements of the kinetochores with the two centromeres opposite each other, but this time the sister chromatids will not be pulled apart as in mitosis.
anaphase 1
In anaphase I the chromatids holding the chromosomes together loosen. The two homologous chromatids of each tetrad are separated into separate poles. Since the chromosomes from each parent can go into either pole this is another means to increase genetic diversity.
telophase 1
In this phase, like in mitosis the chromosomes are moved into opposite poles and the nuclear envelope reforms and the spindle is broken down. Remember that there are two chromosomes, not one as in mitosis.
crossing over: tetrad
genetic analysis of organisms whose four products of meiosis remain together in groups of four called tetrads.
crossing over: synapsis
The synapsis and exchange of chromosomes is such that no segments are lost or gained, and four complete chromosomes emerge in a tetrad.
independent assortment
allele pairs separate independently during the formation of gametes.
haploid
have one set of chromosomes (n=1), which is the same as a gamete (pollen or egg cell). Haploids can be distinguished from diploids (n=2) by using gene markers which are closely linked with the gene under study so they can be visually detected or by their physical characteristics.
prophase 2
In meiosis the cell goes directly from telophase I to prophase II without the interphase. In prophase II the nuclear envelope is again dissolved and the spindle is set up again. Prophase II is identical to prophase of mitosis except that there is half the amount of chromosomes.
metaphase 2
Again the chromosomes move into the center and line up. Now there are two chromosomes, instead of two tetrads, so that the chromatids will split off this time.
anaphase 2
The kinetochores move towards the poles, splitting up the sister chromatids
telophase 2
In telophase II the chromatids concentrate in the poles and the nuclear envelope is reformed and the spindle again is dissolved. The cells divide for the last time, leaving a total of four haploid cells, which have half the chromosomes of a diploid cell. Unlike the daughter cells from mitosis, the daughter cells produced here cannot immediately cycle back to interphase.
• Law of Segregation
Mendel's first law, stating that allele pairs separate during gamete formation and then randomly re-form as paris during the fasion of gametes at fertilization
Law of Independent Assortment
Mendel's second law, stating ahat each allel pairs segregates independently during gamete formation ; applies when genes for two characteristics are located on different pairs of homologous chromosomes
incomplete dominance
A form of intermediate inheritance in which heterozygous alleles are both expressed, resulting in a combined phenotype.
codominance
A condition in which both alleles of a heterozygous pair are expressed independently.
codon A sequence of three bases on messenger RNA that specifies the position of an amino acid in a protein.
multiple alleles
Any of a set of three or more alleles, or alternative states of a gene, only two of which can be present in a diploid organism.
polygenic inheritance
The phenotypic expression of a trait involving the interaction of many genes.