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heredity
The transmission of traits from one generation to the next.
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variation
differences that arise from parent to offspring
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genetics
scientific study of heredity & hereditary variation
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genes
inherited from parentcodes for specific proteinresponsible for traits
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gametes
reproductive cells of sexual reproduction haploid (1/2 of chromosomes)
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somatic cells
cells of body except gameteshumans have 46 chromosomes in these
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locus
gene's specific location along length of chromosome
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asexual reproduction
single individual is sole parentcopies of all genes to offspringno fusion of gametes
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clone
genetically identical individuals
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sexual reproduction
1 gamete each from 2 different parents fuse to form offspring
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life cycle
generation to generation sequence of stages in reproductive history of an organism
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homologs
homologous chromosomes.
Two chromosomes composing a pair have the same length, centromere position, staining pattern
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karotype
number and appearance of chromosomes in nucleus of eukaryotic cell
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sex chromosome
X and Y chromosomes that determine offspring's sex
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autosomes
non-sex determining chromosomes
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diploid cell
any cell with 2 sets of chromosomes denoted as 2n, humans 2(23)=46
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haploid cell
gametes with single set of chromosomesdenoted as n, humans n=23
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fertilization
fusion of haploid cells' nuclei that produces zygote
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zygote
haploid cell that results from fertilization
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alternation of generations
plants & some algae diploid & haploid stages are multicellular.
sporophytemulticellular diploid stage.
spores meiosis in sporphyte produces haploid spores.
gametophyte multicellular haploid stage produced by spore dividing mitotically
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meiosis
cell division that reduces the number of sets of chromosomes from two to one.
reduces chromosome count from diploid to haploid.
Interphase followed by 2 consecutive cell divisionsmeiosis I and meiosis II
4 daughter cells each with only half as many chromosomes as parent
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sister chromatid cohesion
association of sister chromatids all along length
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Prophase I
chromosomes condense homologs loosely pair along lengths.
synapsis occurssynaptonemal complex physically connect paired homologs.
crossing over genetic rearrangement between nonsister.
chromatids involves exchange of corresponding DNA segments.
chiasmata exist at point where crossover occurred.
centrosome movement, spindle formation, nuclear envelope breakdown.
proteins attach to kinetochores.
homologs movetoward plate
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alleles
loci for a gene on a chromosome
different versions of the same gene e.g. coding for eye color
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Prophase I
The nuclear membrane breaks apart, chromosomes condense and form homologous chromosomes. Crossing over may occur and cause offspring diversity.
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Meiosis I
The first of two consecutive cell divisions that produces a cell with half the number of chromosomes as the parent cell
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Meiosis II
The second consecutive cell division
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crossing over
haploid cells that give rise to multicellular individual without fusing with another cell. divides mitotically to generate a multicellular haploid stage called gametophyte
genetic rearrangement between nonsister.
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Metaphase I
Homologous pairs line up in center, Spindle fibers attach to the chromosomes.
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Anaphase I
Homologus pairs seperate and move to opposite ends of the cell.
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Telophase I
Nuclear membrane forms around each set of chromosomes, the cytoplasm divides, forming two new daughter cells
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Prophase 2
Nuclear membrane breaks apart.
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Metaphase II
Sister chromatids line up along the middle of the cell.
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Anaphase II
Sister chromatids separate and are pulled to the opposite end of the cells.
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Telophase II
Chromosomes are single stranded, end up with four new cells, cells are Haploid, nucleus does reappear.
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Recombinant Chromosomes
Individual chromosomes that carry genes derived from two different parents
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sporophyte
the multicellular diploid stage of the alternation of generations. goes through meiosis to produce spores
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chiasmata
criss crossed regions where crossing over has occured.
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gametophyte
alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis. The haploid gametes unite and develop into sporophyte
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