Meiosis Flashcards
(24 cards)
Genes
Units of hereditary
Segment of DNA
Each has specific location- locus
Supressor and expressor genes
Human Chromosome
Somatic Cell- has 46 chromosomes
- two sets of 23
- diploid
- one set from each parent
Gametes-one set of chromoemsoes
-23
-haploid
meiosis
Karyotype
Visual representado of chromosomes in cell
Homologous Pairs
Tetrad (four chromatids)
One from each parent
Autosomes
Same characteristics
Sex Chromosomes
Distinct in their characteristics
X and Y
Determine gender
Plants and Algae
Alternate generations
Both haploid and diploid stages
Fungi and Protists
Haploid multicellular organisms
Mitosis produces gametes
Meiosis
Sexual reproduction
Produces haploid set of chromosomes -eggs and sperm
Chromosomes replicate once
2 cell divisions
Meiosis I
Reduces chromosomes from diploid to haploid
Meiosis II
Produces four haploid daughters
Crossing over
Occurs in prophase I
Increases genetic variability
Chromosomes carry genes from two different parents
Unique Features of Meiosis
Crossign over
Tetrads separate
Chromatids separate
Independent Assortment
Each pair of chromosomes align independently or randomly
Results in genetic variability
Prophase I
Nuclear envelope disappears
Chromatin condenses into chromosomes
Mitotic spindles begin to form
Centrosomes move apart
Homologous pairs appear?
Crossing over happens
Metaphase I
Aligning of the tetrads(homologous pairs) along the mid-line plate
Mitotic spindles fully formed
Anaphase I
Chromosomes move to opposite sides, tetrads/homologous pairs separate
Cell elongates
Telophase I
Cytokinesis happens
Changes from haploid to diploid
Prophase II
Mitotic spindles appear
Metaphase II
Chromosomes line up along the mid-line plate
Anaphase II
Chromatids separate
Cell elongates
Telophase II
Left with four haploid daughter cells
Cytokinesis
Abnormal Chromosome Count
Meiosis malfunction
Homologous pairs fail to separate in meiosis I
Sister chromatids fail to separate in meiosis II
Defect depends the chromosome affected
Down Syndrome
Trisomy 21
Altering of Chromosome Structure
Breakage, rearrangement (matching of non homologous chromosomes)
Deletion or duplication of gene
Might not be a problem depending on the gene
