Meisos
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Chromosome
Rod shaped filamentous bodies present in nucleas & cytoplasm of prokaryotic cell which carries genes
Difference between somatic & gamete
Somatic cells are human body cells with: 46 chromosomes, diploid number Gametes are sex cells with 23 chromosomes and only n
Zygote
Fusion of female gamete and male gamete
Chromosome components
Centromere : holds 2 chromostids Gene: segment of DNA that codes for a trait Chromotids : identical copies making up a chromosome
Homologous chromosomes
Chromosomes that are identical in shape, size & which code genes for same set of characteristics
Karyotype
Image which depicts an organisms chromosomes which determines gender & whether a person has down syndrome
Loci
Genes in same position
Importance of mitosis
Growth (allows zygote to produce more cell in order to grow) Repair & replacement : allow multicellular organism maintain its tissues.
Cytokinesis definition
Process of cytoplasmic division to form two daughter cells
Karyokinesis
Division of nucleas
Meisos definition
Cell division whereby a diploid cell undergoes 2 cell divisions & divides to form 4 dissimilar haploid cells (sex)
Prophase 1
Homologous Chromosomes shorten, visible Nuclear membrane & Nucleolus dissappear Spindle starts to form Chiasma from pairing of homologous pairs
Metaphase 1
Homologous chromosomes line up at equator Centromere of chromosome attaches to extended spindle fibres Random arrangement at equator
Anaphase 1
Spindles contract, shorten & pull chromosomes to opp sides of cell Creating random assortment
Telophase 1
Nuclear membrane and Nucleolus reform Each pole has half no. of chromosomes present in original cell Invagination of cleavage furrow deepens till cytokinesis & karyokinesis occurs to form 2 different daughter cells
Meiosis significance
Process reduces diploid to haploid Produces Gametes for fertilisation Ensures no. of chromosomes in species stays constant over generations Genetic variation
Autosomes
22 pairs of Chromosomes which aren’t sex cells in diploid cell
Bivalent
Homologous chromosomes held together by DNA cross over
Centriole
Organelle in cytoplasm giving rise to spindle fibres during mitosis and meisos
Chiasma
Point where crossing over takes place between chromatids of homologous pair during prophase 1
Mitosis
Process of cell division where resulting daughter cells have same diploid chromosomal no. as original parent cell
Non disjunction
Failure of homologous chromosome to divide leading to extra chromosome or one less chromosome in another gamete
Spindle fibres
Micros tubules that form during cell division
Gonosomes
Last Single pair of sex chromosomes (XX or XY)