Mitosis And Meiosis Flashcards
What are the stages of the cell cycle?
G1 Synthesis G2 Mitosis Cytokinesis
What occurs in G1?
Replication of organelles
Cell enlarges
Proteins made
What occurs in synthesis?
DNA replication
What occurs in G2?
Checks cell for mistakes
Errors repaired
Gets ready to enter mitosis
What happens in G0?
Cell is resting and not replicating
Cells can enter G0 if nutrient deficient
What are telomeres?
Repeated sequences at each end of chromosome/chromatid
What happens in prophase?
Nuclear membrane breaks down
Chromosomes condense
Spindle fibres appear
What happens in prometaphase?
Spindle fibres attach to chromosomes
Chromosomes continue to condense
Centrioles move towards poles
What happens in metaphase?
Chromosomes align along metaphase plate
What happens in anaphase?
Centromeres divide
Sister chromatids move to opposite poles (chromatids now called daughter chromosomes)
What happens in telophase?
Nuclear membrane reforms
Chromosomes decondense
Spindle fibres disappear
What happens in cytokinesis?
Cytoplasm divides
Parent cell becomes 2 daughter cells with identical genetic information
What are homologous chromosomes?
Have the same DNA sequence so same genes
Genes on homologous chromosomes ,at be different variants (alleles)
What are sister chromatids?
Have identical DNA
Have same alleles
Have just been through DNA replication
Joined by centromere
What are non-sister chromatids?
Have same genes
May have different alleles
What is meiosis?
Cell division for germ line cells
4 non-identical cells produced
Diploid (2n) reduced to haploid (n)
Production of eggs and sperm
What happens in prophase 1?
Chromosomes condense Crossing over occurs Nucleolus disappears Spindle fibres form Homologous pairs pair up
What happens in metaphase 1?
Homologous pairs line up along metaphase plate
What happens in anaphase 1?
Homologous pairs pulled apart to opposite poles of cell
What happens in telophase 1?
Nuclear membrane starts to reform
Cleavage
2 non-identical cells formed
What happens in prophase 2?
Nuclear membrane disappears
Spindle fibres form
What happens in metaphase 2?
Chromosomes line up on metaphase plate
What happens in anaphase 2?
Chromatids are separated and move to opposite poles of cell
What happens in telophase 2?
Nuclear membrane forms
Spindle fibres disappear
Chromosomes decondense
What is the product of Meiosis?
4 non-identical haploid daughter cells
How is genetic diversity generated in Meiosis?
Random assortment of chromosomes, don’t line up in numerical order
Crossing over of genetic material at chiasmata
