Cell Division Flashcards
What is happening in the G1 phase of interphase?
First growth phase. Protein synthesis, cytoplasm and number of organelles increase rapidly
What is happening in the S phase of interphase?
Synthesis. DNA replicates if the cell is going to divide
What is happening in the G2 phase of interphase?
Second growth phase. Proteins necessary for cell division are synthesised
What is the joining point of two homologous chromosomes called?
Centromere
Why is mitosis significant in a cell?
Asexual reproduction, growth, repair, replace old cells
What happens in interphase of mitosis and meiosis?
Period of cell growth and development. DNA replication, growth. Most of cells life is spent in interphase
What happens in prophase of mitosis?
Chromosomes form X shape, nuclear envelope disappears , centrioles move to opposite side of nucleus and spindle fibres form
What happens in metaphase of mitosis?
Chromosomes arrange on equator of cell and microtubules attach the chromosomes to the centrioles
What happens in anaphase of mitosis?
Centromere is pulled and divides in two, microtubules pull the chromatids to opposite poles of the cell. Now called chromosomes
What happens in telophase of mitosis?
Chromosomes uncoil and lengthen, nuclear envelope and nucleolus reform. Two new nuclei form and spindle fibres disintegrate
What happens in cytokinesis?
Division of rest of the cell after nucleus divides. In animal cells the cytoplasm pinches in. In plant cells, a new cell plate forms
If cells were described as diploid, how many chromosomes do they have (humans)?
46 chromosomes (2n). Have homologous pairs
If cells were described as haploid, how many chromosomes do they have (humans)?
23 chromosomes (n). Gametes (sperm and egg)
What happens in prophase 1 of meiosis 1?
Chromatin condenses, coils and thickens to become visible. Chromosomes now visible as two chromatids. Centrioles move to opposite poles of cell. Each homologous pair of chromosomes come together to form a bivalent. Called synapsis. Crossing over takes place between the non-sister chromatids of the bivalent. Parts of each chromatid may break and reconnect
What happens in Metaphase 1 of meiosis?
Spindle fibres attach to centromere and move whole chromosome to cell equator. The bivalents arrange themselves randomly at the cell equator resulting in genetic variation. Called independent assortment
What happens in anaphase 1 of meiosis?
Spindle fibres contract and pull chromosomes to opposite poles of cell. Whole chromosomes are pulled (made up of two chromatids each)
What happens in telophase 1 of meiosis?
Two new nuclear envelopes reform (animal cells). Each nucleus contains half the number of original chromosomes. Chromosomes are genetically different from those in original cell. Each cell has a haploid nuclei containing 23 chromosomes (46 chromatids).
What happens in prophase 2 of meiosis?
Nuclear envelope and nucleolus disappear. Chromatin condenses and chromosomes become visible. Centrioles replicate and new spindle fibres form.
What happens in metaphase 2 of meiosis?
Spindle fibres align the chromosomes randomly along the spindle equator. Each chromosome is made up of two chromatids. Genetic variation occurs due independent assortment of chromatids at the equator
What happens in anaphase 2 of meiosis?
Microtubules contract and centromeres divide. Chromatids pulled to opposite poles of the cell by attached spindle fibres. As soon as separated they are called chromosomes
What happens in telophase 2 of meiosis?
Chromosomes uncoil. Each new chromosome may be genetically different from original one. Nuclear envelope and nucleolus reappear and cytokinesis begins. Four haploid cells are produced
What events occur throughout interphase as a whole?
Growth (increase in cell size)
Protein synthesis
ATP synthesis
Replication of organelles
Replication of DNA
Synthesis of ribosomal material
