2.3 Eukaryotic cell cycle Flashcards
What is cell division in prokaryotic cells called?
- Binary fission.
What is cell division in eukaryotic cells called?
- Cell cycle.
What are the 3 steps in the cell cycle?
- Interphase.
- Mitosis.
- Cytokinesis.
What is the cell cycle used for in unicellular organisms?
- Asexual reproduction.
What is the cell cycle used for in multicellular organisms?
- Growth + repair.
What is asexual reproduction?
- Formation of new organisms that does not involve fusion of gametes.
What are chromosomes made of?
- Sequence of nucleotide bases in DNA.
What are the 3 features of chromosomes?
- Shape of each chromosome is characteristic.
- Chromosomes occur in homologous pairs.
- For each species, number of chromosomes is fixed.
What is a centromere?
- Narrow region occupying specific position on each chromosome.
- Only site on each chromosome that spindles can attach to during mitosis.
- Following DNA replication, centromere holds together 2 chromatids.
What is a stomatic cell?
- Any cell in body of multicellular organism other than germ cell or undifferentiated stem cell.
What are homologous chromosomes?
- Pair of c’somes in a diploid cell that have same shape + size.
- Carry same genes in same order although not necessarily same alleles of each gene.
What does diploid mean?
- Contains 2 copies of each c’some.
- In sexually reproducing organisms, one copy from each parent.
How many pairs of c’somes and number of c’somes do humans have?
- 23 pairs.
- 46 c’somes.
What is a karyotype?
- Number + shape of c’somes.
What is a locus (plural loci)?
- Position that a particular gene occupies on a specific c’some.
What are alleles?
- 1 of 2 or more diff forms of same gene.
- Diff alleles of same gene have slightly diff nucleotide sequences.
What does homozygous mean?
- Diploid cells have 2 copies of each gene.
- If 2 copies are same allele of gene, cell is homozygous.
What does heterozygous mean?
- Diploid cell, 2 copies of a gene are diff alleles, cell is heterozygous for this gene.
What are chromatids?
- Following DNA replication, cell has 2 copies of each chromosome.
- When these become visible during cell division, held together by centromeres, briefly called chromatids.
What is a karyogram?
- Images of c’somes cut from copy of photomicrograph are arranged + pasted.
What are sex c’somes?
- c’some that carries genes which determine sex of an organism.
- In mammals, Y c’somes determines maleness.
What is an autosome?
- Any c’some other than a sex c’some.
What is interphase?
- Time between divisions.
What is mitosis?
- Separation of chromatids of each c’some to form 2 new nuclei.
What is cytokinesis?
- Division of cytoplasm.
What are the 3 parts of interphase?
- G1 - 1st growth phase.
- S - Synthesis of DNA.
- G2 - 2nd growth phase.
What happens during the 1st growth phase during interphase?
- Cytoplasm active.
- New organelles formed.
- Intense biochemical activity of growing cell.
What happens during the synthesis of DNA during interphase?
- Chromosomes replicated –> chromatids.
What happens during the 2nd growth phase during interphase?
- More growth of cell.
- Preparation for mitosis.
What is the longest part of the cell cycle?
- Interphase.
What are the stages involved in mitosis?
- Prophase.
- Metaphase.
- Anaphase.
- Telophase.
What is mitosis?
- Nuclear division.
What happens during prophase?
- Super-coiling - c’some shorten + thicken (visible as 2 sister chromatids joined at centromere).
- Centrioles split + move to opp ends of cell –> spindle extends across cell.
- Nuclear envelope disintegrates - c’somes freed into cytoplasm.
What happens during metaphase?
- Nuclear envelope completely gone.
- Spindle fibres attach to centromeres of c’somes.
- Spindle fibres pull c’somes to equator.
What happens during anaphase?
- C’somes break apart at centromere.
- Splits into 2 v-shaped sister chromatids.
What happens during telophase?
- Chromatids reach opp ends of cell.
- Chromatids uncoil + become c’somes again.
- Nuclear envelope reforms around c’somes.
- Cell prepares to slipt cytoplasm + contents (cleavage furrow forms).
What happens in cytokenesis?
- Cell splits into 2 daughter cells.
- Daughter cells identical to each other and parent cell.
What are daughter cells called?
- Clones.
What is a clone?
- 2 or more cells (or organisms) genetically identical.
How are clones made in eukaryotic organisms?
- Mitosis.
Why does mitosis produce clone daughter cells?
- Because DNA directly replicated during interphase.
- Cytoplasm divided down mid-point during cytokinesis.
Where does mitosis commonly occur in animals?
- Epithelial tissues - e.g. skin + lining of intestine.
Where does mitosis commonly occur in flowering plants?
- Found in meristems - actively growing tips of shoot + roots.
- Cambium - vascular bundles.
What is Meristem?
- Group of plant tissues able to divide by mitosis.
What are primary meristems?
- Found at tips of growing shoots and roots.
What are secondary meristems?
- Develop in woody plants, leading to increase in diameter of roots + shoots.
