Cell Divsion & Replication Flashcards
What are homologous chromosomes?
- Homologous chromosomes pairs of matching chromosomes - carry same genes.
what are diploid cells?
- diploid (2n): Cells that carry homologous chromosomes (where n= number of types of chromosomes) and contain two sets of each chromosome.
- Each diploid cell has one set of chromosomes from the father and one set from the mother.
what are haploid cells?
haploid (n): contain only one type of each chromosome. example sex cells
what is mitosis?
- Takes place during growth of an organism and in asexual reproduction.
- Basis of growth, repair, budding and vegetative propagation in multicellular organisms.
- Yields daughter cells that have the same number and types of chromosomes as the parent cell.
what does crossing over mean?
Crossing-over occurs during Prophase I which results in a recombination of genes, increasing variation.
what is a karyotype?
- A karyotype is a pictorial display of the total complement of a species’ chromosomes
what are the 5 stages of Mitosis?
Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
What are the steps in prophase?
- DNA threads or chromatin condense to form distinct , thickened chromosomes.
- Each chromosome consists of two strands (chromatids).
- Series of protein threads create a spindle that extends the length of the cell.
- The two ends of the spindle are called poles, which the middle region is the equator.
- The nuclear membrane breaks down.
What are the steps in metaphase?
- Chromosomes migrate to the centre (equator) of the cell and attach their centromere to an individual spindle fibre.
What are the steps in anaphase?
- The chromatids of each chromosome separate so that they are no longer attached by their centromeres.
- Once separated, the chromatids are called sister chromosomes.
- Each of the identical sister chromosomes are pulled to the opposite poles of the cell.
What are the steps in telophase?
- The chromosomes congregate tightly together at each pole.
- The spindle breaks down and a new nuclear membrane is formed.
- Chromosomes uncoil to revert to chromatin threads.
What are the steps in Cytokinesis?
- During the events of telophase, division of the cytoplasm between the new groups of chromosomes commences.
- The cell membrane constricts across the equator of the cell to form two new cells.
what are the 8 stages of Mitosis?
Prophase I, Metaphase I, Anaphase I, Telophase I & Cytokinesis I, Prophase II, Metaphase II, Anaphase II and Telophase II & Cytokinesis II.
What are the steps in Prophase I ?
- The nucleolus disappears and the nuclear membrane breaks down.
- In animal cells centrioles migrate to opposite poles and spindle fibres form.
- The bivalent chromosomes (two chromatids joined at the centromere) become visible and align themselves in pairs as homologous chromosomes (consisting of 4 sister chromatids, called a tetrad).
- diploid, chromatin → chromones → (synapses) ninds to homologous chromosomes (tetrad) → exchange of gene combinations (crossing over) → nuclear membrane disappear, spindle fibres.
- The chromatids may become entwined and genetic information can be exchanged, called crossing-over
- Chromosomes from the organism’s father can exchange genes with chromosomes from the organism’s mother, resulting in a recombination of genes.
- Gametes have unique combinations of genes that are different from the original parental combinations, increasing variation.
What are the steps in Metaphase I ?
- homologous chromosomes arrange themselves along the equator (middle) of the cell.
- The kinetochore proteins (linking the two chromatids together at the centromere) attach to the spindle fibres.
- Each homologous chromosome (containing two chromatids) randomly aligns itself towards an opposite pole.
