C8 - Cell Replication Flashcards
What is DNA?
The way living things pass on traits (hair colour, eye colour, height)
What is a chromosome?
A single DNA molecule containing many genes
What are genes?
Sections of DNA that code for proteins
What are homologous chromosomes?
2 molecules of DNA that contain the same genes (1 from each parent)
What is the Cell Cycle?
The cycle of creating new cells that all cells exist in - all cells come from pre-existing cells through the completion of this cycle
What are the different phases of the cell cycle?
G1, S, G2, M
In eukaryotic cells, what are the two major stages of the cell cycle?
Interphase and mitotic phase
What is interphase?
When the cell grows and copies its DNA
What is the mitotic phase?
The cell separates it’s DNA into 2 sets and divides its cytoplasm (cytokinesis) forming two new cells
What is cytokinesis?
When a cell divides its cytoplasm to form 2 new cells
Which stages of the Cell Cycle does interphase cover?
G1, S and G2
What is the G1 phase?
The first gap phase, the cell grows physically larger, copes organelles and makes biomolecules important for later steps
What is the S phase?
Synthesis, where DNA replication occurs in the nucleus, and the centrosome (a microtubule-organising structure for seperating DNA) is duplicated
What is the G2 phase?
The second gap phase, where the cell grows more, and makes proteins and organelles. This phase ends when mitosis begins
What is the M phase?
Mitosis, used for growth, repair or asexual reproduction
Does mitosis make diploid or haploid cells?
Diploid cells
Is mitosis cloning?
Yes
Outline the process of mitosis
Interphase: DNA replicates, as do organelles
Prophase: Chromosomes condense and become visible and the nucleus disappears
Metaphase: The spindle fibers have descended and attached to the centromeres and lined the chromosomes up on the cell equator (or metaphase plate)
Anaphase: The spindle fibers pull the chromosomes apart and also push the cells poles apart
Telophase: The chromosomes form chromatin again, and the contractile ring pulls the cell membrane together until the cell divides
Cytokinesis: When the cell divides into two new daughter cells
What is meiosis?
The process of creating four genetically unique daughter cells with half the number of chromosomes
When is meiosis used?
Sexual reproduction only
Does meiosis create diploid or haploid cells?
Haploid (one chromosome)
Outline the first stage of meiosis
Interphase: DNA and organelles replicates
Prophase 1: Homologous chromosomes pair up and ‘stick’ via synapsis, then segments of sister chromosomes switch in a process known as crossing over
Metaphase 1: The pairs all line up in the centre of the cell and are held in place with spindle fibers (independent assortment occurs here)
Anaphase 1: The pairs separate and two chromatids move towards each pole of the cell
Telophase 1: The two cells separate and cytokinesis occurs
Outline the second stage of meiosis
Prophase 2: nucleus of intermediary daughter cells disappear and the centrosomes begin to move towards poles
Metaphase 2: Chromosomes lined up in the centre of the cell
Anaphase 2: Replicated chromosomes split
Telophase 2: Cells divide into 4 individual daughter cells (forming gametes)
What is independent assortment?
Chromosomes go into each new cell randomly, so any mixed chromosome ( chromosome with changed alleles) can go into any of the four daughter cells, creating even more variation
How do prokaryotes reproduce?
Via mitotic binary fission
What is fragmentation?
One part splits into pieces and each develops into a new organism (flatworms)
What is parthenogenesis?
When female produced eggs hatch without fertilisation (worker bees)
What are the different types of twins?
Fraternal: twin eggs fertilised by 2 sperm (different genetics)
Identical: fertilised egg splits into 2 (same genetics)
