Unit 1 (1.6) Flashcards
Cell division
What are the stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
What is prophase?
Nuclear envelope breaks down, chromosomes condense, centrioles move to opposite poles of the cell
What is metaphase?
Sister chromosomes line up at equator, centromeres attach to the spindle fibres
What is anaphase?
Sister chromatids separated and pull apart to opposite a poles
What is telophase?
Nuclear envelope reforms, spindle fibres break down, chromosomes uncoil
What is interphase?
Longest stage of the eukaryotic cell cycle
Cells grow and synthesise new organelles, proteins and DNA in preparation for mitosis.
What is mitosis?
Form of cell division
Produces tow genetically identical diploid daughter cells
Why is mitosis important?
Important for the growth of tissue and repair and replacement of cells.
What are sister chromatids?
A pair of identical chromatids formed by DNA replication, joined by a centromere
What is cytokinesis?
The division of the cytoplasm at the end of mitosis to produce two new daughter cells
Compare mitosis in plant and animal cells
..hint draw a table
What does uncontrolled
Cancerous growths
What is meiosis?
Form of cell division
Produces four genetically different daughter cells (gametes) with a haploid of chromosomes
Involves two divisions
Significance of meiosis in reproduction?
Gametes must be haploid so when they combine during fertilisation, the full number of chromosomes is present. Resulting in a zygote it creates genetic variation
What is meiosis I
First stage of meiosis
Homologous chromosomes separated to form two haploid cells
Draw diagrams to illustrate meiosis I
Prophase I
Metaphase I
Anaphase I
Telophase I
———————> Cytokinesis
Describes what happens during meiosis I
Homologous chromosomes form to pair bivalents
Crossing over occurs at chiasmata
Cell divides into two; independent segregation of homologous chromosomes, each cell contains either a maternal or paternal copy
What are are homologous chromosomes
Pair of chromosomes with genes at the same locus
One maternal and one paternal
Some alleles may be the same while others are different
Define crossing over
Process in meiosis I
Homologous chromosomes pair up, their chromatids wrap around one another and their alleles are exchanged at equivale nt portions of chromatids
Created genetic variation
What is meiosis II
Second stage of meiosis
Sister chromatids separated to form four gametes
What is independent segregation?
The random separation of homologous chromosomes in meiosis I that produces genetic variation
Draw diagrams to illustrate the stages of meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
———————> Cytokinesis
Describe what happens during meiosis II
Independent segregation of sister chromatids
Each cell divides again, producing four haploid cells
How does meiosis produce genetic variation?
Crossing over during meiosis I
Independent assortment homologous chromosomes and sister chromatids
Results in new combination of alleles
Draw a diagram to show cells after each stage of meiosis
Parent cell
After meiosis 1
After meiosis 2
