Cell division - 2 Flashcards
What are chromosomes
Each chromosome is 1
molecule of DNA which is
wrapped around histone
proteins
What is a gene
A gene is a section of DNA
that codes for a protein
What are the stages in the cell cycle
Mitosis
Cytokinesis
G1
S
G2
What happens in Mitosis
Nuclear divison
What happens in cytokinesis
Cell division
division of the cytoplasm
What happens in G1
Biosynthesis
Protein synthesis
organelles replicated
Error checking
What happens in stage S of the cell cycle
Synthesis
DNA replication
What happens in G2
Continued cell growth
Proteins needed for cell division made
DNA checked for errors
What happens at G1 checkpoint
Checks for:
- cell size
- nutrients
- growth factors
- DNA damage
What happens at G2 checkpoint
Checks for:
- DNA damage
- DNA replication completeness
What happens at the spindle checkpoint
Checks for:
- chromosome attachment to spindle metaphase plate
why do organisms use mitosis
Growth of an organism
Repair of tissues
Asexual reproduction
What are the 4 stages of mitosis
Prophase (Preparation)
Metaphase (Middle)
Anaphase (Apart)
telophase (Telophase)
What happens during prophase
Chromosomes condense
Centrioles move to opposite ends of cell
spindle fibres start to form
nuclear envelope breaks down
What happens during metaphase
Chromosomes line up along the middle of the
cell
Chromosomes attached to spindle by their
centromere
Metaphase checkpoint
What happens during anaphase
Centromeres divide, separating sister
chromatids
Spindles contract, pulling chromatids to
opposite ends of the cell - centromere first
What happens during telophase
Chromatids reach opposite ends of cell and
uncoil – now chromosomes
Two nuclear envelopes form
Two nuclei form
What is the difference in mitosis between plants and animals
Plants have no centrioles where as animals do
In plants cytokinesis starts with formation of cell plate where as in animals cytokinesis starts outside
Only meristem undergoes mitosis where as most animal cells undergo mitosis
What are alleles
Different versions of the same gene
What are the differences between mitosis and meiosis
Mitosis produces 2 cells, meiosis produces 4
Mitosis is one division, meiosis is two
Mitosis produces diploid cells, meiosis produces haploid cells
Mitosis produces genetically identical daughter cells, meiosis produces genetically different daughter cells
How does meiosis lead to genetic variation?
During prophase I, homologous chromosomes exchange DNA, which creates genetic variation. This is called crossing-over
Independent assortment of chromosomes in metaphase I
Independent assortment of chromatids in metaphase II
Mutations
