Cell division and mitosis Flashcards
(26 cards)
What is the cell cycle?
Sequence of steps organisms needs for new cells to grow and repair tissues in the body
What are the three main phases of the cell cycle?
- interphase
- mitosis
- cytokinesis
What happens during interphase?
Cells carry out usual functions whilst preparing for cell division involving replicating DNA and organelles
What are the 3 stages of interphase and what happens in each phase?
G1 = when cell grows and makes new proteins to replicate organelles
S phase = when DNA is replicated
G2 = when cell continues to grow and replicated DNA checked for errors
What are cell cycle checkpoints?
Checkpoints assessing whether processes at each phase of cycle have been accurately completed
What are the 3 cell cycle checkpoints?
- G1 checkpoint
- G2 checkpoint
- metaphase checkpoint
What happens at the G1 checkpoint?
Checks the cell has chemicals needed for replication and for damage to DNA
What happens at the G2 checkpoint?
Checks DNA has been replicated without errors (if errors are found cell tries to repair them)
What happens at the metaphase checkpoint?
Each chromosome checked to ensure it’s attached to the spindle
What is the human genome?
46 chromosomes divided into 23 pairs within each cell
What are autosomes?
First 22 pairs of chromosomes which are identical in both males and females
What is the 23rd chromosome and how does it differ in males and females?
Known as the sex chromosome
Male = XY
Female = XX
What is a homologous chromosome pair?
Pair of chromosomes of two homologous chromosomes, one chromosome paternal and the other is maternal
How many chromatids does a chromosome contain?
May contain one or two chromatids depending on stage in cell cycle
during interphase DNA is replicated meaning each chromosome goes from having one chromatid to having two
Describe the structure of a homologous chromosome?
Two chromatids held together by the centromere
chromatids within a chromosome are known as sister chromatids because they are genetically identical
What are diploid cells and what is their formulae?
Cells containing two copies of each chromosome (1 from each parent)
The total number of chromosomes in diploid cells is described as ‘2n’ with ‘n’ representing one set of chromosomes.
What are haploid cells and what is their formulae?
Cells only containing one copy of each chromosome
The total number of chromosomes in haploid cells is described as ‘n
After interphase what are the following 2 stages and what happens?
Mitosis = nucleus divides
Cytokinesis = whole cell and cytoplasm divides
What is mitosis?
Type of cell division in which a parent cell divides to produce two genetically identical daughter cells each containing the same DNA as original parent cell
Why is mitosis used by multicellular organisms?
Growth = unicellular zygotes can divide by mitosis to form multicellular organisms
Cell replacement = cells constantly dying and being replaced using mitosis
Asexual reproduction = some organisms reproduce using mitosis to form genetically identical offspring
Body plan development = mitosis forms different parts of organism
Stem cell production = stem cells divide by mitosis
What are the 4 main stages of mitosis?
- prophase
- metaphase
- anaphase
- telophase
What happens during prophase?
- chromosomes condense and are now visible under microscope
- centrioles migrate to opposite poles and start forming spindle fibres
- nucleolus disappears and nuclear envelope starts to break down leaving the chromosomes free in the cytoplasm
What happens during metaphase?
- chromosomes line up at the cell equator
- each chromosome attaches to the spindle by their centromere
- metaphase checkpoint checks each chromosome to ensure it is attached to the spindle
What happens during anaphase?
- centromeres divide to separate each pair of sister chromatids
- spindle fibres contract and shorten to pull the chromatids to opposite poles
- each chromatid is pulled by its centromere causing them to take on a ‘V’ shape when viewed under a microscope
