Cell Division Flashcards
What is a haploid?
A haploid is a cell with a single set of unpaired chromosomes (n23)
What is a diploid?
A cell with two complete sets of chromosomes (n46)
What is a gamete?
A sex cell
Eg. Sperm, egg, pollen
What is a zygote?
A zygote is formed when two gametes fuse together
What is the significance of mitosis?
1) Growth of multicellular organisms
2) replacement of cells and tissue repair
3) Asexual reproduction
What is gap 0?
Gap 0 is when a cell leaves the cell cycle
Why might a cell leave the cell cycle?
A cell might enter G0 due to:
•Differentiation - cell becomes specialised
•Damaged DNA - stops spread of damaged DNA
• senescene - most normal cells can only divide around 50 times
What is being checked at checkpoint G1?
Cell size
Nutrients
Growth factors
DNA damage
What is being checked at G2?
Cell size
DNA replication
DNA damage
What is the role of Histone?
Histone is a protein that DNA coils around allowing it to pack tightly together and protecting it. These coils then from chromatids.
What is the significance of mitosis?
Growth of multicellular organisms
Replacement of cells and tissue repair
Asexual reproduction
What happens to chromatin when other cell is about to divide?
It condenses
What is the centromere?
The region where two chromatids join together
What is cytokinesis?
Cytoplasmic division
What occurs during the interphase of the cell cycle?
Energy stores increase
Cell grows in size
Organelles replicated
DNA copied
What happens in the mitotic phase of the cell cycle?
The nucleus divides (Mitosis)
The cell divides (Cytokinesis)
What are the 4 stages of mitosis?
Prophase (prepare)
Metaphase (middle)
Anaphase (apart)
Telophase (two)
What happens at the prophase?
Chromosomes become visible
The nucleolus disappears
The nuclear membrane breaks down
Proteins form spindle fibres
What happens during the metaphase?
The chromosomes are lined up at the cell’s equator. Spindle fibres form
What happens at the anaphase?
The spindle fibres begin to shorten pulling the chromatids apart.
This pulls the sister chromatids to opposite poles of the cell
What happens during telophase?
The chromatids have reached the poles of the cell. The nuclear membrane starts to reform and the nucleolus reappears.
Cytokinesis begins.
What happens during cytokinesis?
Actin microfilaments causes the cell surface membrane to pinch inwards creating a furrow. This furrow grows as the cell membrane is pulled in until it fuses, creating two separate cells.
What are the adaptations of erythrocytes (red blood cells)
Biconcave structure to increase SA
No nucleus to increase SA
Contain lots of haemoglobin to store more oxygen
How are new xylem cells produced?
Produced in meristems by differentiating from stem cells
Which stage of meiosis does crossing over occur?
Prophase 1
Which stage of meiosis does independent assortment occur?
Metaphase 1 and 2
What do neutrophils (white blood cells) do?
Ingest bacteria and some fungi via phagocytosis
What are the adaptations of neutrophils?
Attracted to and travel to infection sites by chemicals
Twice the size of erythrocytes
Each neutrophil has a multi-lobed nucleus
What do squamous epithelial cells do?
They make up the walls of alveoli and capillaries as well as the lining of intestines.
What are the adaptations of squamous epithelial cells?
They are flat in shape to facilitate faster diffusion
What is the role of smooth muscle tissue?
Propels substances along the walls of intestines, blood vessels, uterus
What are the adaptations of smooth muscle tissue?
Many blood vessels
Contains actin and myosin allowing the tissue to contract and propel substances
What is the role of skeletal muscle tissue?
They are joined to bones by tendons. Allowing the bones to move
What are the adaptations of skeletal muscle tissue?
It is able to rapidly modify rate of ATP synthesis and blood flow
What is the role of the xylem tissue?
Transport water minerals
What are the adaptations of xylem?
The walls are strengthened with a waterproof material called lignin
What is the role of the phloem tissue?
Transport nutrients such as sucrose
What is the role of guard cells in plants?
Form small openings called stomata which allows carbon dioxide, oxygen and water vapour in and out of the plant
How are guard cells adapted to their role?
They can change shape to prevent excessive water loss
They have thicker walls next to the stomata
What is the role of the epidermis?
Allows carbon dioxide, oxygen and water vapour in and out of the plant
How is epidermis adapted to its role?
Covered by a waxy waterproof cuticle to reduce water loss
Which direction does the xylem transport material?
Upwards
Which direction does the phloem transport material?
Upwards and downwards
What are the sources of stem cells?
Embryonic
Induced pluripotent
Plant meristem
Umbilical cord
Adult
