Cell Divison Flashcards
What is cell continuity?
All cells develop from pre-existing cells
What are the two types of cell division?
Mitosis and meiosis
How many daughter cells are formed by mitosis?
2 daughter cells
How many daughter cells are formed by meiosis?
4 daughter cells
What are the daughter cells of mitosis?
Identical
What are the daughter cells of meiosis
Variations
What are chromosomes?
Coiled threads DNA/protein found in the nucleus and are visible in the nucleus at cell division
What is chromatin?
Unraveled long thin threads of DNA [not dividing]
What is a gene?
It is a short section of DNA which contains the instructions for the formation of protein
What are many of the proteins produced by genes?
Enzymes
What kind of features to genes control?
Eye colour, production of skin pigment [melanin], shape of face, number of fingers
In plants, what do genes control?
Petal colour, leaf shape, fruit taste
What is a haploid cell and symbol
It has one set of chromosome ie it has only one of each type of chromosome in the nucleus
N=2
What is a diploid cell and symbol?
It has two sets of chromosomes ie they are in pairs known as homologous pairs
Symbol : 2n=4
What is the cell cycle composed of [different phases]
Interphase, prophase, metaphase, anaphase, telophase
What are the different phases of mitosis
Prophase, metaphase, anaphase, telophase
Where does mitosis take place?
In somatic cells
What are somatic cells?
Cells that are not associated with the reproductive system
What occurs in interphase?
The cell isn’t dividing, it is preparing for mitosis.
All DNA is duplicated
New cell organelles are made [eg, mitochondria]
A store of ATP energy is built up
What occurs in prophase?
Chromatin shortens and thickens to form chromosome
Nuclear membrane breaks down
Centrioles move towards north and South Poles
The chromosomes continue to contract until it can be seen that each single chromosome is actually composed of 2 halves called sister-chromatids joined at a point called the centromere
What occurs in metaphase?
All chromosomes line up along the equator of the cell
The centrioles produce spindle fibers [made of protein] that attach to the chromosomes at the centromeres
What occurs in anaphase?
The spindle fibers contract pulling sister chromatids apart
Each is now called a chromosome
What occurs in telophase?
Cell membrane contracts along the middle of the cell
A new nuclear membrane forms around each set of chromosomes
A groove called the cleavage furrow [in animal cells] and cell plate [in plant cells] appears at the equator of the cell
The cell membrane tightens so much that the cell divides into two daughter cells
The centrioles duplicate
The nuclear membrane is complete and the chromosomes unravel into chromatin
Why is interphase not a resting phase in the cell cycle?
The cell is still functioning during this phase ; it is preparing for mitosis.
What is a homologous pair?
Consists of two chromosome that have genes for the same features at the same positions
What is the function of mitosis in unicellular organisms?
It is a form of asexual reproduction eg amoeba
What is the function of mitosis in multicellular organisms?
Form of growth and repair
What are the functions of meiosis?
Produces gametes
It halves the chromosome number in gametes so that at fertilisation the correct chromosome number is achieved
Produces genetic variations thigh sexual reproduction
Give an example of meiosis
Egg + sperm n= 23
This ensures when egg and sperm fuse, 2n=46
What is cancer?
Cancer is the uncontrolled growth of cells due to damaged DNA
How is cancer caused?
It is caused when normal genes are altered or mutated to form cancer causing genes called oncogenes
What are carcinogens?
They are any environmental factor which mutates DNA
How does the genetic damage in cancer be inherited or caused by?
Carcinogens
What are three carcinogens/causes of cancer
Chemicals, radiation and viruses
How do chemicals cause cancer?
Nicotine in cigarettes can lead to lung cancer
How does radiation cause cancer?
Uv radiation from the sun = skin burnt - risk of skin cancer increased
X Ray’s damage dividing cells
How do viruses cause cancer?
Some damage oncogenes of cells which may cause cancer eg, some forms of liver cancer may be due to the presence of hepatitis
What is a tumour?
It is a cluster/lump of cells that have grown out of control because the cell lost control of mitosis
There are two types of tumours, what are they
Benign tumour and malignant tumour
What is a benign tumour and give an example
A tumour that will eventually stop growing and will not invade other tissues eg, skin tags, warts
What are malignant tumours?
Cancerous tumours that will not stop growing and can invade other tissues and move from place to place
What are the treatments of cancer?
Chemotherapy - slows mitosis
Surgery - removes affected cells
Radiation
What are two DNA processes in interphase?
Replication
Transcription
After telophase of mitosis, how do 1.animal cells and 2. Plant cells split in two?
Animal - cleavage furrow appears at equator of cell, cell membrane tightens so much it divides
Plant - cell plate appears at equator and cell membrane tightens so much it divides
Name two types of bio molecules that are produced in the cell during interphase of the cell cycle
Protein
Nucleic acid
Name two changes that will have occurred in the cell by the end of interphase
DNA duplicated
Disappearance of nuclear membrane
Suggest why human red blood cells do not undergo cell division?
No nucleus
Give a cellular process that occurs during interphase?
Replication
Respiration
Protein synthesis
State a function of spindle fibres
Cause centromeres to split and divides genetic material in cell
How do spindle fibres carry out their function?
Attach to chromosomes at centromeres and in anaphase they Contract and pull chromosome - separating them
Give one location where mitosis occurs in flowering plants
Meristematic tissue
Give a role of chromosomes
Carries genes
Name one organelle that is replicated at this stage of the cell cycle
Mitochondrial
Give ways in which mitosis differs from meiosis?
Mitosis - two daughter cells, identical
Meiosis - four daughter cells, contain variation
To what are chromosomes attached in metaphase?
Spindle fibres
Give a feature from a diagram which allows you to identify anaphase
Chromosomes are separated
Explain the term diploid number
Number of chromosomes in pairs
How do you know that metaphase is taking place from a diagram
Chromosomes located on equator
What is the diploid number of nucleus undergoing mitosis when
X X X X
Four
