Cell Division Flashcards
What do all cells develop from?
Pre-existing cells
What are the steps to form a new cell and how many are there?
3 steps to form a new cell
- Produce materials it will need
- Grow larger
- Reproduce to form a new cell
What are chromosomes?
Structures in Nucleus, made of DNA and Protein
What do we call chromosomes when they are not dividing?
Chromatin forms a number of clearly distinguishable chromosomes
How many chromosomes does each species have?
Each species has a definite no. of Chromosomes, Humans = 46 chromosomes
How many genes does each chromosomes have?
Each chromosomes has 1000s of genes
Draw and label a pair of homologous chromosomes.
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What is a Haploid?
A Haploid cell has one set of chromosomes, i.e. has only one set of each type of chromosomes in the nucleus.
What is Haploid symbolised by?
the letter n
What is the number of chromosomes in the Haploid cell given as?
n=23
What type of cell are humans eggs and sperm?
haploid n=23
What is a diploid?
A Diploid has two sets of chromosomes, i.e. It has two of each type of chromosome in the nucleus
How are chromosomes organised in a diploid cell?
Chromosomes are in pairs in diploid cell, called homologous pairs.
How is a diploid symbolised as and what is the total no. of chromosomes in a diploid cell given as?
Diploid is symbolised as 2n and total no. of chromosomes in cell is given as 2n = 46
Where do the chromosomes come from in a diploid cell?
In diploid cells, 1 chromosome from the homologous pair comes from the mother and the other comes from the father
What is the cell cycle?
Describes the life of a cell. It includes the period between division when the cell is not dividing, called Interphase.
What is the period when a cell divides called?
Mitosis
What is interphase?
The period between division when the cell is not dividing
How long is interphase?
Longest phase in cell cycle = 90% of a cells life is in interphase
What are chromosomes called in interphase? What is one difference between them and chromosomes?
chromatin
not elongated
What are cells like in interphase, what do they do?
Cell very active in Interphase, produces new mitochondria, chloroplasts etc. and chemicals needed for growth
What is mitosis?
Mitosis is a form of nuclear division in which one nucleus divides to form two nuclei, each containing identicals sets of chromosomes.
What are the two new cells called formed by mitosis? What is one feature of them?
Two new cells called daughter cells and they are IDENTICAL to each other
What are the functions of mitosis in Unicellular Organisms?
Method of reproduction for Amoeba Reproduction that does not involve the joining of 2 cells is called asexual reproduction.
What are the functions of mitosis in multicellular organisms?
Produces new cells, not new individuals
Responsible for growth and renewal and repair of cells
what is important the body does to the rate of cell division?
Rate of cell division (mitosis) is carefully controlled
What sometimes happens to a cell or group of cells in mitosis?
Sometimes a cell or group of cells lose the ability to control the rate of cell division
What happens when a cell or group of cells loves the ability to control the rate of cell division?
They form a mass of cells called a tumour which can be benign or malignant
What does benign mean?
Benign means kind, they are not life threatening and do not invade other tissues. E.g. warts, skin tags. Cells stop dividing after some time.
What is cancer?
Cancer is a group of disorders in which certain cells lose their ability to control both the rate of mitosis and the number of times mitosis takes place.
What are malignant tumours?
Uncontrolled multiplication of abnormal cells
Malignant tumours (cancers) invade other cells and move around the body.
Movement of these cells called Metastasis.
Cancer cells divide indefinitely
What is the movement of cells invaded by malignant cancers called?
metastasis
What are the causes of cancer?
Caused when normal genes are altered to form cancer-causing genes called oncogenes.
Brought about by cancer causing agents called carcinogens e.g. cigarette smoke, asbestos fibres, ultraviolet radiation and some viruses
How can most cancers be cured?
Most cancers can be cured with radiation (burn out cancer), chemotheraphy (chemicals sllow down mitosis and surgery
What is meiosis?
Meiosis is a form of nuclear division in which the daughter nuclei contain half the chromosome number of the parent nucleus.
How many chromosomes do human cells have?
46
Where does meiosis occur in humans and what does it do?
Meiosis occurs in the ovaries and testes to produce gametes called eggs and sperm so there are 23 chromosomes in each egg and sperm.
How many chromosomes are there in each egg and sperm?
There are 23 chromosomes in each egg and sperm.
How many functions of meisosis are in multicellular organisms?
2
What does meiosis allow?
Allows sexual reproduction without increasing the number of chromosomes in the offspring. Allows new combinations of genes.
What is the sentence to help you remember the 4 stages of mitosis?
I Party Monday And Tuesday
interface is not really a stage of mitosis [I]
Draw a diagram of prophase
pg. 162 - 14.23
How many stages of mitosis are there?
4 in total
What happens in the prophase stage?
At end of Interphase, Chromosomes contract and become visible. Each chromosome appears as a duplicated strand. Fibres appear in cytoplasm. Nuclear membrane starts to break down.
What happens at the end of Interphase?
The prophase stage
What happens in metaphase?
Nuclear membrane broken down
Chromosomes thicken even more
Chromosomes line up across the centre of cell
Fibres attach to chromosomes
Each chromosome has 2 fibres attached, 1 from each side of the all.
Draw a diagram of metaphase
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What happens in anaphase?
Fibres contract, chromosomes pulled apart
Each strand is pulled to opposite end of cell
Hence, identical set of genes pulled to each end of the cell.
Draw a diagram of anaphase
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What happens in telophase?
Nuclear membrane forms around each of the 2 sets of chromosomes.
Chromosomes elongate within each nucleus
Mitosis is complete. Once complete, original cells divide to form 2 cells.
Draw a diagram of telophase
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