Gcse Biology Paper 1 Cell Division & Stem Cells Flashcards
Why is Mitosis important?
-helps organisms grow in size and repair damaged tissue.
what are the three main stages of the cell cycle?
- growth
- DNA replication+ mitosis
- Division (cytokinesis)
What happens in the first stage of the cell cycle?
- the cell grows in size
- At the same time increases the number of sub-cellular structures (eg mitochondria, ribosomes)
- The DNA is duplicated
- each cell has full set of DNA
Where are chromosomes found?
The nucleus
What are are chromosomes ?
Chromosomes are string-like structures located inside the nucleus of animal and plant cells.
What’s the chromosome made up of?
The long string like structure that makes up a chromosome is made up of a chemical called deoxyribonucleic acid (DNA)
How many chromosomes do body cells contain?
- Human body cells contain 23 pairs of chromosomes
- In total 46
What do chromosomes carry?
Chromosomes carry a large amount of genes which determine many of our features
What is a gene?
A gene is a section of DNA that codes for proteins
What happens in the first stage of the cell cycle?
-in the first stage the DNA replicates to
form two copies of each chromosome.
-the cell also grows and copies it’s sub cellular structures eg mitochondria and ribosomes
What happens in the second stage of mitosis?
- mitosis takes place
- One set of chromosomes is pulled to each end of the cell
- the nucleus also divides
What happens in the final stage of mitosis?
- in the final stage the cytoplasm and the cell membrane divide
- forming two identical daughter cells
What’s the overall summary of mitosis
-mitosis copies one cell into two
What are the functions of mitosis?
- Mitosis is essential for growth and development of multicellular organisms
- mitosis takes place when a organism repairs itself (eg when a broken bone heals)
- Mitosis happens during asexual reproduction
What is a differentiation?
The process of when cells become specialised
What is a stem cell?
A stem cell is an undifferentiated cell which can give rise to more cells of the Same type and differentiate to form other types of cells
What are the two types of stem cells?
- Embryonic stem cells
- bone marrow stem cells
What is the function of stem cells in embryos?
- Embryonic stem cells can replicate themselves and differentiate into many other cells.
- they can be used to treat conditions like paralysis and diabetes by dividing to replace damaged cells
What is the function of stem cells in bone marrow?
- can differentiate into several cell types to replace dead or damaged tissues.
- e.g bone marrow stem cells can form many different types of blood cells.
What is the function of meristem cells in plant cells?
Meristem cells can differentiate into any type of plant tissue, at any point in the life of the plant.
Where meristem stem cells found?
Roots and buds of a plant
What is therapeutic cloning?
- a cloning method where an embryo is produced with the same genetic makeup as the patient
- the stem cells from the embryo will not be rejected by the patient’s immune system
What are the advantages of cloning plant s using meristem cells?
- can prevent rare plants from becoming extinct
- can produce large numbers of plants with favourable characteristic.
- can produce identical plants for research
What are the issues associated with embryonic stem cells
- embryonic stem cells are sourced from aborted babies/ some people have ethical religious obligations
- development of stem cell therapy is slow expensive and difficult
- adult stem cells infected with viruses could transfer to patients
- if donor stem cells do not have a similar genetic makeup to the patient , immune system could be triggered
