Cell Biology - Cell Division Flashcards
What are chromosomes made up of ?
Consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis
What is a gene?
A section of DNA which codes for a protein
How many chromosomes are found in the nucleus of human body cells?
46
How many chromosomes are found in the nucleus of gametes ?
23
How are chromosomes arranged in the nucleus of a body cell?
Arranged in pairs- 46 chromosomes form 23 pairs
What are the 3 stages of cell cycle?
-replication of DNA and synthesis of organelles
- mitosis
- division of cell
Why is mitosis important?
-For the growth and development of multicellular organisms and replacing damaged cells
-Vital part of asexual reproduction as it -produces genetically identical cells
Helps maintain normal metabolic processes
Describe the first stage of cell cycle
Longest stage- the cell grows and increases in mass, number of organelles (ribosomes, mitochondria) increases, DNA is replicated
Describe the second stage of the cell cycle
Mitosis- each set of chromosomes are pulled to opposite poles of the cell, nucleus divides
Describe the third stage of the cell cycle
The cytoplasm and cell membrane divide to form 2 genetically identical daughter cells
What are stem cells?
Undifferentiated/unspecialised cells that can divide to make different types of cells
What is the function of stem cells in embryos?
Form when an egg and sperm cell fuse to form a zygote
Embryonic stem cells can replicate themselves and differentiate into all types of cells
Embryonic stems cells are able to treat conditions such as paralysis and diabetes by discussing to replace damaged cells
What is the functions of stem cells in adult bone marrow?
-Are found in some organs and tissues
-Can only differentiate into certain types of cells and their capacity to divide is limited but can replace dead or damaged tissues
-Eg bone marrow stem cells can form many types of blood cell
What is the function of stem cells in plant meristems?
Found in tips of the root and shoots
Can differentiate into any type of plant cell throughout their life span
Can be used to make clones of the plant- may be necessary if plant has desirable characteristics(disease resistance)to save plant from extinction
What is therapeutic cloning?
A cloning method where an embryo is produced with the same genetic makeup as the patient and used as a source of stem cells
The stem cells which originate from the embryo won’t be rejected by the patient’s immune system, so can be used to treat certain medical conditions
What are the advantages of cloning plants using meristem stem cells ?
Can prevent rare plants from becoming extinct
Can produce large numbers of identical plants with a desirable characteristic
Used to help plants grow
Can produce identical plants for research
Create genetically modified crops
What issues are associated with the use of stem cells?
-Many embryonic stem cells are sourced from aborted embryos, some people have ethical/ religious objections- interferes with natural process of reproduction
-Development of stem cell therapies is slow, expensive and difficult
- adult stem cells infected with viruses could transfer infections to patients
- removal of embryo results in destruction of the embryo- waste of life
- don’t completely understand process of differentiation so is hard to control stem cells to from the desired cells
Explain advantages and disadvantages of therapeutic cloning
Advantages- used to treat diseases, reduce time for organ transplant, cells of any type can be produced, cells can be used for research, unwanted embryos from fertility clinics could be which would otherwise be discarded, would not be rejected as would have same genetic makeup as patient
Disadvantages- my transfer viral infections, shortage of donors, potential life is killed as removal of stem cells results in destruction of the embryo, money could be better spent in other areas of medicine, unknown side effects, religious objections as it interferes with reproduction
