B2(2.1-2.4) Cell Division Flashcards
What are the roles of chromosomes and where are they found?
-they are found in the nucleus
-they carry the genes that contain the information needed for making new cells
What is a gene?
A gene is a small packet of information that controls a characteristic
How many chromosomes do humans have?
- 46 chromosomes (23 pairs)
Define multicellular.
-An organism that consists of more than one cell
Why do all multicellular eukaryotic organisms require new cells?
-Growth
-Development
-Repair
Define a stem cell.
-Undifferentiated cell that can develop into one or more types of specialised cell
What are two types of stem cell in mammals?
-Adult stem cells
-embryonic stem cells
What are adult stem cells?
-stem cells from adults that can only differentiate into certain specialised cells
Where are adult stem cells found?
Bone marrow
What are embryonic stem cells?
-Stem cells from embryos that can differentiate into any specialised cell.
Where are embryonic stem cells found?
-in early human embryos (usually spare from fertility clinics)
What is therapeutic cloning?
-When patient’s cells are used to create an early embryo clone of themselves - stem cells from that embryo can then be used to treat the patients medical conditions
State one advantage of therapeutic cloning.
-Stem cells from the embryo are not rejected when transplanted because they have the same genes as the patient
State two advantages of using embryonic stem cells.
-Can differentiate into any specialised cell, so can be
used to treat many diseases
-Easier to obtain as they are found in spare embryos
from fertility clinics
State two disadvantages of using embryonic stem cells.
-Ethical issues surrounding their use, as every embryo
is a potential life
-potential risks involved with treatments, such as
transfer of viral infections
State one advantage of using adult stem cells.
-Fewer ethical issues as obtained from adults who can
consent to their use
State two disadvantages of using adult stem cells.
-Can take a long time for a suitable donor to be found
-Can only differentiate into some specialised cell types,
so treat fewer diseases
What are plant meristems?
-An area where rapid cell division occurs in the tips of roots and shoots
State two advantages of using plant meristems to clone
plants.
-Rare species can be cloned to protect them from
extinction
-Plants with special features (e.g., disease resistance)
can be cloned to produce many copies
State one disadvantage of using plant meristems to
clone plants.
-No genetic variation, so, for example, an entire cloned
crop could be destroyed by a disease
What is cell division by mitosis?
-Body cells divide to form two identical daughter cells
What is the purpose of mitosis?
-Growth and repair of cells, asexual reproduction
What happens during the first stage of the cell cycle?
-Cell grows bigger, chromosomes duplicate, number
of subcellular structures (e.g., ribosomes and
mitochondria) increases
What happens during mitosis?
-One set of chromosomes is pulled to each end of the cell and the nucleus divides
What is the second stage of the cell cycle?
-Mitosis
What happens during the third stage of the cell cycle?
-The cytoplasm and cell membrane divide, forming two
identical daughter cells
What is the term for cell division in bacteria?
-Binary fission
