Transcript Stem Cells - Groby Bio Page

Past paper question – Jan 11 Qu 1
Stem Cells
Settler
• Compare mitosis and meiosis
Cell division
division of the nucleus and then the cell
• Mitosis
• Meiosis
• For Growth
• Produces 2 identical
daughter nuclei
• Same number of
chromosomes to parent
cell
• No variation
• For gamete production
• Produces 4 different
daughter nuclei
• Different number of
chromosomes to parent
cell
• Causes Variation
Starter
• Define these words:
1) Gene
2) Locus
3) Allele
4) Mitosis
5) Meiosis
6) Homologous
chromosomes
7) Chromatid
8) Diploid
A. One of the two copies of a chromosome
that are joined together by a centromere
prior to cell division
B. A type of cell division where the
chromosome number is halved
C. One of the different forms of a particular
gene
D. A section of DNA that codes for a
polypeptide
E. A type of cell division where the daughter
cells have the same number of
chromosomes as the parent cell
F. A term referring to a nucleus which
contains two pairs of chromosomes.
G. A pair of chromosomes (one maternal
and one paternal) that have the same
gene loci.
H. The position of a gene on a chromosome
Starter
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Define these words:
Gene
Locus
Allele
Mitosis
Meiosis
Homologous
chromosomes
• Chromatid
• Diploid
A. One of the two copies of a chromosome
that are joined together by a centromere
prior to cell division
B. A type of cell division where the
chromosome number is halved
C. One of the different forms of a particular
gene
D. A section of DNA that codes for a
polypeptide
E. A type of cell division where the daughter
cells have the same number of
chromosomes as the parent cell
F. A term referring to a nucleus which
contains two pairs of chromosomes.
G. A pair of chromosomes (one maternal
and one paternal) that have the same
gene loci.
H. The position of a gene on a chromosome
Stem Cells
Learning Objectives
• Understand and give
examples of how stem cells
can be modified for use in
medicine
• Produce a written summary
for and against stem cell
research
Success Criteria
• Define the term ‘stem cell’
(Grade D-E)
• Explain the meaning of the
term homologous pair of
chromosomes(Grade C)
• Outline the process of cell
division by budding in yeast
(Grade C)
• Construct diagrams to
describe the stages of mitosis
(Grade A-B)
Specialized cells
In a single-celled organism, all the functions necessary for life must be carried out in
one cell. In contrast, multicellular organisms can delegate jobs to particular groups of
cells.
Cells that have adapted to a specific function are known as specialized cells.
Specialized cells are grouped into tissues, which combine to make organs and organ
systems.
Tissues, organs and organ systems
Cells, tissues and organs must cooperate with each other – different ways of
communication – transport systems and communication systems
Plant structure
Students should be aware of the differences between squamous and ciliated
epithelia, xylem and phloem
Stem cells
Adult stem cells in the bone marrow can divide and
differentiate to replace worn out blood cells – erythrocytes
(red blood cells) and neutrophils (white blood cells)
Plants
• Plants are always growing , stem cells can
differentiate into various plant tissues
• Example - Stem cells are found in the
cambium. The vascular cambium forms a ring
inside the shoot and root, the cells divide and
grow out from the ring differentiating as they
move away, to form the xylem and phloem.
Specialised cells - on whiteboards how are each
adapted for their function (in pairs and share)
1. erythrocytes, 2. neutrophils, 3. epithelial cells, 4.
sperm cells and 5. palisade mesophyll cells, 6. root hair
cells , 7. guard cells
Rest
phase
Cells often stop dividing once they are fully differentiated, so where do they
fit into the cell cycle?
Specialized cells move from G1 into a
resting phase known as G0.
A cell may remain in G0 for the
rest of its lifetime, or it may just
rest in this state temporarily.
G0
G0 is also the phase in which stem cells wait until their associated body cells
need replacing.
Task - Stem cells - Using current newspaper
articles have students produce summaries, for
and against stem cell research
Cell differentiation
Chromosome number
A human somatic (body) cell contains 46
chromosomes. These consist of 23 pairs of
homologous chromosomes.
Each pair contains one chromosome
from each parent. Other species have
different numbers of these
homologous pairs.
Sex cells, or gametes, have only one copy of each chromosome: they are haploid. A
somatic cell, containing two of each, is called diploid.
Haploid gametes
All somatic cells in a multicellular organism are genetically identical because they are
the result of mitosis.
They are all descended from a single cell – a zygote.
A zygote is formed when two haploid
gametes fuse.
These gametes are genetically unique
because, unlike somatic cells, they
were formed by a special form of cell
division called meiosis.
Meiosis I and II
Meiosis is the process of cell division underlying sexual reproduction. It is a two-stage
process:
Meiosis I introduces genetic diversity by
randomly dividing a cell’s genes in two. It
results in two haploid cells.
Meiosis II is similar to mitosis. It splits each
chromosome into its two chromatids and places
one in each daughter cell. It results in four
haploid gametes.
Genetic variation
Sexual reproduction creates genetic
diversity within a population, which is
vital to a species’ survival.
Two processes during meiosis
determine the unique genetic makeup of the four daughter cells:
During meiosis I, homologous pairs of chromosomes swap parts of their genetic material.
This is crossing over.
The chromosomes from each pair are randomly allotted to the daughter cells by
independent assortment.
Meiosis: true or false?
Variation from meiosis
Task
1) Look at the diagram to describe the process
of budding in yeast cells
http://www.microbiologybytes.com/video/Sc
erevisiae.html
2) Using page 32 draw a table to compare
natural an artificial clones
3) Answer questions page 33