Download Show Me the Genes! - Brandywine School District

Activity 63: Show Me the Genes!
Essential Question: What role do chromosomes play in
the inheritance of genes?
Review…
In order to produce new cells, humans go through what
processes?
A. Asexual reproduction
B. Sexual reproduction
C. Both
Explain your selection
Review… Cell Division- Mitosis
 How is the function of
cell division in a single
celled organism different
from cell division in a
multicellular organism?
Mitosis
Chromosomes
 Chromosomes are long, fine strands, like very thin spaghetti in
the nucleus of the cell (They contain the organism’s genetic
information.)
 Before the cell divides, it makes copies of its chromosomes so
each new cell has a complete set.
 Chromosomes appear when the nucleus is no longer visible and
the cell
 Each cell in the body contains 46 chromosomes, so during cell
division each cell will have 46 pairs of chromosomes
Stopping to Think…
 What would happen to
the number of
chromosomes in each cell
if copies of them were
not make before cell
division?
Sexual Reproduction
 The 46 chromosomes in our
human cells are sorted into 23
pairs. Each chromosome looks
identical to its partner except
pair number 23 (The sex
chromosome.)
 Females have two X
chromosomes and Males have
an X and a Y chromosome
Cell Division of Sex Cells… Meiosis
 Sex cells are formed by a
type of cell division in which
each cell receives copies of
half of the chromosomes.
 Egg and sperm only contain
23 chromosomes
 When the sperm fertilizes
the egg and the new
organism is formed it will
have 46 chromosomes (Half
from mom and half from
dad)
Meiosis
Stopping to Think…
 Why must the number of
chromosomes in the sperm and egg
be half the number of
chromosomes then the other cells
of an organism?
Putting it all together
 Think of 23 pairs of
chromosomes as 23 pairs of
socks (Egg has 23 and
Sperm has its 23 matching
socks)
 The chromosome of each
pair carry genes for the
same characteristics but the
two alleles of any one gene
can be different
Stopping to Think
 Consider two children with the
same two parents. Would you
expect them to have the same sets
of chromosomes? Explain why or
why not.
So Many Genes
 Human cells contain about 30,000 pairs of different genes.
 Each gene is a small portion of a chromosome.
 The more complex the trait being studies, the greater the
number of different genes which contribute to it. (ExCancer)
 Genes are part of long molecules called DNA
(deoxyribonucleic acid)
 Each chromosome contains long DNA molecule
 A mutation is a mistake made in a gene when DNA is
copied
 Some mutations are small and some more significant (Ex- I
heer that noise, I fear that noise)
Conclusion
 Draw a flow diagram
(a series of pictures)
that shows the
locations and relative
sizes of DNA, genes,
chromosomes, and
cells in a human body.
Write a paragraph to
explain your diagram.