Download Chromosomes, DNA, and Genes

10/13/2013
Chromosomes, DNA,
and Genes
Date _______
DNA
• Made up of nucleotides
• Recipe for making proteins
– Proteins are determined by
the order of nitrogenous
bases
– Proteins are made up of
amino acids…amino acids
are coded for by sets of 3
DNA base pairs
Chromosomes
Organization of DNA
• Includes…
– DNA
– Genes
– Chromosomes
• What are each of the above? What do
they do?
Genes
• Specific location on a chromosome
• Segment of DNA that codes for a particular
protein
• Proteins determine an organism’s
characteristics
• Each chromosome
contains hundreds to
thousands of genes
Organization of DNA
• Contained within the nucleus of a cell
• One long thread of DNA that is tightly coiled
• DNA Chromosome Wrapping
1
10/13/2013
DNA is the Code of Life
• Every organism uses the
exact same building
blocks!
• DNA contains the code for
every protein an
organism needs…
• And every cell in an
organism’s body contains
a complete set of
chromosomes
“Most Chromosomes” award goes to…
• Adder’s tongue fern at 1200 or 1260
chromosomes! (600 or 630 pairs)
Chromosomes…the Details
• In eukaryotic cells…
– Sex chromosomes determine the sex of the
organism—male or female.
• There is only a SINGLE PAIR of sex chromosomes
– Autosomal chromosomes, or autosomes, are all
other
chromosomes not
involved in sex
determination
Trivia!
• Do all organisms have the same amount
of chromosomes?
• What eukaryotic organisms do you think
have more chromosomes?
– Humans: 46 chromosomes (23 pairs)
– Dogs: 78 chromosomes (39 pairs)
– Potatoes: 48 chromosomes (24 pairs)
And the least…
• Jack jumper ant, with only 2
chromosomes! (1 pair)
Where do chromosomes come from?
• All cells EXCEPT sex cells
contain one pair of EVERY
chromosome
– Each pair = 2 chromosomes with
genes for the same types of
proteins
– One chromosome of each pair
comes from mom, one from dad
• This is how you inherit traits from
your parents!
2
10/13/2013
Genes…not the kind you wear!
• Every chromosome has hundreds to
thousands of genes
• Unique characteristics are the result of
different proteins
• There are many unique proteins that an
organism has to make to live and survive
– Closely related organisms may have genes that
code for the same or similar proteins
– Organisms that are not closely related share fewer
genes than organisms more closely related
Question for you:
• Approximately
how many
genes do
humans have?
–20,000
Focus Questions
1. DNA is a recipe for _____________.
2. What is a gene?
3. How many genes does a chromosome hold?
4. Where are chromosomes stored in the cell?
5. How many chromosomes do humans have?
6. What organism has the most chromosomes?
7. What organism has the least chromosomes?
8. How many sex chromosomes do humans have?
9. How many genes do humans have?
10.What are the sex chromosomes for males?
Females?
3