Download Bell Work: 1/25/10

Bell Work: 1/23/13
How DNA
Works:
Use pgs. 134-135 to
create a flow chart
that explains how
DNA works.
Write “Flow Chart” on your bell
work sheet & work with your
group to finish bell work.
A cell’s DNA codes for
proteins that determine
traits, like skin color
“Somebody explain
that one…”
A single strand of
chromatin= DNA
that is coiled around
proteins.
Cell is ready to divide=
packages chromatin
into chromatids.
“Say what!? Why
would DNA coil
around proteins?”
“Copy that…why
would we need to
make copies of our
DNA?”
Two identical
chromatids=a
chromosome ready to
divide
Before division, human
cell=46 chromosomes
(two identical copies of
genetic material)
Objectives
 Describe
the relationship between
genes, chromosomes, and inherited
traits (SPI 0707.4.3)
Base-Pair Matching
1.
2.
3.
4.
Remove the colored bases from the bag and
arrange them in any order in a straight vertical line.
Make sure to fit the sugar notches to the phosphate
tabs.
On “go” one person from your team will go to your
lab table and find the white base that correctly pairs
with the colored base and bring it back to your
group.
After the base pairs are matched up, the next person
goes to find another white base to match it with the
next colored base and so on until your DNA strand is
complete.
The first team to finish correctly, wins…CANDY!
Changes in Genes
Check out pg. 138 & 140!
Changes in the number, type, or order of bases on
a piece of DNA are known as mutations.
 Sometimes bases are left out, extras are added, or
the most common, the wrong base is used.
 Consequences of Mutations:
 improved trait, no change, harmful trait
 Most of the time proteins detect an error and fix it.
 Mutagens, like radiation, can cause mutations in
DNA.
 When scientists manipulate or change individual
genes within organisms it is called genetic
engineering.
 DNA fingerprinting identifies the unique patterns
in an individual’s DNA.
 A clone is an exact copy of another organism’s
genes.


Elbow Partner Questions...

✔
Does every cell contain the same DNA?
Every cell in your body has the same
genes, and DNA. Your cells have all of the
genetic information for your whole body.
Your skin cells have the genetic make up of
your skin and your muscles. Your skin
does not use this extra information.
More Elbow Questions...

✔
✔
How do things get cloned?
To make Dolly, researchers isolated a somatic cell
from an adult female sheep. Next, they transferred
the nucleus from that cell to an egg cell from which
the nucleus had been removed. After a couple of
chemical tweaks, the egg cell, with its new nucleus,
was behaving just like a freshly fertilized zygote. It
developed into an embryo, which was implanted into
a surrogate mother and carried to term.
The lamb, Dolly, was an exact genetic replica of the
adult female sheep that donated the somatic cell
nucleus to the egg. She was the first-ever mammal to
be cloned from an adult somatic cell.
Mutations

Harmful mutations:
Beneficial Mutations:

✔
✔
✔
wild almond tree seeds
“contain an intensely bitter
chemical called amygdalin,
which … breaks down to
yield the poison cyanide.
Occasional individual almond
trees have a mutation in a
single gene that prevents
them from making a poison.
Those non-bitter almond
seeds are the only ones that
ancient farmers would have
planted, at first
unintentionally in their
garbage heaps and later
intentionally in their orchards.
More Mutations…
• Red hair appears in
people with two copies of
a recessive gene on
chromosome 16 which
causes a mutation in the
MC1R protein.
• Red hair has far more of
the pigment pheomelanin
than it has of the dark
pigment eumelanin.
DNA Drawing


Draw a portion of a DNA strand.
You must show the following:
Double helix structure
➔ Phosphate + sugar backbone
➔ Paired bases in the middle (must be correctly
bonded base pairs)
➔
Proteins & RNA

How are proteins related to traits? Proteins are found
throughout cells and cause most of the differences that you can
see among organisms. Proteins act as chemical triggers and
messengers for many of the processes within cells. Proteins
help determine how tall you grow, what colors you can see, and
whether your hair is curly or straight. Proteins exist in an almost
limitless variety. A single organism may have thousands of
genes that code for thousands of proteins.
Help from RNA
 Another type of molecule that helps make proteins is called
RNA, or ribonucleic acid . RNA is so similar to DNA that RNA
can serve as a temporary copy of a DNA sequence.
How & When Copies are Made
• During replication, a
DNA molecule is split
down the middle, where
the bases meet.
• The bases on each side
of the molecule are used
as a pattern for a new
strand.
• DNA is copied every time
a cell divides.
• The job of unwinding,
copying, and re-winding
the DNA is done by the
proteins within a cell.
Famous Last Words…
Paper DNA
Step 1: label the bases
on the paper model with
A, T, G, or C from the
bottom to the top. Color
code the boxes lightly
with colored pencil, using
the DNA guide on the
next slide.
Step 2: “Unzip” the
paper model by cutting it
in half vertically and glue
the pieces in the correct
location on your
worksheet so the bases
match up correctly.
Step 3: Label the empty boxes
using A, T, G, or C and then
color them using the colors on
your DNA Guide (see below).
Remember to match the bases
correctly!
A–T
T–A
G–C
C-G
Step 4: Have me check your
work & build a DNA model!
3-2-1

3 things you learned today…

2 questions you have…

1 way this relates to your daily life…