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Bell Work: 1/23/13How 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
A single strand of chromatin= DNA
that is coiled aroundproteins.
Cell is ready to divide=packages chromatin
into chromatids.
Two identical chromatids=a
chromosome ready to divide
Before division, humancell=46 chromosomes(two identical copies of
genetic material)
“Somebody explain that one…”
“Say what!? Why would DNA coil around proteins?”
“Copy that…why would we need to
make copies of our DNA?”
Objectives
Describe the relationship between genes, chromosomes, and inherited traits (SPI 0707.4.3)
Base-Pair Matching1. 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.
2. 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.
3. 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.
4. 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.
Paper DNAStep 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 4: Have me check your work & build a DNA model!
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
3-2-1 3 things you learned today…
2 questions you have…
1 way this relates to your daily life…
