1. Part 2

2. DNA, Genes, and Chromosomes
Matching
Chromosome DNA Gene
A long, thin thread of genetic material
A small section of DNA
Coiled, rod-shaped DNA 2.
WARM UP – this is not on your sheet – click and see if you can match the terms and then ID the parts of the diagram. 1. 3. 5. 4.

3. (Offspring is made of these cells and many more types.)
What’s the name of the process in which A + B makes C ? ______________
What cells all have identical DNA? (circle them) A B C D E F G H I K L M
Cell K has ________________ DNA to the original fertilized egg (C), because all the cells in the offspring (such as K, L, M) were produced by _________ _______________ from C. (C is also known as a ____________.)
fertilization
Take a moment to examine this entire diagram, then click for questions.
IDENTICAL
CELL
DIVISION
ZYGOTE A G B C D E F H K
(Offspring is made of these cells and many more types.)
white blood cell
(offspring) L
muscle cell I
skin cell 5 M

4. ***These 4 questions are not on your paper – BUT ARE VERY IMPORTANT.
identical
Cell K and the four cells at E have _____________ DNA
CLICK & TRY TO FIGURE OUT WHAT GOES IN THE BLANKS
identical
Cell K and cell M have _____________ DNA
All the cells in the offspring have the exact same “book” of _______, but each one reads ________________ “chapters”, so they _______ (and function) differently.
DNA
different
look
genetic
Cells K & M & L all have the exact same ___________ instructions, but they use ______________ genes in those instructions.
different A G B C D E F
(Offspring is made of these cells and many more types.) K H
white blood cell
(offspring) L
muscle cell I
skin cell M

5. 46 46 23 46 23 46 6 Body Cell Body Cell Sex Cell Body Cell Sex Cell
Chromosomes:
Coiled up sections of DNA
Human Body Cell = 46 Chromosomes
Human SEX Cell = 23 Chromosomes
They are arranged in pairs.
Human Cell
# 0f Chromosomes
Body/Sex Cell
Brain Cell
Skin Cell
Sperm Cell
Muscle Cell
Egg Cell
Liver Cell 46
Body Cell 46
Body Cell 23
Sex Cell 46
Body Cell 23
Sex Cell 46
Body Cell 6

6. Test Your Knowledge! (not on paper)
Challenger: A mouse has 48 chromosomes in each body cell. How many are in the egg and sperm before fertilization? ____________________
Challenger: A plant zygote is a _______________.
Challenger: Two eggs fertilized by two sperm results in _______________.
Challenger: One egg fertilized by one sperm producing one zygote, that splits into 2 zygotes produces ______________________.
24 in egg and 24 in sperm
seed
fraternal twins
identical twins

7. Heredity = + 7 parents offspring
Genes pass from _____________ to __________.
Each parent provides _________ of their chromosomes by the _______ cells.
1/2
sex
offspring
zygote
egg = 23 + 23 46
sperm
cell division

8. Does this diagram show identical twins or fraternal?
zygote
Extra weird mitosis (cell division) happens and makes 1 zygote into 2 zygotes
BONUS TWIN QUESTIONS
Does this diagram show identical twins or fraternal?
What would be different in a diagram of fraternal twin fertilization & growth?
there would be 2 eggs and 2 sperm cells
there would not be the weird mitosis step
The two babies would have just some DNA in common, like brothers or sisters from the same parents.
3. Explain a piece of evidence to defend the claim “Fraternal twins do not have identical DNA.”
Fraternal twins are formed from different sperm & eggs, so they cannot have the same DNA.
Fraternal twins each get a random ½ of mom & dad’s DNA – not the same DNA as each other.