UNIT 3: The Cell and its Environment Biology I DAYSHEET 49: DNA Structure Name: __________________________ Date:_________________ Directions: Write if each of the following statements refer to Mitosis (MI) or Meiosis (ME) 1. This process is used to make more identical cells _____ 2. This process is used to make somatic (body) cells _____ 3. This process is used to make gametes (sex cells) _____ 4. If you scratch your knee or break your bone, you’ll use this process to replace the cells that die____ 5. This process only takes place in the ovaries or testes _____ 6. This process makes diploid cells that have two sets of DNA _____ 7. This process makes haploid cells that have only one set of DNA______ 8. This process makes cells that are genetically different ______

     

1. What does the picture to the left show? 2. Does this happen in mitosis or meiosis? 3. Why is this process important?

1. What does the picture to the left show? 2. Is this a karyotype of a male or female? 3. Does this individual have Trisomy 21 (Down Syndrome)?

Activity 1: Cornell Notes

Biology Objective / Essential Question:

 

Main Ideas / Questions: 1. 2.

Notes: • DNA stands for ________________________________________

• ________________ and _____________ are credited with

discovering that DNA was a ______________________________

• However, _______________________________ took an important

x-ray photograph of DNA that showed that DNA was a double

helix.

Stop-and-Jot:

1. What is the picture below of? Who took this picture?

2. How was the discovery of the double helix an example of

collaboration between scientists? How was it NOT?

Activity 1 Continued: Cornell Notes

Main Ideas / Questions: 3.

Notes: • DNA is a _____________________________ so it is made of

_____________________________________

• Each nucleotide has 3 parts:

• There are four possible nitrogen bases in DNA:

o ______ = adenine

o ______ = thymine

o ______ = cytosine

o ______ = guanine

Stop-and-Jot:

1. In the space below, draw a nucleotide using simple shapes that

contains the nitrogen base adenine. Label the three parts of your

nucleotide. You can use the letter “A” to label the adenine.

2. Which part(s) of your adenine nucleotide would be the same in a

guanine nucleotide? Which part(s) would be different?

Activity 1 Continued: Cornell Notes

Main Ideas / Questions: 4.

Notes: • The ____________ from one nucleotide connects to the

________________ on another nucleotide forming the sugar-

phosphate backbone of DNA

• The 2 strands of DNA are held together by ___________________

___________ between the ____________ on either side.

Stop-and-Jot:

1. Label the DNA molecule below using the following terms:

Nucleotide Sugar Phosphate Backbone Nitrogen Bases Hydrogen Bond

Activity 1 Continued: Cornell Notes

Main Ideas / Questions: 5. 6.

Notes: • The base pair rule states the following:

o _____ will only bond with ______

o _____ will only bond with ______

• Mnemonic Device:

• This means that if you know what bases are on one strand (side) of

the DNA, you can predict what bases are on the

________________________ (opposite) strand.

Stop-and-Jot:

1. If one strand of DNA contains the nitrogen bases A T C G G A T,

what nitrogen bases are on the complementary strand?

2. A DNA molecule has 100 nucleotides. There are 30 adenine

nucleotides. How many of each of the following nucleotides are in the

DNA molecule?

Thymine _______ Guanine ________ Cytosine_____

• DNA stores our _____________________________ information.

• The sequence of ___________________, especially ___________

____________, in DNA is the code for how to make ___________,

and proteins determine our _______________________________.

   

Stop-and-Jot:

1. Why do some people have different eye colors?

Activity 2: Vocabulary Mastery Directions: Pick 6 terms from the notes that you are (a) have the most difficulty with or (b) believe to be the most important terms. Write them down in the chart below and then write the class definition (from your Cornell Notes). When you are done, call your teacher over to check your definitions and get a signature.

Vocabulary Term Class Definition 1.

2.

3.

4.

5.

6.

Activity 3: Biology Vocabulary Master Sheet Directions: Fill in the first two columns of your vocabulary master sheet with your terms and definitions from Activity 2. Once you complete the last two columns, call your teacher over to check your sheet and to receive a signature. Activity 4: Summary Directions: Write a one-paragraph summary of your Meiosis & Sexual Reproduction Cornell Notes. You must include all six of your vocabulary terms from activities 2 and 3 to receive credit for your summary. _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Homework 49: DNA Structure Biology I Name: ________________________ Date:_______________

FLIP FLOP Recall that the nucleus is a small spherical, dense body in a cell. It is often called the "control center" because it controls all the activities of the cell including cell reproduction, and heredity. The nucleus contains the cell’s DNA, or deoxyribonucleic acid. DNA is called a nucleic acid because it was first found in the nucleus. In simple terms, DNA is instructions on how to build proteins. Think of proteins as the building blocks for an organism; proteins make up your skin, your hair, parts of individual cells. How you look is largely determined by the proteins that are made.

1. Write out the full name for DNA. ____________________________

2. DNA is the instructions for building what? ____________________________

3. Where in the cell is DNA located? ____________________________

In 1953, Rosalind Franklin, James Watson and Francis Crick established the structure of DNA. The shape of DNA is a double helix, which is like a twisted ladder. The building blocks of DNA are nucleotides. Each nucleotide is made of a sugar and phosphate (the sides of the ladder), and a nitrogen base (the middle of the ladder). The sugar is deoxyribose.

In the middle of the ladder are pairs of 4 types of nitrogen bases. The bases are known by their letters A, G, T, C, which stand for Adenine, Guanine, Thymine, and Cytosine. The bases can occur in any order along a strand of DNA. The order of these bases is the code for building proteins.

Label the thymines T.

Label the adenines A. Label the guanines G. Label the cytosines C.

DNA!

Notice: Which colors (nitrogen bases) are always paired together?

Nitrogen Base

Sugar

Deoxyribose

Phosphate

What is this building block of DNA called?

These bases always bond in a certain way. Adenine will only bond to thymine. Guanine will only bond with cytosine. This is known as the "Base-Pair Rule".

Because of the base-pair rule, if you are given one side of DNA, you can tell what is on the other side (the complementary strand.) For example, if there is an A on one side, there must a T on the other side; if there is a G on one side, there must be a C on the other side

Example: Write the complementary strand for the DNA segments below using the base pairing rules (The first one has been done for you).

1) A T G C T A T G G A C C

T A C G A T A C C T G G

2) G T T A C G C T A C G A A T C T A C

3) T A C C A T G A C G C T

The base pairing rules are important to memorize and are important for a process called DNA replication.

The two sides of the DNA ladder are held together loosely by weak chemical bonds. The DNA can actually "unzip" when it needs to replicate - or make a copy of itself. DNA needs to copy itself when a cell divides, so that the new cells each contain a copy of the DNA. Without these instructions, the new cells wouldn't have the correct information. The hydrogen bonds are represented by small circles.

DNA Replication – When a strand of DNA is pulled apart and copied

During DNA replication, the base pair rule helps DNA make an exact copy of itself. Each side of the old DNA can be used as template (model) for building a new side. In the end, you have 2 pieces of DNA that are EXACTLY the same! This is really important because if there is something that changes in the DNA, it could cause harm to your body.

DNA Replication:

When the two sides of a DNA are pulled apart, they have the sequence shown below. Fill in the new pieces of DNA:

Old New New Old

A T

T A

T A

C G

G C

What do you notice about the 2 DNAs you have at the end?