Biology STAAR

DNA

"The Blueprint of Life"

DNA stands for...
DeoxyriboNucleic Acid

It is found in all cells,
packed tightly within
chromosomes within the
nucleus.

Segments of DNA code for
traits - what we call
GENES.

Watson and Crick had a few clues to help them solve the puzzle….

Clue 1: When viewing a DNA sample,
Chargaff noted that there were four bases.
He measured the amount of each in several samples:

A (Adenine)

T (Thymine) G (Guanine)

C (Cytosine)

Sample 1

20%

20%

30%

30%

Sample 2

32%

32%

18%

18%

Sample 3

18%

18%

32%

32%

Do you see the pattern?

A
(Adenine)

T
(Thymine)

G
(Guanine)

C
(Cytosine)

Sample
Q

15

35

Sample
Z

25

25

Use Chargaff’s rule to complete the table:

Labelling

In Sample 2, move the numbers to where they belong. Predict the % of adenine and cytosine that would be present in Sample 2.

Drag labels to their correct position on the image

20

30

-made of repeating subunits called nucleotides
(monomer of a nucleic acid)

What is a nucleotide?

Has three parts:

PHOSPHATE
DEOXYRIBOSE (sugar)
BASE (A,T,G,C)

Phosphate

Sugar

Base

DNA molecule

Base-Pair Rule

Adenine <==> Thymine

Guanine <==> Cytosine

The sides of the DNA ladder
are phosphate & sugar

held together by hydrogen
bonds

Drag and Drop

The figure X is pointing to the building block of DNA, which is called a ​

Placeholder

Drag these tiles and drop them in the correct blank above

nucleotide.

monosaccharide.

amino acid.

fatty acid.

Labelling

Label the parts of the DNA molecule.

Drag labels to their correct position on the image

nucleotide

phosphate

hydrogen bond

deoxyribose

nitrogen base

Base Pair Rule

One side: A T A T C A T G C G G G

Other side:

AT GC!
Use the base pairing rule to figure out the
complementary DNA strand.

Multiple Choice

Choose the complementary DNA of the following DNA sequence.

ATA CGA TTG

• UAU GCU AAC

• TAT GCT AAC

• ATA CGA TTG

Your sequence of
A, T, C and G’s is what determines
your unique traits.

Your genes code for proteins.

Dropdown

The individuality of a organism is determined by the organism's ​

Select answer

DNA REPLICATION
the process by which DNA makes a copy of itself
(before cell division can occur)

SEMI-CONSERVATIVE - half of the old strand is saved

DNA Replication occurs in 3 steps:
1.

DNA helicase enzyme unwinds
the DNA.

2.

DNA polymerase enzyme builds
the new DNA strands one
nucleotide at a time.

3.

At the end, you get 2 identical
strands of DNA (each with one
original strand and one newly
created strand)

Multiple Choice

DNA Replication occurs during the S phase of mitosis. The
purpose of this process occurring before cell division is

• So each daughter cell can receive unique genetic material

• So each daughter cell can receive an equal number of
  mitochondria

• So each daughter cell can receive an identical copy of the
  genetic material

• So each daughter cell can produce different proteins

Multiple Choice

Why will the knowledge of the human genome enable scientists to better understand proteins involved in human diseases?

• DNA contains the information used to make proteins.

• Nucleic acid molecules have shapes similar to those of proteins.

• The bases that make up DNA are also present in RNA.

• Chromosomes can combine to form proteins.

Multiple Choice

Nitrogenous bases are located on both sides of the DNA double helix. What is the significance of the nitrogenous bases?

• The number of adenine and cytosines determines the type of RNA that will be produced.

• The order of nitrogenous bases determines the order of amino acids in the proteins synthesized.

• The amount of thymine molecules in DNA determines the length of the genes.

Now, we are going to review Protein Synthesis.
Remember, DNA has the instructions on how to make
the proteins. But, proteins are produced on the
ribosome. So, DNA needs to use a messenger RNA
(mRNA) to deliver its message to the ribosome.

Steps to Protein Synthesis:
1. Transcription - DNA is used to build a mRNA

(inside the nucleus)

2. Translation - mRNA is used to build the protein (on

the ribosome)

Drag and Drop

RNA is single-stranded, contains Uracil instead of Thymine, and has ribose sugar.



One component of the genetic code that differs in DNA and RNA is ​

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the presence of Uracil (U) in RNA codons.

the presence of Thymine (T) in RNA codons.

that RNA has deoxyribose sugar.

In transcription the DNA is used to make the
mRNA by using the complementary base
pair rule. Look at the example below:

DNA: TAC CCC GGA TAT
mRNA: AUG GGG CCU AUA

Notice that U replaces T in mRNA!

In translation, the mRNA is read
and used to build a protein
(chain of amino acids). We can
use the charts on the next slide
to see what amino acids each
mRNA codon calls for.

Protein Synthesis

DNA → T A C C A T G G A A A T A C T

RNA →A U G G U A C C U U U A U G A

Amino Acids → Met - Val - Pro - Leu (STOP)

If a gene is actively being used to make mRNA and then produce a protein,
then we say that gene is EXPRESSED. If a gene is turned off, then it is not
expressed.

Drag and Drop

RNA has ​

Placeholder

instead of thymine as a nitrogen base.

Drag these tiles and drop them in the correct blank above

uracil

adenine

cytosine

Dropdown

The process by which DNA is used to produce mRNA occurs in the ​

Select answer

is called ​

Select answer

Hotspot

Which process represents transcription?

Drag and Drop

Transcribe the following sequence of DNA into mRNA.

TAC TTG GGC

​

Placeholder

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AUG AAC CCG

UAC UUG GGC

AUG ACC CGG

Multiple Choice

A mistake in the DNA sequence is called a/an

• mutation.

• nucleotide.

• amino acid.

• monosaccharide.

Dropdown

If a mutation occurs that codes for a protein that increases an organism's fitness in their environment, then that mutation will likely ​

Select answer

in frequency in the population, leading to microevolution.