2.1 The Structure of DNA Lesson

2.1 The Structure of DNA

STAAR Reporting Category 2 Mechanisms of Genetics

Unit 1A Gene Expression

B.7A identify components of DNA, explain how the nucleotide sequence specifies some traits of an organism, and examine scientific explanations for the origin of DNA

• DNA stands for deoxyribonucleic acid.

• DNA is like a set of instructions that tells our cells how to grow, function, and reproduce.

• It's often called the "blueprint of life."

What is DNA?

DNA is located in the nucleus of every cell.

Where is DNA?

Multiple Choice

DNA is found in living AND nonliving things.

• True

• False

Multiple Choice

Where is DNA located in the cell?

• the cytoplasm

• the cell membrane

• the nucleus

• the vacuole

• DNA looks like a twisted ladder.

• This is called a double helix.

• Imagine holding two pieces of string and twisting them together.

What is the shape of DNA?

How is DNA Structured?

​Long strands of DNA are formed from repeating nucleotides.

How is DNA Structured?

Each nucleotide is made of 3 parts.

Multiple Choice

What is the shape of DNA?

• double hexide

• double helix

• double axel

Labelling

Label the 3 parts of a nucleotide.

Drag labels to their correct position on the image

nitrogenous base

deoxyribose sugar

phosphate group

Labelling

Label the 3 parts of a nucleotide.

Drag labels to their correct position on the image

nitrogenous base

deoxyribose sugar

phosphate group

Labelling

Label the 3 parts of a nucleotide.

Drag labels to their correct position on the image

phosphate group

nitrogenous base

deoxyribose sugar

How is DNA Structured?

• The phosphate group and the deoxyribose sugar make the DNA "backbone".

• The phosphate group and the deoxyribose sugar are connected by a STRONG covalent bond.

How is DNA Structured?

• Nitrogenous bases make the "middle of the ladder"

• There are 4 nitrogenous bases:

• adenine

• thymine

• cytosine

• guanine

How is DNA Structured?

adenine and thymine are base pairs

​cytosine and guanine are base pairs

How is DNA Structured?

The order of billions of the 4 nitrogenous bases creates the genetic code for all living organisms.

Multiple Choice

Which 2 parts of a nucleotide form the "backbone" of DNA?

• phosphate group and nitrogenous base

• deoxyribose sugar and nitrogenous base

• phosphate group and deoxyribose sugar

Multiple Choice

Which part of the nucleotide creates the genetic code for all living things?

• deoxyribose sugar

• phosphate group

• nitrogenous base

Multiple Choice

Which parts of the nucleotide are connected by a covalent bond?

• deoxyribose sugar and phosphate group

• phosphate group and phosphate group

• nitrogenous base and phosphate group

Multiple Choice

Which parts of the nucleotide are connected by a hydrogen bond?

• deoxyribose sugar and phosphate group

• phosphate group and nitrogenous bases

• adenine, thymine, cytosine, guanine

Labelling

Label the diagram with the correct nitrogenous base pair.

Drag labels to their correct position on the image

G (guanine)

T (thymine)

C (cytosine)

A (adenine)