Chapter 13 - DNA

Question 1

What is DNA short for?

Answer 1

Deoxyribosenucleic acid

Question 2

What are histones?

Answer 2

Special proteins that are bound to DNA

Question 3

Why are DNA strands coiled around histones?

Answer 3

So that the long molecules can fit into small spaces

Question 4

What is chromatin?

Answer 4

The tangled network formed by coiled DNA that is not dividing

Question 5

What are genes?

Answer 5

Sections of DNA molecules

Question 6

What is the genetic code?

Answer 6

The stored information that determines the structure and activities of the cell

Question 7

What does each DNA molecule consist of?

Answer 7

• deoxyribose (a 5 carbon sugar)
• a phosphate group
• pairs of nitrogenous bases forming cross-links between the sugar molecules in the two strands

Question 8

What are the four different nitrogen bases?

Answer 8

• adenine
• thymine
• guanine
• cytosine

Question 9

What bond is present between the nitrogenous bases?

Answer 9

A weak hydrogen bond

Question 10

What shape is DNA in?

Answer 10

A double helix

Question 11

Which base pairs pair up?

Answer 11

A —> T

G —> C

Question 12

What happens in replication?

Answer 12

• the two linked chains separate because of the weak hydrogen bonds
• these separated sections serve as templates for nucleotides that will form the new half

Question 13

What is synthesis?

Answer 13

The combing of small molecules to make larger molecules

Question 14

What does the genetic code in DNA do?

Answer 14

Provides instructions for protein synthesis

Question 15

Why can different cells make different proteins even though they are identical?

Answer 15

Different genes are activated in different cells

Question 16

What makes up the genetic code?

Answer 16

The order in which the four bases occur in DNA

Question 17

What is a triplet?

Answer 17

A sequence of three base that is the code for a particular amino acid

Question 18

What is DNA?

Answer 18

• a very large molecule made of two strands of nucleotide that are joined by bonds between the nucleotide bases
• the two strands are twisted into a double helix
• found in the nucleus and mitochondria of the cell

Question 19

Why can DNA not leave the nucleus?

Answer 19

The molecule is too large

Question 20

What does RNA consist of?

Answer 20

A single strand of sugars and phosphates, with single bases

Question 21

What is the purpose of RNA only having one strand?

Answer 21

It is small enough to pass through the nuclear pores

Question 22

What is transcription?

Answer 22

A process by which the mRNA is formed using the code in the DNA molecule

Question 23

How does transcription start?

Answer 23

Transcription is triggered by chemical messengers that enter the nucleus and bind to the relevant gene

Question 24

What makes the DNA come apart?

Answer 24

Enzymes called helicases, usually 17 base pairs at a time

Question 25

What does DNA polymerase do?

Answer 25

Copies the coding from the DNA by forming a complementary mRNA molecule

Question 26

What tells DNA polymerase to stop copying?

Answer 26

A sequences of bases within the gene

Question 27

What is mitochondrial DNA?

Answer 27

The DNA found in the mitochondria

Question 28

What are the differences between DNA found in the nucleus and mitochondrial DNA?

Answer 28

• mitochondrial DNA is in the form of circular molecules that are not bound to proteins
• mtDNA has 37 genes

Question 29

What do the genes on mtDNA do?

Answer 29

• 24 contain the code for making transfer RNA molecules

- 13 have instructions for making some enzymes involved in cellular respiration

Question 30

What is acetylation and what does it do?

Answer 30

Acetylation is the adding of an acetyl group (CH3CO) to a histones protein that enhances gene expression

Question 31

What is methylation and what does it do?

Answer 31

Methylation is the adding of a methyl group (CH3) to a histones which inhibits gene expression