DNA Structure and Replication - Ch. 10

Question 1

What’s the structure of DNA?

Answer 1

2 polynucleotide strands wrapped around each other in a double helix

Question 2

What does a nucleotide monomer consist of?

Answer 2

1. Deoxyribose (5-Carbon Sugar) 2. Phosphate Group 3. A Nitrogenous Base

Question 3

What are the 4 nitrogenous bases for DNA?

Answer 3

Adenine (A), Guanine (G), Thymine (T), Cytosine (C)

Question 4

Which DNA nitrogenous bases are PURINES (2 rings)?

Answer 4

Adenine (A) and Guanine (G)

Question 5

Which DNA nitrogenous bases are PYRIMIDINES (single ring)?

Answer 5

Thymine (T) and Cytosine (C)

Question 6

Adenine (A) always pairs with _____

Answer 6

Thymine (T)

Question 7

Guanine (G) always pairs with _______

Answer 7

Cytosine (C)

Question 8

How does DNA replicate?

Answer 8

Parent strands separate. Complementary strands are made and lined up in the correct order. New strands are sealed up. Result: 2 DNA strands

Question 9

semiconservative replication

Answer 9

every DNA molecule is half “old”, half “new”

Question 10

What are the 2 stages of protein synthesis?

Answer 10

Transcription and Translation

Question 11

What is transcription?

Answer 11

the transfer of genetic information from DNA to mRNA. mRNA carries the copied instructions for protein assembly to the ribosome. It occurs in the nucleus.

Question 12

What occurs during the first step of transcription (initiation)?

Answer 12

1. RNA polymerase binds to promoter DNA (beginning of a gene) 2. Portion of chromosome unwinds 3. RNA nucleotides base pair with template strand

Question 13

What occurs during the second step of transcription (elongation)?

Answer 13

RNA molecule grows

Question 14

What occurs during the third step of transcription (termination)?

Answer 14

RNA polymerase reaches terminator (end) and detaches. mRNA molecule is now done.

Question 15

What is translation?

Answer 15

the transfer of information from mRNA to a protein. Transfer RNA (tRNA) serves as an interpreter. Translation occurs in the cytoplasm.

Question 16

mRNA is read as a series of ____

Answer 16

codons (a 3 nucleotide sequences that specifies a particular amino acid)

Question 17

What is AUG?

Answer 17

A codon that serves as the start signal. It codes for Met.

Question 18

What does transfer tRNA do?

Answer 18

transfers amino acids from cytoplasm to ribosome. tRNA is a polynucleotide with 2 “ends” (attachment sites): -amino acid end -anticodon end

Question 19

What’s an anticodon? What is the anticodon for AUG?

Answer 19

An anticodon is a 3 nucleotide sequence complementary to the mRNA codon. AUG . . . UAC

Question 20

What occurs during the first step of translation (initiation)?

Answer 20

1. mRNA binds to ribosome (small subunit) 2. tRNA (anticodon) base-pairs with mRNA (codon) 3. Large subunit of ribosome attaches

Question 21

What occurs during the second step of translation (elongation)?

Answer 21

1. Each amino acid added one at a time 2. tRNA “transfers” amino acid from cytoplasm to ribosome 3. Anticodon (on tRNA) matches codon on mRNA 4. Amino acids bonded together with peptide bond

Question 22

What occurs during the third step of translation (termination)?

Answer 22

1. Elongation continues until a STOP codon is reached 2. Primary protein structure complete 3. Protein is released from ribosome

Question 23

If the DNA template strand reads: ATGGACTCA TACCTGAGT What is the mRNA (codon) and tRNA (anticodon)?

Answer 23

ATGGACTCA TACCTGAGT mRNA: AUGGACUCA tRNA: UACCUGAGU

Question 24

What’s the difference between DNA and RNA?

Answer 24

Question 25

What are the different types of mutations?

Answer 25

**Base Subsitution **

Silent Mutation- no effect on amino acid sequence​​​

Missense- codes for wrong amino acid

Nonsense- codes for a stop codon

Base Insertion/Deletion (Frameshift Mutation)

adding or deleting a base from the “reading frame”

Spontaneous Mutation- errors during DNA replication or recombination

Question 26

What’s the name of the enzyme (during DNA replication) that helps break the hydrogen bonds that hold the two strands of the molecule together (allowing it to “unzip”)?

Answer 26

Helicase. They separate double-stranded DNA into single strands allowing each strand to be copied.

Question 28

How many nucleotides would be needed to code for a protein that is 60 amino acids long?

Answer 28

Each amino acid has a 3-nucleotide sequence called a codon. Therefore, a protein that is 60 amino acids long needs 180 nucleotides (60 x 3)