Chapter 6 and 10 Lec. 1

Question 1

Genes

Answer 1

A sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic

Question 2

Macromolecules and genes

Answer 2

DNA, RNA, Protein

Question 3

3 stages of gene flow

Answer 3

Replication: DNA duplication.
Transcription: information from DNA transferred to RNA.
-mRNA
-tRNA
-rRNA
Translation: information in RNA used to build polypeptides.

Question 4

The central dogma of genetics

Answer 4

DNA to RNA to protein
Eukaryotes: each gene is transcribed individually.
Prokaryotes: multiple genes may be transcribed together.

Question 5

DNA structure

Answer 5

Four nucleotides found in DNA
-Adenine
-Guanine
-Cytosine
-Thymine 
Backbone of DNA chain alternating phosphates and pentose sugar deoxyribose.

Question 6

DNA structure II

Answer 6

All cells and some viruses have double strand DNA. 
Strands antiparalell. 
Strands have complementary base. 
-adenine and thymine 
-guanine and cytosine
Strands form double helix.

Question 7

Double Helix

Answer 7

Size of DNA molecule expressed in base pairs.
1000 base pairs= 1 kilobase pairs= 1kbp.
1000000 base pairs= 1 megabase pairs= 1 mbp

Question 8

Double Helix II

Answer 8

Hydrogen bonds hold strands together.
-Adenine-thymine: 2 H-bonds
-Guanine-cytosine: 3 H-bonds
High heat breaks H-bonds causing denaturation.
GC-rich DNA melts at a higher temperature than AT-rich DNA.

Question 9

Supercoiling

Answer 9

Supercoiled DNA: DNA further twisted to save space.
-Negative supercoiling: double helix under wound
-Positive supercoiling: double helix overwound
Relaxed DNA: DNA has number of turns predicted by number of base pairs.
DNA gyrase: introduces supercoils into DNA.

Question 10

The genetic code

Answer 10

Genetic code: triplet of nucleic acid bases (codon) encodes a single amino acid.

• Degenerate code: multiple codons encode a single amino acid.
• Anticodon: on t RNA recognizes codon
• Wobble: irregular base pairing allowed at third position position of tRNA.

Question 11

Translation and the genetic code

Answer 11

Stop codons: terminate translation.
Start codon: translation begins with AUG.
Reading frame: triplet code requires translation to begin at the correct nucleotide.
Shine Dalgarno sequence: ensures proper reading frame.
Open reading frame: AUG followed by a number of codons and a stop codon in the same reading frame.

Question 12

Mutations and Mutants

Answer 12

Mutation: Heritable change in DNA sequence.
Mutant: A strain of any cell or virus differing from parental strain in genotype.
Wild-type strain: A strain isolated from nature.

Question 13

Genotype vs. Phenotype

Answer 13

Genotype: nucleotide sequence of the genome.
Phenotype: observable properties.

Question 14

Mutants

Answer 14

Selectable mutations:
-growth advantage under certain conditions
-easy to detect
Nonselectable mutations:
-Have neither an advantage nor a disadvantage over parent
-Hard to detect

Question 15

Screening

Answer 15

Tedious
Involves replica plating:
-useful for identification of cells with a nutritional requirement for growth (auxotroph).

Question 16

Molecular basis of mutation

Answer 16

Induced mutations:
-made environmentally or deliberately 
-result from exposure
Spontaneous mutations:
-occur without external intervention.