Ch. 4 Flashcards
1
Q
Functional unit of genetic information is the ___.
A
Gene
2
Q
Genes are in cells and are composed of ___.
A
DNA
3
Q
Three informational macromolecules in cell:
A
DNA
RNA
Protein
4
Q
Genetic information flow can be divided into three stages:
A
Replication
Transcription
Translation
5
Q
Replication
A
DNA is duplicated
6
Q
Transcription
A
Information from DNA is transferred to DNA
7
Q
Translation
A
Information in RNA is used to build polypeptides
8
Q
mRNA (messenger RNA)
A
Encodes polypeptides
9
Q
tRNA (transfer RNA)
A
Plays role in protein synthesis
10
Q
rRNA (ribosomal RNA)
A
Plays role in protein synthesis
11
Q
Genes transcribed in eukaryotes
A
Each gene is transcribed individually
12
Q
Genes transcribed in prokaryotes
A
Multiple genes may be transcribed together
13
Q
Four nucleotides are found in DNA:
A
Adenine
Guanine
Cytosine
Thymine
14
Q
Backbone of DNA chain is alternating phosphates and the pentose sugar ____.
A
Deoxyribose
15
Q
Two strands are ___
A
Antiparallel
16
Q
All cells and some viruses have DNA in ____ molecules
A
Double-stranded
17
Q
Two strands have ___ base sequences
A
Complementary
18
Q
Adenine always pairs with ___.
A
Thymine
19
Q
Guanine always pairs with ___.
A
Cytosine
20
Q
Two strands form a ___ ___.
A
Double helix
21
Q
Size of DNA molecule is expressed in ___ ___.
A
Base pairs
22
Q
Supercoiled DNA
A
DNA is further twisted to save space
23
Q
Negative supercoiling
A
Double helix is underwound
24
Q
Positive supercoiling
A
Double helix is overwound
25
Relaxed DNA
DNA has number of turns predicted by number of base pairs
26
DNA gyrase
Introduces supercoils into DNA
27
Genome
Entire complement of genes in cell or virus
28
Chromosome
Main genetic element in prokaryotes
"Housekeeping" genes
29
Plasmids
Replicate separately from chromosome
Genetic element that is expendable and rarely contains genes for growth under all conditions
30
R plasmid
Resistance plasmids, usually antibiotic resistant
31
Col plasmid
Contain genes that code for bacteriocins which are proteins that inhibit or kill other bacteria
32
Fertility plasmids
Capable of conjugation and result in the expression of sex pili
33
Virulence plasmid
Turn the bacterium into a pathogen
34
Transposable elements
Segment of DNA that can move from one site to another site on the same or a different DNA molecule
35
Three main types of transposable elements:
Insertion sequences
Transposons
Special viruses
36
In several pathogenic bacteria, virulence characteristics are encoded by ___ ___.
Plasmid genes
37
Virulence factors:
- Enable pathogen to colonize
- Enable pathogen to cause host damage
- hemolysin
- enterotoxin
38
Bacteriocins
Proteins produced by bacteria that inhabit or kill closely related species or even different strains of the same species
39
Genes encoding bacteriocins are often carried on ___.
Plasmids
40
DNA replication is ___.
Semiconservative
41
____ catalyze the addition of dNTPs.
DNA polymerases
42
___ is primary enzyme replicating chromosomal DNA.
DNA polymerase III
43
Primer made from RNA by ___.
Primase
44
DNA synthesis begins at the _____ in prokaryotes
Origin of replication
45
Replication fork
Zone of unwound DNA where replication occurs
46
What unwinds the DNA?
DNA helicase
47
Connecting DNA fragments on the lagging strand
- DNA synthesis on lagging strand continues until it reaches previously synthesized DNA
- DNA polymerase I removes the RNA primer and replaces it with DNA
- DNA ligase seals nicks in the DNA
48
Replisome
Complex of multiple proteins involved in replication
49
DNA synthesis is ___ in prokaryotes.
Bidirectional
50
Transcription is carried about by ___.
RNA polymerase
51
RNA polymerase recognizes DNA sites called ___.
Promoters
52
Promoter
Site of initiation of transcription
53
Promoters are recognized by __ __ of RNA polymerase.
Sigma factor
54
Transcription stops at specific sites called ___ ___.
Transcription terminators
55
Two regions within promoters that are highly conserved:
Pribnow box
| -35 region
56
Pribnow box
Located 10 bases before the start of transcription
57
-35 region
Located about 35 bases upstream of transcription
58
Unit of transcription
Unit of chromosome bounded by sites where transcription of DNA to RNA is initiated and terminated
59
An mRNA encoding a group of cotranscribed genes is called a ___ mRNA.
Polycistronic
60
Operon
A group of related genes cotranscribed on a polycistronic mRNA
61
Amino acids are linked by peptide bonds to form a ___.
Polypeptide
62
The linear array of amino acids in a polypeptide is called its ___ ___.
Primary structure
63
The chemical properties of the amino acid are related to their ___ ___.
Side chain
64
Genetic code
A triplet of nucleic acid bases encodes a single amino acid
65
Degenerate code
Multiple codons encode a single amino acid
66
___ on tRNA recognizes codon.
Anticodon
67
Wobble
Irregular base pairing allowed at third position of tRNA
68
Stop codons
Terminate translation (UAA, UAG, UGA)
69
Start codon
Translation begins with AUG
70
Reading frame
Triplet code requires translation to begin at the correct nucleotide
71
Shine-Dalgarno sequence
Ensures proper reading frame
72
Open reading frame (ORF)
AUG followed by a number of codons and a stop codon in the same reading frame
73
Transfer RNA
At least one tRNA per amino acid
74
Anticodon
Three bases of tRNA that recognize three complementary bases on mRNA
75
Ribosomes
Sites of protein synthesis
76
Translation is broken down into three main steps:
Initiation
Elongation
Termination
77
Initiation
Two ribosomal subunits assemble with mRNA
78
Elongation
Amino acids are brought to the ribosome and are added to the growing polypeptide
79
Termination
Occurs when ribosome reaches a stop codon
80
Secondary structure
Interactions of the R groups force the molecule to twist and fold in a certain way
81
Tertiary structure
Three-dimensional shape of polypeptide
82
Quaternary structure
Number and types of polypeptides that make a protein
83
Denaturation
- occurs when proteins are exposed to extremes of heat, pH, or certain chemicals
- causes the polypeptide chain to unfold
- destroys the secondary, tertiary, and/or quaternary structure of the protein
84
The biological properties of a protein are usually lost when it is ___.
Denatured
85
Some require assistance from ___ ___ or ___ for folding to occur.
Molecular chaperones or chaperonins
86
DNA -> DNA
Replication
87
DNA -> RNA
Transcription
88
RNA -> protein
Translation
89
Enterotoxin
GI Tract
| Living organism
90
Endotoxin
LPS
| Organism dies
91
Exotoxin
Living organism
Ex. Neurotoxin
