Biology Final Exam Review

Front 1

Chargaff's Rule

Back 1

in any species there is an equal number of A and T bases, and an equal number of G and C bases

Front 2

Franklin concluded that ..

Back 2

there were two anti-parallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecule's interior

Front 3

Helicase

Back 3

unwinds parental double helix at replication forks

Front 4

Single-strand Binding Protein

Back 4

binds to and stabilizes single-stranded DNA until it can be used as a template

Front 5

Topoisomerase

Back 5

relieves "overwinding" strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands

Front 6

Primase

Back 6

synthesizes an RNA primer at 5' end of leading strand and of each Okazaki fragment of lagging strand

Front 7

DNA polymerase III

Back 7

using parental DNA as a template, synthesizes new DNA strand by covalently adding nucleotides to the 3' end of a pre-existing DNA strand or RNA primer

Front 8

DNA polymerase I

Back 8

removes RNA nucleotides of primer from 5' end and replaces them with DNA nucleotides

Front 9

DNA ligase

Back 9

joins 3' end of DNA that replaces primer to rest of leading strand and joins Okazaki fragments of lagging strand

Front 10

Chromatin

Back 10

a complex of DNA and protein, and is found in the nucleus of eukaryotic cells

Front 11

Histones

Back 11

proteins that are responsible for the first level of DNA packing in chromatin

Front 12

Euchromatin

Back 12

loosely packed chromatin

Front 13

DNA to RNA

Back 13

during transcription, one of the two DNA strands called the template strand provides a template for ordering the sequence of nucleotides in an RNA transcript

Front 14

RNA to protein

Back 14

-during translation, the mRNA base triplets, called codons are read in the 5' to 3' direction
-each codon specifies the amino acid to be placed along a polypeptide
-each codon specifies the addition of only one of the 20 amino acids

Front 15

Three Stages of Transcription

Back 15

-Initiation
-Elongation
-Termination

Front 16

RNA polymerase binding and Initiation of Transcription

Back 16

-promoters signal the initiation of RNA synthesis
-transcription factors mediate the binding of RNA polymerase and the initiation of transcription in eukaryotes
-the completed assembly of transcription factors and RNA polymerase II bound to a promoter is called a transcription initiation complex
-a promoter called a TATA box is crucial in forming the initiation complex in eukaryotes

Front 17

Introns

Back 17

long noncoding stretches of nucleotides that lie between coding regions.(they are cut out)

Front 18

Exons

Back 18

other regions (similar to introns) that are expressed, usually translated into amino acid sequences

Front 19

RNA splicing

Back 19

removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

Front 20

Three Stages of Translation

Back 20

-Initiation
-Elongation
-Termination

Front 21

Mutations

Back 21

changes in the genetic material of a cell

Front 22

Point mutations

Back 22

chemical changes in just one base pair of a gene
*the change of a single nucleotide in a DNA template strand can lead to the production of an abnormal protein

Front 23

Missense mutations

Back 23

still code for an amino acid, but not the right amino acid

Front 24

Nonsense mutations

Back 24

change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein

Front 25

Insertions and Deletions

Back 25

additions of losses of nucleotide pairs in a gene.
-may alter the reading frame producing a frameshift mutation

Front 26

Gene expression in bacteria is controlled by the operon model

Back 26

operator-- regulatory switch is a segment of DNA usually positioned within the promoter
operon-- entire stretch of DNA that includes the operator, the promoter, and the genes that they control

Front 27

Repressible Operon

Back 27

one that is usually on; binding of a repressor to the operator shuts of transcription

Front 28

Inducibe Operon

Back 28

one that is usually off; a molecule called an inducer activates the repressor and turns on transcription

Front 29

Differential Gene Expression

Back 29

the expression of different genes by cells with the same genome
*errors in gene expression can lead to diseases including cancer

Front 30

Regulation of Chromatin Structure

Back 30

-genes with highly packed heterochromatin are usually not expressed
-genes that are loosely associated with protein (euchromatin) are more likely to be expressed
-chemical modifications to histones and DNA of chromatin influence both chromatin structure and gene expression

Front 31

Histone acetylation

Back 31

acetyl groups are attached to positively charged lysines in histone tails
-this process loosens chromatin structure, thereby promoting the initiation of transcription

Front 32

Roles of Transcription Factors

Back 32

-to initiate transcription, eukaryotic RNA polymerase requires the assistance of proteins called transcription factors
-general transcription factors are essential for the transcription of all protein-coding genes
-in eukaryotes, high levels of transcription of particular genes depend on control elements interacting with specific transcription factors

Front 33

Proto-oncogenes can be converted to oncogenes by

Back 33

-Movement of DNA within the genome: if it ends up near the active promoter, transcription may increase
-Amplification of a proto-oncogene: increases the number of copies of the gene
-Point mutations in the proto-oncogene or its control elements: causes an increase in gene expression

Front 34

Tumor-Suppressor Genes

Back 34

help prevent uncontrolled cell growth

Front 35

Tumor-Suppressor Proteins

Back 35

-Repair damaged DNA
-Control Cell adhesion
-Inhibit the cell cycle

Front 36

Viruses cause cancer in three ways:

Back 36

1. Introduction of an oncogene (v-onc) into a cell
2. Activation of a proto-oncogene
3. Inactivation of a tumor suppressor protein

Front 37

Viruses are ...

Back 37

very small infectious particles consisting of nucleic acid enclosed in a protein coat, and in some cases, a membranous envelope

Front 38

Viral Genomes

Back 38

- double or single stranded DNA
-double or single stranded RNA

Front 39

Lytic Cycle

Back 39

phage reproductive cycle that culminates in the death of the host cell
-produces new phages and digests the host's cell wall, releasing the progeny viruses
-phages that reproduce only by the lytic cycle is called a virulent phage

Front 40

Lysogenic Cycle

Back 40

replicates the phage genome without destroying the host
-the viral DNA molecule is incorporated into the host cell's chromosome
-every time the host divides, it copies the phage DNA and passes the copies to daughter cells

Front 41

Viruses cause cancer in three ways:

Back 41

1. Introduction of an oncogene (v-onc) into a cell
2. Activation of a proto-oncogene
3. Inactivation of a tumor suppressor protein

Front 42

Viruses are ...

Back 42

very small infectious particles consisting of nucleic acid enclosed in a protein coat, and in some cases, a membranous envelope

Front 43

Viral Genomes

Back 43

- double or single stranded DNA
-double or single stranded RNA

Front 44

Lytic Cycle

Back 44

phage reproductive cycle that culminates in the death of the host cell
-produces new phages and digests the host's cell wall, releasing the progeny viruses
-phages that reproduce only by the lytic cycle is called a virulent phage

Front 45

Lysogenic Cycle

Back 45

replicates the phage genome without destroying the host
-the viral DNA molecule is incorporated into the host cell's chromosome
-every time the host divides, it copies the phage DNA and passes the copies to daughter cells