Genetics

Question 1

Elements of Nucleic Acids

Answer 1

CHONP

Question 2

Elements of Proteins

Answer 2

CHONS

Question 3

Purines

Answer 3

Double ringed nitrogenous bases
Guanine and Adenine

Question 4

Pyrimidines

Answer 4

Single-ringed nitrogenous bases
Cytosine, Thymine, Uracil

Question 5

DNA vs RNA

Answer 5

RNA contains ribose instead of deoxyribose and RNA is the primer for DNA replication. Also used for Gene Expression

Question 6

Significance of 5’ and 3’ ends on Nucleotides

Answer 6

Nucleotides have 5 carbons. Nitrogenous bases attach at 1’ carbon, phosphate groups are attached to the 5’ carbon. Nucleotides connect with each other at the 5’ and 3’ ends.

Question 7

What causes the double-helix shape of DNA?

Answer 7

Strong hydrogen bonds cause each strand to curl around each other, creating double-helix shape

Question 8

How are DNA strands read? How are they built?

Answer 8

Read: 3’ –> 5’
Built: 5’ –> 3’
Why? DNA strands are anti-parallel.

Question 9

Griffith

Answer 9

Discovered that bacteria can transfer genetic information through a biochemical agent (tested rats with pneumonia because of the capsule of the pathogenic var. and the non-capsule var.)

Question 10

Avery, Macleod & McCarty

Answer 10

discovered that DNA was the genetic factor that caused the death of Griffith’s mice, not protein. used enzymes (DNAse & Proteases) to prove it

Question 11

Chargaff

Answer 11

determined the ratios of the four DNA nucleotides. His work provided evidence of the base pairing rules. (grinded up animal meat and noticed different percentages of certain nucleotides, like 20% G 20% C 30% A 30% T)

Question 12

Hershey & Chase

Answer 12

Proved genetic information was made from DNA (not protein) by seeing which radio-labeled molecule was injected into infected bacteria by viruses

Question 13

Franklin

Answer 13

used x-ray diffraction to detect the shape of DNA

Question 14

Crick & Watson

Answer 14

did not do any experiments, made models using data from previous experiments (Franklin) and described the double-helix structure of DNA (suggested DNA could act as a template for making more DNA and could mutate)

Question 15

Enzymes of DNA Replication in order

Answer 15

1. Helicase
2. Primase
3. DNA Polymerase III
4. DNA Polymerase I
5. Ligase

Question 16

DNA Replication

Helicase

Answer 16

opens up DNA at the origin and creates replication fork

Question 17

DNA Replication

Primase

Answer 17

builds RNA primer piece in the 5’ –> 3’ direction

Question 18

DNA Replication

DNA Polymerase III

Answer 18

builds the DNA strands by adding nucleotides to the RNA primer and immediately checks and replaces incorrect bases

Question 19

Leading Strand

Answer 19

continuously synthesized strand of DNA in the 5’ –> 3’ direction

Question 20

Lagging Strand

Answer 20

discontinuously synthesized strand that creates short segments called Okazaki fragments

Question 21

DNA Replication

DNA Polymerase I

Answer 21

replaces RNA primers with DNA

Question 22

DNA Replication

Ligase

Answer 22

joins all the Okazaki fragments together

Question 23

Semi-Conservative

Answer 23

After replication, each chromosome retains an old copy of the DNA and a new copy that was newly synthesized

Question 24

Mutation Repair

DNA Polymerase III

Answer 24

corrects DNA base errors replication itself

Question 25

# Mutation Repair DNA Polymerase I

Answer 25

immediately corrects DNA base errors AFTER replication

Question 26

# Mutation Repair Excision Repair

Answer 26

DNAses cut out damaged DNA DNA Polymerases synthesize DNA DNA Ligases piece DNA back together

Question 27

# Mutation Repair Photoactivation

Answer 27

Photolysases are light activated and repair DNA IN BACTERIA ONLY

Question 28

Xeroderma Pigmentosum

Answer 28

patients lack DNA repair system in skin cells causing higher rates of mutation (thymine dimers). No protection from UV and results in multiple skin cancers prior to age 20.

Question 29

Gene Expression Steps

Answer 29

1. Transcription 2. Translation

Question 30

Transcription

Answer 30

**Initiation**: RNA Polymerase binds to promoter region (TATA box) and unzips DNA **Elongation**: RNA Polymerase makes one RNA strand from one DNA template using RNA nucleotide **Termination**: RNA Polymerase reaches termination site and transcript is released

Question 31

Translation

Answer 31

**Initiation**: mRNA binds to small ribosome subunit. 1st tRNA ANTIcodon binds to mRNA START codon bringing MET to the P-site. Large ribosome subunit binds so translation machinery is set up and ready for use **Elongation**: 2nd tRNA binds to 2nd mRNA codon at A-site bringing 2nd amino acid. 1st and 2nd aa form peptide bond and produces dipeptide. Ribosome translocates along mRNA by one codon so dipeptide at P-site, new codon is at A-site and old empty tRNA departs from E-site. 3rd RNA codon at A-site **Termination**: Ribsome reaches stop codon (UAG, UGA, UAA) at A-site and translation stops. Polypeptide is released and ribosome subunits disband.

Question 32

Constitutive Genes

Answer 32

permanently expressed genes since their products are essential (ATP)

Question 33

Operons

Answer 33

groups of structural genes that can be turned off or on in response to environmental conditions

Question 34

Repressible operon

Answer 34

genes that are typically expressed. turned off when end product is no longer needed. Anabolic

Question 35

Inducible operon

Answer 35

genes typically silent/not expressed. Turned on when inducer (substrate or enzyme pathway) enters cell. Catabolic

Question 36

Lactose Operon

Answer 36

1. Repressor protein (I Gene product) is attached to operator site and blocks operon expression 2. RNA polymerase at promoter site is blocked and can't transcribe structural genes 3. Lactose INDUCES operon ON and inactivates Repressor protein so operator is not blocked anymore 4. RNA Polymerase binds to promoter and transcribes mRNAs which are translated into enzyme proteins - OPERON STRUCTURAL GENES are not expressed and enzyme products catabolize LACTOSE needed

Question 37

# Protein Folding 1° structure

Answer 37

straight amino acid structure sequence

Question 38

# Protein Folding 2° structure

Answer 38

pleating/helical structure formed from intermolecular bonds (helix-shaped)

Question 39

# Protein Folding 3° structure

Answer 39

3D protein folding upon itself

Question 40

# Protein Folding 4° strucure

Answer 40

two or more polypeptides interfolded together

Question 41

# Protein Folding Prion Diseases

Answer 41

Prions are misfolded proteins. These misfolded proteins cause others to change and disrupts the normal functioning

Question 42

Spontaneous Mutation

Answer 42

Mistakes just happen and are not always corrected (during replication or at any time)

Question 43

Mutagens

Answer 43

substances that increase the number of mutations above the spontaneous rate

Question 44

Types of Mutagens

Answer 44

* Chemical: benzene, aflatoxin, cigarette smoke, base analogs * Physical: Ionizing (x-rays, gamma rays) and Non-Ionizing (UV creating Thymine Dimers) * Biological: HPV (cervical cancer), Hep B (liver cancer)

Question 45

# Point Mutations on Gene Expression Same Sense

Answer 45

Same/similar amino acid incorporated. Product = same polypeptide | Thh cat sat onn the mat. ## Footnote Substitution Mutation

Question 46

# Point Mutations on Gene Expression Missense

Answer 46

Different amino acid inserted into polypeptide. Products = non-functioning protein/structure | The bat sat onn the mat. ## Footnote Substitution Mutation

Question 47

# Point Mutations on Gene Expression Nonsense

Answer 47

Stop codon sequence inserted into polypeptide --> terminated. Product = short peptide | The cat. ## Footnote Substitution Mutation

Question 48

# Point Mutations on Gene Expression Frameshift

Answer 48

every codon is misread if nucleotides are not added/lost in triplets. Product = VERY different protein | The eca tsa ton nth ema t. ## Footnote Addition/Deletion Mutation

Question 49

# Transfer of Beneficial Mutations Transformation

Answer 49

Uptake of DEAD cell DNA by DNA TRANSPORTER protein into living recipient --> **recombinant**

Question 50

# Transfer of Beneficial Mutations Conjugation

Answer 50

F+ donor has F PLASMID and produces sex pili to attach to recipeint cell. Rolling copy of plasmid DNA passes from donor to F- recipient along conjugation bridge --> **Recombinant F+ cell**

Question 51

# Transfer of Beneficial Mutations Hfr (high frequency) conjugation

Answer 51

Hfr+ donor cell sends rolling copy of both plasmid genes and adjacent chromosomal genes to F- recipient --> **Recombinant Hfr+ cell**

Question 52

# Transfer of Beneficial Mutations Transduction

Answer 52

bacteriophage picks up bacterial genes and transfers them from 1st bacterial host to 2nd --> **Recombinant cell **

Question 53

# Transfer of Beneficial Mutations Transposons

Answer 53

jumping genes jump around chromosome and between bacterial cells --> **Recombinant cells**

Question 54

Results of bacterial mutations?

Answer 54

* bacterial populations develop increased virulence, increased ABX resitistance, and increased disinfectant resistance * Beneficial mutants multipily and spread if there's "selection pressure" * Over time, we would face the inability to treat infections, increase in patient suffering and mortality ## Footnote overuse of ABX creates selection pressure for ABX resistant pathogen survivors

Question 55

Ames Test

Answer 55

test used to test the potenital mutagenic factors of some chemicals using "wild" Salmonella

Question 56

# Ames Test Auxotroph Mutant

Answer 56

His- mutant that could not grow on minimal medium

Question 57

# Ames Test Back-Mutant/Revertant

Answer 57

Mutant "mutant" that mutates back to normal (spontaneous mutation) (His- --> His+)

Question 58

# Ames Test Potential Mutagen

Answer 58

His- mutants are exposed to a factor and can mutate back to normal His+. The more colonies that grow, the more suspicious the factor is mutagenic