Molecular Basis of Inheritance

Nucleosides

Phosphate groups

Base pairs

Sugar molecules

Griffith and Avery

Watson and Crick

Hershey and Chase

Meselson and Stahl

Cytosine

Adenine

Thymine

Uracil

$3.4$ nm

$34$ nm

$0.34$ nm

$20$ nm

Thymine

Deoxyribose

Phosphate group

Double-stranded structure

The two strands are parallel to each other

The backbone is formed by sugar and nitrogenous bases

Adenine forms three hydrogen bonds with Thymine

The pitch of the helix is $3.4\text{ nm}$

$3.4\text{ \AA}$

$34\text{ \AA}$

$20\text{ \AA}$

$2\text{ \AA}$

One

Two

Three

None

3.4 nm

34 nm

0.34 nm

340 nm

Cytosine

Thymine

Uracil

Guanine

Nucleoid

Chromatosome

Centromere

Kinetochore

Solenoid

Nucleosome

Chromatid

Chromosome

Histone

DNA

RNA

NHC protein

Cytoplasm

Ribosome

Nucleus

Mitochondria

5

10

20

2

H3 histone

Linker DNA and H1 histone

H4 histone

$147 \text{ bp}$ of DNA

Both use histones for packaging

Neither uses histones for packaging

Bacterial DNA is packaged with non-histone proteins; human DNA uses histones

Bacterial DNA is not packaged at all; human DNA is

DNA can be packed without forming knots, allowing for easy expansion and folding.

DNA is permanently locked and cannot be accessed by RNA polymerase.

Only circular DNA can be stored in the nucleus.

Histones can be recycled during transcription.

2.2 meters

About 31 cm

10 μ m

1 mm

Histone $H1$

Topoisomerase II

DNA Ligase

Helicase

ATP only

Pyrophosphate from dNTPs

GTP only

Glucose

To provide a template

To provide a free $3'$-OH group for DNA polymerase

To unwind the DNA

To provide energy

One

Hundreds

Thousands

None

Towards the replication fork

Away from the replication fork

In both directions

Not possible

Haploidy

Diploidy

Polyploidy

Monosomy

DNA Ligase

Topoisomerase

Helicase

SSBP

DNA dependent RNA polymerase

DNA dependent DNA polymerase

RNA dependent DNA polymerase

RNA dependent RNA polymerase

DNA Polymerase $\alpha$

DNA Polymerase $\delta$

DNA Polymerase $\gamma$

DNA Polymerase $\beta$

The polymerase will incorporate an Adenine opposite the Uracil.

The polymerase will incorporate a Guanine opposite the Uracil.

The polymerase will skip the base entirely.

The polymerase will stop replication.

A DNA template

All four dNTPs

A free $3'-OH$ group (primer)

ATP for each phosphodiester bond

A polypeptide chain

A new DNA strand

An RNA molecule

A ribosome

rRNA

tRNA

mRNA

snRNA

Exons

Introns

5' Cap

Poly-A tail

Terminator

Promoter

Structural gene

Exon

$5'$ end of the coding strand

$3'$ end of the template strand

$3'$ end of the coding strand

$5'$ end of the template strand

mRNA requires splicing

Transcription occurs in the nucleus

DNA-dependent RNA polymerase is the primary enzyme

Capping occurs at the $5'$ end of mRNA

$3' \rightarrow 5'$

$5' \rightarrow 3'$

Both directions

Depends on the organism

RNA to DNA

DNA to RNA

RNA to Protein

DNA to Protein

Capping

Splicing

Tailing

Polymerization of deoxyribonucleotides

tRNA

18S rRNA

mRNA

snRNA

16

64

128

256

Nirenberg, Khorana, and Holley

Watson and Crick

Hershey and Chase

Meselson and Stahl

Start codon

Stop codon

Anticodon

Degenerate codon

It only acts as a stop signal

It acts as the primary start signal for translation

It codes for Tryptophan

It is only found in bacterial DNA

Valine

Tryptophan

Serine

Proline

$5' - \text{AUG} - 3'$

$3' - \text{UAC} - 5'$

$5' - \text{UAA} - 3'$

$3' - \text{CAU} - 5'$

A single base is used for only one codon

Adjacent codons share one base

The code can be read in multiple frames simultaneously

One tRNA can bind to multiple codons

U to C

U to A

U to G

None of these, as Serine is 6-fold degenerate

Proline

Glycine

No third amino acid will be formed

Alanine

5-AAAAAA-3

5-GGGGGG-3

5-UUUUUU-3

5-CCCCCC-3

Nucleus

Cytoplasm

Nucleolus

Lysosome

$UAA$

$UAG$

$UGA$

$GUA$

P site

A site

E site

T site

Valine

Methionine

Formyl-methionine

Leucine

DNA

mRNA

rRNA

tRNA

Does not require GTP for binding

Binds directly to the P-site of the ribosome

Lacks an anticodon loop

Carries more than one amino acid

$5'-AUG-3'$

$5'-UAC-3'$

$5'-ATG-3'$

$5'-UAA-3'$

They are removed by the ribosome before translation starts.

They interact via proteins like PABP and eIF4G to circularize the mRNA, promoting ribosome recycling.

They act as the actual codons for the first and last amino acids.

They prevent the mRNA from entering the ribosome.

Long polypeptide chains

Ribosomes stalled with only the initiator tRNA in the P-site

Deacylated tRNAs in the E-site

Completed proteins waiting for release

$5'-GGU-3'$

$5'-UGG-3'$

$5'-ACC-3'$

$5'-UCC-3'$

At all times in all cells

Only when their products are needed

Randomly during the life cycle

Only during cell death

Transacetylase

Permease

Hydrolase

Isomerase

Operator

Promoter

Repressor

Structural gene $z$

Bacteria

Humans

Plants

Fungi

Regulatory genes

Structural genes

Promoter genes

Operator genes

Transcription of the $z, y,$ and $a$ genes starts.

The $i$ gene is silenced.

Lactose is transported into the cell.

The mRNA is spliced into smaller fragments.

It has a negative impact on the growth of the cell.

The regulatory protein (repressor) inhibits transcription.

The inducer has a negative charge.

It only occurs in Gram-negative bacteria.

Transcription would stop immediately.

mRNA would be synthesized but could not be translated into protein in the cytoplasm.

DNA replication would become faster.

The $lac$ operon would be permanently induced.

One transcription factor regulates all genes in the genome.

A specific combination of multiple transcription factors is required to turn a gene on or off.

Genes are only expressed if they are combined into an operon.

Both DNA and RNA act as templates for protein synthesis.

It acts as a substrate for $\beta$-galactosidase.

It acts as an allosteric effector that activates the CAP protein.

It binds to the $lac$ repressor to increase its affinity for the operator.

It is a transcription factor that binds directly to the TATA box.

Very small portion

Exactly $10\%$

A large portion

No portion at all

Caenorhabditis elegans

Arabidopsis

Drosophila melanogaster

Oryza sativa

Linear

Life

Legal

Linkage

Protein synthesis

Generating genetic maps

Energy production

Cell division

The Expressed Sequence Tags of the Y chromosome

The physical map and sequence data of Chromosome 1 finished in 2006

The Sanger protein sequencing protocol

The initial cost estimate records of the NIH

DNA isolation

Sequence assembly and alignment

ELSI policy making

Genetic mapping using microsatellites

They were used to sequence the DNA directly

They were used to cut the long DNA polymers into smaller, manageable fragments

They were used to join the human DNA with the BAC vectors

They were used to identify the SNP locations

The possibility of 'genetic profiling' leading to denial of insurance based on a predisposition to a disease.

The fear that sequencing DNA will cause the DNA to become radioactive and harm the researcher.

The concern that knowing the human sequence will make the species stop evolving.

The risk that computers used for bioinformatics will develop consciousness and hide the data.

$3$ million

$300$ million

$30,000$

$300,000$

They provide essential clues about chromosome structure, dynamics, and the history of evolution.

They can be converted into essential vitamins within the nucleus when the cell is under stress.

They act as backup copies of the exons in case a mutation occurs in the coding region.

They are the primary sequences that code for the lipid bilayer of the nuclear envelope.

The child's $DNA$ bands are completely unique and do not correspond to either parent.

The child's $DNA$ bands match the maternal grandmother's profile only.

Every $VNTR$ band in the child's profile must be present in either the mother's or the father's profile.

The child's $DNA$ bands match the father's profile exactly, showing no maternal contribution.

Identical for all humans

Unique to an individual (except identical twins)

Always changing with age

Different in blood and hair of the same person

Because they are the same in everyone

Because they show high variability between individuals

Because they are easy to convert to proteins

Because they are only found in plants

Transcription

Density gradient centrifugation

Translation

Cell division

Centrifugation

Capillary action or vacuum blotting

Heating the gel to $100^{\circ}C$

Using a manual scraper

To join the probe to the target DNA

To cut the genomic DNA into smaller fragments at specific sites

To separate the two strands of the DNA double helix

To remove the phosphate group from the DNA backbone

They code for enzymes required for DNA replication

They do not code for any proteins

They are only found in prokaryotic organisms

They are only $10$ base pairs long in total

Southern blotting with large $VNTR$ probes.

$STR$ analysis using $PCR$.

Bulk $DNA$ density gradient centrifugation.

Whole genome sequencing.

By identifying the exact age of an individual animal.

By assessing genetic diversity and detecting inbreeding in endangered populations.

By determining the diet of an animal from its $DNA$.

By increasing the mutation rate in a captive population.

Agarose gel allows $DNA$ to move only by gravity.

The pore size of agarose gel can be controlled to separate $DNA$ fragments based on their molecular size.

Agarose gel chemically reacts with $DNA$ to change its color.

Agarose gel is the only medium that can withstand the high temperatures of Southern blotting.

Both are equally stable

DNA is catalytic, while RNA is not

DNA evolved from RNA

RNA has thymine

Kill the bacteria

Mix the isotopes

Detach viral particles from bacteria

Lyse the bacterial cells

The mouse transformed into a bacteria

The R-strain bacteria transformed into S-strain

The S-strain transformed into R-strain

The DNA transformed into protein

Adenine

Guanine

Cytosine

Thymine

The single-stranded nature of DNA allows it to fold into complex shapes that shield its nitrogenous bases from reacting with water.

The presence of a $2'$-OH group on the deoxyribose sugar acts as a chemical buffer that prevents phosphodiester bond cleavage.

The double-stranded structure and complementary base pairing allow for a template-based repair mechanism to fix damaged sequences.

DNA is more stable because its phosphate-sugar backbone is located on the inside of the helix, away from cellular enzymes.

Chemically more reactive

More stable and less prone to degradation

Single-stranded

Only found in the cytoplasm

DNA

RNA

Both mutate at the same rate

Neither can mutate

It used humans as test subjects.

It proved that RNA is not present in viruses.

It provided undeniable proof that convinced the scientific community that DNA is the genetic material.

It showed that transformation can occur in eukaryotes.

TMV has a protein coat that induces mutations.

TMV genetic material is RNA, which is less stable than DNA.

Human DNA is protected by a nuclear membrane.

TMV lives in a more mutagenic environment.

The phosphodiester bonds are broken, destroying the genetic information.

The hydrogen bonds between strands break, but they can re-anneal when cooled.

The DNA is converted into RNA.

The DNA is converted into proteins.

Phosphodiester bonds

Nitrogenous bases

Presence of Uracil

Ability to replicate

Mitochondria

Nucleus

Ribosome

Golgi body

Slower

Faster

Same

Zero

It makes DNA more flexible

It increases stability against spontaneous deamination

It makes DNA soluble

It allows DNA to stay in the cytoplasm

The code is triplet in nature

The code is nearly universal across all life forms

The code is read from $5'$ to $3'$ on mRNA

All of the above

Single-stranded

Double-stranded with complementary sequences

Highly reactive

Located in the cytoplasm

The Citric Acid Cycle

The Splicing of hnRNA

Electron Transport Chain

Cell Wall Synthesis

DNA is faster to replicate than RNA

DNA's stability allows for larger genomes and lower mutation rates, enabling higher complexity

DNA can catalyze more reactions than RNA

DNA was more readily available in the environment

Synthesizing long complex proteins like collagen

Synthesizing short random peptides that might have stabilized RNA structures

Replicating the entire RNA genome

Creating lipid bilayers for the cell

The ability to form G-U wobble base pairs

The presence of phosphate groups

The phosphodiester bond

The $5'$ to $3'$ polarity

Switched off

Switched on

Mutated

Replicated

$i$

$p$

$o$

$z$

Operator

Promoter

Inducer

Structural gene

Enzymes are made only when needed

Enzymes are always present

Lactose is never used

Glucose is never used

Glucose

Tryptophan

Lactose

cAMP

DNA replication

The genetic code

Regulation of gene expression

Protein synthesis mechanism

RNA polymerase is bound to the operator

Repressor is bound to the operator

Lactose is bound to the repressor

$\\beta$-galactosidase levels are very high

It allows the repressor to be regulated independently of the lactose metabolism genes.

It prevents the repressor from being transcribed by RNA polymerase.

It ensures the repressor is always present even if the operon structural genes are deleted.

It allows the repressor to bind to the promoter instead of the operator.

It will grow normally on lactose.

It will produce $\beta$-galactosidase but cannot take up lactose from the medium efficiently.

It will take up lactose but cannot digest it.

It will produce only transacetylase.

A single gene that codes for multiple proteins.

A cluster of structural genes under the control of a single promoter and regulatory region.

The protein that binds to the DNA to start transcription.

The mRNA molecule after it has been processed.