Molecular Biology and DNA Replication Quiz

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Questions and Answers

What is the main function of DNA Polymerase during DNA replication?

To join lagging strand fragments together

To synthesize new DNA strands by adding nucleotides (correct)

To separate the DNA strands

To add RNA Nucleotides to the strands

How does the replication of the Leading and Lagging strands differ?

The Leading strand is replicated continuously and the Lagging strand in fragments. (correct)

The Leading strand is replicated in fragments while the Lagging strand is continuous.

Both strands are replicated continuously but require different enzymes.

Only the Leading strand is replicated by DNA Polymerase.

What is the purpose of phylogenetics?

To analyze genetic mutations in a single species

To classify organisms based solely on physical traits

To identify fossil remains of ancient species

To study the evolutionary history and relationships of organisms (correct)

What is the role of ligase in DNA replication?

To join fragments of DNA on the Lagging strand Signup and view all the answers

What do scientists primarily use to estimate the time since lineages diverged?

Molecular clocks derived from DNA sequences Signup and view all the answers

How is the divergence time between eagles and humans and rats and mice calculated?

By subtracting the age of the common ancestors of each group Signup and view all the answers

What occurs during the initial heating phase of PCR?

DNA strands separate due to high temperature Signup and view all the answers

Which of the following is NOT a requirement for PCR?

An RNA Primer Signup and view all the answers

What assumption is made when using DNA sequences as molecular clocks?

Mutation rates are constant over time Signup and view all the answers

Which of the following outcomes is indicated by a greater similarity in DNA sequences between two species?

They likely shared a more recent common ancestor Signup and view all the answers

What component of RNA is different from that of DNA?

RNA contains Uracil instead of Thymine Signup and view all the answers

Which of the following applications can use PCR amplification?

Forensic evidence in crime-solving Signup and view all the answers

Which type of RNA is involved in bringing amino acids to the ribosome during protein synthesis?

tRNA Signup and view all the answers

What is the function of tRNA in protein synthesis?

It transports specific amino acids to the ribosome for polypeptide formation. Signup and view all the answers

What is the role of RNA polymerase in transcription?

Adding nucleotides to the growing mRNA strand. Signup and view all the answers

During RNA splicing, what are introns?

Non-coding regions that are removed from the primary mRNA transcript. Signup and view all the answers

What are exons?

Coding regions that are retained in the mature mRNA. Signup and view all the answers

What initiates the translation of mRNA into a protein?

The recognition of a start codon. Signup and view all the answers

What type of bond links amino acids together in a polypeptide chain?

Peptide bonds. Signup and view all the answers

What is alternative RNA splicing?

Generating multiple types of proteins from a single gene by retaining different exons. Signup and view all the answers

What ensures the accuracy of codon-anticodon pairing during translation?

Complementary base pairing between mRNA codons and tRNA anticodons. Signup and view all the answers

What is the primary result of speciation?

Formation of a new species Signup and view all the answers

Which factor is essential for the process of speciation?

Isolation Signup and view all the answers

What type of speciation occurs due to geographical barriers?

Allopatric Speciation Signup and view all the answers

Which of the following barriers can lead to sympatric speciation?

Behavioral changes Signup and view all the answers

In genomic sequencing, what do computer programs primarily analyze?

Base sequence similarities Signup and view all the answers

What has the comparison of genomes from different species revealed?

Many genes are highly conserved Signup and view all the answers

Which of the following sequences best describes a significant step in speciation?

Isolation → Mutation → Natural selection → New species Signup and view all the answers

After many generations of mutation and selection, what prevents two sub-populations from interbreeding?

Genetic divergence Signup and view all the answers

What is the outcome of a missense mutation?

It produces a protein with altered amino acid properties. Signup and view all the answers

What happens during a nonsense mutation?

The translation process is prematurely terminated. Signup and view all the answers

Which mutation type involves the retention of introns or exclusion of exons?

Splice-site mutation Signup and view all the answers

What mutation is characterized by an additional DNA nucleotide being inserted?

Insertion Mutation Signup and view all the answers

What is a consequence of a frameshift mutation?

All subsequent codons and amino acids are affected. Signup and view all the answers

Which type of chromosome mutation involves reversing a section of a chromosome?

Inversion Mutation Signup and view all the answers

In a translocation mutation, a section of a chromosome is:

attached to a different chromosome. Signup and view all the answers

What is a common effect of chromosome mutations?

They may lead to lethal outcomes. Signup and view all the answers

What determines the function of proteins in a cell?

The variety of shapes they have Signup and view all the answers

What type of stem cell can differentiate into all cell types that make up an organism?

Pluripotent stem cells Signup and view all the answers

Which statement accurately describes tissue stem cells?

They are involved in the growth and repair of specific tissues. Signup and view all the answers

What is one therapeutic use of stem cells?

Repairing damaged corneas in the eye Signup and view all the answers

What distinguishes embryonic stem cells from tissue stem cells?

Embryonic stem cells can differentiate into all cell types. Signup and view all the answers

What ethical issue is associated with the use of embryonic stem cells?

It involves the potential destruction of embryos. Signup and view all the answers

Meristems in plants are similar to stem cells in animals because they both can:

Self-renew and differentiate. Signup and view all the answers

Which characteristic is NOT true about tissue stem cells?

They can differentiate into any type of cell. Signup and view all the answers

Signup and view all the answers

Study Notes

DNA Structure

DNA is a double-helix composed of repeating DNA nucleotides.
Each nucleotide has three components: a phosphate group, a deoxyribose sugar, and an organic base.
The two DNA strands in a double helix are antiparallel.
The 3' end of the strand has a deoxyribose sugar, and the 5' end of the strand has a phosphate group.
DNA nucleotides are joined together by strong chemical bonds between the phosphate group of one nucleotide and the deoxyribose sugar of another. This forms a sugar-phosphate backbone.
The two strands are held together by complementary base pairing.
Adenine pairs with Thymine (2 hydrogen bonds)
Cytosine pairs with Guanine (3 hydrogen bonds)

DNA Organisation

DNA is found in linear chromosomes within the eukaryotes' nucleus (e.g. plant, animal & fungi).
DNA is found in circular chromosomes within prokaryotes' cytoplasm and in mitochondria and chloroplasts of eukaryotes.
DNA is found in plasmids in the cytoplasm of prokaryotes and yeast cells.
DNA is tightly coiled and packaged with associated histone proteins.

DNA Replication

DNA is replicated by DNA polymerase prior to cell division.
DNA polymerase requires primers to start replication.
A primer is a short strand of nucleotides that binds to the 3' end of the template DNA.
DNA polymerase adds DNA nucleotides using complementary base pairing to the deoxyribose (3') end of the new strand.
DNA replication occurs in one direction on the leading strand and in fragments on the lagging strand.
Fragments on the lagging strand are joined by ligase.

Polymerase Chain Reaction(PCR)

PCR amplifies DNA using complementary primers targeting specific sequenced regions.
Primers are short DNA sequences complementary to target sequences.
Repeated heating and cooling cycles amplify the target DNA region.
DNA is heated to 92-98°C to separate strands.
Cooled to 50-65°C for primers to bind to target sequences.
Heated to 70-80°C for heat-tolerant DNA polymerase to replicate the region.
Each cycle doubles the amount of DNA.
PCR needs a DNA template, nucleotides, primers, heat-tolerant polymerase, and pH buffer.
PCR has practical applications in forensic science, paternity testing, and diagnosing genetic disorders.

Gene Expression

Gene expression involves the transcription and translation of DNA sequences.
Only a fraction of genes are expressed in a cell at any given time.
Transcription and translation involve three types of RNA: mRNA, tRNA, and rRNA.
RNA is single-stranded and composed of nucleotides with ribose sugar, phosphate, and one of four bases (Cytosine, Guanine, Adenine, and Uracil).
mRNA carries a copy of DNA's code from the nucleus to the ribosome.
tRNA carries the specific amino acid to the ribosome.
rRNA and proteins form ribosomes.

Transcription

RNA polymerase moves along DNA, unwinding it and breaking hydrogen bonds between bases.
RNA polymerase synthesizes a primary mRNA transcript using RNA nucleotides via complementary base pairing.
Uracil in RNA is complementary to Adenine.

RNA Splicing

Some DNA transcribed is non-coding (introns) and must be removed.
RNA splicing involves removing introns and joining coding regions (exons).
The order of exons remains unchanged during splicing.
Alternative splicing allows for multiple proteins to be expressed from one gene.

Translation

tRNA is involved in translation of mRNA into a polypeptide at a ribosome.
Translation starts at a start codon and ends at a stop codon.
Anticodons bond to codons by complementary base pairing.
Peptide bonds link amino acids together.
tRNA leaves the ribosome as the polypeptide forms.

Protein Structure

Amino acids are linked by peptide bonds to form polypeptides.
Polypeptide chains fold to form a protein's three-dimensional shape held together by hydrogen bonds.
Protein shape determines function.
Phenotype is determined by the proteins produced as a result of gene expression.

Cellular Differentiation

Cellular differentiation is where a cell expresses certain genes to produce proteins specific to its function.
Stem cells are unspecialized cells that can divide and/or differentiate.
Embryonic stem cells can differentiate into all cell types in the organism, and are therefore pluripotent.
Tissue stem cells are involved in growth, repair, and renewal of tissues.
They're multipotent, meaning they can differentiate into a limited range of cell types within a tissue.
Therapeutic uses of stem cells involve repairing damaged or diseased organs or tissues.

Ethical Issues

Use of embryonic stem cells raises ethical concerns, involving the destruction of potential life.

Genomic Sequencing

Genomic sequencing determines the sequence of nucleotide bases in individual genes or entire genomes.
Computer programs identify base sequences that are similar to known genes.
Bioinformatics is essential for analyzing genomic data.
Many genomes, particularly of disease-causing organisms, pest species, and model organisms, have been sequenced.
Gene conservation across organisms has implications for understanding evolutionary relationships.

Phylogenetics

Phylogenetics studies evolutionary history and relationships.
Sequence data is used to determine relationships between species.
Fossil evidence aids in mapping out evolutionary events, including the order in life's evolution, and the last universal ancestor.

Mutations

Mutations are changes in DNA that alter or prevent protein synthesis.
Single-gene mutations involve alterations in DNA nucleotide sequences.
Substitution mutations: replacing one DNA nucleotide with another
Insertion mutations involve inserting an extra DNA nucleotide.
Deletion mutations involve removing a DNA nucleotide.
Frame-shift mutations occur when insertions or deletions cause a change in the reading frame of the DNA sequence, which drastically alters protein structure.
Splice-site mutations affect the process of RNA splicing by altering the recognition sequences.
Nonsense mutations create premature stop codons, leading to shorter proteins.
Missense mutations change an amino acid in the protein.

Speciation

Speciation: Formation of new species.
Isolation (geographic, behavioral, ecological) prevents gene flow between populations.
Mutations create genetic variation within and between populations.
Natural Selection favors more suitable mutations.
Different reproductive isolation mechanisms create separate species.

Molecular Clocks

DNA or protein sequences are used to estimate when species diverged during evolution.
Differences in nucleotide/amino acid sequences reflect evolutionary time.
Divergence rates must be assumed constant for reasonable estimates.

Pharmacogenetics and Personalised Medicine

Pharmacogenetics uses genome information to choose appropriate drugs for diseases.
Personalised medicine uses an individual's genome for selecting the most effective drugs and dosage.

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Description

Test your knowledge on key concepts of molecular biology, including DNA replication, phylogenetics, and PCR. This quiz covers the roles of various enzymes, the differences between leading and lagging strands, and the significance of molecular clocks in estimating divergence times. Perfect for students in biology classes or anyone interested in genetics!