Genetics: DNA and Cell Division

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Questions and Answers

What is the primary function of plasmids in bacteria and archaea?

They carry the entire genetic information of the organism.

They are essential for all cell functions.

They can confer advantages under specific conditions. (correct)

They are responsible for cellular respiration.

Which statement is true about R plasmids?

They are essential for conjugation.

They are involved in nitrogen fixation.

They range in size from 100 bp to 10 kbp.

They confer resistance to antibiotics and other inhibitors. (correct)

What can be a consequence of carrying multiple antibiotic resistance genes on a single R plasmid?

Enhanced ability to survive under selective pressures. (correct)

Decrease in plasmid replication.

Reduction in metabolic efficiency.

Increased sensitivity to antibiotics.

What is one essential role of plasmids in the process of conjugation?

To facilitate the transfer of genetic material between cells. Signup and view all the answers

What is the size range of plasmids?

1 kbp to more than 1 mbp Signup and view all the answers

How do transposons relate to antibiotic resistance?

They can carry antibiotic-resistance genes. Signup and view all the answers

What is a characteristic of the genetic information encoded on plasmids?

It varies in importance depending on environmental conditions. Signup and view all the answers

Which of the following is NOT a function associated with plasmids?

Regulating metabolic processes for cellular respiration. Signup and view all the answers

What is the primary function of DNA Polymerase III during DNA replication?

Synthesizing the majority of the DNA sequence Signup and view all the answers

Which enzyme is responsible for unwinding the DNA double helix?

DNA Helicase Signup and view all the answers

In which direction does DNA replication proceed during synthesis?

5’ to 3’ Signup and view all the answers

What is the role of the single-stranded binding protein (Ssbp) during DNA replication?

To stabilize the unwound single-stranded DNA Signup and view all the answers

Which part of the DNA is created by primase during DNA synthesis?

RNA primer Signup and view all the answers

What is the function of DNA Ligase in the DNA replication process?

Sealing gaps in DNA after primer removal Signup and view all the answers

How does DNA synthesis differ between the leading and lagging strands?

Leading strand is synthesized more quickly than the lagging strand Signup and view all the answers

What initiates DNA replication at the origin of replication in prokaryotes?

Helicase binding Signup and view all the answers

What ensures the accurate replication of DNA to maintain fidelity?

Enzymatic proofreading by polymerases Signup and view all the answers

What happens to supercoiled DNA during replication?

It gets relaxed Signup and view all the answers

What role does DNA Polymerase I serve in the replication process?

Removes RNA primers and replaces them with DNA Signup and view all the answers

What do hydrogen bonds connect in the DNA structure?

Nucleotides across complementary strands Signup and view all the answers

What characterizes the leading strand during DNA synthesis?

It is synthesized continuously Signup and view all the answers

Which statement about the replication fork is true?

It is a zone of unwound DNA where replication occurs. Signup and view all the answers

What is the primary method that bacteria use to package their DNA?

Supercoiling Signup and view all the answers

Which type of supercoiling is typically harder to unwind during DNA replication?

Positive supercoiling Signup and view all the answers

What are sister chromatids?

Identical copies of a chromosome attached at the centromere Signup and view all the answers

How is the structure of eukaryotic chromosomes primarily organized?

Around histone proteins Signup and view all the answers

Which of the following is true about trisomy?

Usually results in miscarriage Signup and view all the answers

What type of chromosomes are autosomes?

Chromosomes not involved in determining sex Signup and view all the answers

What is the characteristic of a diploid cell?

Contains two copies of each chromosome Signup and view all the answers

Which structure in a chromosome is responsible for holding sister chromatids together?

Centromere Signup and view all the answers

What describes the genome size in relation to an organism's complexity?

Larger genomes usually reflect greater complexity Signup and view all the answers

What distinguishes sex chromosomes from autosomes?

Sex chromosomes determine the genetic sex of an individual Signup and view all the answers

What indicates positive supercoiling in DNA?

Higher stress and tighter twisting of the helix Signup and view all the answers

In eukaryotic cells, how is DNA organized when preparing for cell division?

The DNA is duplicated and then organized into sister chromatids Signup and view all the answers

Which type of chromosomes are typically referred to as the 'last pair' in humans?

Sex chromosomes Signup and view all the answers

What is the total time in minutes for DNA polymerase to complete replication of a 4.6mbp DNA strand?

76 minutes Signup and view all the answers

Which enzyme is responsible for connecting DNA fragments on the lagging strand during replication?

DNA Ligase Signup and view all the answers

During DNA replication in prokaryotes, what type of replication occurs?

Bidirectional replication Signup and view all the answers

What are the precursors needed to synthesize RNA?

NTPs Signup and view all the answers

What is the first step of the transcription process in bacteria?

Initiation Signup and view all the answers

What triggers the termination of RNA transcription?

Reaching a specific sequence Signup and view all the answers

How many different types of rRNA are produced in bacteria?

3 types Signup and view all the answers

What initiates the binding of RNA polymerase to the DNA during transcription?

Pribnow box Signup and view all the answers

In what direction does RNA synthesis occur during transcription?

5' to 3' Signup and view all the answers

What is the role of the sigma factor during transcription?

To identify the promoter region Signup and view all the answers

Which of the following statements is true about the transcription process in bacteria?

Terminator sequences are essential. Signup and view all the answers

Before translation, what must happen to the primary transcript?

It must be spliced. Signup and view all the answers

In archaea, how many subunits does RNA polymerase have?

13 subunits Signup and view all the answers

What happens if both strands of the template are used in transcription?

The amino acid sequence will differ. Signup and view all the answers

What is the outcome when a nucleus from Organism A’s egg cell is replaced by a nucleus from Organism B?

The egg cell produces a clone of Organism B. Signup and view all the answers

What is the primary benefit of using plasmids in bacteria?

They can carry antibiotic resistance genes. Signup and view all the answers

Which of the following describes the role of bacteriocins encoded by plasmids?

They combat closely related bacterial species. Signup and view all the answers

What are the two main informational macromolecules involved in encoding the phenotype of an organism?

Proteins and nucleic acids Signup and view all the answers

What process is responsible for the conversion of DNA to RNA?

Transcription Signup and view all the answers

Which enzyme is responsible for translating RNA into proteins?

Ribosomes Signup and view all the answers

In partial cloning, which type of cells are primarily utilized to synthesize organs?

Somatic stem cells Signup and view all the answers

How do plasmids contribute to the spread of antibiotic resistance among bacteria?

Through horizontal gene transfer. Signup and view all the answers

What significant role do proteins play in an organism?

They catalyze biochemical processes. Signup and view all the answers

Which of the following is NOT a step in the flow of genetic information?

Diversity Signup and view all the answers

Which statement best describes the Central Dogma?

It describes the flow of genetic information to protein synthesis. Signup and view all the answers

Which of the following is a misconception about plasmids?

They are essential for aerobic respiration. Signup and view all the answers

What limits the effectiveness of penicillin in certain bacterial strains?

Alteration of penicillin-binding proteins. Signup and view all the answers

Partial cloning is primarily accepted for which purpose?

Synthesize organs and tissues. Signup and view all the answers

Study Notes

DNA Structure

E. coli has a genome of ~5 million base pairs
Histones are found in eukaryotes and archaea
Bacteria do not have histones
DNA consists of two strands twisted into a double helix
DNA molecules and proteins are organized into chromosomes
DNA can coil in two directions: positive and negative
Positive supercoiling is more "stressful" and happens in most archaea
Negative supercoiling is more relaxed and allows for easier unwinding of the molecule, this occurs in the majority of prokaryotes and bacteria

Cell Division and Chromosomes

During cell division, the entire chromosome is duplicated, forming sister chromatids
Daughter cells receive identical copies of the chromosomes
Each eukaryotic cell has a characteristic number of chromosomes
Diploid cells have two pairs of each type of chromosome
Humans have 46 chromosomes
Trisomy is a condition where an individual has an extra chromosome, most cases are fatal, trisomy 21 is Down syndrome
Chromosomes are organized into autosomes (non-sex chromosomes) and sex chromosomes
Sex chromosomes differ between males and females, the last pair

Karyotyping

Karyotyping reveals the characteristics of an individual's chromosomes
It is a visual representation of the chromosomes
Genome size shows the complexity of an organism, larger genomes are more complex

Genetic Elements

Plasmids are found in many bacteria and archaea
Plasmids contain genetic information that is not essential for cell function, but it might give an advantage to the cell
Plasmids can confer a selective growth advantage
Plasmids range in size from 1kbp to more than 1mbp
R plasmids are resistance plasmids that confer antibiotic resistance
R plasmids contain many antibiotic resistance genes

Cloning

Dolly the sheep was the first successfully cloned mammal
Dolly was cloned by removing the nucleus from an egg cell and implanting the nucleus from a donor cell
In humans, partial cloning is more accepted, it is used to synthesize organs and uses somatic stem cells

Antibiotic Resistance

Penicillin and other beta-lactam antibiotics inhibit penicillin-binding proteins
Resistance to penicillin occurs due to modified cross-linking enzymes
Antibiotic resistance can mis-spread via plasmids, which can transfer from one bacteria to another via horizontal gene transfer

The Central Dogma

The flow of genetic information includes replication, transcription, and translation
This flow is known as the central dogma
The central dogma describes how genetic information is turned into proteins

Transcription

Transcription is the process of DNA to RNA
RNA polymerase is the main enzyme involved

Translation

Translation is the process of RNA to protein
Ribosomes are the main enzyme involved
Viruses are also involved in replication, transcription, and translation, but they can violate the central dogma

DNA Replication

There are 5 DNA polymerases involved in DNA replication
DNA Polymerase I: plays a lesser role in DNA replication
DNA Polymerase II: repairs DNA damage
DNA Polymerase III: primary enzyme for replication of chromosomal DNA
DNA Polymerase IV: repairs DNA damage
DNA Polymerase V: repairs DNA damage
Replication occurs ONLY from the 5' end to the 3' end of the DNA strand
DNA replication requires extraordinary fidelity to prevent gene mutations
Gene mutations can cause irregularities in an organism
Gene mutations can also render genes useless or different
The origin of replication in prokaryotes is a specific DNA sequence where replication begins
Replisomes move to the origin of replication and initiate replication
Replisomes contain the enzymes necessary to replicate DNA
Helicase unwinds the DNA double helix to create the replication fork
Single-strand binding proteins (Ssbp) help to stabilize the unwound DNA strand, preventing it from rewinding
The replication fork is the point on the DNA where replication occurs
DNA polymerase III adds nucleotides at a rate of 1000 per second
Primase creates a short RNA primer to initiate DNA synthesis.
DNA polymerase III synthesizes the majority of the new DNA sequence
DNA polymerase I removes the RNA primer and replaces it with DNA
DNA ligase seals the gaps left by the removal of the RNA primer
DNA replication is antiparallel, with one strand running from 5’ to 3’ and the other from 3’ to 5’
The leading strand is synthesized continuously in a 5’ to 3’ direction
The lagging strand is synthesized discontinuously in a 5’ to 3’ direction
Synthesis of the lagging strand requires the creation of Okazaki fragments
Okazaki fragments are short segments of DNA that are ligated together to form the complete lagging strand
DNA is supercoiled to maximize space inside the cell and allow for compacting into a small space
Supercoiling is relaxed during replication to allow for proper unwinding and replication
Replication is done on BOTH STRANDS of DNA

Applications

Understanding DNA replication helps to develop new treatments for diseases caused by gene mutations
Replication errors are a major cause of cancer initiation and progression
DNA polymerase inhibitors are commonly used in chemotherapy to prevent cancer cell replication.

DNA Replication

DNA polymerase adds 1000 nucleotides per second.
It takes 76 minutes to complete replication of a 4.6mbp coli genome.
Leading and lagging strands are replicated simultaneously during DNA replication.
Replication is bidirectional in prokaryotes due to their circular chromosome structure.
The replisome is a complex of proteins involved in replication, including enzymes that move as one.
DNA ligase seals the nicks in DNA fragments on the lagging strand.

Transcription

Transcription is the process of synthesizing RNA from a DNA template strand.
RNA polymerase is the primary enzyme responsible for transcribing DNA to mRNA.
The sigma factor identifies the promoter region and determines the direction of transcription.
The sigma factor attaches RNA polymerase to the promoter region and is then released allowing transcription to start.
Transcription occurs from 5' to 3', similar to DNA replication, with the template strand oriented in the 3' to 5' direction.
RNA polymerase does not require a primer to initiate transcription.
Transcription uses ribonucleotides (NTPs) instead of deoxyribonucleotides (dNTPs).
RNA polymerase can transcribe both strands of DNA, resulting in different amino acid sequences, hence the need for a single strand template.

Transcription Initiation

The sigma factor recognizes the promoter region on DNA, including the Pribnow box (-10 region) and TTGACA (-35 region).
The Pribnow box (-10 region) is located 10 bases before the start of transcription and is also known as a TATA box.
The TTGACA (-35 region) is located 35 bases before the start of transcription.
Different sigma factors recognize different promoter sequences.

Transcription Elongation

RNA polymerase makes copies of DNA using RNA.
The RNA polymerase employs A-U and G-C base pairing, as opposed to DNA's A-T and G-C pairing.

Transcription Termination

Transcription terminates when RNA polymerase reaches a specific sequence that signals the end of the process.
The RNA transcript is released, and the process allows for translation.

Transcription in Bacteria

Bacteria transcribe genes into operons (DNA segments transcribed into one RNA molecule bounded by initiation and termination sites).
Operons ensure efficient expression of genes needed for a specific function.
Most genes encode proteins, but some genes produce non-protein-coding RNAs like rRNA and tRNA, which are involved in protein synthesis.
The process of transcription involves the production of a primary transcript containing intervening sequences that need to be removed before translation.
These intervening sequences do not code for proteins, are known as jumping genes, and are removed from the sequence.
The final RNA product corresponds to the RNAs involved in the translation process.

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Description

This quiz covers key concepts in genetics related to DNA structure and the processes of cell division. Understand the differences in chromosome organization between prokaryotes and eukaryotes, as well as the implications of genetic conditions like trisomy. Test your knowledge of these fundamental biological principles.