Lecture 3 Review

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Questions and Answers

What mechanism allows for the replication of the lagging strand in chromosomes?

Continuous synthesis of DNA

Special mechanism involving telomerase (correct)

Direct repair of DNA

Use of histone proteins

What is the approximate length of the diploid human genome?

2.1 m (correct)

6.369 million bp

4.5 billion bp

700 m

Which structure facilitates the compaction of DNA in chromosomes?

Histone proteins

Nucleosome (correct)

Telomeres

Chromatin fibers

How do chromosomes behave during mitosis in terms of structure?

They are in their most compact form Signup and view all the answers

What role do telomeres play in DNA organization?

They prevent chromosomes from shortening Signup and view all the answers

What is the accuracy rate of DNA polymerase during DNA replication?

1 error in every 10,000,000 bases Signup and view all the answers

What role do RNA primers play in DNA synthesis?

They provide a free 3’-OH group for DNA synthesis. Signup and view all the answers

How many replication origins are estimated to exist in the human genome?

20,000 Signup and view all the answers

Which direction does DNA polymerase synthesize DNA?

5’-3’ direction Signup and view all the answers

What are Okazaki fragments?

Fragments of DNA on the lagging strand Signup and view all the answers

What is the consequence of the 'end-replication problem' in DNA synthesis?

The leading strand cannot be fully synthesized. Signup and view all the answers

What happens to RNA primers after DNA synthesis?

They are removed and replaced with DNA. Signup and view all the answers

Which of the following statements is true about DNA polymerase's function?

It requires a 3’-OH group for DNA synthesis. Signup and view all the answers

What is the function of primase in DNA replication?

To synthesize RNA primers. Signup and view all the answers

How fast can DNA polymerase replicate deoxynucleotides?

1,000 deoxynucleotides/second Signup and view all the answers

What is the significance of the orientation of the sugar-phosphate backbone in DNA?

It maintains the anti-parallel structure of the double helix. Signup and view all the answers

How many base pairs are typically involved in one complete turn of the DNA helix?

10 base pairs Signup and view all the answers

What is the length of the total DNA present in a human body?

2.1 m Signup and view all the answers

In which direction does DNA polymerase add new deoxynucleotides during replication?

5' to 3' Signup and view all the answers

What type of replication does DNA undergo?

Semi-conservative replication Signup and view all the answers

What is the total number of base pairs estimated in the human genome?

6.4 billion Signup and view all the answers

Which of the following statements is true regarding DNA base-pairs?

Base pairs are found on the inside of the DNA helix. Signup and view all the answers

What is the estimated total number of cells in the human body?

30 trillion cells Signup and view all the answers

What type of bond is typically considered the strongest among chemical interactions?

Covalent bond Signup and view all the answers

Which type of interaction is primarily responsible for the folding of proteins in an aqueous environment?

Hydrophobic interactions Signup and view all the answers

Which of the following correctly describes a hydrogen bond?

A weak interaction involving a hydrogen atom with another electronegative atom Signup and view all the answers

What is the primary monomer that makes up nucleic acids such as DNA and RNA?

Nucleotide Signup and view all the answers

What defines the sequence of the genetic code within DNA?

Hydrogen bonds between base pairs Signup and view all the answers

What type of reaction links monomers to form biological macromolecules?

Condensation reaction Signup and view all the answers

Which of the following best describes the primary structure of DNA?

A double helix with anti-parallel strands Signup and view all the answers

In DNA, which nucleotide base pairs with adenine?

Thymine Signup and view all the answers

How many different nucleotide bases are present in DNA?

4 Signup and view all the answers

What type of bond connects the sugar and phosphate groups in a DNA strand?

Phosphodiester bond Signup and view all the answers

What defines the '5' end' of a DNA molecule?

The presence of a phosphate group Signup and view all the answers

Which of the following interactions is primarily responsible for the stability of the double helix structure of DNA?

Hydrogen bonds between base pairs Signup and view all the answers

What is the role of rRNA in the cell?

Structural component of ribosomes Signup and view all the answers

What type of biological macromolecule is primarily formed from amino acids?

Proteins Signup and view all the answers

Study Notes

Chemical Bonds and Interactions

Covalent bonds are strong bonds formed between atoms, sharing electrons. An example is the bonds in CO2 (O=C=O).
Non-covalent bonds are weaker than covalent bonds.
Ionic bonds are bonds that dissociate in water, resulting in ions (charged atoms or molecules). NaCl is an example. Interactions between ions are called electrostatic interactions in biochemical molecules.
Hydrogen bonds (H-bonds) are important for the genetic code. They form between a hydrogen atom and a highly electronegative atom like nitrogen or oxygen, and these interactions occur between bases in DNA & RNA.
Van der Waals interactions: Atoms interact strongly when they have complementary shapes.
Hydrophobic interactions: Hydrophobic parts of molecules associate to avoid water molecules. This drives the folding of proteins.

In-Class Polling

This course uses Poll Everywhere for in-class polling.
Students need to download or use the website (polleverywhere.com) to access polling information.
Instructions for creating a Poll Everywhere account are available,
Instructions include using a Cornell NetID email address and password.

Nucleic Acids (DNA)

DNA replication is a biological process visualized in an animation.
Learning objectives include understanding different classes of molecules in cells, types of monomers, base-pairing, nucleic acid structure, DNA replication, and eukaryotic DNA organization.
The reading materials include chapters 82-83, 179-192, and 209-225 of ECB6.

Today's Lecture

The lecture covers the "central dogma"
The course will examine macromolecules found in cells, focusing on nucleic acids and DNA.

The "Central Dogma" of Molecular Biology

DNA sequence dictates mRNA sequence.
mRNA sequence dictates protein sequence.
DNA's role is to store genetic information (genes) within a nucleus.
mRNA carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm.
Protein synthesis (translation) occurs in the cytosol.

Macromolecules in Cells

In a typical eukaryotic cell, macromolecules constitute approximately 70% of the cellular mass (excluding water).
The percentages include RNA (6%), protein (15%), and polysaccharides (2%).
Other cellular components include inorganic ions and smaller molecules—constituting approximately 4%. Phospholipids and DNA also make up a small amount of the structure.

Polymer Structure

Monomers combine to form polymers. Examples include monosaccharides forming polysaccharides, amino acids forming polypeptides (proteins), and nucleotides forming nucleic acids (DNA/RNA).
Mononucleotides are the building blocks of nucleic material.

Building Blocks of Nucleic Acid (DNA)

Deoxynucleotides are the monomers of DNA or other nucleic material.

Nucleic Acids (DNA and RNA)

DNA, deoxyribonucleic acid, is the genetic material.
RNA, ribonucleic acid, is involved in information transfer, among other functions.

Deoxynucleotides in DNA

The components of deoxynucleotides are a phosphate group, a deoxyribose sugar, and a base.
DNA uses four different kinds of bases: adenine, cytosine, guanine, and thymine.

Deoxynucleotides in DNA Phosphate Group

Deoxynucleotides carry phosphate groups, appearing as mono-, di-, or triphosphates.

Deoxynucleotides form polymers

Deoxynucleotides link together via phosphodiester linkages to form DNA polymers.

The DNA Polymer

DNA forms a double helix from two antiparallel strands.
The bases in DNA pair specifically (A with T, and C with G).
Hydrogen bonds hold the base pairs together along the DNA helix's centre.

DNA Replication

DNA replication is semi-conservative.
DNA polymerase needs a 3' OH group to initiate the synthesis process; RNA primers provide this.
DNA replication proceeds in a 5’ to 3’ direction and involves the use of replication forks.
DNA Polymerase requires RNA primers to initiate synthesis since the polymerase needs a 3' OH.
This is a key step for DNA replication, especially in lagging strands, which are replicated discontinuously.
Okazaki fragments are formed on the lagging strand.
The end-replication problem involves a loss of DNA at each replication cycle, because of the lack of 3'-OH groups for the lagging strand at the chromosome's end.
Telomerase addresses the end-replication problem.

DNA Organization in Cells

In cells, DNA is organized into chromosomes.
Chromosomes are highly compacted structures, aiding in the fit of DNA within the cell nucleus.
Chromatin is formed from histone proteins that pack and organize the DNA.
The different levels of organization include the 2nm DNA helix, and "beads-on-a-string" organization, followed by 30nm, and 300nm chromatin fibers.
During mitosis, chromosomes are highly condensed to allow segregation of chromosomes during cell division.

Section Activity

The section activity for this week involves fluorescence microscopy.

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Description

Test your knowledge on the mechanisms of DNA replication, chromosome structure, and the behavior of chromosomes during mitosis. This quiz covers important aspects of genetics and cellular biology, including the role of telomeres and DNA compaction. Perfect for students studying cellular biology or genetics!