DNA Structure and Gene Function

Questions and Answers

The building blocks of DNA are called?

Amino Acids

Proteins

Monosaccharides

Nucleotides (correct)

Nucleotides in DNA are made of three basic components: a sugar called _____, a _ group, and a nitrogenous ____.

Deoxyribose, phosphate, base

Cytosine, Thymine (in DNA), and Uracil (in RNA) are all classified as _____ bases.

Pyrimidine

DNA contains four kinds of nitrogenous bases: , , , and _.

Cytosine, Adenine, Thymine, Guanine Signup and view all the answers

The complementary nitrogen bases in DNA are joined by _____ bonds.

Hydrogen Signup and view all the answers

In DNA, the order of the nitrogen bases is the _______ to make proteins.

Sequences Signup and view all the answers

A specific sequence of nitrogen bases (segment of DNA) that codes for a protein is known as a _____

Gene Signup and view all the answers

Adenine and Guanine are both classified as ______ bases.

Purine Signup and view all the answers

Who discovered that A=T and G=C?

Erwin Chargaff Signup and view all the answers

Who used X-ray diffraction to discover the double-helical structure of DNA?

Rosalind Franklin Signup and view all the answers

Who are the scientists credited with building the first correct model of the structure of DNA?

James Watson & Francis Crick Signup and view all the answers

If Adenine is 31.5%, what is Thymine?

31.5%, they are equal Signup and view all the answers

If guanine is 28.5%, what is Cytosine?

28.5%, they are also equal Signup and view all the answers

What are hydrogen bonds?

The bond shared between pyrimidine and purine bases Signup and view all the answers

What is Deoxyribose sugar?

Sugar in DNA Signup and view all the answers

What is a Phosphate Group?

A molecule in the backbone of DNA and RNA that links adjoining bases together. Signup and view all the answers

What is a Nucleotide?

Nitrogen base + sugar (ribose or deoxyribose) and phosphate group Signup and view all the answers

If the DNA sequence was TACCGATA, what would the alternate sequence be?

ATGGCTAT (G=C + A=T) Signup and view all the answers

If the DNA sequence was AAGGCTA, what would the alternate sequence be?

TTCCGAT (G=C + A=T) Signup and view all the answers

What is DNA ligase?

An enzyme involved in DNA synthesis that fills in the gaps between the Okazaki fragments. Signup and view all the answers

What are Single Strand Binding Proteins?

They bind to and stabilize single-stranded DNA. Signup and view all the answers

What is the sequence of the lagging strand?

3' 5' Signup and view all the answers

What is the sequence of the leading strand?

5' 3' Signup and view all the answers

What are Okazaki fragments?

Short lengths of single-stranded DNA made on the lagging strand. Signup and view all the answers

What is the lagging strand?

The strand where DNA replication moves away from the replication fork. Signup and view all the answers

What is the leading strand?

The strand where replication moves towards the replication fork. Signup and view all the answers

What is DNA polymerase?

An enzyme that joins individual nucleotides to produce a new strand of DNA. Signup and view all the answers

What is DNA Helicase?

Enzyme that unzips DNA. Signup and view all the answers

What is DNA Primase?

RNA polymerase that makes RNA primer. Signup and view all the answers

What is the first step in eukaryotic DNA replication?

DNA unzips Signup and view all the answers

What specific enzyme has the function to unzip the double helix before replication begins?

Helicase Signup and view all the answers

Does DNA replication take place in the same direction along both strands of the DNA molecule that is being replicated?

False Signup and view all the answers

What does it mean that the two strands of DNA are complementary?

Each strand can be used to make a new strand. Signup and view all the answers

Sugars and phosphates make up what part of a DNA molecule?

Backbone, sides Signup and view all the answers

After DNA replication there are ____ new DNA molecules produced; each has both one original strand and one new strand.

2 Signup and view all the answers

DNA replication occurs in what part of a cell?

The Nucleus Signup and view all the answers

During what part of the cell cycle does replication occur?

During the S phase of Interphase Signup and view all the answers

Study Notes

DNA Structure

Nucleotides are the fundamental building blocks of DNA.
Each nucleotide consists of deoxyribose sugar, a phosphate group, and a nitrogenous base.
DNA contains four nitrogenous bases: Cytosine (C), Adenine (A), Thymine (T), and Guanine (G).
Pyrimidines include Cytosine, Thymine, and Uracil (only in RNA), while purines are Adenine and Guanine.
Hydrogen bonds link complementary nitrogenous bases, facilitating the double-helix structure.

Gene Function

The sequence of nitrogen bases in DNA encodes the information necessary for protein synthesis.
A segment of DNA that encodes a specific protein is termed a gene.

Key Figures in DNA Discovery

Erwin Chargaff established that the amount of Adenine equals Thymine (A=T) and Guanine equals Cytosine (G=C).
Rosalind Franklin utilized X-ray diffraction to uncover DNA's double-helix structure.
James Watson and Francis Crick are recognized for creating the first accurate model of DNA.

DNA Pairing and Replication

If Adenine comprises 31.5% of the DNA, Thymine also occupies 31.5%.
If Guanine is 28.5%, so is Cytosine.
The DNA sequence can be translated into its complementary sequence (e.g., TACCGATA becomes ATGGCTAT).

DNA Replication Mechanics

DNA ligase is the enzyme that connects Okazaki fragments during replication.
Single Strand Binding Proteins stabilize single-stranded DNA during replication.
DNA helicase unwinds the double helix, enabling replication to proceed.
DNA can be synthesized in two strands: leading strand (5' to 3') towards the replication fork and lagging strand (3' to 5') away from it.

Characteristics of DNA Strands

Okazaki fragments are short DNA sequences synthesized on the lagging strand.
The backbone of a DNA molecule consists of alternating sugars and phosphate groups, forming the sides of the helix.
After replication, two new DNA molecules are produced, each containing one original strand and one new strand.

Cell Cycle and DNA Replication

DNA replication occurs within the nucleus of eukaryotic cells.
Replication takes place during the S phase of Interphase when the DNA unzips for synthesis.
Complementary DNA strands enable the reconstruction of each strand during replication, ensuring genetic fidelity.

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Description

Explore the basics of DNA structure, including nucleotides and nitrogenous bases. Understand how genes encode protein synthesis and the key figures who contributed to DNA discovery. Test your knowledge on these fundamental concepts of molecular biology.