The structure of DNA & Replication

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Questions and Answers

During DNA replication, which enzyme is responsible for unwinding the double helix structure by breaking the hydrogen bonds between base pairs?

DNA Polymerase
Primase
Helicase (correct)
Ligase

In the context of DNA structure, what is the significance of the term 'antiparallel'?

It signifies that the nitrogenous bases are oriented in the same direction on both strands to facilitate proper base pairing.
It refers to the identical sequence of nucleotides on both DNA strands.
It indicates that the two DNA strands run in opposite directions, with one strand running 5' to 3' and the other 3' to 5'. (correct)
It describes the parallel arrangement of phosphate groups and deoxyribose sugars.

What is the primary function of DNA ligase in DNA replication?

To add complementary nucleotides to the template strand.
To seal gaps between Okazaki fragments on the lagging strand. (correct)
To initiate the synthesis of RNA primers.
To unwind the double helix structure.

Why is maintaining high genetic diversity important for a species?

It allows the species to adapt to changing environmental conditions and avoid inbreeding. (D)

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Which of the following best explains the universality of the genetic code?

All living organisms use the same DNA code to synthesize proteins, indicating a shared ancestry. (B)

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What is the role of the start codon AUG in protein synthesis?

It codes for the amino acid methionine and initiates translation. (A)

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According to the central dogma of molecular biology, what is the correct sequence of information flow in a cell?

DNA → RNA → Protein (D)

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During transcription, what type of RNA molecule carries the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm?

mRNA (messenger RNA) (D)

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What is the primary function of tRNA (transfer RNA) in translation?

To carry amino acids to the ribosome and match them to the appropriate codon on the mRNA. (A)

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Which of the following characteristics of DNA contributes to its stability for accurately passing on genetic information?

The protection of genetic information by the double-helix structure. (A)

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Flashcards

What is DNA?

Deoxyribonucleic acid, a molecule present in the nucleus of cells, containing genetic instructions for all known living organisms.

What is a nucleotide?

A subunit of DNA consisting of a deoxyribose sugar, a phosphate group, and an organic base.

What is DNA replication?

The process of creating an exact copy of DNA, ensuring genetic information is passed on.

What is Helicase?

Enzyme that unzips the DNA double helix by breaking the hydrogen bonds between base pairs.

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What is DNA Polymerase?

Enzyme that adds complementary nucleotides to the template strand during DNA replication.

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What is Ligase?

Enzyme that seals the gaps between DNA fragments, forming a continuous strand.

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What are mutations?

Changes in DNA sequences that create genetic variation.

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What is the universality of the genetic code?

All living organisms utilize the same DNA code to synthesize proteins.

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What are Stop Codons?

UAA, UAG, and UGA. These codons signal the end of translation.

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What is a Start Codon?

AUG. This codon signals the start of protein synthesis.

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Study Notes

DNA, or deoxyribonucleic acid, is a chemical substance present in the nucleus of all cells in all living organisms.
It is a large molecule composed of a long chain of subunits called nucleotides.
Each nucleotide contains a deoxyribose sugar, a phosphate group (-PO4), and an organic base.
The phosphate group is located on the 5' end, while deoxyribose is on the 3' end.
DNA is antiparallel to ensure the proper connection of guanine, cytosine, adenine, and thymine nitrogenous bases.

Replication

DNA replication is the process of creating an exact copy of DNA to ensure genetic continuity.
Helicase unwinds the double helix by breaking hydrogen bonds.
DNA Polymerase adds complementary nucleotides.
Ligase seals gaps to form two identical DNA strands.

Mutation and Variation

Mutations are changes in DNA sequences that generate genetic variation, which drives evolution and diversity.
High genetic diversity enables species to adapt to environmental changes and avoid inbreeding.
Inbreeding, common in small, isolated populations, can reduce a species' ability to survive and reproduce.

Universality of Genetic Code

The genetic code is universal, with all living organisms using the same DNA code to build proteins.
Stop codons include UAA, UAG, and UGA.
The start codon is AUG.

Stability and Adaptability

DNA's helix structure protects genetic information and ensures both stability for genetic inheritance and adaptability for evolution.
Base nucleotides include guanine, cytosine, adenine, and thymine (GCAT).

Central Dogma

The central dogma of molecular biology involves DNA transcription and translation to synthesize proteins that direct the function of an organism.
Transcription converts DNA to RNA.
Translation converts RNA to amino acids.
mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA) are types of RNA.