Biology Lecture 2 - Functions of DNA Flashcards

Questions and Answers

What are the three main functions of DNA?

To store information, to replicate faithfully (preserve information), to have the ability to mutate (to add variability to information).

How do these three functions of DNA relate to its physical structure?

TBD

How are DNA sequences related to DNA information content?

TBD

Why do we need mutations?

To add variability to our sequences for adaptation and survival to different conditions and threats to the body (pathogens, disease, etc.). Signup and view all the answers

How does DNA store information?

Information is carried by the sequence of bases; a gene is the entire DNA sequence necessary to produce a functional protein or RNA. Signup and view all the answers

What type of information does DNA carry?

It codes for proteins and different RNAs (r, t, small regulatory), and regulatory signals. Signup and view all the answers

What is the coding sequence?

It codes for proteins and RNAs. Signup and view all the answers

What are regulatory sequences?

They control DNA replication, how many times a gene is transcribed, and therefore how many times a protein is made. Signup and view all the answers

How do we preserve DNA information?

With the central dogma; from DNA to RNA to protein, we cannot go backwards. Signup and view all the answers

Outline gene expression.

Starts with dsDNA and DNA synthesis (replication), then RNA synthesis (transcription) where mRNA is made from the template strand, then protein synthesis (translation) coding from mRNA. Signup and view all the answers

Describe dsDNA.

It is a double helix with polarity 5' to 3', complementary and antiparallel strands, 2.0 nm in diameter, 10 base pairs per turn, one complete turn is 3.4 nm long. Signup and view all the answers

What does replicating faithfully mean?

Two strands of parental DNA separate, each serves as a template for synthesis of a new daughter strand by complementary base pairing. Signup and view all the answers

What makes DNA semi-conservative?

When it replicates, it keeps one old strand with one new strand, so the old strand stays alive and active. Signup and view all the answers

Who proved the semi-conservative theory for DNA?

Meselson and Stahl. Signup and view all the answers

What were the three theories of DNA replication?

Semi-conservative, conservative, dispersive. Signup and view all the answers

What is the semiconservative theory?

Each daughter duplex consists of one old and one new strand. Signup and view all the answers

What is the conservative theory?

Old duplex is reassembled and new duplex composed of two completely new strands. Signup and view all the answers

What is the dispersive theory?

Sections of the old duplex are dispersed randomly to the two daughter duplexes. Signup and view all the answers

How did Meselson and Stahl prove the semi-conservative theory?

By using culture mediums of E. coli and nitrogen tags of different weights, they grew the bacteria, centrifuged them, and observed the gradients. Signup and view all the answers

Why did Meselson and Stahl use nitrogen tags?

Because nitrogen would be incorporated into the new DNA generated by E. coli. Signup and view all the answers

Describe semi-conservative replication.

Parental DNA strands separate; each serves as a template for a new daughter strand. Signup and view all the answers

What happens if there is a mutation in one of the parental strands?

Only one of the new strands will have the mutation while the other will stay normal. Signup and view all the answers

What is the third function of DNA?

Having the ability to mutate and add variability to the genetic code. Signup and view all the answers

What do mutations do?

They can add possible alterations to the protein product. Signup and view all the answers

Define colinearity in regards to mutations.

If you have a mutation in DNA, it will be transferred to mRNA and noticed in the translated protein as well. Signup and view all the answers

What is a silent mutation?

A mutation in DNA that is not reflected in the protein product. Signup and view all the answers

What is a mis-sense mutation?

A change that results in a change in amino acid and change in protein. Signup and view all the answers

What is a nonsense mutation?

A mutation that results in a stop codon being introduced into the sequence. Signup and view all the answers

What happens if a mutation occurs in the regulatory sequence?

The gene might be transcribed more than it should be, or you may not be able to transcribe the protein. Signup and view all the answers

What happens when you have mutations and natural selection?

Evolution occurs, as it selects for better alleles that help you survive. Signup and view all the answers

What is a knockout mutation?

A mutation that causes the protein not to be made, therefore it has been knocked out. Signup and view all the answers

Study Notes

Functions of DNA

Main functions include: storing information, faithfully replicating for information preservation, and enabling mutations to increase variability.

Importance of Mutation

Mutations provide genetic variability essential for adaptation and survival against pathogens and diseases.

DNA Information Storage

Information is conveyed through the sequence of nucleotide bases.
A gene encompasses the entire DNA sequence needed to produce functional proteins or RNA.

Content of DNA

Carries information that codes for proteins and various types of RNA including regulatory signals.
The coding and regulatory sequences are both crucial for proper gene function.

Gene Expression Process

Begins with double-stranded DNA (dsDNA) synthesis, followed by RNA synthesis (transcription) to produce mRNA from the template strand.
The other strand is the coding strand, resembling mRNA, which is then translated to synthesize proteins.

Structure of dsDNA

Characterized by a double helix structure with strands that run antiparallel and are complementary.
Contains a minor and major groove, with a diameter of 2.0 nm, 10 base pairs per helical turn, and each turn measuring 3.4 nm.

Semi-conservative Replication

During replication, each parental strand serves as a template for a new daughter strand, ensuring the preservation of genetic information.
Maintains one old strand with one new strand in each daughter duplex.

Evidence for Semi-conservative Theory

Meselson and Stahl conducted experiments using nitrogen isotopes to demonstrate that DNA replication is semi-conservative.
Their results showed the presence of hybrid DNA strands indicating old and new DNA combinations.

Implications of Mutations

One strand’s mutation affects only one daughter strand; thus, the two new duplexes can differ, potentially leading to cell death if the mutation is severe.
Mutations can alter protein products or have no effect at all, as seen in silent mutations, where the amino acid remains unchanged.

Types of Mutations

Silent Mutation: No effect on protein product; same amino acid produced despite the base change.
Mis-sense Mutation: Results in a different amino acid, altering the protein structure.
Nonsense Mutation: Introduces a premature stop codon, terminating protein synthesis early.

Effects of Regulatory Sequence Mutations

Can lead to excessive or insufficient transcription of genes, affecting protein levels.

Role of Mutations in Evolution

Mutations, combined with natural selection, drive evolution by favoring advantageous alleles that improve survival, leading to increased prevalence in the population.

Knockout Mutation

Causes a gene to be non-functional, resulting in the absence of the associated protein.

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Description

This quiz focuses on the fundamental functions of DNA, including its roles in storing information, replication, and mutation. Each flashcard prompts users to explore how these functions relate to DNA's physical structure and sequences. Dive deep into the molecular basis of genetics with these engaging questions!