Mutations in Genetics

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Questions and Answers

What is a mutation that involves the addition of an extra nucleotide into a DNA sequence called?

Point mutation

Insertion (correct)

Deletion

Substitution

What major effect can a frame shift caused by an insertion or deletion mutation have on protein synthesis?

Creates additional amino acids without altering their sequence

Causes premature termination of the polypeptide chain (correct)

Results in the same primary protein structure

Increases the production of enzymes

What type of mutation occurs when there is a loss of a nucleotide from the normal DNA sequence?

Duplication

Translocation

Deletion (correct)

Insertion

From which cells can mutations be inherited to the next generation?

Gametes Signup and view all the answers

What term describes changes in the structure or number of whole chromosomes?

Chromosome mutations Signup and view all the answers

What effect can an insertion of three nucleotides have on the resulting protein?

May alter the tertiary structure of the protein Signup and view all the answers

What role do DELLA proteins play in seed germination?

They inhibit transcription factors and maintain seed dormancy. Signup and view all the answers

How does oestrogen affect gene expression?

By interacting with transcription factors and modifying protein shapes. Signup and view all the answers

Which characteristic of organisms is an example of continuous variation?

Height in humans. Signup and view all the answers

What initiates the breakdown of DELLA proteins in the context of gibberellins?

Gibberellins binding to the GID 1 receptor. Signup and view all the answers

Which of the following best explains gene mutations?

They are changes in the DNA sequence which can be inherited if in reproductive tissues. Signup and view all the answers

How are characteristics showing discontinuous variation typically controlled?

By few or often a single gene. Signup and view all the answers

What is the primary effect of cystic fibrosis on mucus production?

The mucus becomes stickier than usual. Signup and view all the answers

What type of mutation results in the premature termination of a polypeptide chain?

Nonsense mutation Signup and view all the answers

What is the result of a mis-sense mutation?

Another amino acid is produced in place of the original. Signup and view all the answers

How does sickle cell anemia affect red blood cells?

It alters their shape to be crescent-shaped. Signup and view all the answers

Why do dominant alleles normally not spread in populations?

People with them often do not reproduce. Signup and view all the answers

What happens when the repeat sequence CAG in the huntingtin gene is mutated?

There are excessive repeats of glutamine in the protein. Signup and view all the answers

What is a characteristic of repressible enzymes?

Their production is continuously active. Signup and view all the answers

What role do allosteric sites play in enzyme regulation?

They allow binding of substances that regulate enzyme production. Signup and view all the answers

What is the role of the repressor protein in the lac operon system when lactose is absent?

It binds to the operator, blocking transcription. Signup and view all the answers

What happens to the repressor protein when lactose is present in the medium?

It undergoes a structural change that allows RNA polymerase to attach. Signup and view all the answers

Which enzyme hydrolyzes lactose into glucose and galactose?

Beta-galactosidase Signup and view all the answers

Which genes are involved in the production of lactose permease and beta-galactosidase?

Gene Y and Gene Z Signup and view all the answers

What is the purpose of the transcription factors in eukaryotic cells?

They assist RNA polymerase in binding to DNA for transcription. Signup and view all the answers

Which component of the lac operon is responsible for switching the structural genes on and off?

Operator Signup and view all the answers

Why does E. coli only express the genes for lactose metabolism when lactose is available?

To conserve energy and resources. Signup and view all the answers

Which of the following statements regarding the lac operon is true?

The lac operon consists of structural genes, an operator, and a promoter. Signup and view all the answers

What is the primary function of lactose permease in E. coli?

It acts as a transport protein for lactose uptake. Signup and view all the answers

What happens when the primary repressor protein binds to the operator?

Transcription of the structural genes stops. Signup and view all the answers

Study Notes

Mutations

Mutations are changes in the DNA sequence of an organism.
Mutations in body cells are not heritable.
Mutations during gamete formation can be inherited, leading to differences between individuals.
Chromosome mutations involve changes in chromosome structure or number.
Gene mutations (point mutations) affect a single gene locus, creating different alleles.

Gene Mutations: Insertions

Insertion mutations add extra nucleotides to the DNA sequence.
This shifts the reading frame (triplet code) during translation, altering amino acid sequences in the protein.
Frame shifts can create premature STOP codons, resulting in shorter, non-functional polypeptide chains.
This can disrupt biochemical pathways and have detrimental effects on the organism.
Insertions of multiples of three nucleotides do not cause a frame shift but can still affect tertiary protein structure.

Gene Mutations: Deletions

Deletion mutations remove nucleotides from the DNA sequence.
This also shifts the reading frame, altering the amino acid sequence of the protein.
Deletions often result in non-functional proteins and disrupt biochemical pathways.
Cystic fibrosis is an example of a genetic disorder caused by a deletion mutation.

Gene Mutations: Substitutions

Substitution mutations replace one nucleotide with another.
Three types of substitution mutations exist:
- Nonsense mutations: result in a STOP codon, creating a shorter, non-functional protein.
- Missense mutations: result in a different amino acid being coded for. This can change a protein's function. (e.g., sickle cell anemia)
- Silent mutations: result in the same amino acid being coded for, with no apparent effect on the polypeptide.

Huntington's Disease

Huntington's disease is a dominant genetic disorder.
It results in a progressive deterioration of brain cells.
Symptoms appear after age 30.
The huntingtin gene (HTT) on chromosome 4 codes for a protein with many repeats of the amino acid glutamine.
An increased number of CAG repeats in the HTT gene leads to more glutamine repeats in the protein, causing the disease.
The more repeats, the earlier and more severe the symptoms.

Control of Protein Synthesis

Repressible enzymes are produced continuously but their production can decrease when the product of the reaction increases.
Inducible enzymes are produced only when needed, triggered by the presence of a specific molecule (e.g. substrate).
Lac operon in E.coli controls inducible enzymes involved in lactose metabolism:
- Structural genes: code for enzymes necessary for lactose metabolism
- Operator: regulates the expression of structural genes
- Promoter: where RNA polymerase binds
- Regulatory gene: codes for a repressor protein
- Repressor protein binds to operator when no lactose is present, blocking RNA polymerase from transcribing structural genes
- Lactose converts to allolactose, which binds to the repressor protein, changing its shape and allowing RNA polymerase to bind, triggering transcription of structural genes.
Eukaryotic transcription involves transcription factors that bind to promoter or enhancer regions, initiating transcription.
Oestrogen is an extracellular factor, binding to oestrogen receptor (ER), creating an initiation complex
Gibberellins are plant growth regulators that break down DELLA proteins, activating transcription factors involved in germination.

Variation

Phenotypic variation can be classified into continuous and discontinuous.
Continuous variation involves a range of phenotypes without distinct classes (e.g., height, mass).
Continuous variation is controlled by many genes (polygenes) and influenced by the environment.
Discontinuous variation involves distinct phenotype classes with little overlap (e.g., blood types, some genetic diseases).
Discontinuous variation is typically controlled by a few genes.
Genetic variation results from mutations in reproductive tissues, crossing over during meiosis, random assortment of chromosomes, random mating, and random fusion of gametes.
Environmental factors influence genetic expression in many species. (e.g., arctic foxes, Siamese cats)

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Description

Explore the world of mutations and their impact on genetics. This quiz covers types of mutations, including gene insertions and deletions, and their effects on protein synthesis and organism traits. Test your understanding of how these genetic changes can lead to variations among individuals.