Gene Regulation and Control Mechanisms

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Questions and Answers

What is the consequence of a nonsense mutation?

It always leads to the production of a longer protein.

It results in a protein that is truncated at the stop codon. (correct)

It introduces a new amino acid into the protein sequence.

It has no effect on protein translation.

Which condition is associated with the inability to synthesize ß globin?

Sickle cell anemia

Cystic fibrosis

Beta thalassemia (correct)

Amyotrophic lateral sclerosis (ALS)

What occurs during a frameshift mutation?

Chromosome segments are exchanged between homologous chromosomes.

A point mutation replaces one base with another.

One or more nucleotides are added or deleted. (correct)

A segment of DNA is duplicated.

What defines translocation in genetics?

A chromosome loses a segment and another gains it. Signup and view all the answers

Which mutation results from the removal of nucleotides from the DNA sequence?

Deletion Signup and view all the answers

Which of the following mutations does NOT alter the reading frame?

Substitution Signup and view all the answers

What is the role of transcription factors in gene regulation?

They bind to DNA and help RNA polymerase bind. Signup and view all the answers

What is typically the result of chromosomal inversions?

Genes may be disrupted or come under new control. Signup and view all the answers

Which statement about spontaneous mutations is true?

They arise from errors in the genetic machinery. Signup and view all the answers

Which type of mutation can still allow for proper protein function despite a change in DNA?

Silent mutation Signup and view all the answers

What distinguishes somatic cell mutations from gamete mutations?

Somatic mutations usually go unnoticed unless significant numbers are involved. Signup and view all the answers

What is the primary function of translational control in gene regulation?

It controls how often mRNA transcripts are translated into proteins. Signup and view all the answers

Which statement best describes chromosomal mutations?

They can involve multiple genes and larger structural changes. Signup and view all the answers

How do housekeeping genes function in relation to an organism's needs?

They are constantly produced regardless of the organism's needs. Signup and view all the answers

What type of mutation is described as a change in the base sequence that leads to a different amino acid being added during protein synthesis?

Missense mutation Signup and view all the answers

Which level of gene regulation directly involves the splicing of introns and exons?

Posttranscriptional control Signup and view all the answers

Study Notes

Control Mechanisms and Mutations

Approximately 20,000 genes code for proteins in humans.
Not all proteins are required all the time.
Examples of proteins used only when needed: insulin.
Housekeeping genes are always needed and constantly made.
Transcription factors are proteins that turn genes on when needed, binding to DNA and helping RNA polymerase bind.

Genes

Some genes are always needed and are constantly made, called housekeeping genes.
Proteins that turn genes on when needed are called transcription factors.
They bind to DNA enabling RNA polymerase to bind.

Transcription Factor

This is a diagram showing the process.

Gene Regulation

Genes can be switched on and off based on the organism's needs.
Four levels of control: transcriptional, post-transcriptional, translational, and post-translational control.

Transcriptional Control

Controls which genes are transcribed from DNA to mRNA.

Post-transcriptional Control

Controls what introns and exons are involved in mRNA splicing.

Translational Control

Controls how frequently and quickly mRNA is translated into proteins.

Post-translational Control

Controls how proteins must pass through the cell membrane to be functional which affects how quickly they become active.

Mutations

Errors in the DNA sequence that are inherited.
Mutations can have negative, positive or no effect on organisms.
Diploid organisms have two copies of each gene. If a mutation occurs in one copy, the other may compensate.

Types of Mutations

Mutations can be categorised into single-gene or chromosome mutations:
- Single gene mutations involve changes in the nucleotide sequence of one gene.
- Chromosome mutations involve changes in chromosomes, and may involve many genes.

Types of Mutations - Further Detail

Mutations in somatic cells (body cells) are usually unnoticed unless many cells are affected and not passed on to the next generation.
More serious mutations are found in gametes (sperm and egg cells). These can be passed on to offspring.
Point mutations affect a specific base pair and are also known as single-base substitutions.

Types of Point Mutations

Silent mutation: This type of mutation does not change the amino acid coded for, and therefore does not cause any phenotypic change. One example is a change from a U to a C, for example UUU and UUC both code for Phenylalanine. Usually silent mutations occur in the mRNA introns and therefore are normally removed.
Missense mutation: A change in the base sequence of DNA which changes a codon, leading to a different amino acid placed into the protein sequence. Examples include Sickle cell anemia, Cystic Fibrosis, and ALS. Missense mutations can sometimes be beneficial when making new antibodies.
Nonsense mutation: A DNA sequence change leads to a stop codon instead of an amino acid codon. During translation, only the portion of the protein before the stop codon is produced. This resulting fragment is often broken down by cell proteases (enzymes) making this mutation often lethal to the cell. These mutations, like Missense mutations, arise from substitutions.

Beta Thalassemia

Individuals with Beta Thalassemia lack the synthesis of beta-globin, a part of normal hemoglobin.
Beta globin is normally 146 amino acids long.
A mutation in the gene codes for a stop codon instead of an amino acid at position 39.
Red blood cells (RBC's) are small and rupture easily, leading to a need for multiple blood transfusions throughout the life of the patient.

Deletion Mutation

One or more nucleotides are removed from the DNA sequence. This drastically alters the protein, resulting in a defective protein.

Insertion Mutation

An additional nucleotide is placed into a DNA sequence.
Similar effects to deletions, insertion mutations can alter the reading frame, called frameshift mutations.

Translocation Mutation

At the chromosomal level, the relocation of base pairs from one part of the genome to another. This often happens between two nonhomologous chromosomes.
A segment of one chromosome breaks off and releases a fragment while a similar event happens in another chromosome.

Inversion Mutation

A chromosomal segment reverses its orientation. - There is no loss or gain of genetic material, but the gene may be disrupted.

Deletion and Duplication

Parts of a chromosome can be deleted or duplicated.
There are diagrams to visually aid these concepts.

Causes of Mutations

Some mutations are caused by errors in the genetic machinery—spontaneous mutations.
Exposure to mutagenic agents can induce mutations (e.g., UV rays, benzene, nuclear energy).

Cancer

A group of diseases characterized by abnormal cell division.
Loss of regulatory mechanisms controlling cell growth.

Cancer (specific genes):

In cancer cells, genes coding for differentiation (developing into a specific type of cell) are repressed or imperfect.
Genes coding for proliferation (cell reproduction) are often left on.
Proto-oncogenes, such as the P53 gene, are left on.
The P53 gene usually stops cell progression and rapid division.

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Description

Explore the fascinating world of gene regulation and control mechanisms in this quiz. Learn about housekeeping genes, transcription factors, and the various levels at which genes can be controlled. Test your understanding of how genes can be switched on and off in response to cellular needs.