genetic mechanisms and evolution in biology: genes,mutations, and phylogenetics

What is a mutation within a gene?

A change in the nucleotide sequence of a gene that alters its coding region, potentially modifying the protein's amino acid sequence or function.

How does a mutation in regulatory DNA affect gene expression?

It alters when, where, and how much a gene is expressed without changing the gene itself.

What occurs during gene duplication and divergence?

A gene is duplicated, producing two copies that may accumulate mutations and diverge in function over time.

What is exon shuffling?

The recombination of exons from different genes, creating new hybrid genes with novel protein domain combinations.

What is transposition in genetics?

The movement of mobile genetic elements (transposons) within the genome, which can disrupt gene function or alter regulation.

What is horizontal gene transfer?

The direct transfer of genetic material between different organisms, commonly seen in bacteria, introducing new genes.

What are germ-line cells?

Cells that give rise to gametes (sperm and egg) and are responsible for passing genetic information to the next generation.

What are somatic cells?

Non-reproductive cells that make up the body's tissues and organs but do not transmit genetic information to offspring.

What is the consequence of mutations in germ-line cells?

They can be inherited by the next generation and contribute to genetic variation and evolution.

What is the consequence of mutations in somatic cells?

They affect only the individual and cannot be passed to offspring, often leading to diseases like cancer.

What is a point mutation?

A mutation caused by a change in a single nucleotide, which can affect gene function.

How can mutation rates be measured?

By using large bacterial populations, such as E. coli, and counting rare revertant colonies that restore function.

What is the significance of lactose tolerance in humans?

It evolved due to natural selection after cattle domestication, allowing some adults to digest lactose into adulthood.

What mutations allowed for lactase persistence?

Two independent point mutations in regulatory DNA that kept the lactase gene active in adults.

What selective advantage did lactose tolerance provide?

It offered a nutritional benefit in societies that raised cattle, enhancing survival and reproductive success.

What regions show high lactose tolerance?

Northern Europe, parts of Africa, and among pastoralist groups.

What regions show low lactose tolerance?

East Asia, Native American, and Indigenous Australian populations, where milk consumption was historically rare.

What is the role of mutations in evolution?

Mutations generate genetic variation, which is essential for adaptation and evolutionary change across all life forms.

What happens to a zygote formed from a germ-line mutation?

The zygote and all its cells will carry the mutation, affecting both germ-line and somatic cells.

What is the difference between heritable and non-heritable mutations?

Heritable mutations occur in germ-line cells and can be passed to offspring, while non-heritable mutations occur in somatic cells and affect only the individual.

What is the impact of somatic mutations on an individual?

They can lead to serious consequences, such as cancer, due to the accumulation of mutations in body cells.

What is the significance of the E. coli experiment in understanding mutations?

It demonstrates that mutations are random events and can be quantified in large populations.

What is the primary function of germ-line cells?

To ensure the continuity of genetic information across generations through gamete production.

How do mutations contribute to genetic disorders?

Germ-line mutations can lead to heritable genetic disorders passed to offspring.

What is the relationship between mutations and adaptation?

Mutations create genetic diversity, which is the raw material for natural selection and adaptation to changing environments.

What is lactose tolerance in adults an example of?

Recent human evolution driven by dietary adaptation and cultural practices like cattle domestication.

How does gene duplication occur?

Through unequal crossing-over between short repetitive DNA sequences on homologous chromosomes.

What happens during misalignment of homologous chromosomes?

They can pair incorrectly at non-identical repeated sequences during meiosis.

What is the outcome of unequal crossing-over?

One chromosome receives a duplicated gene while the other loses the gene entirely.

What is the significance of gene duplications and deletions?

They are a major source of genetic variation and genome evolution.

Which primate is most closely related to humans?

Chimpanzees, sharing the most recent common ancestor.

What is the estimated DNA sequence difference between humans and chimpanzees?

About 1.2%.

When did humans and chimpanzees diverge from a common ancestor?

Approximately 5-7 million years ago.

What is leptin and what does it regulate?

Leptin is a hormone that regulates appetite and metabolism.

How many nucleotide differences exist in the leptin gene between humans and chimpanzees?

Five nucleotides, with four being silent mutations.

What does the conservation of the exon region in the leptin gene indicate?

It reflects strong evolutionary pressure to maintain the protein's function.

What is a retrotransposon?

A mobile genetic element that moves within the genome through an RNA intermediate.

How do retroviruses reproduce?

By hijacking a host cell's machinery to replicate and synthesize proteins.

What is the process of reverse transcription in retroviruses?

The conversion of viral RNA into DNA by the enzyme reverse transcriptase.

What happens to the viral DNA after reverse transcription?

It integrates into the host's chromosome, becoming a permanent part of the cell's genome.

What is the role of the host's RNA polymerase in retroviral replication?

It transcribes the integrated viral DNA to produce new viral RNAs.

What are mobile genetic elements and their significance?

They are sequences that can move within the genome, contributing to genetic diversity.

What is the significance of conserved genetic sequences across species?

They allow tracing of evolutionary relationships and highlight essential functions.

What is the role of the small ribosomal subunit rRNA gene in evolutionary studies?

It provides insights into the conservation of genetic information across distantly related species.

What are silent mutations?

Mutations that do not change the amino acid sequence of a protein.

What is the difference between exons and introns in genes?

Exons are coding regions that are conserved, while introns are noncoding regions that accumulate mutations.

What is the evolutionary significance of gene duplications?

They allow duplicated genes to diverge and acquire new functions over time.

What is the relationship between dietary adaptation and genetic evolution?

Dietary changes can drive genetic adaptations, such as lactose tolerance in adults.

What does the phylogenetic tree illustrate about primate evolution?

It shows the evolutionary relationships among modern primates, indicating closeness of humans to chimpanzees.

How do mutations accumulate after species diverge from a common ancestor?

Mutations occur independently in each lineage, leading to genetic differences.

What is the role of repetitive DNA sequences in gene duplication?

They flank genes and can misalign during meiosis, leading to unequal crossing-over.