BIOL214 E3

What is the difference between negative and positive control in gene regulation?

Negative control: uses repressors to inhibit transcription

Positive control: uses activators to enhance transcription

What does “inducible” mean in gene regulation?

The operon is usually off but can be turned on in response to a specific inducer

What makes the lac operon a negative inducible operon?

The lac repressor is active by default and inhibits transcription; lactose (inducer) inactivates it, allowing transcription

How does catabolite repression affect the lac operon?

Low glucose → high cAMP → CAP activation → enhanced transcription of the lac operon

How does the trp operon function in E. coli?

It’s a negative repressible operon. Tryptophan activates the repressor to shut off transcription when tryptophan is abundant

What role do histones and nucleosomes play in eukaryotic gene regulation?

They influence chromatin structure; condensed chromatin represses transcription, while decondensed chromatin promotes it

How do miRNAs and siRNAs regulate gene expression?

Both use the RISC complex; imperfect binding (miRNA) blocks translation, perfect binding (siRNA) leads to mRNA degradation

What is Mendel’s Principle of Segregation?

Alleles separate during gamete formation; each gamete gets one allele

What is Mendel’s Principle of Independent Assortment?

Alleles of different genes assort independently during meiosis if they are on different chromosomes

What is a test cross and why is it used?

Crossing an unknown genotype with a homozygous recessive to determine the unknown’s genotype

What is epistasis?

Interaction between genes where one gene masks or modifies the expression of another

How does incomplete dominance differ from codominance?

Incomplete dominance results in a blended phenotypes (e.g. pink flowers)

Codominance expresses both alleles equally (e.g. AB blood type)

What does a recombination frequency of 50% indicate?

Genes are either on different chromosomes or so far apart they assort independently.

What does a chi-square test measure in genetics?

It compares observed offspring ratios to expected ones to test genetic hypotheses

Who demonstrated that genes are located on chromosomes?

Thomas Hunt Morgan using fruit fly eye color mutations

What is the significance of Alfred Sturtevant’s work?

he created the first genetic map based on recombination frequencies

What was the key observation in Morgan's fruit fly experiment that suggested sex linkage?

Only males had white eyes in the F2 generation of the initial cross

What is a reciprocal cross, and why is it important?

A reciprocal cross switches the sexes of the individuals with specific traits. It helps determine if a trait is sex-linked

What is recombination frequency and how is it calculated?

Recombination frequency = (recombinants / total offspring) × 100. It indicates gene distance on a chromosome

What is the difference between autosomal and sex-linked traits?

Autosomal traits are on chromosomes 1–22; sex-linked traits are on the X or Y chromosomes

What is the Hardy-Weinberg principle used for?

To predict allele and genotype frequencies in a non-evolving population

What are the 5 conditions required for Hardy-Weinberg equilibrium?

No mutation, no migration, no selection, random mating, and large population size

What is the Hardy-Weinberg equation?

p² + 2pq + q² = 1

where p and q are allele frequencies

Define genetic drift

Random changes in allele frequency, more impactful in small populations

What is gene flow?

Movement of alleles between populations, which increases genetic similarity

Why is mutation considered the ultimate source of genetic variation?

It introduces new alleles into a population

How is a chi-square test used in population genetics?

To determine if observed genotype frequencies deviate from expected Hardy-Weinberg values

Prokaryotes, Eukaryotes, or Both: Transcription occurs in cytosol

Prokaryotes; they lack a defined nucleus

Prokaryotes, Eukaryotes, or Both:

Transcription and translation can occur simultaneously

Prokaryotes; their lack of a nucleus allows for this process to happen at the same time

Prokaryotes, Eukaryotes, or Both:

Transcription occurs in the nucleus

Eukaryotes; they have a defined nucleus where transcription takes place

Prokaryotes, Eukaryotes, or Both:

RNA processing occurs before translation

Eukaryotes; they undergo RNA processing, including splicing and modification of the mRNA, before translation can occur

Prokaryotes, Eukaryotes, or Both:

Additional proteins assist binding of RNA polymerase

Both; some transcription factors are required in both to assist in the binding of RNA polymerase to the promoter region

Prokaryotes, Eukaryotes, or Both:

Contains promoter regions

Both; they both have promoter regions that are essential for the initiation of transcription by RNA polymerase