BIO121 Exam 2

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What occurs during Meiosis I that reduces ploidy?

The segregation of homologous chromosomes reduces the chromosome number from diploid (2n) to haploid (n).

What is the significance of Crossing Over in genetic variation during meiosis?

Crossing Over leads to new combinations of alleles on chromatids by exchanging segments of DNA.

How does Independent Assortment contribute to genetic variation?

Independent Assortment occurs when homologous pairs orient randomly during Metaphase I, leading to different combinations of maternal and paternal chromosomes.

What does Mendel's Principle of Segregation state?

During Anaphase I, homologous chromosomes separate, ensuring each gamete receives only one allele for a gene.

What is a Punnett Square used for?

A Punnett Square is used to predict the genotype and phenotype frequencies of offspring from parental gametes.

How do mutations impact gene structure and function?

Mutations can alter the DNA sequence, affecting protein structure and function, with varying impacts ranging from silent to frameshift mutations.

How can a mutation in the DNA coding strand lead to a Silent Mutation?

A silent mutation involves a nucleotide change that does not alter the amino acid sequence due to the degeneracy of the genetic code.

What characterizes X-linked traits compared to autosomal traits?

X-linked traits show different inheritance patterns in males and females, while autosomal traits affect both sexes equally.

What happens if the G1 phase is improperly regulated?

If G1 is prolonged or checkpoints are bypassed, cells may not enter S phase or may replicate uncontrollably, leading to cancer.

What is the Central Dogma of molecular biology?

The Central Dogma describes the flow of genetic information from DNA to RNA (transcription) and from RNA to protein (translation).

What role do proto-oncogenes play in cancer?

Mutations in proto-oncogenes can transform them into oncogenes, promoting inappropriate cell division and contributing to cancer.

Why are older individuals more susceptible to cancer?

Older individuals have accumulated mutations over their lifetime, increasing the likelihood of developing cancerous cells due to more opportunities for errors in cell division.

What is the consequence of a frameshift mutation?

A frameshift mutation alters the reading frame of mRNA, leading to a completely different amino acid sequence and typically the production of a non-functional protein.

What is the outcome when E. coli is exposed to an antibiotic in a culture?

The antibiotic will initially inhibit growth, but over generations, resistant bacteria may proliferate, leading to an increased minimum inhibitory concentration (MIC) of the antibiotic.

How do mutations contribute to heritable genetic variation?

Mutations introduce new alleles into the gene pool, providing the raw material for evolution and potential adaptations through natural selection.

What is the end product of Meiosis II in humans?

Four haploid gamete cells with unique genetic combinations.

What does Mendel's Principle of Independent Assortment state?

Alleles for different genes segregate independently of each other during gamete formation.

What is the difference between a missense and a nonsense mutation?

A missense mutation results in a different amino acid, while a nonsense mutation results in a premature stop codon.

What is the function of tumor suppressor genes?

Tumor suppressor genes regulate cell division by detecting DNA damage and initiating repair or apoptosis, thus preventing uncontrolled cell growth.

Which types of RNA are essential for protein synthesis?

Messenger RNA (mRNA), Transfer RNA (tRNA), and Ribosomal RNA (rRNA).

Why are X-linked recessive disorders more prevalent in males?

Males have only one X chromosome, so a single recessive allele on it will express the trait, whereas females need two copies (one on each X chromosome) to express it.

How does natural selection drive the evolution of antibiotic resistance in bacteria?

Antibiotics act as a selective pressure, favoring the survival and reproduction of bacteria with pre-existing resistance mutations, leading to a resistant population.

What is synapsis in Meiosis I?

Synapsis is the pairing of homologous chromosomes to form bivalents (or tetrads) during Prophase I of meiosis.

What are alleles?

Alleles are different forms of a gene, occupying the same locus on homologous chromosomes.

Define homozygous and heterozygous.

An individual is homozygous if they have two identical alleles for a particular gene (e.g., $AA$ or $aa$), and heterozygous if they have two different alleles (e.g., $Aa$).

What is a point mutation?

A point mutation is a type of gene mutation where a single nucleotide base is changed, inserted, or deleted from a DNA or RNA sequence.

What is the difference between a somatic mutation and a germline mutation?

A somatic mutation occurs in non-reproductive cells and is not passed to offspring, while a germline mutation occurs in gametes (sperm/egg) and is heritable.

What is the primary role of cell cycle checkpoints?

Cell cycle checkpoints are control points that monitor the cell cycle for DNA damage and proper chromosome duplication, ensuring orderly progression and preventing uncontrolled division.

What is the G0 phase of the cell cycle?

The G0 phase is a non-dividing state where cells exit the cell cycle and cease proliferation, often reversibly, due to differentiation or resource limitations.

Where does transcription primarily occur in eukaryotic cells?

Transcription primarily occurs in the nucleus of eukaryotic cells.

Where does translation primarily occur in eukaryotic cells?

Translation primarily occurs on ribosomes in the cytoplasm of eukaryotic cells.

What is the genetic code?

The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins (amino acid sequences) by living cells.

Why can females be carriers of X-linked recessive traits without expressing the phenotype?

Females have two X chromosomes; if one carries a recessive allele for a trait, the other X chromosome often carries a dominant, functional allele that masks the recessive one, making her a carrier.

What is an adaptation in an evolutionary context?

An adaptation is a heritable trait that helps an organism survive and reproduce in its environment.

What is a selective pressure in natural selection?

A selective pressure is any environmental factor or