Exam 3 Review

What are the key differences between sexual and asexual reproduction?

Sexual reproduction promotes genetic diversity but requires significant resources, while asexual reproduction is energy-efficient but produces genetically identical offspring.

What is the purpose of meiosis?

Meiosis reduces chromosome number from diploid (2N) to haploid (N) and introduces genetic diversity through crossing over and independent assortment.

What happens during Prophase I of meiosis?

Homologous chromosomes are tightly held together at the synaptonemal complex, the chromosomes begin to condense, and crossing over occurs at chiasmata.

What is independent assortment in meiosis?

Independent assortment occurs when maternal and paternal chromosomes orient randomly during Metaphase I and migrate to poles.

What is crossing over and when does it occur?

Crossing over is the exchange of genetic material between homologous chromatids that occurs during Prophase I.

What are the stages of meiosis?

Meiosis I (Reductional Division) and Meiosis II (Equational Division).

What does Mendel's Principle of Segregation state?

Each organism carries two alleles per gene, which separate during gamete formation.

What is a monohybrid cross?

A breeding experiment that examines the inheritance of one trait, resulting in a 3:1 phenotypic ratio.

What is an example of codominance?

The AB blood type, where both A and B alleles are fully expressed.

What is pleiotropy?

A single gene affects multiple traits, such as in Marfan syndrome.

What does nondisjunction lead to?

Nondisjunction can lead to monosomy (missing one chromosome) or trisomy (extra chromosome), such as Down syndrome.

What is the significance of telomeres?

Telomeres are nucleotide sequences at the ends of eukaryotic chromosomes that prevent chromosomal shortening during replication.

What is the role of RNA polymerase in transcription?

RNA polymerase binds to promoters and synthesizes mRNA during transcription.

What does the genetic code consist of?

The genetic code is written for mRNA and consists of triplet codons that code for specific amino acids.

What are introns and exons?

Introns do not code for amino acids, while exons do; introns are removed during mRNA splicing.

What is the function of spliceosomes?

Spliceosomes are complexes that remove introns and join exons during pre-mRNA processing.

What is a silent mutation?

A mutation that changes a codon but does not affect the amino acid sequence of the protein.

What is a missense mutation?

A mutation that causes a change in an amino acid in a protein, which may or may not affect its function.

What is a nonsense mutation?

A mutation that changes a codon to a stop codon, potentially leading to a truncated, nonfunctional protein.

What are frameshift mutations?

Mutations caused by insertions or deletions of nucleotides, which shift the reading frame and alter the downstream amino acid sequence.

What did Griffith's experiment demonstrate?

Griffith's experiment showed that a 'transforming principle' from dead bacteria could change non-virulent bacteria into virulent forms.

What is the function of helicase in DNA replication?

Helicase unwinds the DNA strands, separating them to allow replication.

What is the Meselson and Stahl experiment?

An experiment that demonstrated that DNA replication is semi-conservative by tracking DNA densities.

What is the role of telomerase?

Telomerase is an enzyme that lengthens telomeres and prevents chromosome shortening during cell division.

What is the significance of the Barr body?

A Barr body is an inactivated X chromosome in females, which prevents overexpression of X-linked genes.

What does

The genetic code is redundant, meaning multiple codons can code for the same amino acid.

What are linked genes?

Genes that are located on the same chromosome and are usually inherited together.

What is an allele?

Different versions of a gene that may produce varying traits in an organism.

What does the term locus refer to?

The specific location of a gene on a chromosome.

What is the purpose of a testcross?

A testcross is used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

What is genetic variation and how is it introduced?

Genetic variation is introduced through processes like crossing over and independent assortment during meiosis.

What are the effects of mutations?

Mutations can lead to changes in protein structure and function, potentially causing genetic disorders.

How do eukaryotic and prokaryotic gene expression differ?

In eukaryotes, transcription and translation occur separately; in prokaryotes, they happen simultaneously.

What regularities did Mendel establish regarding inheritance?

Mendel established principles such as segregation of alleles and independent assortment of genes.

What are the three stages of transcription?

Initiation, elongation, and termination.

What is the function of topoisomerase during DNA replication?

Topoisomerase relieves the tension in the DNA strand caused by unwinding.

What change occurs in chromosomes during crossing over?

Segments of homologous chromosomes are exchanged, creating recombinant chromosomes.

What is alternative splicing?

A process that allows a single gene to produce multiple proteins by removing different combinations of introns.

What does the 5’ cap do?

The 5’ cap protects mRNA and aids in ribosome attachment during translation.

What changes can lead to a frameshift mutation?

Insertion or deletion of nucleotides in a DNA sequence that shifts the reading frame.

What is an example of a condition caused by trisomy?

Down syndrome, which is caused by the presence of an extra chromosome 21.

What is the difference between a monosomic and a trisomic zygote?

A monosomic zygote has one less chromosome than normal, while a trisomic zygote has one extra chromosome.

What is the role of ligase during DNA replication?

Ligase joins Okazaki fragments on the lagging strand to create a continuous DNA strand.

What is the significance of Chargaff's rules?

Chargaff's rules state that the amount of adenine equals thymine and the amount of cytosine equals guanine in DNA.

What was the conclusion of Morgan's experiment with fruit flies?

Morgan concluded that the gene for eye color is located on the X chromosome, as demonstrated by the inheritance of red and white eyes.

How does gene expression differ in prokaryotes and eukaryotes?

In prokaryotes, transcription and translation occur simultaneously, whereas in eukaryotes, they are separated by the nuclear membrane.

What do mutations in oncogenes signify?

Mutations in oncogenes can lead to uncontrolled cell division and cancer.

What is a translocation mutation?

A mutation that involves a segment of DNA being moved to a non-homologous chromosome.

What function do ribosomes serve in translation?

Ribosomes translate mRNA codons into amino acids, helping to assemble proteins.

What happens to chromosomes during Telophase I of meiosis?

Haploid cells are formed, each containing duplicated chromosomes.

What does the term 'polygenic inheritance' mean?

Polygenic inheritance refers to traits that are influenced by multiple genes, such as height and skin color.

What can lead to epistasis in genetics?

Epistasis occurs when one gene modifies the expression of another gene, potentially masking its effects.

What is the primary function of tRNA in translation?

tRNA transports amino acids to the ribosome and matches them with corresponding mRNA codons.

What are the key products of meiosis?

Meiosis produces four genetically unique haploid daughter cells.

What is the significance of protein synthesis?

Protein synthesis is crucial for the function and structure of cells and organisms, affecting overall phenotype.

What defines a genetic disorder?

A genetic disorder is a health condition caused by abnormalities in genes or chromosomes.

What is the primary function of DNA polymerase?

DNA polymerase synthesizes new DNA strands by adding nucleotides complementary to the template strand.

What is Down syndrome an example of?

Down syndrome is an example of a genetic condition caused by trisomy, specifically trisomy 21.

What is a characteristic of Mendelian inheritance?

Mendelian inheritance is characterized by discrete inheritance patterns, such as dominant and recessive traits.

What impact do mutations have in evolution?

Mutations can introduce new genetic variations that can enhance adaptation and evolution.

What components are essential for DNA replication?

Key components include DNA polymerase, helicase, primase, ligase, and a template strand.

What role does the poly-A tail play after transcription?

The poly-A tail facilitates the export of mRNA out of the nucleus and protects it from degradation.

What are homologous chromosomes?

Homologous chromosomes are pairs of chromosomes containing the same genes, but possibly different alleles from each parent.

How does a deletion mutation affect genes?

A deletion mutation results in the loss of a segment of DNA, which can disrupt the coding sequence and cause functional changes.

What does the term 'dominance' refer to in genetics?

Dominance refers to the relationship between alleles where one allele masks the effect of another in determining a phenotype.

What is the structure of a nucleotide?

A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.

What is the function of spliceosomes?

Spliceosomes are responsible for removing introns from pre-mRNA and joining exons to form mature mRNA.

What is the main significance of the ribosomal sites (A, P, E)?

These sites are functional areas in the ribosome where tRNA molecules bind during translation, facilitating polypeptide synthesis.

What is the role of a release factor in translation termination?

A release factor binds to the stop codon in the ribosome, leading to the release of the newly synthesized polypeptide chain.

How does independent assortment contribute to genetic diversity?

Independent assortment allows for the random distribution of maternal and paternal chromosomes to gametes, leading to variation.

What is the significance of the TATA box in transcription?

The TATA box is a DNA sequence that indicates where a sequence can be read and decoded, playing an essential role in initiation of transcription.

What does it mean if a mutation is 'silent'?

A silent mutation means that despite a change in the DNA sequence, there is no change in the resultant amino acid or protein.

What do frameshift mutations commonly cause?

Frameshift mutations commonly result in significant changes to the protein synthesized due to alteration in the reading frame.

What is the central dogma of molecular biology?

The central dogma states that genetic information flows from DNA to RNA to protein.

What are two examples of non-Mendelian inheritance patterns?

Examples of non-Mendelian inheritance include codominance and incomplete dominance.

What is the function of genetic operators?

Genetic operators control the transcription of genes, often responding to environmental conditions.

What is an insertion mutation?

An insertion mutation occurs when one or more nucleotide pairs are added to a DNA sequence, potentially disrupting gene function.

What is the primary role of messenger RNA (mRNA)?

mRNA carries the genetic information from DNA to the ribosome, where it is translated into protein.

In what ways can mutations be beneficial?

Beneficial mutations can provide advantages, such as increased resistance to disease or improved adaptability to environments.

What is genetic mapping?

Genetic mapping is the process of locating genes on a chromosome and determining their distances from one another.

What are the roles of the different types of RNA in protein synthesis?

mRNA carries genetic information, tRNA brings amino acids, and rRNA forms the core of ribosomes.

How do environmental factors influence gene expression?

Environmental factors can lead to changes in gene expression through mechanisms such as epigenetics.

What condition does aneuploidy lead to in humans?

Aneuploidy can lead to conditions such as Down syndrome, Turner syndrome, or Klinefelter syndrome.

How does a point mutation affect protein synthesis?

A point mutation may change one amino acid in a protein, potentially altering its function, or it may have no effect.