GEN GQ1

1. Law of Segregation - Each organism has two alleles for a trait, and these alleles separate during gamete formation.

2. Law of Independent Assortment - Genes for different traits assort independently during gamete formation.

3. Law of Dominance - Some alleles are dominant over others, determining the observed trait in heterozygous individuals.

1. What are the fundamental laws of inheritance described by Gregor Mendel?

-Dominant traits: Require only one dominant allele to be expressed (e.g., brown eyes).
-Recessive traits: Require two copies of the recessive allele to be expressed (e.g., blue eyes).

2. How do dominant and recessive traits differ in terms of inheritance? Provide examples of each.

-Genotype is the genetic makeup of an organism (e.g., Bb for brown eyes).
-Phenotype is the physical expression of a trait (e.g., brown eyes). They relate to Mendelian inheritance as genotype determines phenotype.

3. What is the difference between genotype and phenotype, and how do they relate to Mendelian inheritance?

A Punnett square is a diagram used to predict the probability of offspring inheriting particular traits by displaying all possible genetic combinations from parental alleles.

4. What is a Punnett square, and how is it used to predict the probability of offspring inheriting particular traits?

-Homozygous individuals: Have two identical alleles for a trait (AA or aa)
Heterozygous individuals: Have two different alleles (Aa).
-This affects inheritance, as homozygous recessive individuals express recessive traits, while heterozygous individuals express the dominant trait.

5. What are the key differences between homozygous and heterozygous alleles? How do they affect the inheritance of traits?

Mendel's Law of Segregation states that allele pairs separate during gamete formation, ensuring that each gamete carries only one allele for each gene.

6. What is Mendel's law of segregation, and how does it explain the separation of alleles during gamete formation?

Genes for different traits assort independently of one another during gamete formation, contributing to genetic variation in offspring.

7. How does Mendel's law of independent assortment contribute to genetic variation in offspring?

A form of inheritance where neither allele is completely dominant, resulting in a blended phenotype (e.g., red and white flowers producing pink offspring).

8. How does incomplete dominance differ from complete dominance in terms of phenotype expression?

A genetic scenario where both alleles in a heterozygous organism are fully expressed (e.g., AB blood type, where both A and B antigens are present).

9. What is codominance, and how does it result in the expression of both alleles in a heterozygous organism?

Traits controlled by multiple genes, resulting in a wide range of phenotypes (e.g., skin color, height), unlike single-gene traits, which follow Mendelian inheritance.

10. What are polygenic traits, and how do they differ from single-gene traits in terms of inheritance?

A chromosome is made of DNA and proteins, tightly coiled to fit within the cell nucleus. It contains genes, the units of heredity.

11. What is the structure of a chromosome, and how is genetic material organized within it?

-Autosomes are non-sex chromosomes (pairs 1-22 in humans)
-Sex chromosomes (X and Y) determine an organism's sex and influence sex-linked traits.

12. What is the difference between autosomes and sex chromosomes, and how do they relate to the inheritance of traits?

Meiosis reduces chromosome number by half, producing genetically diverse gametes through recombination and independent assortment. Crossing over occurs during Prophase I, where homologous chromosomes exchange genetic material, increasing genetic variation.

13. What is the role of meiosis in chromosomal inheritance, and how does it ensure genetic diversity in offspring? Explain the process of crossing over during meiosis

The failure of chromosomes to separate properly during meiosis, leading to an abnormal chromosome number. This can cause disorders like Down syndrome (trisomy 21), where an individual has an extra chromosome 21.

14. What is non-disjunction, and how can it lead to genetic disorders such as Down syndrome?

Traits carried on the X or Y chromosome affect males and females differently. Males (XY) are more likely to express X-linked recessive traits (e.g., hemophilia) since they have only one X chromosome.

15. How does the presence of sex-linked genes on the X and Y chromosomes affect inheritance patterns, particularly in males and females?

In females (XX), one X chromosome is randomly inactivated in each cell to prevent an excess of X-linked gene expression, forming a Barr body.

16. What is X-inactivation, and how does it affect the expression of X-linked traits in females?

Traits on the Y chromosome (e.g., male sex determination via the SRY gene) are passed only from father to son, as females do not inherit a Y chromosome.

17. How does the inheritance of traits on the Y chromosome differ from those on the X chromosome, particularly with regard to male inheritance patterns?

-Deletions (loss of a gene segment)
-Duplications (extra gene copies)
-Inversions (reversed gene segments)
-Translocations (gene segments swap between non-homologous chromosomes).
-These mutations can alter gene expression and inheritance.

18. How do chromosomal mutations, such as deletions, duplications, inversions, and translocations, affect gene expression and inheritance?

A visual representation of an individual's chromosomes, used to detect abnormalities like extra or missing chromosomes (e.g., trisomy 21 in Down syndrome).

19. What is a karyotype, and how can it be used to identify chromosomal abnormalities in individuals?

Disorders like Turner syndrome (XO, missing an X chromosome) and Klinefelter syndrome (XXY, an extra X chromosome) result from chromosomal abnormalities, affecting development and fertility.

20. How does the study of chromosomal principles help explain the inheritance of genetic disorders like Turner syndrome or Klinefelter syndrome?

-Karyotyping provides a complete chromosome set visualization,
-G-banding helps identify structural variations
-fluorescence in situ hybridization (FISH) detects specific DNA sequences
-genomic hybridization (CGH) compares DNA content between samples.

What are the key cytological techniques used to study chromosomes, and how do they differ in their applications?

FISH uses fluorescent probes to bind specific DNA sequences, allowing detection of chromosomal abnormalities like deletions, duplications, and translocations, aiding in genetic disorder diagnosis.

How does fluorescence in situ hybridization (FISH) help in detecting chromosomal abnormalities?

Karyotyping helps detect chromosomal abnormalities in genetic disorders, prenatal testing, and cancer research by analyzing chromosome number and structure.

What is the significance of karyotyping in clinical and research settings?

G-banding stains chromosomes with Giemsa dye, producing distinct banding patterns that help identify structural chromosome variations such as deletions, duplications, and translocations.

How does G-banding technique aid in identifying structural chromosome variations?

-autopolyploidy (multiple chromosome sets from the same species)
-allopolyploidy (chromosome sets from different species).
-It occurs through errors in meiosis, fertilization, or hybridization.

What are the different types of polyploidy, and how do they occur?

Polyploidy increases genetic variation in plants, often leading to larger size and improved resilience. In animals, it is rare but occurs in some amphibians and fish. In humans, polyploidy is usually lethal.

What are the effects of polyploidy in plants, animals and humans?

Polyploidy can create reproductive barriers, leading to speciation, especially in plants, where new polyploid species can arise from hybridization.

How can polyploidy lead to speciation in certain organisms?

-Aneuploidy involves the loss or gain of individual chromosomes (e.g., trisomy or monosomy). Aneuploidy often results from nondisjunction.
-polyploidy is the gain of whole chromosome sets. Aneuploidy often results from nondisjunction.

What is the difference between aneuploidy and polyploidy, and what are the common causes of aneuploidy?

Nondisjunction occurs when chromosomes fail to separate in meiosis, leading to aneuploidy. Examples include Down syndrome (trisomy 21), Turner syndrome (X0), and Klinefelter syndrome (XXY).

How does nondisjunction contribute to aneuploidy, and what are some examples of human disorders caused by it?

A chromosome consists of chromatids, a centromere (for attachment of spindle fibers), telomeres (for stability), and chromatin (DNA-protein complex for packaging genetic material).

What are the main structural components of a chromosome, and what are their functions?

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and transcriptionally inactive, mainly involved in structural support.

How do euchromatin and heterochromatin differ in terms of structure and function?

Telomeres protect chromosome ends from deterioration and prevent fusion. Their shortening is associated with aging and cell senescence.

What is the role of telomeres in chromosome stability and aging

-Deletions: Remove genetic material, leading to missing genes and potential loss-of-function mutations.
-Duplications: Repeat genetic segments, increasing gene dosage and possibly causing overexpression.
-Inversions: Flip a chromosome segment, potentially disrupting gene regulation or function.
-Translocations: Exchange chromosome segments, which can create fusion genes or misregulate gene expression, sometimes leading to diseases like cancer.

What are the major types of chromosomal rearrangements, and how do they impact genetic function?

-Deletions remove genes, causing loss-of-function mutations
-Duplications increase gene dosage
-Inversions may disrupt gene function
-Translocations can create fusion genes.

How do deletions, duplications, inversions, and translocations affect an organism's genome and phenotype?

Genes close together on the same chromosome tend to be inherited together due to genetic linkage, reducing independent assortment.

What are the consequences of chromosomal rearrangements in human diseases, such as cancer?

Genes close together on the same chromosome tend to be inherited together due to genetic linkage, reducing independent assortment.

How does linkage affect the inheritance of genes located close together on the same chromosome?

Recombination and crossing over shuffle genetic material during meiosis, increasing genetic diversity and enabling evolution.

What is the significance of recombination and crossing over in genetic diversity?

Recombination frequency measures the likelihood of crossover events, helping geneticists determine gene distances in linkage map

How is recombination frequency used to determine genetic distances between genes?

Geneticists use chromosome mapping to locate genes by analyzing recombination rates or cytological markers.

How do geneticists use chromosome mapping to locate genes on chromosomes?

Linkage maps estimate gene distances based on recombination frequency, while cytogenetic maps use microscope analysis to visualize chromosome locations. They complement each other in gene mapping.

What is the difference between linkage maps and cytogenetic maps, and how do they complement each other in genetic studies?

Bacteria develop antibiotic resistance through mutations, horizontal gene transfer (transformation, transduction, conjugation), efflux pumps, enzymatic degradation, and target modification.

What are the major genetic mechanisms by which bacteria develop antibiotic resistance?

Bacteriophages transfer genes between bacteria via transduction, introducing genetic variation and potentially spreading antibiotic resistance genes.

How do bacteriophages contribute to bacterial evolution and gene transfer?

These bacteria resist multiple antibiotics due to gene acquisition via plasmids, mutations, and horizontal gene transfer, making infections harder to treat.

What distinguishes multi-drug-resistant bacteria from regular bacterial strains?

Bacteriophage T4 is a lytic phage that infects bacteria, injecting its DNA and hijacking the host's machinery to produce new viral particles, killing the host cell.

Describe the role of Bacteriophage T4 in bacterial genetics.

Bacteriophage Lambda can undergo both lytic and lysogenic cycles, integrating into the bacterial genome, while T4 strictly follows a lytic cycle.

How does Bacteriophage Lambda differ from Bacteriophage T4 in genetic exchange?

Point mutations, insertions, deletions, and frameshift mutations can alter gene function, potentially providing antibiotic resistance or metabolic advantages.

What types of mutations commonly occur in bacterial genes, and how do they affect bacterial survival?

Bacteria transfer genes in one direction through transformation, transduction, or conjugation, allowing for rapid adaptation and genetic diversity.

Explain the process and significance of unidirectional gene transfer in bacteria.

-transformation (uptake of free DNA)
-transduction (virus-mediated transfer)
-conjugation (direct cell-to-cell transfer).

What are the three primary mechanisms of genetic exchange in bacteria?

Bacteria incorporate foreign DNA from the environment into their genome, which can introduce new traits such as antibiotic resistance.

How does transformation allow bacteria to incorporate foreign DNA into their genome?

Transformation occurs when bacteria uptake naked DNA, influenced by:
-competence factors (cell surface proteins and transcription factors that induce DNA uptake)
-environmental conditions
-DNA availability

What is the mechanism of transformation, and what factors influence its efficiency?

Conjugation is the transfer of genetic material via direct cell contact, usually mediated by an F plasmid, enabling gene sharing among bacteria.

Explain the process of conjugation and how it facilitates gene transfer in bacterial populations.

Interrupted mating experiments determine the sequence of gene transfer, helping map bacterial genes based on their transfer times.

How can conjugation be used to map genes in E. coli?

-Plasmids are small, circular DNA molecules that replicate independently
-episomes can integrate into the bacterial genome, influencing adaptation and resistance.

What are plasmids and episomes, and how do they influence bacterial adaptation?

By analyzing the order and timing of gene transfer in conjugation experiments, scientists can determine the relative positions of genes on the bacterial chromosome.

How can gene mapping be conducted using conjugation data?

The F factor (fertility plasmid) allows bacteria to form a pilus for conjugation; in sexduction, it transfers chromosomal genes via the F' plasmid.

What is the role of F factors in bacterial conjugation and sexduction?

Transduction occurs when a bacteriophage accidentally packages bacterial DNA and transfers it to another bacterium, contributing to genetic diversity.

Describe the process of transduction and its role in bacterial genetic variation.

Partial diploids (merodiploids) contain two copies of certain genes, allowing researchers to study gene interactions and map closely linked genes.

How can partial diploids be used to map closely linked genes in bacteria?

Genetic exchange enhances bacterial adaptability, allowing them to evolve resistance, exploit new niches, and survive changing environments.

What is the evolutionary significance of genetic exchange in bacteria?

Mutations, gene transfer, mobile genetic elements, and environmental pressures drive bacterial genome evolution over time.

What factors contribute to the evolution of bacterial genomes over time?

Understanding bacterial genetics helps develop targeted therapies, new antibiotics, and strategies to counteract resistance mechanisms.

How can knowledge of bacterial genetics aid in the development of new treatments for antibiotic-resistant infections?

-DNA is composed of deoxyribonucleotides (deoxyribose sugar, phosphate group, and nitrogenous bases: A, T, C, G).
-RNA consists of ribonucleotides (ribose sugar, phosphate, and bases A, U, C, G).

1. What is the molecular composition of DNA and RNA?

Phosphate groups form the backbone, sugars provide structural integrity, and nitrogenous bases enable base pairing for replication and transcription.

2. How do the chemical subunits of DNA and RNA contribute to their function?

-DNA is double-stranded, has deoxyribose sugar, and uses thymine (T).
-RNA is single-stranded, has ribose sugar, and uses uracil (U) instead of thymine.

3. What are the key structural differences between DNA and RNA?

The double-helix structure provides stability through complementary base pairing and allows semi-conservative replication, ensuring accurate genetic transmission.

4. How does the double-helix structure of DNA support genetic stability and replication?

DNA exists in B-form (most common), A-form (compact, in dehydrated conditions), and Z-form (left-handed helix, involved in gene regulation).

5. What are the alternate forms of the DNA double helix, and how do they differ?

Negative supercoiling helps compact DNA, reduces torsional stress, and facilitates transcription and replication by unwinding the double helix.

6. What role does negative supercoiling play in DNA structure in vivo?

Friedrich Miescher discovered nuclein (later identified as DNA) in 1869, recognizing it as a distinct biomolecule in cell nuclei.

7. Who discovered nuclein, and what was its significance in molecular biology?

Avery, MacLeod, and McCarty expanded on Griffith's transformation experiment by using purified biomolecules to identify DNA as the "transforming principle." They treated bacterial extracts with enzymes that degrade proteins, RNA, or DNA. Only when DNA was destroyed did transformation fail, proving that DNA, not proteins or RNA, carries genetic information. This was further confirmed by Hershey and Chase's bacteriophage experiment.

8. How was it proven that DNA, rather than proteins, carries genetic information?

Griffith's experiment with Streptococcus pneumoniae demonstrated that a "transforming principle" (later identified as DNA) could transfer genetic traits.

9. What experiments demonstrated that DNA mediates transformation in bacteria?

Hershey and Chase used bacteriophage T2 to prove that DNA, not protein, is the genetic material. They labeled viral DNA with radioactive phosphorus-32 (which marks DNA) and viral proteins with sulfur-35 (which marks proteins). After allowing the phages to infect bacteria, they observed that only phosphorus-32 entered the bacterial cells, while sulfur-35 remained outside. This demonstrated that DNA, not protein, carries genetic instructions for viral replication.

10. How did Hershey and Chase's bacteriophage T2 experiment confirm that DNA is the genetic material?

Some viruses, like retroviruses and RNA viruses, use RNA instead of DNA to store and transmit genetic information (e.g., HIV, SARS-CoV-2).

11. In what ways does RNA serve as the genetic material in some viruses?

-Viral chromosomes can be DNA or RNA, linear or circular.
-Prokaryotic chromosomes are circular
-eukaryotic chromosomes are linear and organized in a nucleus.

12. How do viral and prokaryotic chromosomes differ from eukaryotic chromosomes?

-DNA
-histone proteins (for packaging),
-non-histone proteins (for regulation and structure)

13. What is the chemical composition of eukaryotic chromosomes?

Chromatin is packed by wrapping DNA around histones to form nucleosomes, which further coil into higher-order structures.

14. How is chromatin packaged within eukaryotic chromosomes?

Nucleosomes are DNA-histone complexes that compact DNA and regulate gene expression. Each nucleosome consists of 147 base pairs wrapped around histone proteins.

15. What are nucleosomes, and how do they contribute to DNA packaging?

The human X chromosome contains approximately 1 million nucleosomes, depending on its length and condensation state.

16. How many nucleosomes are present in a human X chromosome?

-Unique DNA sequences code for proteins
-repetitive sequences (e.g., satellite DNA) play structural or regulatory roles.

17. What is the difference between unique and repetitive DNA sequences in chromosomes?

Centromeres are chromosomal regions where spindle fibers attach during cell division, ensuring proper chromosome segregation.

18. What are centromeres, and why are they essential for chromosome function?

Telomeres protect chromosome ends from degradation and prevent fusion, with their shortening linked to aging and cell senescence.

19. How do telomeres contribute to chromosome stability and aging?

Histones help package DNA into chromatin, regulate gene expression, and play a role in epigenetic modifications affecting cellular function.

20. What is the role of histone proteins in chromosome organization?