Questions and Answers
What is the Law of Segregation about?
What defines dioecious organisms?
What is Klinefelter syndrome?
47, XXY
What does the SRY gene encode for?
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The X chromosome has Xic which contains _____ that forms condensed DNA.
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Transformation is the process of bacteria taking DNA from another bacterium.
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What is the process called when DNA polymerase uses dNTPs for DNA replication?
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How does the Lac operon work when lactose is present?
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What is an example of a gene interaction where both genes must be present to be expressed?
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Match the following definitions to their terms.
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What type of mutation leads to a stop codon?
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What type of chromosomal mutation results in the addition of an entire chromosome?
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Carcinomas are types of cancers that arise from which tissue type?
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Study Notes
Mendelian Genetics
- Law of Segregation: Each organism carries two alleles for each trait, which segregate during gamete formation.
- Law of Independent Assortment: Genes for different traits assort independently during meiosis, although gene linkage can affect this.
Sex Determination
- Monoecious organisms possess both male and female reproductive structures (hermaphrodites).
- Dioecious organisms are distinctly male or female.
- Monoecious reproduction involves meiosis in stamen producing haploid pollen grains, while pistil forms haploid nuclei that develop into an embryo.
- Dioecious sexual determination in mammals follows XY/XX and in birds follows ZW/ZZ systems.
- Klinefelter syndrome (47, XXY) and Turner syndrome (45, X) are examples of chromosomal anomalies affecting sex characteristics.
- SRY gene encodes for testis determining factor (TDF), crucial for male gonad formation.
- X chromosome has X-inactivation center (Xic) with Xist gene, leading to Barr body formation (inactive X chromosome).
Gene Interactions
- Loss of function mutations can be amorphic (no protein function) or hypomorphic (reduced function).
- Gain of function mutations may be hypermorphic (increased function), antomorphic (disturbed function), or neomorphic (new function).
- X-linkage affects mostly males; affected males do not pass traits to sons.
- Mitochondrial diseases follow maternal inheritance.
- Epistasis types include:
- Complementary gene action: both genes needed (9:7 ratio).
- Recessive epistasis: a recessive allele masks another (9:3:4 ratio).
- Dominant epistasis: a dominant allele masks another gene (12:3:1 ratio).
- Duplicate gene action: both genes can produce a phenotype unless both are absent (15:1 ratio).
Cloning Techniques
- RFLP detects mutations by analyzing fragment lengths after restriction enzyme digestion.
- Cloning vectors vary in size: Plasmids (<20kb), Bacteriophages (25-30kb), Cosmids (30-40kb), BACs (100-500kb), YACs (200kb-2Mb).
- cDNA is synthesized from mRNA using reverse transcriptase, representing only expressed genes.
DNA Sequencing & PCR
- dideoxynucleotides (ddNTPs) terminate DNA strand elongation during sequencing.
- PCR consists of denaturation, primer annealing, and primer extension.
- Southern blot identifies specific DNA sequences, while Northern blot targets mRNA.
- In situ hybridization is utilized in developmental genetics.
Linkage & Chromosome Mapping
- Recombination Frequency (RF) indicates centromere distance; closer genes exhibit fewer crossover events.
- RF calculation: (number of recombinants / total progeny) x 100%.
- Dihybrid and trihybrid crosses analyze linkage and distances between multiple loci through product ratios.
Bacterial Genetics
- Bacteria grow in nutrient broth or minimal media; E. coli divides every 20 minutes.
- Phases of growth: lag phase (adaptation), log phase (rapid growth), stationary phase (nutrient depletion).
- Transformation, transduction, and conjugation describe mechanisms for genetic exchange among bacteria.
Prokaryotic Gene Expression Regulation
- Constitutive expression involves constant transcription; regulated expression relies on environmental factors.
- Control mechanisms include negative repression and positive activation.
- The lac operon, induced by lactose, illustrates regulatory gene expression through repressor and activator binding.
Eukaryotic Gene Expression Regulation
- RNA polymerase II drives protein-coding transcription.
- Enhancer regions regulate gene expression; promoter and proximal control elements initiate transcription.
- Chromatin structure is modulated by histone acetylation (promoting transcription) and DNA methylation (suppressing transcription).
Genetic Mutations
- Types of base pair mutations: silent, missense (functional changes), nonsense (premature stop codons).
- Mutations can be induced (from environmental agents) or spontaneous (replication errors).
- DNA repair mechanisms exist, including photoreactivation and various excision repair pathways.
Population Genetics
- Allele frequencies are influenced by natural selection, mutations, migration, genetic drift, founder effects, and bottlenecks.
- The evolutionary clock measures time elapsed through the mutation rate.
Chromosomal Mutations
- Chromosomal structure includes p and q arms, centromeres, kinetochore, and telomeres.
- Chromosome abnormalities can be numerical (aneuploidy, polyploidy) or structural (deletions, duplications, translocations).
- Uniparental disomy results from inheriting two copies of a chromosome from one parent.
Cancer Genetics
- Cancer arises from accumulated mutations affecting cell proliferation and regulation.
- Types of cancer include carcinomas, sarcomas, and adenocarcinomas.
- Hallmarks of cancer include rapid growth, evasion of apoptosis, limitless replication, and metastasis.
- Oncogenes promote cell division; tumor suppressor genes inhibit it. Mutations activate proto-oncogenes or inactivate tumor suppressors.
Applications of Genetics
- Insulin production involves using recombinant DNA technology to produce active insulin from separate subunits.
- Genetic engineering enhances agriculture through selective breeding, herbicide resistance, and insecticide incorporation.
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Description
Test your understanding of Mendelian genetics, including the Laws of Segregation and Independent Assortment. Explore concepts related to monoecious and dioecious organisms and how sex determination occurs. This quiz covers critical principles essential for mastering genetics.
