Biology Chapter on Probability and Genetics
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Questions and Answers

What is characteristic of blunt ends in DNA fragments?

  • Contain 5' overhangs
  • Include 3' overhangs
  • Are typically shorter than sticky ends
  • Have no overhangs (correct)

Which type of break results in a DNA fragment with 5' overhang?

  • Sticky 5' ends (correct)
  • Sticky 3' ends
  • Blunt ends
  • None of the above

What technique is commonly used to purify genomic DNA fragments of a specific size?

  • Western blotting
  • Northern blotting
  • Gel electrophoresis (correct)
  • PCR amplification

What is the primary purpose of creating sticky ends during DNA manipulation?

<p>To facilitate ligation between fragments (B)</p> Signup and view all the answers

Which type of DNA end is characterized by a 3' overhang?

<p>Sticky 3' ends (A)</p> Signup and view all the answers

What is the outcome of a monohybrid cross according to Mendel's experiments?

<p>3:1 ratio (A)</p> Signup and view all the answers

According to the product rule of probability, what is the method for determining the probability of two independent outcomes?

<p>Multiply the probabilities of each outcome (D)</p> Signup and view all the answers

Which ratio represents the result of a dihybrid cross in Mendelian genetics?

<p>9:3:3:1 ratio (D)</p> Signup and view all the answers

What does the addition rule in probability deal with?

<p>Mutually exclusive outcomes (B)</p> Signup and view all the answers

What does Mendel's principle of equal segregation imply?

<p>Gametes are formed in equal proportions (B)</p> Signup and view all the answers

In probability calculations, how is the subtraction principle generally applied?

<p>Determining 1 minus the probability of the complement (C)</p> Signup and view all the answers

What is the binomial theorem primarily used for in probability?

<p>Describing outcomes of multiple coin flips (C)</p> Signup and view all the answers

How does independent assortment affect the formation of gametes during meiosis?

<p>It leads to the production of unique gamete types (A)</p> Signup and view all the answers

What is a characteristic of a dominant pattern of inheritance?

<p>It appears in every generation. (A)</p> Signup and view all the answers

What is one feature of recessive inheritance in humans?

<p>Unaffected parents can have affected offspring. (C)</p> Signup and view all the answers

How can an abnormal allele be dominant over a normal allele?

<p>By having no protein production at all. (D)</p> Signup and view all the answers

What is required to determine the probability of an individual being affected by a recessive trait?

<p>All available information about the individual. (A)</p> Signup and view all the answers

Which statement about normal alleles is accurate?

<p>They usually encode functional proteins. (C)</p> Signup and view all the answers

How many gamete types are produced in a dihybrid cross?

<p>4 (D)</p> Signup and view all the answers

Which of the following statements about abnormal alleles is false?

<p>They are always recessive. (B)</p> Signup and view all the answers

In what way does dominance relate to the production of proteins?

<p>Dominant alleles can encode normal proteins or none at all. (D)</p> Signup and view all the answers

What is the role of ddNTPs in DNA sequencing?

<p>They inhibit chain elongation. (D)</p> Signup and view all the answers

What is the primary purpose of paired-end sequencing?

<p>It corrects assembly despite repetitive sequences. (C)</p> Signup and view all the answers

What does SNP stand for?

<p>Single Nucleotide Polymorphism (A)</p> Signup and view all the answers

What does SSR represent in genetics?

<p>Simple Sequence Repeats (C)</p> Signup and view all the answers

How can disease alleles be diagnosed in embryos?

<p>Using PCR techniques. (B)</p> Signup and view all the answers

What is the primary use of SNP microarrays?

<p>To detect multiple SNPs simultaneously. (C)</p> Signup and view all the answers

In genetics, what function does a testcross serve?

<p>To identify the genotype of an individual. (A)</p> Signup and view all the answers

Which of the following describes the concept of probability frequency in genetics?

<p>It measures how frequently a given genotype appears in a population. (B)</p> Signup and view all the answers

What is the expected connection between SNPs and forensic analysis?

<p>SNPs serve as unique identifiers for individuals. (B)</p> Signup and view all the answers

What is a major challenge in sequencing repetitive genome regions?

<p>They can cause misassembly during sequencing. (C)</p> Signup and view all the answers

What is the primary consequence of a chromosomal inversion?

<p>Reduction in fertility due to unbalanced gametes (A)</p> Signup and view all the answers

What is the average length of an open reading frame (ORF)?

<p>$3/64N20$ codons. (D)</p> Signup and view all the answers

What is the significance of the DNA Index System (CODIS)?

<p>It combines genotypes to identify individuals in a population. (C)</p> Signup and view all the answers

How can miRNAs influence gene expression?

<p>By regulating mRNA stability (D)</p> Signup and view all the answers

Which of the following accurately defines aneuploidy?

<p>The presence of an abnormal number of chromosomes (B)</p> Signup and view all the answers

Why is it necessary to clone specific DNA fragments in research?

<p>To isolate and analyze particular genes or alleles. (D)</p> Signup and view all the answers

What is the role of enhancers in gene regulation?

<p>They enhance transcriptional activity (A)</p> Signup and view all the answers

What is typically a characteristic of transgenic organisms?

<p>They contain genes from a different species (B)</p> Signup and view all the answers

Which term describes a situation where hybrids possess complete sets of chromosomes from both parent species?

<p>Allopolyploidy (A)</p> Signup and view all the answers

What is an effect of genomic instability commonly found in cancer cells?

<p>Increased mutation rate (D)</p> Signup and view all the answers

What is the primary purpose of spectral karyotyping (SKY)?

<p>To visualize and identify chromosomal rearrangements (B)</p> Signup and view all the answers

What happens during a pronuclear injection in gene cloning?

<p>DNA is injected into a fertilized egg (D)</p> Signup and view all the answers

Which phenomenon is primarily associated with intergenerational epigenetic changes?

<p>Transgenerational gametes (C)</p> Signup and view all the answers

How does the CRISPR/Cas9 system facilitate targeted gene editing?

<p>By cutting DNA at specific sites (B)</p> Signup and view all the answers

Which of the following statements about ploidy is incorrect?

<p>Triploid organisms always exhibit normal fertility. (C)</p> Signup and view all the answers

In terms of gene expression, what role do insulators play?

<p>Prevent enhancer-promoter interactions (A)</p> Signup and view all the answers

Which type of mutation results in a prototroph from an auxotroph?

<p>Reverse mutation (C)</p> Signup and view all the answers

What does the Ames Test mainly identify?

<p>Mutagenic substances (C)</p> Signup and view all the answers

In Muller's Test, what is primarily screened for?

<p>Forward mutations (A)</p> Signup and view all the answers

What is a characteristic of auxotrophs?

<p>They require supplements for growth. (D)</p> Signup and view all the answers

What type of mutation does a missense result in?

<p>A substitution that leads to a different amino acid (B)</p> Signup and view all the answers

How can prototrophs be detected in a culture of auxotrophs?

<p>Using selective screening (C)</p> Signup and view all the answers

What is the purpose of a complementation test?

<p>To reveal whether mutations are alleles of the same gene (B)</p> Signup and view all the answers

What happens during a nonsense mutation?

<p>The protein is truncated (B)</p> Signup and view all the answers

What is the function of tRNAs in protein synthesis?

<p>To translate mRNA into amino acids (C)</p> Signup and view all the answers

What does a prototroph need to be able to grow?

<p>No growth factor supplements (A)</p> Signup and view all the answers

Which of the following is a characteristic of reverse mutations?

<p>They restore the original function of a gene. (D)</p> Signup and view all the answers

Which type of mutation is associated with a substitution that changes an amino acid sequence?

<p>Missense mutation (D)</p> Signup and view all the answers

Which of the following best defines a prototroph?

<p>A normal strain that does not require supplements (C)</p> Signup and view all the answers

What role do selection and screening play in mutation analysis?

<p>They facilitate the identification of significant mutations. (B)</p> Signup and view all the answers

Flashcards

Blunt Ends

DNA fragments with no overhangs on either end, meaning both strands terminate at the same position.

Sticky Ends

DNA fragments with single-stranded overhangs on either end. These overhangs can be complementary, allowing the fragments to anneal together.

5' Overhang

When a DNA fragment has a single-stranded overhang at the 5' end.

3' Overhang

When a DNA fragment has a single-stranded overhang at the 3' end.

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Gel Electrophoresis

A technique used to separate DNA fragments based on their size. Smaller fragments move faster through the gel.

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Probability of an event

The likelihood of a specific event occurring, calculated by dividing the number of favorable outcomes by the total number of possible outcomes.

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Independent events

Events where the outcome of one does not influence the outcome of the other.

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Dependent events

Events where the outcome of one event affects the outcome of the other.

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Sum Rule of Probability

Used to calculate the probability of either one OR the other of two mutually exclusive events happening. Add the probabilities of the individual events.

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Product Rule of Probability

Used to calculate the probability of two independent events both happening. Multiply the probabilities of the individual events.

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Mendel's Law of Independent Assortment

During gamete formation, alleles for different traits separate independently from each other. This leads to diverse combinations of traits in offspring.

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Monohybrid Cross

A cross between two individuals that differ in one trait, resulting in a 3:1 phenotypic ratio in the F2 generation.

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Dihybrid Cross

A cross between two individuals that differ in two traits, resulting in a 9:3:3:1 phenotypic ratio in the F2 generation.

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Gamete Types

The different combinations of alleles that a parent can contribute to their offspring. In a dihybrid cross, there are four possible gamete types.

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Proportion in Dihybrid Cross

The offspring of a dihybrid cross exhibit a specific ratio of phenotypes, usually a 9:3:3:1 ratio. This reflects the combinations of alleles inherited.

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Human Pedigrees

Diagrams used to trace the inheritance of traits through generations in a family. They help visualize the transmission of genes.

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Mendelian Traits

Traits controlled by a single gene, with clear dominant and recessive alleles. They follow simple inheritance patterns.

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Dominance Pattern

The way a dominant allele expresses itself in the phenotype. A dominant allele will always be expressed, even in the presence of a recessive allele.

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Recessive Pattern

The way a recessive allele expresses itself in the phenotype. A recessive allele is only expressed if two copies of the recessive allele are present.

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Conditional Probability

Calculating the probability of an event happening, given that another event has already happened. This is crucial in understanding pedigrees.

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DNA Library

A collection of DNA fragments cloned into vectors, representing the entire genome of an organism.

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Sanger Sequencing

A method of DNA sequencing that uses dideoxynucleotides (ddNTPs) to terminate DNA chain elongation at specific bases.

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Paired-End Sequencing

Sequencing both ends of a DNA fragment, used to improve genome assembly by overcoming repeat regions.

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Genome Annotation

The process of identifying genes, regulatory elements, and other functional features within a genome.

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Open Reading Frame (ORF)

A sequence of DNA that encodes a protein, starting with a start codon and ending with a stop codon.

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Single Nucleotide Polymorphism (SNP)

A variation in a single nucleotide that occurs in at least 1% of the population.

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Simple Sequence Repeat (SSR)

A repeating sequence of DNA, often used as a genetic marker.

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PCR

Polymerase Chain Reaction, a technique used to amplify specific DNA sequences.

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Disease Alleles

Variations in DNA sequences that can lead to genetic diseases.

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Forensic DNA Profiling

Using SNPs and SSRs to identify individuals based on their unique DNA patterns.

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CODIS

Combined DNA Index System, a database used by law enforcement to store and compare DNA profiles.

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Positional Cloning

Identifying a gene associated with a disease by its location in the genome.

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Testcross

A cross between an individual with an unknown genotype and a homozygous recessive individual.

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SNP Microarrays

A technology that allows for the detection of millions of SNPs in a single DNA sample.

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Genome Sequencing

Determining the complete DNA sequence of an organism.

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Reverse Mutation

A genetic change that restores a mutant gene back to its original, functional form. It's like reversing a mistake in the DNA code.

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Auxotroph

A mutant microbe that requires a specific nutrient (like an amino acid) that the original, wild-type version could make itself.

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Prototroph

A normal microorganism that can synthesize all the nutrients it needs to grow.

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Ames Test

A test using bacteria to screen chemicals for their potential to cause mutations. It's a way to see if a chemical is a mutagen.

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Forward Mutation

A change in the DNA sequence that leads to a new mutant phenotype, which is a detectable change in the organism.

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Muller's Test

A genetic test in fruit flies (Drosophila) used to assess the rate of X-ray induced lethal mutations.

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Complementation Test

A genetic test used to determine if two mutations are in the same gene or in different genes. It helps figure out if mutations 'work together' to create a phenotype.

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Supplementation Test

A genetic test used to determine if a mutation can be 'rescued' by the addition of a specific compound, like an amino acid. It's about seeing if providing a missing component 'fixes' the problem.

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Genetic Code

The set of rules by which information encoded in genetic material (DNA or RNA) is translated into proteins. It's a dictionary that translates DNA 'letters' into protein 'words.'

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Colinear

The linear relationship between the sequence of nucleotides in DNA and the sequence of amino acids in the corresponding protein. It means the order in DNA directly maps to the order of protein building blocks.

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Non-Overlapping

The feature of the genetic code where the same nucleotide sequence is not read twice to code for different amino acids. Each codon is read independently.

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Missense Mutation

A point mutation in DNA that results in a change in a single amino acid in the protein sequence. It's like changing one letter in a word, giving a different meaning.

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Nonsense Mutation

A mutation in DNA that introduces a premature stop codon. This leads to a truncated, incomplete protein.

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tRNA

A molecule that acts as an adapter between the genetic code in mRNA and the amino acids used to build proteins. It bridges the language gap between DNA and protein.

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DNA Synthesis

The process of creating a new DNA strand using an existing DNA strand as a template. It involves the sequential addition of nucleotides to the new strand by an enzyme called DNA polymerase.

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ddNTPs in DNA Synthesis

Modified nucleotides that lack a hydroxyl group at the 3' position. They are used in DNA sequencing to terminate DNA synthesis at specific points.

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Chromosome Mutation

Alterations in the structure or number of chromosomes, potentially affecting gene expression and leading to various genetic disorders.

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Deletion Mutation

A type of chromosomal mutation where a portion of a chromosome is lost, removing genes and potentially altering gene expression.

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Inversion Mutation

A type of chromosomal mutation where a segment of a chromosome breaks off, flips, and reattaches, reversing the order of genes within that segment.

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Duplication Mutation

A type of chromosomal mutation where a segment of a chromosome is duplicated, resulting in an extra copy of genes within that segment.

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Translocation Mutation

A type of chromosomal mutation where a portion of one chromosome breaks off and attaches to another chromosome, leading to an exchange of genetic material.

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Spectral Karyotyping (SKY)

A technique that uses fluorescent probes to visualize different chromosomes, allowing for the detection of chromosomal rearrangements.

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Haploinsufficiency

A condition where having only one functional copy of a gene is not sufficient for normal function, leading to phenotypic consequences.

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Chromosomal Inversion Consequence

Chromosomal inversions can lead to reduced fertility due to the formation of unbalanced gametes during meiosis.

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Chromosomal Translocation Consequence

Chromosomal translocations can also result in reduced fertility due to the production of unbalanced gametes.

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Ploidy

The number of sets of chromosomes present in a cell.

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Euploid

A cell or organism with the normal number of chromosomes for its species.

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Aneuploid

A cell or organism with an abnormal number of chromosomes, often due to errors during cell division.

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Polyploid

A cell or organism with more than two sets of chromosomes.

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Monoploid

A cell or organism with a single set of chromosomes (haploid).

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Odd Ploidy and Meiosis

Organisms with an odd number of chromosome sets (e.g., triploid) are often sterile because meiosis cannot produce balanced gametes.

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Triploid

An organism with three sets of chromosomes (3n).

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Study Notes

Probability

  • Probability of an event (P(event)) = (number of favorable outcomes) / (total number of outcomes)
  • Independent vs. dependent events
  • Sum rule for mutually exclusive events (either/or)
  • Product rule for independent events (both)
  • Order not specified = multiply by number of outcomes
  • Binomial theorem: used for calculating probabilities related to events with multiple possible outcomes

Mendel's Laws & Meiosis

  • Monohybrid crosses: always result in a 3:1 ratio in the F2 generation
  • Dihybrid crosses: always result in a 9:3:3:1 ratio in the F2 generation
  • Meiosis and equal segregation: heterozygotes produce gametes with equal frequency
  • Independent assortment: dihybrids produce gametes with equal frequency for different gene combinations.

Human Pedigrees

  • Human traits: controlled by single genes and are often related to diseases.
  • Dominant patterns appear in every generation.
  • Recessive patterns affect individuals, but unaffected parents can also have affected offspring.
  • Conditional probability: is necessary to evaluate scenarios in which some information about affected or unaffected individuals and their parents is known.

Dominance

  • Normal alleles (wild-type) = functional proteins.
  • Abnormal alleles may vary (non-functional, partially functional, or have novel functions).
  • Dominance is determined by : (1) normal protein production, (2) no protein production, or (3) abnormal product.
  • Incomplete dominance: in-between phenotypes show (heterozygous phenotype lies between the two homozygous phenotypes)
  • Codominance: both characteristics shown in heterozygous phenotype.
  • Blood types: exhibit codominance and complete dominance.

Gene Interactions

  • Complex traits involve multiple genes and interactions.
  • This can lead to continuous (quantitative) or discontinuous (discrete) traits.
  • Interaction of two or more genes = additive interactions.
  • Epistatic interactions: modify the expression of other genes.
  • Recessive epistasis: one gene masks or prevents expression of another.

Sex Chromosomes

  • Genes on the Y chromosome determine maleness (SRY gene).
  • X-linked inheritance: males inherit X chromosomes from their mothers only.
  • Dosage compensation: cells compensate for the different copies of X chromosomes (Barr bodies).

Linkage

  • Genes on the same chromosome = linked genes
  • Linked genes are inherited together more often than expected by chance.
  • Linkage alters the expected 9:3:3:1 dihybrid ratio.
  • Recombination frequency represents the proportion of recombinant offspring.
  • Linkage groups = all genes on one chromosome.

Mutation

  • Mutations are changes in DNA sequences.
  • Point mutations: substitution, deletion or insertion.
  • Forward mutations: normal to mutant, reverse mutations: mutant to normal.
  • Mutations can result in loss-of-function, gain-of-function, amorphic or hypomorphic mutations.
  • Bacterial mutations are tested by auxotrophs and prototrophs.
  • How to detect prototrophs: screen or selection tests.
  • Drosophila : Muller's Test used to screen for mutations.

Interpreting the Genetic Code

  • tRNA acts as an adaptor between codons and amino acids.
  • Nonsense mutations: result in premature stop codons (truncating the protein).
  • Nonsense suppressor mutations: restore protein function by changing the tRNA to allow it to incorporate a stop codon.
  • Wobble: flexibility in the third base position (allows some degeneracy).
  • Genetic code is degenerate - more than one codon = one amino acid

Genetic Structure & Classification of Alleles

  • DNA sequence corresponds to the primary structure of mRNA, which consequently corresponds to the amino acid sequence of proteins.
  • Types of mutations: loss-of-function (amorphic, hypomorphic), gain-of-function (hypermorphic, neomorphic), antimorphic

Cloning & Sequencing Genomic DNA

  • Constructing genomic DNA libraries: by fragmenting genomic DNA and cloning fragments into vectors
  • Genomic DNA purification using gel electrophoresis
  • Cloning vectors: tools for inserting DNA fragments into
  • Sequencing: determines the order of nucleotides in a DNA molecule.

Positional Cloning

  • Finding a gene by locating associated genetic markers.
  • Mapping a gene by combining data on various loci.

Chromosome Mutations

  • Deletion -loss of a segment
  • Duplication- extra segment
  • Inversion- segment reversal
  • Translocation - transfer between nonhomologous chromosomes (reciprocal or non-reciprocal).

Ploidy

  • Euploid: correct number of chromosome sets.
  • Aneuploid: abnormal number of chromosome sets.
  • Monoploid: one set of chromosomes.
  • Polyploid: more than two sets of chromosomes.

Human Gene Regulation

  • Gene regulation involves control at different levels.
  • Promoters determine basal levels of transcription.
  • Enhancers can activate or repress gene expression.
  • Chromatin structure affects transcription.
  • Posttranscriptional mechanisms regulate gene expression.

Epigenetics

  • Programmed : Imprinting, Insulators, CpG islands
  • "Unprogrammed": Intergenerational, transgenerational
  • Epigenetics phenomena: changes in gene expression without changing the DNA sequence.

GMOs/Cloning

  • GMOs (genetically modified organisms): by inserting genes of interest into the organism.
  • Cloning animals: create a genetically identical copy of an organism. Methods for inserting transgenes include pronuclear injections, utilizing transgenic farm animals (e.g., producing drugs from milk).
  • Genome editing by CRISPR/Cas9 used to create knockouts and knockins.

Cancer

  • Characteristics of cancer cells: uncontrolled cell growth, immortality, and genomic instability (leading to metastasis).

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Description

This quiz covers key concepts in probability as applied to genetics, including Mendel's laws, meiosis, and the analysis of human pedigrees. Learn how to calculate probabilities in genetic crosses and understand inheritance patterns of traits. Test your knowledge with questions related to both independent and dependent events and their implications in genetics.

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