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?

To facilitate ligation between fragments Signup and view all the answers

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

Sticky 3' ends Signup and view all the answers

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

3:1 ratio 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?

Multiply the probabilities of each outcome Signup and view all the answers

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

9:3:3:1 ratio Signup and view all the answers

What does the addition rule in probability deal with?

Mutually exclusive outcomes Signup and view all the answers

What does Mendel's principle of equal segregation imply?

Gametes are formed in equal proportions Signup and view all the answers

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

Determining 1 minus the probability of the complement Signup and view all the answers

What is the binomial theorem primarily used for in probability?

Describing outcomes of multiple coin flips Signup and view all the answers

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

It leads to the production of unique gamete types Signup and view all the answers

What is a characteristic of a dominant pattern of inheritance?

It appears in every generation. Signup and view all the answers

What is one feature of recessive inheritance in humans?

Unaffected parents can have affected offspring. Signup and view all the answers

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

By having no protein production at all. Signup and view all the answers

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

All available information about the individual. Signup and view all the answers

Which statement about normal alleles is accurate?

They usually encode functional proteins. Signup and view all the answers

How many gamete types are produced in a dihybrid cross?

4 Signup and view all the answers

Which of the following statements about abnormal alleles is false?

They are always recessive. Signup and view all the answers

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

Dominant alleles can encode normal proteins or none at all. Signup and view all the answers

What is the role of ddNTPs in DNA sequencing?

They inhibit chain elongation. Signup and view all the answers

What is the primary purpose of paired-end sequencing?

It corrects assembly despite repetitive sequences. Signup and view all the answers

What does SNP stand for?

Single Nucleotide Polymorphism Signup and view all the answers

What does SSR represent in genetics?

Simple Sequence Repeats Signup and view all the answers

How can disease alleles be diagnosed in embryos?

Using PCR techniques. Signup and view all the answers

What is the primary use of SNP microarrays?

To detect multiple SNPs simultaneously. Signup and view all the answers

In genetics, what function does a testcross serve?

To identify the genotype of an individual. Signup and view all the answers

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

It measures how frequently a given genotype appears in a population. Signup and view all the answers

What is the expected connection between SNPs and forensic analysis?

SNPs serve as unique identifiers for individuals. Signup and view all the answers

What is a major challenge in sequencing repetitive genome regions?

They can cause misassembly during sequencing. Signup and view all the answers

What is the primary consequence of a chromosomal inversion?

Reduction in fertility due to unbalanced gametes Signup and view all the answers

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

$3/64N20$ codons. Signup and view all the answers

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

It combines genotypes to identify individuals in a population. Signup and view all the answers

How can miRNAs influence gene expression?

By regulating mRNA stability Signup and view all the answers

Which of the following accurately defines aneuploidy?

The presence of an abnormal number of chromosomes Signup and view all the answers

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

To isolate and analyze particular genes or alleles. Signup and view all the answers

What is the role of enhancers in gene regulation?

They enhance transcriptional activity Signup and view all the answers

What is typically a characteristic of transgenic organisms?

They contain genes from a different species Signup and view all the answers

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

Allopolyploidy Signup and view all the answers

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

Increased mutation rate Signup and view all the answers

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

To visualize and identify chromosomal rearrangements Signup and view all the answers

What happens during a pronuclear injection in gene cloning?

DNA is injected into a fertilized egg Signup and view all the answers

Which phenomenon is primarily associated with intergenerational epigenetic changes?

Transgenerational gametes Signup and view all the answers

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

By cutting DNA at specific sites Signup and view all the answers

Which of the following statements about ploidy is incorrect?

Triploid organisms always exhibit normal fertility. Signup and view all the answers

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

Prevent enhancer-promoter interactions Signup and view all the answers

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

Reverse mutation Signup and view all the answers

What does the Ames Test mainly identify?

Mutagenic substances Signup and view all the answers

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

Forward mutations Signup and view all the answers

What is a characteristic of auxotrophs?

They require supplements for growth. Signup and view all the answers

What type of mutation does a missense result in?

A substitution that leads to a different amino acid Signup and view all the answers

How can prototrophs be detected in a culture of auxotrophs?

Using selective screening Signup and view all the answers

What is the purpose of a complementation test?

To reveal whether mutations are alleles of the same gene Signup and view all the answers

What happens during a nonsense mutation?

The protein is truncated Signup and view all the answers

What is the function of tRNAs in protein synthesis?

To translate mRNA into amino acids Signup and view all the answers

What does a prototroph need to be able to grow?

No growth factor supplements Signup and view all the answers

Which of the following is a characteristic of reverse mutations?

They restore the original function of a gene. Signup and view all the answers

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

Missense mutation Signup and view all the answers

Which of the following best defines a prototroph?

A normal strain that does not require supplements Signup and view all the answers

What role do selection and screening play in mutation analysis?

They facilitate the identification of significant mutations. Signup and view all the answers

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.