Exam Preparation Notes

Exam Format

• 80 questions.

Preparation Strategies

• Active Learning: Engage with the material actively; don't just passively read or memorize.
• Review Strategy: After completing a lecture (e.g., Lecture One, Lecture Two), dedicate an hour to thoroughly study that material.
• Complex Problems: Break down large, complex problems into smaller, manageable ones.
  • Example: If a problem involves five genes, solve five individual problems instead of attempting to solve them simultaneously.
• Conceptual Understanding:
  • Focus on understanding how things work rather than just memorizing facts or definitions.
  • Understanding the concepts, not just memorizing terms.

Exam Layout

• Question 1: Generally from Lecture One.
• Question 80: Generally from forensic science material.
• The exam questions will follow the approximate order of topics covered throughout the semester, starting from the beginning and ending with the most recent material.
• The layout is not perfect as question placement can depend on page formatting.

Specific Material

Experiment Understanding

• You should understand the concepts of experiments (e.g., Hershey-Chase experiment, Avery-MacLeod-McCarty experiment) and what they were trying to demonstrate.

DNA Structure

• You must know the specific bonds in the DNA structure.
• Understand the overall structure of DNA and its important features. Don't delve into excessive detail.

Meselson-Stahl Experiment

• Elegant experiment proving the semi-conservative model of DNA replication.
• They used different isotopes of nitrogen, N^{14} (lighter) and N^{15} (heavier).
• E. coli bacteria were grown in N^{15} media for many generations, so all the bases (A, T, C, G) in their DNA contained heavy nitrogen.
• Density gradients separate DNA based on size (lighter material at the top, heavier at the bottom).

Experiment Steps:

1. Bacteria grown in N^{15} media
   • Every base had the heavy nitrogen.
   • DNA isolated from these bacteria formed a band lower on the density gradient.
2. Transfer to N^{14} Media:
   • Bacteria initially grown in N^{15} were transferred to N^{14} media, for replication.
   • During replication, new DNA strands were synthesized using N^{14}.

Semi-Conservative Replication:

• Parental strand (heavy) separates, and a new (daughter) strand is made alongside each parental strand.
• First generation in N^{14}:
  • DNA had one strand of N^{15} (parental) and one strand of N^{14} (new).
  • When run on a density gradient, it showed one intermediate band.
• Calculation:
  • If N^{15} + N^{15} = 30 (original parental strand weight).
  • Then N^{15} + N^{14} = 29 (intermediate weight).
• Second generation in N^{14}:
  • Two bands appeared.
  • One at the intermediate weight (29) and one at the lighter weight because of the new strands.
• With more generations, the N^{15} band gets fainter (less of it), while the N^{14} band gets thicker (more of it).
• This experiment confirmed the semi-conservative model of replication.

Alternative Replication Models:

• Conservative Model:
  • Would produce two distinct bands after one replication round (one heavy, one light).
  • The Meselson-Stahl experiment disproved this model.
• Dispersive Model:
  • Random breakage and reassembly of DNA.
  • Would result in one band at an intermediate weight, but this band would remain constant over generations.

Eugenics

• Understand the definition of eugenics.
• Difference between positive and negative eugenics.
  • Positive eugenics: Doing something for everybody.
  • Negative eugenics: Selecting who you do something for.
• Recognize examples of positive and negative eugenics.
• Understand the scientific reasons why eugenics is not a valid approach.

Epigenetics

• Understand the effect of methylation and acetylation on DNA structure.
• Understand what methylation and acetylation allows to happen (or prevents from happening).
• Be aware of epigenetic ratios.

Problem Solving

Heritability

• Heritability problems will resemble those from previous tests but are not as in-depth.
  • Example: Given an individual with a specific genotype displaying incomplete dominance and another with complete dominance, determine the offspring genotypes and phenotypes.

Mapping

• Understand concepts related to gene mapping and recombination frequency.
  • Example: With 18% recombination, understand the relationship between gene locations.

Chromosome Rearrangements

• Understand chromosome rearrangement problems.
• Inversion loops: More complicated problems involve inversion loops.
• Pericentric vs. Paracentric: Know the definition of pericentric and paracentric inversions (whether or not they involve the centromere).

Inversion Problem Example:

• Given:
  • Original Chromosome: A-B-C-D-Centromere-E-F-G-H
  • Inversion: A-D-C-Centromere-E-F-G-B-H (inversion between D and G)
  • The inversion would be drawn as: A-D-C-G-F-E-Centromere -B-H
• If there is a crossover between E and F. During meiosis, chromosomes pair up, the genes must match up exactly
• The chromosome with the inverted segment forms a loop to allow for proper pairing.
• When identifying the location of the inversion find where the inversion is in the sequence given.

Multiple Alleles and Blood Type

• For every gene, two alleles are inherited.
• Multiple Alleles: More than two alleles exist in the population for a particular gene (e.g., ABO blood type).
• ABO Blood Type:
  • Alleles: A, B, and O (i).
  • Individuals have only two alleles.
• Possible Genotypes and Phenotypes:
  • Type A: AA or AO (A is dominant to O).
  • Type B: BB or BO (B is dominant to O).
  • Type AB: AB (Codominance).
  • Type O: OO (Homozygous recessive).
• Codominance: A and B are codominant; both alleles are expressed.

RH Factor

• Simple Mendelian dominance.
• Positive is dominant to negative.
  • RH+ can be homozygous or heterozygous.
• Only way to be Rh- is to be homozygous recessive.
• Genotypes:
  • RH+/RH+ or RH+/RH- = RH Positive.
  • RH-/RH- = RH Negative.

MN Blood Group

• Codominance.
• MM = Type M.
• NN = Type N.
• MN = Expresses both M and N antigens.

Reciprocal Translocations

• Trading the same amount of information between non-homologous chromosomes.
• During meiosis, genes must still match up so chromosomes form a cross structure.
• Alternate and adjacent segregation patterns.
• Unbalanced gene dosage leads to non-viable gametes.
• Nonreciprocal translocation, different amounts of information are moved.

DNA and PCR, Sanger Sequencing

• Understand what these techniques are and how they work.
• DNA barcoding: Know the genes used. How PCR functions.
• Review information in the lecture and the corresponding Canvas page.

Bird Sex Chromosomes

• Z and W.
• Males are ZZ (homogametic).
• Females are ZW (heterogametic).