Download GENETICS MIDTERM QUICK REVISION FLASHCARDS 2026 and more Exams Genomics in PDF only on Docsity!
GENETICS MIDTERM QUICK REVISION
FLASHCARDS 2026
โ In mammals, which sex is heterogametic? Answer: Males (XY). โ In birds, which sex is heterogametic? Answer: Females (ZW). โ What does Turner syndrome (XO) indicate about sex determination? Answer: At least one X is required; no Y results in a female phenotype. โ What does Klinefelter syndrome (XXY) indicate about sex determination? Answer: The presence of a Y chromosome results in a male phenotype. โ What determines maleness in humans? Answer: The presence of the Y chromosome, specifically the SRY gene.
โ What is the function of the SRY gene? Answer: It initiates testis development. โ What is the phenotype of an XY individual without the SRY gene? Answer: Female. โ What is the phenotype of an XX individual with the SRY gene? Answer: Male. โ What causes androgen insensitivity syndrome (AIS)? Answer: A mutation in the androgen receptor. โ Why are individuals with AIS phenotypically female? Answer: Their cells cannot respond to testosterone. โ What are parental outputs of meiosis? Answer: Gametes with original allele combinations. โ What are recombinant outputs of meiosis? Answer: Gametes with new allele combinations due to crossing over.
Answer: 1% recombination frequency. โ If genes are 20 cM apart, what is the expected percentage of recombinants? Answer: 20%. โ How do recombination frequencies indicate gene position? Answer: Lower recombination frequency indicates that genes are closer together. โ Why is recombination frequency capped at 50%? Answer: Multiple crossovers can restore parental combinations, making genes appear unlinked. โ What molecular activities occur during crossing over? Answer: DNA breakage, strand invasion, DNA synthesis, and ligation. โ What is Mendel's law of independent assortment? Answer: Genes on different chromosomes assort independently. โ What is the evidence for independent assortment? Answer: Dihybrid cross 9:3:3:1 ratio.
โ When does independent assortment apply? Answer: Genes on different chromosomes or far apart on same chromosome. โ What does a Punnett square show? Answer: All possible genotype combinations of offspring. โ How can probability replace Punnett squares? Answer: Multiply probabilities of independent events. โ What is the multiplication rule in probability? Answer: Multiply independent probabilities. โ What is the addition rule in probability? Answer: Add mutually exclusive probabilities. โ What is the F2 ratio of a dihybrid cross? Answer: 9:3:3:1. โ How do you solve dihybrid crosses without Punnett squares? Answer: Split into single crosses, then multiply probabilities.
โ What happens in early prophase I? Answer: Synapsis begins. โ What happens in late prophase I? Answer: Crossing over occurs. โ What is a tetrad (bivalent)? Answer: A pair of homologous chromosomes consisting of four chromatids. โ Why is the formation of a tetrad unique to meiosis? Answer: Homolog pairing does not occur in mitosis. โ How do chromosomes align during metaphase in mitosis? Answer: They align individually. โ How do chromosomes align during metaphase I in meiosis? Answer: Homologous pairs align. โ What separates during mitosis? Answer: Sister chromatids.
โ What separates during meiosis I? Answer: Homologous chromosomes. โ If 2n = 6, how many chromosomes are present at metaphase I? Answer: 6 chromosomes (3 pairs). โ What is the ploidy of a cell after meiosis I? Answer: Haploid. โ What is the state of chromatids after meiosis II? Answer: They are single chromatids. โ What is Mendel's law of segregation? Answer: Alleles separate into different gametes. โ How does meiosis explain Mendel's law of segregation? Answer: Homologous chromosomes separate during meiosis I. โ How does the timing of meiosis differ between males and females? Answer: Males undergo continuous meiosis; females begin in the embryo, pause, and finish at fertilization.
โ What is the standard assumption for outsiders in a rare disease pedigree? Answer: Outsiders are assumed to be homozygous unaffected. โ What is the standard assumption for outsiders in a common disease pedigree? Answer: Outsiders may be carriers. โ What are pseudoautosomal regions? Answer: Homologous regions found on both the X and Y chromosomes. โ Why are pseudoautosomal regions important? Answer: They allow for pairing between the X and Y chromosomes during meiosis. โ What did Griffith show? Answer: Transformation โ What did Avery show? Answer: DNA is genetic material โ What did Hershey-Chase show?
Answer: DNA not protein is genetic material โ What are the 3 properties of DNA? Answer: Replication, storage, variation โ What is semiconservative replication? Answer: One old strand + one new strand โ What did Meselson-Stahl show? Answer: Semiconservative replication โ What is the leading strand? Answer: Continuous synthesis โ What is the lagging strand? Answer: Discontinuous synthesis โ In what direction does DNA polymerase work? Answer: 5' โ 3' โ What does DNA polymerase require to function? Answer: Primer + template
โ What are the three steps of PCR? Answer: Denature, anneal, and extend. โ What temperature is used to denature DNA? Answer: ~95ยฐC โ What temperature is used to anneal primers? Answer: ~55-65ยฐC โ What temperature is used to extend DNA? Answer: ~72ยฐC โ What is an amplicon? Answer: The target DNA region. โ At which cycle does the true amplicon first appear? Answer: Cycle 3. โ What is the role of primers in PCR? Answer: They define the target region and provide a 3' OH group. โ How does gel electrophoresis work?
Answer: DNA moves toward the positive electrode, with smaller fragments moving farther. โ What does a DNA gel show? Answer: Genotype. โ What does an RNA gel show? Answer: Gene expression. โ What are ddNTPs? Answer: Chain-terminating nucleotides. โ Why do ddNTPs stop DNA synthesis? Answer: They lack a 3' OH group. โ What is the difference between Sanger and SMRT sequencing? Answer: Sanger produces short reads, while SMRT produces long reads and allows for parallel sequencing. โ What is a gene? Answer: DNA encoding RNA/protein.
Answer: Sex linkage. โ What is a testcross? Answer: Cross with homozygous recessive. โ Why is a testcross useful? Answer: Reveals genotype. โ What is the F2 monohybrid phenotype ratio? Answer: 3:1. โ What is the F2 monohybrid genotype ratio? Answer: 1:2:1. โ What result would Meselson-Stahl show after 2 generations? Answer: Two bands: one hybrid, one light. โ What would dispersive replication predict over generations? Answer: Gradual lightening but no distinct bands. โ How did Cairns experiment differ from Meselson-Stahl?
Answer: Used microscopy to visualize replication bubbles instead of density gradients. โ How do you identify leading vs lagging strand in a replication fork? Answer: Leading strand follows fork direction; lagging strand is synthesized away from fork. โ What is processivity in DNA replication? Answer: Number of nucleotides added before polymerase falls off. โ Why do eukaryotes have multiple origins of replication? Answer: Larger genomes require faster replication. โ What are the two roles of telomeres? Answer: Protect chromosome ends and prevent loss of coding DNA. โ How does telomerase extend DNA? Answer: Uses RNA template to add repeats to 3' end. โ Why is telomerase linked to aging? Answer: Telomere shortening limits cell divisions.
โ How do you predict recombinant phenotypes from cM? Answer: Percent recombination = percent recombinant phenotypes. โ How do you determine gene order from recombination frequencies? Answer: Genes with smallest distances are closest together. โ What changes when diagramming multiple chromosome pairs in meiosis? Answer: Independent assortment increases combinations. โ How do you indicate uncertainty in pedigree genotypes? Answer: Use probabilities or multiple possible genotypes. โ How does conditional probability apply in pedigrees? Answer: Adjust probability based on known outcomes. โ How can progeny ratios indicate LOF vs GOF? Answer: Recessive ratios suggest LOF; dominant ratios suggest GOF. โ
