memory refresh 6302
Q1 What is the chromosome theory of heredity?
A1 The chromosome theory of heredity states that genes are located on chromosomes and that chromosome behavior during meiosis explains Mendelian inheritance patterns such as segregation and independent assortment.
Q2 What is an organism’s C-value?
A2 The C-value is the amount of DNA in a haploid nucleus and represents total genome size rather than gene number.
Q3 What is the C-value paradox?
A3 The C-value paradox is the observation that genome size does not correlate with organismal complexity, meaning some simpler organisms have larger genomes than humans.
Q4 What are the three major categories of eukaryotic DNA?
A4 Non-repetitive DNA (single-copy genes), moderately repetitive DNA (transposable elements and multicopy genes), and highly repetitive DNA (satellite DNA at centromeres and telomeres).
Q5 What is non-repetitive DNA?
A5 Non-repetitive DNA consists mainly of unique, single-copy genes and unique regulatory sequences.
Q6 What is moderately repetitive DNA?
A6 Moderately repetitive DNA includes transposable elements and multicopy gene families such as rRNA and histone genes.
Q7 What is highly repetitive satellite DNA?
A7 Highly repetitive DNA consists of short sequences repeated many times, typically found at centromeres and telomeres.
Q8 What are multicopy genes and why do they exist?
A8 Multicopy genes are genes present in multiple copies because their products are required in large amounts, such as rRNAs, tRNAs, and histones.
Q9 How can multicopy genes be arranged in the genome?
A9 They can be dispersed throughout the genome, clustered in one region, or arranged in tandem arrays.
Q10 For a typical human gamete, what are c and n?
A10 n = 23 chromosomes and c = 1c, representing one haploid set of DNA.
Q11 For a typical human somatic cell, what are c and n?
A11 n = 46 chromosomes and c = 2c, representing two copies of the haploid DNA content.
Q12 What is somatic polyploidy?
A12 Somatic polyploidy occurs when somatic cells contain more than the normal diploid DNA content due to DNA replication without normal cell division or cell fusion.
Q13 How do skeletal muscle cells become multinucleated?
A13 Skeletal muscle cells form by fusion of multiple myoblasts, producing one cell containing multiple diploid nuclei.
Q14 How do megakaryocytes become polyploid?
A14 Megakaryocytes undergo endomitosis, replicating DNA without cell division, resulting in a highly polyploid nucleus.
Q15 Why are mature red blood cells not diploid?
A15 Mature mammalian red blood cells eject their nucleus and therefore contain no nuclear DNA.
Q16 What are the four key lab techniques: coloured stains, fluorescent stains, hybridization probes, and antibodies?
A16 Coloured stains show overall chromosome structure, fluorescent stains emit light under specific wavelengths, hybridization probes bind complementary DNA sequences, and antibodies bind specific proteins.
Q17 What are the main parts of a metaphase chromosome?
A17 Sister chromatids, centromere, p arm, q arm, and telomeres.
Q18 What are key features of a Drosophila polytene chromosome?
A18 Bands, interbands, transcriptional puffs, chromocenter, and distinct chromosome arms such as 2L and 3R.
Q19 What are the three types of genetic maps?
A19 DNA sequence maps (base-pair resolution), genetic maps (recombination distances in centimorgans), and cytogenetic maps (band-based chromosomal locations).
Q20 What are the main causes of aneuploidy?
A20 Non-disjunction during mitosis or during meiosis I or meiosis II.
Q21 What are the main causes of chromosome rearrangements?
A21 Improper repair of double-strand DNA breaks and non-allelic homologous recombination.
Q22 What is a contiguous gene syndrome?
A22 A disorder caused by deletion of multiple adjacent genes, resulting in a phenotype reflecting combined gene loss.
Q23 How is mRNA processed?
A23 mRNA processing includes 5′ capping, removal of introns by splicing, and addition of a 3′ poly-A tail.
Q24 What are canonical splice site sequences?
A24 The 5′ splice donor begins with GU and the 3′ splice acceptor ends with AG, usually preceded by a polypyrimidine tract.
Q25 What is intron phase?
A25 Intron phase describes where an intron interrupts a codon: phase 0 between codons, phase 1 after the first base, and phase 2 after the second base.
Q26 What is nonsense-mediated decay?
A26 Nonsense-mediated decay is a surveillance pathway that degrades mRNA containing premature stop codons to prevent production of truncated proteins.
Q27 What does standard PCR detect?
A27 Standard PCR detects the presence, absence, or size of a specific DNA region.
Q28 What does methylation-sensitive PCR detect?
A28 It detects DNA methylation status by using restriction enzymes that cut only unmethylated DNA before amplification.
Q29 How does automated Sanger sequencing work?
A29 Fluorescently labeled ddNTPs terminate DNA synthesis, fragments are separated by capillary electrophoresis, and colored peaks indicate base identity.
Q30 What does a heterozygous position look like in Sanger sequencing?
A30 Two overlapping peaks at the same nucleotide position.
Q31 What is a sequence logo?
A31 A graphical representation of sequence conservation where letter height indicates frequency and information content.
Q32 When would you use aCGH?
A32 To detect genome-wide copy number changes such as deletions or duplications.
Q33 When would you use DNA sequencing?
A33 To detect specific base changes or small mutations in DNA.
Q34 What is the parent-of-origin procedure?
A34 It combines SNP haplotype information with methylation patterns to determine whether a mutation was inherited from the mother or father.
Q35 What is Plasmidsaurus used for?
A35 It is used for low-cost long-read sequencing of plasmids to verify cloning constructs.
Q36 What are tiling microarrays?
A36 Tiling microarrays contain probes covering continuous genomic regions to detect copy number changes or binding patterns.
Q37 What are genotyping microarrays?
A37 Genotyping microarrays contain probes for known SNP positions to determine genotype and allele frequencies.
Q38 What is a one-channel microarray?
A38 A microarray where one DNA sample is analyzed and intensity is compared computationally to reference data.
Q39 What is a two-channel microarray?
A39 A microarray where test and reference DNA are labeled with different dyes and hybridized simultaneously to compare copy number.
Q40 How is aCGH data interpreted?
A40 Log2(test/reference) values around 0 indicate normal copy number, negative values indicate deletions, and positive values indicate duplications.
Q41 What techniques can detect somatic mosaicism?
A41 Deep sequencing, SNP arrays, and high-resolution aCGH can detect mosaicism depending on the proportion of affected cells.
Q42 Which techniques cannot detect balanced rearrangements?
A42 aCGH cannot detect balanced translocations or inversions because no DNA copy number changes occur.