BSCI222 Exam 2

What does COC stand for in genetics?

Coefficient of coincidence

How is the coefficient of coincidence (COC) calculated?

COC = (observed n 2x crossover) / (expected n 2x crossover)

What does a COC value less than 1 indicate?

It indicates interference, meaning one crossover prevents another from occurring.

What is the maximum recombination frequency?

50%

What organism is commonly used to study genetic linkage?

Drosophila melanogaster

What is the purpose of FISH in genetics?

To identify the chromosomal location of a gene or the site of its mRNA product.

What are the three main components of a nucleotide?

A pentose sugar, one to three phosphate groups, and one to four nitrogenous bases.

What is the primary structure of proteins?

The amino acid sequence.

What is Chargaff's Rule?

Adenine pairs with Thymine, and Cytosine pairs with Guanine.

What are the two main types of nucleic acids?

Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA).

What is the structure of DNA?

A double helix formed by two complementary and antiparallel nucleotide strands.

What type of bond links nucleotides in DNA?

Phosphodiester bonds.

What is the melting temperature (Tm) of DNA?

The temperature at which 50% of DNA samples are double-stranded and 50% are single-stranded.

What is the significance of the 2+4 rule in DNA?

It is used to calculate the melting temperature (Tm) based on the number of A/T and G/C pairs.

What is the role of proteins in the cell?

Proteins perform numerous biological functions and are polymers of amino acids.

What is the function of the ribosome in protein synthesis?

To join amino acids together by forming peptide bonds.

What is the difference between primary, secondary, tertiary, and quaternary protein structures?

Primary is the amino acid sequence, secondary is local folding (like alpha helices), tertiary is overall 3D shape, and quaternary is multiple polypeptide chains.

What is the significance of the lock and key hypothesis?

It describes how the structure of a protein determines its function.

What is Complete Androgen Insensitivity Syndrome?

A genetic disorder where XY fetuses are insensitive to androgens, resulting in external female characteristics.

What are the nitrogenous bases found in DNA?

Adenine (A), Thymine (T), Guanine (G), Cytosine (C).

What are the nitrogenous bases found in RNA?

Adenine (A), Uracil (U), Guanine (G), Cytosine (C).

What is the role of Franklin and Wilkins in DNA research?

Their X-ray crystallography work suggested the helical structure of DNA.

What is the significance of the 3'-5' phosphodiester bond?

It links the 3' carbon of one nucleotide to the 5' carbon of another, forming the DNA backbone.

What is the function of the R group in amino acids?

It determines the specific properties and identity of each amino acid.

What is the primary function of DNA?

To store and transmit genetic information.

What is the relationship between structure and function in proteins?

The specific structure of a protein determines its function.

What is the average distance between bases in DNA?

0.34 nm

What are the three forms of DNA mentioned?

A, B, and Z DNA

What is a hairpin structure in nucleotides?

A secondary structure formed when sequences on the same strand are inverted complements.

Why is DNA considered stable?

It is double-stranded and redundant, which protects the sequence and prevents tangling.

What does paleogenetics involve?

The extraction and analysis of DNA from ancient remains.

What is environmental DNA (eDNA)?

DNA that can be sampled from the environment to study past ecosystems.

What is supercoiling in DNA?

The coiling of the DNA double helix by overwinding or underwinding.

What role do topoisomerases play in DNA structure?

They add or remove rotations in DNA by breaking strands, rotating ends, and rejoining broken ends.

What is the composition of eukaryotic chromatin?

⅓ DNA, ⅓ histones, and ⅓ nonhistone proteins.

What are the two types of chromatin?

Euchromatin and heterochromatin.

What is the difference between euchromatin and heterochromatin?

Euchromatin is less condensed and contains many genes, while heterochromatin is more condensed and contains few genes.

What are polytene chromosomes?

Chromosomes created by repeated rounds of DNA replication without cell division.

What is the function of histones in DNA?

They help organize chromosomes and form nucleosomes.

What happens when H1 histone is removed?

The DNA becomes relaxed.

What is the C-value paradox?

The lack of correlation between genome size and apparent complexity in eukaryotes.

What are unique-sequence DNA and gene families?

Unique-sequence DNA consists of unique genes, while gene families are similar copies of unique DNA sequences that arose through duplication.

What are tandem repeat sequences?

Moderately repetitive DNA sequences that consist of repeated patterns unrelated to transposons.

What are SINEs and LINEs?

Short interspersed elements (SINEs) are non-coding sequences, while long interspersed elements (LINEs) are longer repetitive sequences.

What is the role of nucleolus organizer regions (NORs)?

They consist of tandemly repeated sequences coding for ribosomal RNA (rRNA).

What is the significance of chromosomal territories?

They prevent chromosomes from becoming entangled and allow for organized interactions during interphase.

What is the role of protein kinases in cells?

They transfer phosphates from ATP to proteins, a process called phosphorylation.

What is the function of phosphatases?

They reverse phosphorylation, returning proteins to their non-phosphorylated state.

What is the function of condensin?

It is a protein complex that folds chromatin and compacts chromosomal DNA.

What are the characteristics of eukaryotic DNA sequence variation?

Eukaryotic DNA contains unique sequences, moderately repetitive sequences, and transposable elements.

What is the purpose of the ENCODE project?

To identify all functional elements in the human genome.

What is the melting temperature in relation to DNA?

It refers to the temperature at which DNA denatures or separates into single strands.

Where are NORs located in humans?

On the short arms of acrocentric chromosomes 13, 14, 15, 21, and 22.

What is the function of telomeres?

To prevent the loss of genes as chromosome ends wear down; they are non-coding DNA caps.

What are centromeres?

The binding site of spindle fibers, consisting of large arrays of repetitive DNA.

What is the structure of a centromere?

A constricted region of a chromosome where spindle fibers attach, consisting of satellite DNA.

What are microsatellites?

Tandem repeats of 2-5 base pair lengths in specific regions of the genome, often with no known function.

What is DNA fingerprinting?

A method used in crime scene investigations to identify individuals based on their DNA profiles.

What is the Combined DNA Index System (CODIS)?

A system used by the FBI that includes a panel of 13 STRs, each with many alleles on different chromosomes.

What is the probability of two random people having the same DNA profile?

1 in 10 billion.

What is the purpose of PCR in DNA profiling?

To produce a pattern of DNA fragments from STR loci.

How was DNA fingerprinting used in the World Trade Center collapse?

To identify victims when usual means of identification were ineffective.

What evolutionary advantage does DNA fingerprinting provide in paternity cases?

It allows for the identification of the most virile male for reproduction and a caring male for child-rearing.

What is a genome?

The total DNA complement of a cell, which is dynamic and subject to mutations.

How do transposons contribute to macroevolution?

By inserting new bits of DNA throughout the genome, potentially leading to beneficial changes.

What are the two classes of transposons?

Class I (retrotransposons) and Class II (DNA transposons).

What is transposition?

The movement of transposons within the genome.

What is the role of transposase?

To cleave the ends of transposons and facilitate their movement within the genome.

What is conjugation in bacteria?

A natural gene transfer mechanism that can spread antibiotic resistance through R plasmids.

What proteins are involved in the immune system's customization of antibodies?

RAG-1 and RAG-2.

What are endogenous retroviruses (ERVs)?

Viral DNA that can be passed to the next generation if it infects germline cells.

How do transposons cause mutations?

By inserting into genes and disrupting their function or promoting DNA rearrangements.

What is the metabolic burden associated with transposable elements?

The energy and time required to replicate large numbers of transposable elements.

What is the role of DNA helicase in DNA replication?

To unwind DNA at the replication fork.

What does DNA primase do?

Synthesizes a short RNA primer to provide a 3'-OH group for DNA nucleotide attachment.

What is the function of DNA ligase?

Joins Okazaki fragments by sealing breaks in the sugar-phosphate backbone of DNA.

What is the role of single-strand binding proteins during DNA replication?

To attach to single-stranded DNA and prevent secondary structures from forming.

What is the function of DNA polymerase III?

To elongate a new DNA strand during replication.

What is the role of DNA gyrase?

To relieve the torque that builds up during DNA unwinding at the replication fork.

What are the fixed sites where DNA replication occurs called?

Replication factories

What is the origin of replication in E. coli?

A single origin about 245 base pairs long, mostly A/T base pairs.

What proteins bind to the origin of replication in E. coli?

Special initiator proteins, specifically DnaA.

What structures are formed as DNA opens during theta replication?

Two Y-shaped structures called replication forks.

At what speed does E. coli replicate its DNA?

At a rate of over 1000 nucleotides per second.

How does linear eukaryotic replication differ from theta replication?

Eukaryotic replication has thousands of origins and each fork moves at 500-5000 nucleotides/min.

What is the role of helicase in DNA replication?

Helicase unwinds the DNA at the origin of replication.

What prevents the DNA double helix from becoming too tightly wound during replication?

DNA gyrase, a topoisomerase II.

What are single-strand binding proteins (SSBs) responsible for?

Coating separated strands of DNA to prevent them from re-annealing.

What is the primary function of DNA polymerase III in bacteria?

To synthesize DNA by adding nucleotides to the growing chain.

What is required for DNA polymerases to start synthesizing DNA?

A pre-existing chain or a short stretch of nucleotides called a primer.

What are Okazaki fragments?

Small fragments of DNA synthesized on the lagging strand during replication.

How are RNA primers removed and replaced during DNA replication?

By the activity of DNA polymerase I.

What is the end-replication problem?

The gap left after the last primer is removed from the lagging strand.

What enzyme is responsible for the replication of chromosome ends?

Telomerase.

What is the significance of telomere length in aging?

Decreasing telomere length contributes to aging; shorter telomeres are associated with premature aging.

What effect does chronic psychological stress have on telomere length?

It shortens telomere length.

What is the relationship between telomerase activity and germ cells?

Germ cells and certain stem cells have telomerase activity, while most somatic cells do not.

What lethal effect does the toxin a-Amanitin have?

It inhibits RNA polymerase II, which produces mRNA.

How can changes in gene expression lead to macroevolution?

By switching on the same genes in different patterns to produce large phenotypic changes.

What is the genetic toolkit concept?

The idea that expression differences in a single gene can lead to significant morphological changes.