Spring Gene 314 Lab- Final Exam UPDATED ACTUAL
Questions and CORRECT Answers
What identifies parental phenotypes? The parental phenotypes are the most frequent offspring because they represent
the original allele combinations from the heterozygous parent without
recombination.
What identifies double crossovers? Double crossovers are the least frequent classes because two crossover events in
the same region are rare.
Why are double crossovers important? They allow you to determine gene order because they show which gene is flipped
relative to the parental arrangement.
What is 1 map unit? 1 map unit (centimorgan) equals a 1% chance that a crossover occurs between two
genes during meiosis.
Recombination frequency formula? Recombination frequency = (number of recombinant offspring / total offspring) ×
100, representing crossover frequency.
What is interference? Interference is the phenomenon where one crossover reduces the probability of
another nearby crossover occurring.
Coefficient of coincidence formula? CoC = observed double crossovers / expected double crossovers, measuring
how many DCOs actually occurred vs expected.
If CoC = 1, what does that mean? A CoC of 1 means crossovers occur independently, so there is no interference.
If interference = 1, what does that mean? Interference = 1 means complete interference, so no double crossovers occur at
all.
What are linked genes? Linked genes are genes located close together on the same chromosome that
tend to be inherited together.
How do you find the middle gene? The middle gene is identified by comparing parental and double crossover
phenotypes—the gene that changes position is in the middle.
What is a testcross? A testcross is a cross between a heterozygous individual and a homozygous
recessive individual to reveal gamete types.
What contributes to map distance? Map distance is calculated using both single crossover and double crossover
events because both reflect recombination.
Why divide DCO by 2? Each DCO produces two recombinant classes, so dividing by 2 isolates one
specific phenotype class.
High recombination means? A high recombination frequency indicates the genes are far apart and more likely
to undergo crossover.
, Low recombination means? A low recombination frequency indicates the genes are close together and rarely
separated by crossover.
What is coupling? Coupling (cis configuration) means dominant alleles are on one chromosome and
recessive alleles on the homologous chromosome.
What is repulsion? Repulsion (trans configuration) means each chromosome carries one dominant
and one recessive allele.
Expected DCO formula? Expected DCO frequency = (recombination frequency of region 1 × region 2) ×
total offspring.
What reduces DCO frequency? Interference reduces DCO frequency by preventing nearby crossover events.
Why include DCO in map distance? DCOs must be included because they represent recombination events that would
otherwise be underestimated.
What do restriction enzymes do? Restriction enzymes recognize specific DNA sequences and cut the DNA
backbone at those sites, generating fragments.
What is a DNA palindrome? A DNA palindrome is a sequence that reads the same 5'→3' on both strands,
allowing enzymes to bind symmetrically.
What is a blunt end? A blunt end is produced when both DNA strands are cut at the same position,
leaving no overhang.
What is a sticky end? A sticky end is produced when cuts are staggered, leaving single-stranded
overhangs that can base-pair with complementary sequences.
5' overhang means? A 5' overhang occurs when the cut leaves unpaired nucleotides extending from
the 5' end of the DNA strand.
3' overhang means? A 3' overhang occurs when the cut leaves unpaired nucleotides extending from
the 3' end.
EcoRI recognition site? EcoRI recognizes the sequence GAATTC and cuts to produce 5' sticky ends useful
in cloning.
HindIII recognition site? HindIII recognizes AAGCTT and produces sticky ends with complementary
overhangs.
BamHI recognition site? BamHI recognizes GGATCC and generates sticky ends for DNA recombination
experiments.
DNA base pairing? In DNA, adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C)
via hydrogen bonds.
RNA uses what instead of T? RNA uses uracil (U) instead of thymine, pairing with adenine during transcription.
A pairs with in RNA? In RNA, adenine pairs with uracil (A-U) instead of thymine.
Questions and CORRECT Answers
What identifies parental phenotypes? The parental phenotypes are the most frequent offspring because they represent
the original allele combinations from the heterozygous parent without
recombination.
What identifies double crossovers? Double crossovers are the least frequent classes because two crossover events in
the same region are rare.
Why are double crossovers important? They allow you to determine gene order because they show which gene is flipped
relative to the parental arrangement.
What is 1 map unit? 1 map unit (centimorgan) equals a 1% chance that a crossover occurs between two
genes during meiosis.
Recombination frequency formula? Recombination frequency = (number of recombinant offspring / total offspring) ×
100, representing crossover frequency.
What is interference? Interference is the phenomenon where one crossover reduces the probability of
another nearby crossover occurring.
Coefficient of coincidence formula? CoC = observed double crossovers / expected double crossovers, measuring
how many DCOs actually occurred vs expected.
If CoC = 1, what does that mean? A CoC of 1 means crossovers occur independently, so there is no interference.
If interference = 1, what does that mean? Interference = 1 means complete interference, so no double crossovers occur at
all.
What are linked genes? Linked genes are genes located close together on the same chromosome that
tend to be inherited together.
How do you find the middle gene? The middle gene is identified by comparing parental and double crossover
phenotypes—the gene that changes position is in the middle.
What is a testcross? A testcross is a cross between a heterozygous individual and a homozygous
recessive individual to reveal gamete types.
What contributes to map distance? Map distance is calculated using both single crossover and double crossover
events because both reflect recombination.
Why divide DCO by 2? Each DCO produces two recombinant classes, so dividing by 2 isolates one
specific phenotype class.
High recombination means? A high recombination frequency indicates the genes are far apart and more likely
to undergo crossover.
, Low recombination means? A low recombination frequency indicates the genes are close together and rarely
separated by crossover.
What is coupling? Coupling (cis configuration) means dominant alleles are on one chromosome and
recessive alleles on the homologous chromosome.
What is repulsion? Repulsion (trans configuration) means each chromosome carries one dominant
and one recessive allele.
Expected DCO formula? Expected DCO frequency = (recombination frequency of region 1 × region 2) ×
total offspring.
What reduces DCO frequency? Interference reduces DCO frequency by preventing nearby crossover events.
Why include DCO in map distance? DCOs must be included because they represent recombination events that would
otherwise be underestimated.
What do restriction enzymes do? Restriction enzymes recognize specific DNA sequences and cut the DNA
backbone at those sites, generating fragments.
What is a DNA palindrome? A DNA palindrome is a sequence that reads the same 5'→3' on both strands,
allowing enzymes to bind symmetrically.
What is a blunt end? A blunt end is produced when both DNA strands are cut at the same position,
leaving no overhang.
What is a sticky end? A sticky end is produced when cuts are staggered, leaving single-stranded
overhangs that can base-pair with complementary sequences.
5' overhang means? A 5' overhang occurs when the cut leaves unpaired nucleotides extending from
the 5' end of the DNA strand.
3' overhang means? A 3' overhang occurs when the cut leaves unpaired nucleotides extending from
the 3' end.
EcoRI recognition site? EcoRI recognizes the sequence GAATTC and cuts to produce 5' sticky ends useful
in cloning.
HindIII recognition site? HindIII recognizes AAGCTT and produces sticky ends with complementary
overhangs.
BamHI recognition site? BamHI recognizes GGATCC and generates sticky ends for DNA recombination
experiments.
DNA base pairing? In DNA, adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C)
via hydrogen bonds.
RNA uses what instead of T? RNA uses uracil (U) instead of thymine, pairing with adenine during transcription.
A pairs with in RNA? In RNA, adenine pairs with uracil (A-U) instead of thymine.
