BIOD 210 GENETICS MODULE 1 TO 7 EXAM
EXAM SCRIPT 2026 QUESTIONS WITH
ANSWERS GRADED A+
◉ How does the configuration of alleles affect the progeny's
phenotypic ratios. Answer: If the parents are trans, the majority of
the progeny will have their nonrecombinant phenotype. (and vice
versa)
◉ In a testcross, completely linked genes produce only two types of
progeny, what are they. Answer: Both nonrecombinants, in equal
proportions
◉ Interchromosomal is to __________________ ___________ as is
intrachromosomal is to ______________ _____________.. Answer: -
Interchromosomal (Independent Assortment)
-Intrachromosomal (Crossing Over)
◉ (T/F): Crossing over occurs randomly.. Answer: True
◉ 2 genes far apart are ___ likely to crossover than 2 genes close
together. Answer: MORE
,◉ 1% Recombination Frequency =. Answer: 1 map unit
◉ Two-Point Test Cross:. Answer: Cross between an individual
heterozygous at two loci and an individual homozygous for recessive
alleles at those loci.
◉ In a two-point cross, if two genes are at 50% recombination
frequency, what does this tell us about the genetic map?. Answer:
They are likely on two different chromosomes or are in different
linkage groups.
◉ What is a three-point testcross? Why is it better than a 2 point
cross?. Answer: -3 linked genes
-Only one cross is needed rather than multiple 2 point crosses
-3 point crosses don't miss double crossovers
◉ What are the 7 steps of creating a genetic map from a 3 point
testcross?. Answer: 1. Determine gene order (DCO's)
2. Rewrite genes in correct order
3. Locate crossovers
4. Calculate recombination frequencies
5. Construct gene map
6. Calculate coefficient of coincidence
7. Calculate interference
,◉ How can you find the theoretical proportion of DCO's?. Answer:
Multiply each of the SCO's probabilities together.
◉ Define interference.. Answer: The degree to which one crossover
interferes with additional crossovers in the same region (because
they are not completely independent events)
◉ What is the coefficient of coincidence?. Answer: Observed
DCO's/Expected DCO's
◉ How can you find interference?. Answer: 1 - COC
◉ Define quantitative genetics.. Answer: the genetic analysis of
complex characteristics
◉ What's the difference between discontinuous and continuous
traits?. Answer: -Discontinuous (possess only a few distinct
phenotypes)
-Continuous (possess traits that lie on a scale)
◉ Why are some characteristics continuous?. Answer: -polygenic
-environmental influences
-wide range of phenotypes
, -multifactorial
◉ What is a truly continuous trait?. Answer: a type of quantitative
trait that can display an infinite amount of phenotypes (height,
weight, etc.)
◉ What is a meristic trait?. Answer: a type of quantitative trait that
takes the form of integers (litter size
◉ Why are meristic traits considered quantitative if they don't hold
an infinite number of phenotypes?. Answer: They are still traits that
are influenced by a variety of genetic and environmental influences
◉ What is a threshold characteristic?. Answer: A type of quantitative
trait that is either absent or present (ASD or other threshold
diseases)
◉ Why are threshold characteristics still quantitative?. Answer:
Although threshold characteristics exhibit only two phenotypes,
they are considered quantitative because they also are determined
by multiple genetic and environmental factors.
◉ How do additive polygenic traits work?. Answer: Many genes that
add up and tell you what your phenotype looks like.
EXAM SCRIPT 2026 QUESTIONS WITH
ANSWERS GRADED A+
◉ How does the configuration of alleles affect the progeny's
phenotypic ratios. Answer: If the parents are trans, the majority of
the progeny will have their nonrecombinant phenotype. (and vice
versa)
◉ In a testcross, completely linked genes produce only two types of
progeny, what are they. Answer: Both nonrecombinants, in equal
proportions
◉ Interchromosomal is to __________________ ___________ as is
intrachromosomal is to ______________ _____________.. Answer: -
Interchromosomal (Independent Assortment)
-Intrachromosomal (Crossing Over)
◉ (T/F): Crossing over occurs randomly.. Answer: True
◉ 2 genes far apart are ___ likely to crossover than 2 genes close
together. Answer: MORE
,◉ 1% Recombination Frequency =. Answer: 1 map unit
◉ Two-Point Test Cross:. Answer: Cross between an individual
heterozygous at two loci and an individual homozygous for recessive
alleles at those loci.
◉ In a two-point cross, if two genes are at 50% recombination
frequency, what does this tell us about the genetic map?. Answer:
They are likely on two different chromosomes or are in different
linkage groups.
◉ What is a three-point testcross? Why is it better than a 2 point
cross?. Answer: -3 linked genes
-Only one cross is needed rather than multiple 2 point crosses
-3 point crosses don't miss double crossovers
◉ What are the 7 steps of creating a genetic map from a 3 point
testcross?. Answer: 1. Determine gene order (DCO's)
2. Rewrite genes in correct order
3. Locate crossovers
4. Calculate recombination frequencies
5. Construct gene map
6. Calculate coefficient of coincidence
7. Calculate interference
,◉ How can you find the theoretical proportion of DCO's?. Answer:
Multiply each of the SCO's probabilities together.
◉ Define interference.. Answer: The degree to which one crossover
interferes with additional crossovers in the same region (because
they are not completely independent events)
◉ What is the coefficient of coincidence?. Answer: Observed
DCO's/Expected DCO's
◉ How can you find interference?. Answer: 1 - COC
◉ Define quantitative genetics.. Answer: the genetic analysis of
complex characteristics
◉ What's the difference between discontinuous and continuous
traits?. Answer: -Discontinuous (possess only a few distinct
phenotypes)
-Continuous (possess traits that lie on a scale)
◉ Why are some characteristics continuous?. Answer: -polygenic
-environmental influences
-wide range of phenotypes
, -multifactorial
◉ What is a truly continuous trait?. Answer: a type of quantitative
trait that can display an infinite amount of phenotypes (height,
weight, etc.)
◉ What is a meristic trait?. Answer: a type of quantitative trait that
takes the form of integers (litter size
◉ Why are meristic traits considered quantitative if they don't hold
an infinite number of phenotypes?. Answer: They are still traits that
are influenced by a variety of genetic and environmental influences
◉ What is a threshold characteristic?. Answer: A type of quantitative
trait that is either absent or present (ASD or other threshold
diseases)
◉ Why are threshold characteristics still quantitative?. Answer:
Although threshold characteristics exhibit only two phenotypes,
they are considered quantitative because they also are determined
by multiple genetic and environmental factors.
◉ How do additive polygenic traits work?. Answer: Many genes that
add up and tell you what your phenotype looks like.
