Week 9
True/False: Somatic mutations can be passed down to offspring
False
When a deletion chromosome pairs with a normal chromosome during prophase I, it is the deletion chromosome that loops out.
False
What are the three subtypes of quantitative traits discussed in class and an example of each?
1. Continuous - height
2. Meristic - litter size
3. Threshold - type 2 diabetes
What does broad sense solve for? What does narrow sense solve for?
Broad sense: proportion of the phenotypic variance due to genetic variance
Narrow sense: proportion of the phenotypic variance due to additive genetic variance (measure of resemblance)
What is the outcome of a Robertsonian Translocation?
"New" metacentric chromosome and a short fragment that is often lost
Define missense, nonsense, and silent
Missense: changes the amino acid in the amino acid sequence
Nonsense: introduces an early stop codon
Silent: does not alter the resulting protein
In one species of cats, chromosome I has the segments ABCDEFG and chromosome V has the segments LMNOPQR. If one cat of this species has chromosomes ABCDPQR and LMNOEFG, what type of mutation occurred?
reciprocal translocation
In a watermelon population, the number of seeds is determined by four genes (A, B, C, and D genes) of equal effect that act additively. A dominant allele contributes 30 seeds, and a recessive allele contributes 10 seeds. In this population, watermelons with genotypes AabbCCDd and aaBbCcDD have the same number of seeds.
True
Given the following values, calculate narrow sense heritability:
Additive genetic variance = 78
Dominance genetic variance = 30
Gene interaction variation = 15
Environmental variance = 200
Genetic-environmental interaction variance = 6
0.24
What are the two methods for mapping quantitative traits discussed in lecture? Which would be better for a study that examines a single specific trait?
*QTL mapping (Quantitative Trait Loci)
GWAs (genome-wide association studies)
What type of mutation would occur if a three nucleotide bases are inserted together into the middle of a reading frame?
Inframe
What type of mutation is occurring in the chromosome segment below:
A B * C D E F G -----> A D C * B E F G
pericentric inversion
A series of unlinked genes contributes equally to determine the number of spots on a ladybug. Two pure breeding lines are crossed, one with 2 spots and one with 8 spots. The resulting bugs are crossed. Assuming that each gene has two alleles, one that adds additively and one that does not, how many genes contribute to ladybug spots?
3 genes
The narrow-sense heritability in sheep is 0.42. The phenotypic variance is 0.73, and the environmental variance is 0.25. What is the additive genetic variance?
0.31
What are three mechanisms that can cause aneuploidy?
loss of centromere, nondisjunction, Robertsonian translocation
How would you classify a mutation that causes a mutant phenotype to become a wildtype phenotype?
Reverse
What is the equation used to find how many chromosomes would be found in nullisomy, monosomy, trisomy, and triploid? Solve for a diploid individual with
2n = 36
2n-2 = 34
2n-1 =35
2n+1 =37
3n = 54
n=18
Guinea pig weight is determined by a pair of alleles at 2 independent loci. Each dominant allele contributes 2 lb and each recessive allele contributes 0.5 lb. If two heterozygous pigs have a litter, what frequency of the offspring is expected to be 6.5 lbs?
1/4
The broad sense heritability of bat’s wing span was calculated to be 0.45. If the phenotypic variance was 273, what is the genetic variance?
122.85
A nondisjunction event occurs. After fertilization, the zygotes present are trisomic and monosomic. Where did the nondisjunction occur?
a. Meiosis I
b. Meiosis II
c. Mitosis
Meiosis I
What type of mutation occurred below? Be as specific as possible
GGG GCU AUA CGU
GGG GCU AUA GGU
Single base substitution, transversion, missense
Species I has 2n = 42 chromosomes and species II has 2n = 38. How many chromosomes would be found in an allotriploid of these species?
59 or 61
5 caterpillars were measured. Their lengths (in cm) were
7, 9, 6, 11, 8
Calculate the mean, variance, and standard deviation
8.2 cm
3.7 cm 2
1.92 cm
The phenotypic variance for an outbred strain of frogs is 634. The phenotypic variance for an inbred strain of frogs is 271. What is the broad sense heritability and interpret the value.
0.57
Explain the mechanism that causes Familial Down Syndrome
Robertsonian translocation between chromosomes 14 and 21