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Genetics Test 1
Terms in this set (79)
Alleles of linked genes recombine:
what is the relationship between A and B
They are in cis
A mutant strain of Neurospora is grown and is labeled an arginine auxotroph. What does this mean?
A mutant that requires the amino acid arginine to grow is called an arginine auxotroph.
If mutant 1 complements mutant 2, and mutant 2 complements mutant 3, but mutant 3 fails to complement mutant 1, how many genes have been identified by these 3 mutations?
For linked genes, recombinant gametes form more often than parental gametes.
a linkage map can not be more than 100 centimorgans.
Gene interaction produces deviation from the expected mendelian ratio of phenotypes in the progeny of a dihybrid selfcross. Which of the following ratios is most likely due to interaction between genes in the same pathway?
What phenotypic ratio in the progeny of a dihybrid self cross is evidence of recessive epistatis?
In a dihybrid test cross, 110 progeny show recombinant phenotypes and 290 show parental phenotypes, how far apart are these genes?
27.5 map units
Can we detect crossing over between sister chromatids, or crossing over in homozygotes, when we look at the progeny of a cross?
A mutation in a gene that functions in a metabolic pathway can cause disease because
The individual is deficient in the end product of the pathway
Mendel crossed Y/Y;R/R (yellow wrinkled) peas with y/y;r/r (green smooth) peas and selfed the F1 to obtain the F2. What proportion of the F2 individuals were pure-breeding?
In hogs, a dominant allele B results in a white belt around the body. At a separate locus, the dominant allele S causes fusion of the two parts of the normally cloven hoof resulting in a condition known as syndactyly. A belted syndactylous sow was crossed to an unbelted cloven-hoofed boar, and in the litter there were:
25% belted syndactylous
25% belted cloven
25% unbelted syndactylous
25% unbelted cloven
The ratio of phenotypes in the progeny tells us what type of cross was performed. The genotypes of the parents can best be represented as which of the following?
B/b;S/s * b/b;s/s
If an individual has 10 gene pairs, how many different gametes can be formed if 5 of the gene pairs are homozygous and the remaining 5 gene pairs are heterozygous?
Consider the following cross examining five unlinked genes. Identify what proportion of the progeny will be genotypically identical to parent 2?
Parent 1: A/a; B/b; C/c; D/d; E/e
Parent 2: A/A; b/b; C/c; D/d; E/e
Which of the following is TRUE with respect to haploid and diploid cells?
In diploid cells, meiosis I results in the formation of two haploid cells
Meiosis I is about to start in a cell of a plant in which 2n = 18. At this stage, the cell has:
18 replicated chromosomes, and a total of 36 chromatids
What process occurring during meiosis ensures independent assortment?
the pairing of homologous chromosomes during meiosis 1
Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci, or "polygenes") that work in an equal and additive manner. Each QTL has two alleles (i.e., A and a); each allele represented by a capital letter produces one dose of yellow pigment, while alleles represented with lower case letters do not produce any pigment at all.
Assuming no effects by the environment, how many different shades of yellow fruit color are there?
If a plant of genotype A/a is selfed, and numerous offspring are scored, what proportion of the progeny is expected to have homozygous genotypes?
A mutation occurs in a germ cell of a pure-breeding, wild-type male mouse prior to DNA replication. The mutation is not corrected, and the cell undergoes DNA replication and a normal meiosis producing four gametes. How many of these gametes will carry the mutation?
What is the mechanism that ensures Mendel's first law of segregation?
segregation of homologous chromosomes during meiosis I
In pet rabbits, brown coat color is recessive to black coat color. A black female rabbit gives birth to four black-coated and three brown-coated baby rabbits. What can be deduced about the genotype of the baby rabbits' father?
He is most likely homozygous brown.
"Dumpy" is a commonly used mutant phenotype in the nematode worm C. elegans. Two "Dumpy" individuals are crossed to each other, and this cross produces 210 "Dumpy" and 68 wild-type individuals. If one of the two "Dumpy" individuals used in this cross was mated with a wild type, what "Dumpy": wild-type ratio would we observe in the offspring?
A very common type of red-green colorblindness in humans is caused by a mutation in a gene located on the X chromosome. Knowing that the mutant allele is recessive to the wild type, what is the probability that the son of a woman whose father is colorblind is going to also be colorblind? ( her father is colorblind)
A recessive X-linked gene mutation is known to generate premature baldness in males but is without effect in women. If a heterozygous female marries an affected male, what proportion of their children (assume they have 4 girls and 4 boys) is expected to be prematurely bald?
Sperm and eggs are _________ cells, which are formed by a specific type of cell division called ______.
When do chromatids form?
During S phase
What separates during meiosis 1?
A null mutation of a haplosufficient gene would be recessive to the wildtype allele.
Females are the heterogametic sex.
In the purple penguin, an allelic series occurs at the p locus on an autosome. All alleles affect the color of feathers: pd = dark-purple, pm = medium-purple, pl = light-purple, and pvl = very pale purple. The order of dominance is pd > pm > pl > pvl. If a pl/pvl female is crossed to a pd/pmmale, the ratio of phenotypes expected among the baby penguins would be:
1 dark purple :1 medium purple
In chickens, the dominant allele Cr produces the creeper phenotype (having extremely short legs). However, the creeper allele is lethal in the homozygous condition. If two creepers are mated, what proportion of the living progeny will be creepers?
Pleiotropic alleles affect _________ traits.
Two purebreeding parental lines produce red or white flowers, respectively. When they are cross pollinated, the flowers of the F1 plants are pink. This is an example of _____.
In the fruitfly Drosophila melanogaster, red and yellow eye pigments are synthesized through the pterin pathway. These, plus the brown pigment synthesized through the ommochrome pathway, produce the dark red Drosophila eye color. A part of the pterin pathway (simplified) is shown below.Consider the genes encoding Enzyme 1 ("e1"), Enzyme 2 ("e2") and Enzyme 3 ("e3"), respectively. What are their predicted genetic interactions?
e1 is recessively epistatic to e2 and to e3.
Two new pure-breeding strains of mouse (strain 1 and strain 2) have been obtained. Crosses between strain 1 and wild type, as well as crosses between strain 2 and wild type and between strain 1 and strain 2 always produce 100% wild-type mice.
What kind(s) of interactions can be deduced from these results?
Complementation and dominance of wildtype to mutant
In certain breeds of rabbits, the t/t genotype results in a specific malformation of the teeth. However, in any given rabbit population, only about 75% of the individuals with a t/t genotype actually have the teeth malformation.
What best describes this situation?
75% penetrance of tooth malformation
Variegated leaves are seen when _____
mutant and wild type chloroplasts segregate into separate daughter cells during mitosis.
If gene A and gene B are 25 map units apart, and gene A and gene C are 5 map units apart, what is the distance between gene B and gene C?
genes B and C are either 20 or 30 map units apart
If a genetics student counts 442 parental types and 437 recombinant types in the progeny of a dihybrid test cross, the two genes under consideration are most likely
The synaptonemal complex ______
•holds a bivalent together
•forms during meiosis 1
•holds homologous pairs of chromosomes together
•holds the chromatids in a tetrad together
How many degrees of freedom would there be in a χ2 test of a dihybrid test cross?
In pathway analysis, mutants that grow on most of the compounds carry mutations in genes for enzymes that are needed __________ of the pathway.
Near the beginning
Males are ________ for the X chromosome and show the phenotype associated with the allele they carry.
Piebald spotting, which occurs to different extents in each hound, is an example of _________.
Black is dominant to brown in Labrador retrievers. A dog breeder mated two black labs and noticed an unusual ratio in the coat color of the progeny. The dog breeder's friend in Biol 450 explained the results as recessive epistasis. What was the ratio of coat colors?
9 black : 3 brown : 4 yellow
In medel's crosses the dominant phenotype is revealed in the F1
The genotype A/a; Bc/bC; D/d refers to ______ chromosome pairs, where ______ are linked.
3: B and C
Hybrid vigor is observed when the F1 heterozygote performs better than either of its homozygous parentals.
Which of the following does not contribute to genetic variation?
crossing overing between sister chromatids
The purpose of using the χ2-test in genetics is to determine how well the observed results fit the expected results
What is the most likely explanation for the pattern of inheritance observed in the pedigree below?
In a diploid organism, what stage of cell division would the chromosomes diagrammed below be going through?
Pairing of homologous chromosomes in Meiosis 1 is important because
it allows recombination and ensures homologs separate
The second division of meiosis is similar to mitosis in that
sister chromatids segregate
A bivalent consists of ____ tetrad(s), ____ dyad(s) and, ______ chromatid(s)
1: 2: 4
The phenotype of a heterozygous genotype helps determine if a gene is haplosufficient or haploinsufficient because
If the phenotype looks like wild type the gene is haplosufficient
Which of the following statements is correct
Meiosis only occurs in diploid cells
Males are _________for genes on the X chromosome
Which of the following genotypes would breed true?
AA BB cc DD EE
A scientist discovers a mouse with short whiskers. She crosses it to a wild type (long
whiskered) mouse and after several litters she counts 21 long whiskered mice and 23 short
whiskered mice. What can she determine from these results?
The short whisker form is dominant to wild type
When do chromatids form?
In an autosomal recessive disorder, an unafflicted child of two heterozygous (carrier) parents has a _______ chance of being a carrier
Meiotic recombination can be detected in the offspring when crossing over occurs between_____________ of the ___________.
non-sister chromatids; tetrad
When two genes, A and B, show linkage in meiosis, the percentage (%) of parentals from the AB/ab x ab/ab testcross is expected to be __________.
greater than 50%
True or False. Chiasmata (or crossovers) occur less frequently between two genes when the genes are far apart on the same chromosome.
A Recombination Frequency (RF) of 0.15 is equal to a map distance of _____________
In humans, what is ploidy level (before DNA replication) of a meiocyte?
Two segregation ratios are characteristic of single gene inheritance.
Using the A and a symbols, what are the crosses and the progeny genotypes for each?
Self Cross A/a x A/a → 1 A/A: 2 A/a: 1 a/a ; Test Cross A/a x a/a → 1 A/a: 1 a/a
What is the most likely mode of inheritance in this pedigree?
This pedigree shows the occurrence of color blindness in a family. What is the probably that the unborn child (marked by a "?"), will be color blind?
If genes assort independently, a dihybrid self cross produces progeny phenotypes in the ratio
The brilliant undergraduate researcher performs a test cross between a mutant and a homozygous recessive. All the progeny display the mutant phenotype. What does the undergraduate research tell his mentor?
The genotype of the mutant is homozygous dominant
In complementation tests, m1 was found to complement m2, while m1 did not complement m3 nor m4. In addition, m5 was unable to complement m2. How many genes are present among the mutants?
Maria has blood type A and Maria's mother has blood type O. Maria's husband, Ian, has blood type AB. What is the probability of Ian and Maria having a baby with blood type B?
In humans, alkaptonuria (black urine disease) results from _______________ homogentisic acid leading to discoloration of the urine.
True or False. In snapdragons, a heterozygote has pink flowers, intermediate between the two homozygotes having red and white flowers, respectively. The pink heterozygote demonstrates codominance.
An allele that affects more than one trait is called
Recommended textbook explanations
Biocalculus: Calculus for the Life Sciences
Fundamentals of Biochemistry: Life at the Molecular Level
Charlotte W. Pratt, Donald Voet, Judith G. Voet
Lehninger Principles of Biochemistry
David L Nelson, Michael M. Cox
Modern Biology: Student Edition
Janet L. Hopson, Postlethwait
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