The Chromosomal Basis of Inheritance

In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female?
1. 2:1 (male to female)
2. 1:2 (male to female)
3. 1:1 (male to female)
4. 4:3 (male to female)
5. 3:1 (male to female)
Which of the following statements is TRUE regarding genomic imprinting?
1. It explains cases where the gender of the parent from whom an allele is inherited affects the expression of that allele
2. It is greatest in females because of the larger maternal contribution of cytoplasm.
3. It may explain the transmission of Duchenne's muscular dystrophy.
4. It explains sex-linked inheritance in which the sex of the parent carrying the mutant allele determines whether male or female offspring will be affected.
5. It is found in X-inactivation in human females during early embryonic development.
If inheritance of a human trait is sex-linked (on the X chromosome) and recessive, any of the following could result EXCEPT that
1. expression of th etrait might "skip" a generation
2. the trait could be more common in females than males
3. all females might become homozygous for the trait
4. the gene for the trait might mutate to a dominant allele
5. females could be a mosaic of two cell types
The following is a list of chromosomal alternations. Which one of these would automatically cause two of the others?
1. deletion
2. duplication
3. inversion
4. reciprocal translocation
5. nonreciprocal translocation
The finding that defective genes behave differently in offspring depending on whether they belong to the maternal or paternal chromosomes is implicated in which of the following?
1. Prader- Willi syndrome
2. fragile X syndrome
3. Angelman syndrome
4. Only A and C are correct
5. A, B, and C are correct
Fragile X syndrome is more common in males than in females. One explanation for this is
1. genomic imprinting by the mother
2. sex-linked inheritance
3. uniparental disomy
4. Only A and C are correct
5. A, B, and C are correct
What do all human males inherit from their mother?
1. mitochondral DNA
2. X chromosome
3. male-pattern baldness trait
4. Only A and B are correct
5. A, B, and C are correct
A mammalian zygote with which of the following chromosomal abnormalities will NEVER develop into a viable embryo?
1. YO
2. XO
3. XXX
4. XXY
5. XXXXY
All of the following statements are true about chromosomal inversions EXCEPT:
1. They do not alter phenotype
2. They involve breakage of a chromosome
3. They do not change the normal balance of genes
4. The change the orger of the genes on the chromosome.
What does independent assortment refer to?
1. the separation of alleles in anaphase I
2. the random arrangement of chromosomal tetrads at metaphase I
3. the separation of chromatids at anaphase II
4. the random arrangement of gene loci on a chromosome
5. the fact that any pair of chromatids in a tetrad can cross over
A Barr body is normally found in the nucleus of which kind of human cell?
1. unfertilized egg cells only
2. sperm cells only
3. somatic cells of a female only
4. somatic cells of a male only
5. both male and femal somatic cells
The particular position of a gene on a chromosome is known as a(n)
1. allele
2. tetrad
3. chiasma
4. locus
5. map distance
The frequency of crossing over between any two linke genes is
1. higher if they are recessive
2. difficult to predict
3. determined by their relative dominance
4. the same as if they were not lined
5. proportional to th edistance between them.
A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision who father is color-blind marries a color-clind male. what is the probablity that this couple's son will be color-blind?
1. 0%
2. 25%
3. 50%
4. 75%
5. 100%
A man who carries an X-linked allele will pass it on to
1. all of his daughters.
2. half of his daughters.
3. all of his sons.
4. half of his sons.
5. all of his children.
Which of the following is a sex-influenced trait?
1. male-pattern baldness
2. white eyes in fruit flies
3. nemophilia
4. color blindness
5. Truner syndrome
An achondroplastic dwarf man with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their femal children might be expected to be color-blind dwarfs?
1. all
2. none
3. half
4. one out of four
5. three out of four
An achondroplastic dwarf man with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their male children would be color-blind and normal height?
1. all
2. none
3. half
4. one out of four
5. three out of four
An achondroplastic dwarf man with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. They have a daughter who is a dwarf with normal color vision. What is the probablility that she is heterozygous for both genes?
1. 0
2. 0.25
3. 0.50
4. 0.75
5. 1.00
If a human interphase nucleus contained three Barr bodies, it can be assumed that the person
1. is a female
2. is a male
3. has 4 X chromosomes
4. has Turner syndrome
5. has Down syndrome
Barring in chickens is due to a sex-linked dominant gene (B). the sex of chicks at hatching is difficult to determine, but barred chicks can be distinguished from non-barred at that time. to use this trait so that at hatching all chicks of one sex are differently colored from those of the opposite sex, what cross would you make?
1. barred males x barred females
2. barred males x non-barred females
3. non-barred males x barred females
4. non-barred males x non-barred females
5. None of the above crosses will produce differently barred chicks
In heritance of two different traits at two different loci can be complicated by all of the following EXCEPT
1. the presence of the two loci on one chromosome.
2. independent assortment of chromosomes.
3. epistatic interactions between the two loci
4. environmental modification of phenotype
5. parental imprinting of genes.
C = normal c = color-blindness Y = Y chromosome

If color-blindness is sex-linked, what is the genotype of individual III-2?
1. CC
2. Cc
3. cc
4. CY
5. cY
C = normal c = color-blindness Y = Y chromosome

If color blindness is sexlinked, what is the genotype of individual I-2?
1. CC
2. Cc
3. cc
4. CY
5. cY
What is the probability that individual III-1 is heterozygous?
1. 0.25
2. 0.33
3. 0.50
4. 0.66
5. 0.75
What is the probability that individual III-3 is homozygous?
1. 0
2. 0.25
3. 0.5
4. 0.75
5. 1.0
Individual III-1 could be homozygous or heterozygous. When she has children, which of the following possible fathers would be most informative of her genotype?
1. a normal man
2. a color-blind man
3. a normal man but only if his mother was color-blind
4. a color-blind man, but only if his mother was color-blind
5. All of the above would be equally informative.
In this pedigree, several of the characteristics of sex-linked recessive traits are apparent. Which one is NOT demonstrated in this pedigree?
1. More males than females demonstrate the trait.
2. Females serve as "carriers" for the trait by being heterozygous.
3. The occurrence of the trait skips generations.
4. Daughters of affected fathers are normal unless their mother is also affected.
There is good evidence for linkage when
1. two genes occur together in the same gamete
2. a gene is associated with a specific phenotype
3. two genes work together to control a specifc characteristic
4. genes do not segregate independently during meiosis
5. two characteristitic are caused bya single gene
A human individual is phenotypically female but her interphase somatic nuclei do not show the presence of sex chromatin (Barr bodies). Which of the following statements concerning her is probably true?
1. She has Klinefelter syndrome.
2. She has an extra X chromosome
3. She has Turner syndrome
4. She has the normal number of sex chromosomes
5. she has two Y chromosomes
If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number (n) of the four resulting gametes?
1. n+1; n+1; n-1; n-1
2. n+1; n-1;n;n
3. n+1; n-1; n-1; n-1
4. n+1; n+1 n; n
5. n-1; n-1; n; n
In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown above. What is the order of these genes on a chromosome map?
1. rb-cn-vg-b
2. vg-b-rb-cn
3. cn-rb-b-vg
4. b-rb-cn-vg
5. vg-cn-b-rb
Which of the following two genes are closest on a genetic map of Drosophila?
1. b and vg
2. vg and cn
3. rb and cn
4. cn and b
5. b and rb
Male calico cats are the result of
1. sex-linked inheritance.
2. nondisjunction, where the male calico presumably has two X chromosomes
3. incomplete dominance of multiple alleles.
4. recessive alleles retaining their fundamental natures even when expressed.
5. a reciprocal translocation.
People who have red hair usually have freckles. This can best be explained by
1. linkage
2. reciprocal translocation
3. independent assortment
4. sex-influenced inheritance
5. nondisjunction
Vermilion eyes is a sex-linked recessive characteristic in fruit flies. If a female having vermilion eyes is crossed with a wild-type male, what proportion of the F1 males will have vermilion eyes?
1. None
2. 25%
3. 50%
4. 75%
5. 100%
In humans, male-pattern baldness is controlled by a gene that occurs intwo allelic forms. Allele Hn determines nonbaldness and allele Hb determines pattern baldness. The interaction of these two alleles in the heterozygous condition is of special interest because in teh presence of male hormone, allele Hn is dominant over Hb. If a man an dwoman both with genotype Hn/Hb have many children, approximately what percentage of their male children would be expected to eventually be bald?
1. 0%
2. 25%
3. 33%
4. 50%
5. 75%
The diploid chromosome number in honeybees is 32. What is the number of chromosomes in the somatic cells of a male honeybee?
1. 4
2. 8
3. 16
4. 32
5. 64
Which of the following is the sex chromosome makeup of a hen?
1. XX
2. XY
3. XO
4. ZZ
5. ZW
Which of the following is the sex chromosome makeup of a male grasshopper?
1. XX
2. XY
3. XO
4. ZZ
5. ZW
The sequene of genes on teh chromosome of a certain common fly is THMORGAN. You find a population of this fly on the top of a mountain. When you cross it with normal flies, the number of offspring is reduced. Instuding its chromosome, you find that it has a sequendce of genes of TGMORHAN. Which of the following best explains this?
1. A deletion occurred
2. A duplication occurred
3. A single inversion occurred.
4. A traslocation occurred.
5. Two inversions occurred.
The sequene of genes on the chromosome of a certain common fly is THMORGAN. You find a population of this fly on the top of a mountain. When you cross it with normal flies, the number of offspring is reduced. Instuding its chromosome, you find that it has a sequendce of genes of TGMORHAN. You find a second population that you believe is intermediate between the two. What should its sequence of genes be?
1. THMORGAN
2. TGROMHAN
3. THROMGAN
4. TGMORHAN
5. Either B or C
A certian type of grass has a diploid chromosome number of 8. A similar species of grass has a diploid chromosome number of 10. Interspecifc hybridization between teh two species results in sterile hydrids that can, nonetheless, reproduce vegetatively. The chromosome number of those hydrids would be
1. 9
2. 16
3. 18
4. 20
5. 36
Blueprints contain the information to construct a building. Each floor of the building is represented by a set of blueprints (instructions). Thus, an individual blueprint page is analogous to a gene, and the blueprints for an entire floor would be analogous to a chromosome. That being the case, aneuploidy would result in
1. an entire duplicate building
2. a building that has an extra floor
3. a building lacking a floor
4. a building in which one floor has an extra room
5. either B or C
In the following list, which term is LEAST related to the others?
1. trisomic
2. monosomic
3. aneuploidy
4. triploid
5. nondisjunction
In the following list, which term is LEAST related to the others?
1. fragile X syndrome
2. X inactivation
3. Mary Lyon
4. tortoise-shell coat pattern in cats
5. Barr body
In the following list, which term is LEAST related to the others?
1. hemizygous
2. wild type
3. sex-linked genes
4. homogametic
5. hemophilia
In the following list, which term is LEAST related to the others?
1. genetic recombination
2. karyotypes
3. parental types
4. linkage map
5. recombinants
In the following list, which term is LEAST related to the others?
1. nondisjunction
2. duplication
3. inversion
4. translocation
5. deletion
The statement, "The X and Y chromosome determine sex" is inaccurate and misleading. Which of the following statements is MOST accurate?
1. Genes on the X and Y chromosomes determine sex.
2. Genes on the X chromosome that are not present on the Y determine sex.
3. Genes on the Y chromosome that are not present on the X determine sex.
4. a variety of genes on other chromosomes play various roles in determining sex, and teh activity of those genes is controlled by a small number of genes on teh X and/or Y chromosomes.
5. A variety of genes on the X and /or Y chromosomes play various roles in determining sex, and the activity of those genes is controlled by a small number of genes on other chromosomes.