Biology Exam 2
a woman and a male are both heterozygous for a recessive allele for a rare genetic disease. if they have two children, what is the probability that both of them will be affected?
1/16
Given a pair of 6-sided dice, what is the probability of rolling a total of 3?
1/18
Given a pair of 6-sided dice, what is the probability of rolling "double 6s"
1/36
a phenotypically normal male and phenotypically normal female, whose father was colorblind, have a child. what is the probability that it is blind?
1/4
a woman and a male are both heterozygous for a recessive allele for a rare genetic disease. if they have one child, what is the probability that he or she will be affected?
1/4
In a case of incomplete dominance, what is the phenotypic ratio of offspring from a Bb X Bb cross?
1:2:1
eye color in fruit flies is x-linked, with white color recessive to red. what offspring do you get when you cross a heterozygous red-eyed F with a red-eyed male?
2 red females: 1 red male: 1 white male
Cotton is a tetraploid (4n=52). After a cotton plant goes through meiosis, how many chromosomes does the pollen grain have?
26
A cactus is 4n=24. What are its gametes?
2n=12
a woman and a male are both heterozygous for a recessive allele for a rare genetic disease. if they have two children, what is the probability that the first will be affected and the second unaffected?
3/16
a woman and a male are both heterozygous for a recessive allele for a rare genetic disease, if they have two children, what is the probability that at least one of them will be affected?
7/16
homologous chromosomes separate but sister chromatids do not separate
Anaphase I
During meiosis, genetic variability is introduced during which of the following phases? SELECT ALL THAT APPLY. a. prophase II b. telophase I c. metaphase II d. anaphase II e. prophase I f. metaphase I
E & F
A mother with a genotype AB at a locus and a father with genotype BB have a child with a genotype AAB. Where did the nondisjunction occur?
Meiosis II in mother
homologous pairs line up in the center of the cell, with bivalents oriented randomly with respect to each other
Metaphase I
chromosomes align in the center of the cell
Metaphase II
What is NOT a difference between mitosis and meiosis?
Mitosis occurs in two rounds of cell division; meiosis occurs in one
spindles attach to kinetochores on chromosomes Meiosis II
Prometaphase II
chiasmata present
Prophase I
Crossing over occurs in ______ and independent assortment occurs in _______.
Prophase I and Metaphase I
the nuclear envelope breaks down and the chromosomes condense
Prophase II
Daughter cells are ready to move into prophase II
Telophase I and Cytokinesis
the nuclear envelope reforms and the cytoplasm divides
Telophase II and Cytokinesis
a phenotypically normal male and phenotypically normal female, whose father was colorblind, have a child. what is the female's genotype?
X+XC
a phenotypically normal male and phenotypically normal female, whose father was colorblind, have a child. what is the male's genotype?
X+Y
A cell in prophase I of meiosis has ______________ as much DNA as each of the daughter cells following cytokinesis of meiosis II. a. four times b. twice c. one quarter d. half
a
A cross involving an autosomal gene versus a sex-linked gene would differ in that: a. the phenotype outcomes of females compared to males could be different b. a Punnett square could not be utilized for solving a cross involving a sex-linked gene c. both parents would have two copies of a sex-linked gene d. only autosomal genes observe the law of segregation
a
A woman and a man are both heterozygous for a recessive allele for a rare genetic disease. If they have one child, what is the probability that he or she will be affected? If they have two children, what is the probability that at least one of them will be affected? a. 1/4, 7/16 b. 1/4, 3/4 c. 7/16, 1/4 d. 3/4, 1/4 e. 3/4, 7/16
a
According to the principle of segregation, a heterozygous plant with alleles Aa will produce: a. gametes in the ratio of 1 A allele:1 a allele b. gametes with only the A allele c. gametes with only the a allele d. gametes in the ratio of 3 A alleles:1 a allele e. some gametes with the A allele and some with the a allele, but in no predictable ratio
a
Consider a diploid organism with a haploid complement of four chromosomes. At prophase I, how many total chromosomes will be present in a cell? a. 8, four pairs of homologous chromosomes b. 4, one complete set of chromosomes c. 16, four pairs of homologous chromosomes and two sister chromatids per chromosome d. 12, four pairs of homologous chromosomes and their haploid complement
a
Deletions that eliminate a multiple of three nucleotides can: a. delete amino acids in a polypeptide chain b. shorten chromosomes from the telomeres inward c. cause nonsense mutations in a reading frame d. only occur in somatic cells e. cause frameshift mutations in a reading frame
a
For an X-linked gene, which of the following genotype options are possible? a. a female can be homozygous or heterozygous for this gene b. a female or a male can be heterozygous for this gene c. a female or a male can be homozygous for this gene d. a male can be homozygous for this gene e. a male can be heterozygous for this gene
a
For this question, assume the parent not mentioned in the answers in unaffected. Inheritance due to a rare X-linked dominant mutation can be distinguished from inheritance due to a rare autosomal dominant mutation because, in the X-linked case: a. affected fathers do not have affected sons b. the two possibilities cannot be distinguished c. affected fathers do not have affected daughters d. affected mothers do not have affected daughters e. affected mothers do not have affected sons
a
In meiosis, recombination occurs: a. only during prophase I and involves exchange between chromatids of homologous (non-sister) chromosomes b. during prophase I and II and involves exchange of chromosome fragments between all four chromatids c. during prophase I and II and involves exchange of chromosome fragments between sister chromatids d. only during prophase I and involves exchange of chromosome fragments between sister chromatids
a
If the yellow and green seeded plants are true breeding, what is the genotype(s) of the F1 generation?
all YG
different versions of a gene or locus
alleles
sister chromatids separate
anaphase II
-don't skip generations -affected parents can have an unaffected child
autosomal dominant traits
-can skip generations -unaffected parents can have an affected child
autosomal recessive traits
A cell in prophase I of meiosis has ______________ as many chromosomes as each of the daughter cells following cytokinesis of meiosis II. a. half b. twice c. four times d. one quarter
b
Consider the tryptophan codon 5′-UGG-3′ in the standard genetic code. Can a single base change in this codon create a synonymous mutation? Can a single base change in this codon create a nonsense codon? a. no; no b. no; yes c. yes; no d. yes, yes
b
Diploid somatic cells of elephants have 56 chromosomes. If nondisjunction of one of a male elephant's chromosomes occurs in meiosis I, at the end of meiosis the four resulting sperm are expected to have the chromosome complement: a. 29, 29, 28, 28 b. 29, 29, 27, 27 c. 28, 28, 28, 28 d. 56, 56, 57, 55 e. 28, 28, 29, 27
b
Given equal probabilities of the birth of a boy or girl, what is the probability that a group of four siblings includes all boys? All girls? All boys or all girls? a. 1/8; 1/16; 3/8 b. 1/16; 1/16; 1/8 c. 1/16; 1/16; 1/64 d. 1/16; 1/8; 3/8
b
If you crossed two heterozygous yellow-seed pea plants (genotypes Aa), the relative frequency of: a. homozygous yellow-seed plants (genotype AA) in the offspring would be ¼ b. all of these choices are correct c. green-seed plants (genotype aa) in the offspring would be ¼ d. the a allele in each parent's gametes would be ½ e. the A allele in each parent's gametes would be ½
b
When X-linked traits are recessive, a. males who express the trait receive the recessive allele from their fathers b. males who express the trait receive the recessive allele from their mothers c. males who express the trait must receive recessive alleles from both parents d. males who express the trait must have two X chromosomes
b
Which of the following events occur during anaphase I of meiosis? a. in females, the two X chromosomes remain together b. in males, the X chromosome is segregated from the Y chromosome c. homologous chromosomes move as one unit d. the chromosome number is doubled during this phase of meiosis e. the centromeres of the chromosomes divide
b
Which of the following is a nonsense mutation? a. UGU-->UGC b. UGU-->UGA c. UGU-->UGG
b
Hemophilia is a sex-linked recessive trait in humans. If a carrier female (heterozygous for the trait) mated with a nonaffected male, what would be the expected outcome(s)? SELECT ALL THAT APPLY. a. none of the sons would have hemophilia b. none of the daughters would have hemophilia c. half the daughters would have hemophilia d. half the sons would have hemophilia e. none of the offspring would have hemophilia
b & d
Consider an A-T versus G-C single-nucleotide polymorphism (SNP) in the human genome. This means that the DNA molecules in the population at this site have which combinations of base pairs? a. A-T or A-C or G-T or G-C b. A-C or G-T c. A-T or G-C d. A-T or G-T or G-C e. A-T or A-G or G-C
c
If blending inheritance was an accurate model of transmission genetics, which of the following would be true? a. Variation in natural populations would increase over time b. Variation would increase in some populations, decrease in some populations, and remain the same in some populations c. Variation in natural populations would decrease over time d. Mutation would not contribute to variation in natural populations e. Variation in natural populations would remain the same over time
c
If you tracked an individual X chromosome from a male to his first generation offspring, then to his second generation offspring, what pattern would you see? a. his X chromosome would be found only in his daughters and grandsons b. his X chromosome would be found only in his sons and grandsons c. his X chromosome would be found only in his daughters, then in both his granddaughters and grandsons d. his X chromosome would be found only in his sons, then in both his granddaughters and grandsons e. his X chromosome would be found only in his daughters and granddaughters
c
In pea plants, flowers are either white or purple; the purple color is produced by pigments called anthocyanins. The production of anthocyanins is a two-step process: the first is controlled by the C gene and the second by the P gene. Both genes must produce functional proteins for anthocyanin to be produced. For each gene, the dominant (C and P) alleles produce functional proteins. Which of the following genotypes will produce white (no pigment) flowers? a. CcPP only b. ccPP only c. ccPP and CCpp d. ccPP and CcPP e. CCpp only
c
Phenotypic variation among individuals is not always visible and can include which of the following trait characteristics? a. only behavioral differences b. only developmental differences c. developmental, physiological, and behavioral differences d. developmental and physiological differences e. only physiological differences
c
Sister chromatids are separated during: a. meiosis II only b. meiosis I and mitosis c. meiosis II and mitosis d. meiosis I only e. mitosis only
c
The FoxP2 gene is thought to be involved in language in humans. At prophase I, how many copies of the FoxP2 gene are present in a cell? a. eight copies, one on each sister chromatid in a pair of homologous chromosomes b. eight copies, one on each strand of each chromatid per homologous pair c. four copies, one on each sister chromatid in a pair of homologous chromosomes d. two copies, one on each homologous chromosome
c
The second meiotic division resembles mitosis because: a. spindle microtubules attach from opposite directions to the centromere of each sister chromatid pair b. sister chromatids are separated during anaphase II to become the chromosomes of the daughter cells c. all of these choices are correct d. the daughter cells have the same number of chromosomes as the parent cell e. chromosomes decondense during telophase II
c
Which of the following happens during prophase I of meiosis? a. recombination between sister chromatids of nonhomologous chromosomes b. recombination between sister chromatids of homologous chromosomes c. recombination between non-sister chromatids of homologous chromosomes d. recombination between non-sister chromatids of nonhomologous chromosomes
c
Which of the following is a missense mutation? a. UGU-->UGA b. UGU-->UGC c. UGU-->UGG
c
Which of the following is most likely to result in a nonfunctional polypeptide? a. silent and missense mutations are the most likely to result in a nonfunctional polypeptide b. a missense mutation c. a nonsense mutation d. a transition mutation e. a silent mutation
c
With independent assortment, the ratio of phenotypes in the F2 generation of a cross between true-breeding strains (AA bb x aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer? a. dominant for the A trait and recessive for the B trait b. recessive for both traits c. dominant for one trait and recessive for the other d. dominant for both traits
c
What is NOT a source of variation generated by meiosis?
crossing over during prophase II
A male child is born with an XYY constitution of sex chromosomes. The parents are normal XX and XY individuals, so their child's genotype must be the result of nondisjunction in the formation of one of their gametes. When (and in whom) could the nondisjunction have taken place? a. in the father in meiosis I b. in the mother in meiosis I c. in the father in mitosis d. in the father in meiosis II e. in the zygote at the first mitotic division
d
In a population of organisms with 4 alleles, how many homozygous genotypes are possible? How many heterozygous genotypes are possible? a. 3; 4 b. 4; 4 c. 4; 10 d. 4; 6 e. 3; 3
d
Large chromosomal inversions can cause problems in which of the following processes? a. reciprocal translocation b. none of the other answers are correct c. mitosis d. meiosis e. DNA replication
d
The statement that, in garden peas, yellow seed is dominant to green seed means that: a. when a true-breeding yellow seed parent is crossed with a true-breeding green seed parent, all offspring will have green seeds b. when a true-breeding yellow seed parent is crossed with a true-breeding green seed parent, ¾ of the offspring will have yellow seeds and ¼ will have green seeds c. we can't predict seed color in the offspring of a true-breeding yellow seed parent and a true-breeding green seed parent d. when a true-breeding yellow seed parent is crossed with a true-breeding green seed parent, all offspring will have yellow seeds e. when a true-breeding yellow seed parent is crossed with a true-breeding green seed parent, ½ of the offspring will have yellow seeds and ½ will have green seeds
d
Which of the following statements applies to frameshift mutations? a. they cause the insertion or deletion of a single amino acid from the polypeptide chain b. they are most common in non-coding regions of the genome c. they create a premature stop codon at the site of mutation d. they change the amino acid sequence downstream from the mutant site
d
_____ mutations affect only the individual in which they occur; _____ mutations are passed from parent to offspring. a. somatic; point b. germ-line; point c. germ-line; somatic d. somatic; germ-line e. point; germ-line
d
How many PAIRS of homologous chromosomes are there in a gamete produced from a 2n=16 organism? a. 4 b. 8 c. 16 d. none
d. none
phenotype associated with this allele is seen when it's homozygous or heterozygous
dominant allele
Flower color in snapdragons is due to a gene with incomplete dominance: CRCR plants have red flowers, CRCW have pink flowers, and CWCW plants have white flowers. What types and ratios of flower color are expected among the progeny of a cross of pink x white? a. 1 red:2 pink:1 white b. all pink c. all white d. 1 red:1 pink e. 1 pink:1 white
e
In a diploid individual, one chromosome carries A and B genes, and the homologous chromosome carries different forms (alleles) of these same genes, a and b. If there is a single crossover between these two genes involving non-sister chromatids during prophase I of meiosis, the resulting four gametes are: HINT: Draw the tetrad with the four alleles (A, B, a, b) during prophase I, then modify it to show the single crossover event. a. AB, ab, AB, ab b. AaBb, AaBb, AaBb, AaBb c. AB, AB, ab, ab d. Ab, Ab, aB, aB e. AB, Ab, aB, ab
e
Which of the following chromosomal mutations differentiate humans and chimps? a. duplications b. deletions c. inversions d. translocations e. more than one of the above f. none of the above
e
You are given two true-breeding groups of rabbits. The first group has floppy ears and white coat color. The second group has straight ears and black coat color. When you perform a cross of these two groups to obtain an F1 generation, you see that all of your rabbits have floppy ears and grey coat color. Which of the following possibilities appears to be supported by what you see in the F1 generation? a. straight ears are dominant over floppy ears; black coat color is dominant over white coat color b. floppy ears are dominant over straight ears; black coat color is dominant over white coat color c. straight ears are dominant over floppy ears; coat color is determined by incomplete dominance d. floppy ears are dominant over straight ears; white coat color is dominant over black coat color e. floppy ears are dominant over straight ears; coat color is determined by incomplete dominance f. straight ears are dominant over floppy ears; white coat color is dominant over black coat color
e
In a protein-coding region of DNA, the insertion of a single base pair is a:
frameshift mutation
an insertion of deletion that is not an exact multiple of three nucleotides changes the reading frame of translation *VERY DAMAGING
frameshift mutation
genetic makeup at one or more loci
genotype
In humans, what types of mutations can be inherited?
germ cell mutations
"haploid genotype"
haplotype
All of the alleles found on one chromosome represent that chromosome's:
haplotype
genotype with two different alleles
heterozygous
In the absence of crossing-over, A and a represent alleles on:
homologous chromosomes
genotype with two of the same allele
homozygous
heterozygote phenotype is in between homozygotes
incomplete dominance
Why was the idea of "blending inheritance" considered a problem for Darwin's theory of evolution by natural selection?
it should lead to variation being lost over time
any specific position in the genome
locus
divides chromosome number in half
meiosis
the nonmutant gene expresses normal B-globin
nonmutant
a nucleotide substitution that creates a stop codon *VERY DAMAGING
nonsense mutation
a nucleotide substitution that changes the amino acid
nonsynonymous mutation (missense mutation)
The efficiency of an enzyme at catalyzing a reaction is a:
phenotype
measurable traits or characteristics
phenotype
What is correct regarding meiosis I vs meiosis II?
ploidy is cut in half during meiosis I but remains the same during meiosis II
spindles attach to kinetochores on chromosomes Meiosis I
prometaphase I
If an organism only needs one functional copy of an enzyme, a loss-of-function mutant copy would be:
recessive
phenotype associated with this allele is only seen when it's homozygous
recessive allele
a nucleotide substitution that does NOT change the amino acid
synonymous mutation (silent mutation)
different alleles at a VNTR locus differ in:
the number of copies of the repeated sequence they have
-males are more likely to be affected -males don't pass the trait onto their sons -daughters of affected males are carriers
x-linked recessive traits
