Exam #3 2020 Flashcards


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1

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel’s law of segregation?

Which of the following statements about the law of segregation is correct?

The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

It describes the inheritance of different chromosomes relative to one another.

2

When Thomas Hunt Morgan crossed red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies, but all the white-eyed flies were male. Which of these best explains Morgan's result?

The gene involved is located on the X chromosome.

3

In cats, an X-linked locus is responsible for fur color. There are two known alleles at this locus. One results in black fur color; the other results in orange fur color. A heterozygote animal has patches of orange and black fur (tortoiseshell). Which of the following explains the patches of color in female heterozygote cats?

Random X inactivation affects fur color

4

The SRY gene is best described as ________.

a gene present on the Y chromosome whose product regulates male development

5

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as an X-linked recessive allele in humans. A woman whose father had G6PD is planning a family with a man who has no history of the disease. What proportion of their sons are expected to have the disease?

1/2

6

Which of the following statements regarding gene linkage is correct?

The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

7

The chromosomal alteration that results from a chromosome fragment joined to a nonhomologous chromosome is called a ________.

translocation

8

Which of the following statements describes the most likely result of a defect in meiosis that results in the failure of spindle microtubules to bind some kinetochores?

The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy.

9

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients' muscles weaken over time because they have a lack or decreased levels of dystrophin, a muscle protein. Which of the following correctly predicts the probability of muscular dystrophy in female children?

One-half of the daughters of an affected man and a carrier woman would have this condition.

10

A recombination frequency of 50% indicates ________.

the two genes are likely to be located on different chromosomes

11

What is an allele?

an alternative version of a gene

12

Which of the following is true about a plant with the genotype AABbcc?

it is homozygous at two loci

13

Which of the following statements correctly describes the terms monohybrid cross and dihybrid cross?

A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.

14

Mendel crossed true breeding yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6,022 yellow and 2,001 green (8,023 total). Which of the following statements correctly describes the relationship of the allele for green seeds to the allele for yellow seeds?

The green allele is recessive to the yellow allele.

15

Having polydactyly (extra digits on hands and feet) is a dominant trait. A man has polydactyly. His wife and oldest daughter do not have polydactyly. The couple's second child has polydactyly. What is the probability that their next (third) child will have extra digits?

1/2

16

Assuming independent assortment at all loci, what is the probability that a cross between the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring?

1/8

17

Gene S controls the sharpness of spines in a type of cactus. Cacti with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cacti have dull spines. Also, a second gene, N, determines whether or not cacti have spines. Homozygous recessive nn cacti have no spines at all. The relationship between genes S and N is an example of which of the following inheritance patterns?

epistasis

18

What is the difference between heterozygous and homozygous individuals?

All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.

19

When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.

gametes, progeny

20

True or false? The same phenotype can be produced by more than one genotype.

True

21

True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.

False

22

If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?

None

23

Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?

25

24

A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?

ttpp

25

What fraction of the offspring from a cross between two animals with the genotype AaBbCc are expected to be homozygous recessive for the three traits?

1/64

26

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (CRCW) offspring of red (CRCR) and white (CW CW) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

roan × roan

27

A man with type A blood marries a woman with type B blood. Their child has type O blood.

What is the genotype of the man?

What is the genotype of the woman?

What is the genotype of the child?

What genotypes would you expect in future offspring from this marriage? Select all that apply.

In what frequencies would you expect the offspring genotypes? Indicate the frequency of each genotype by dragging the labels to the table. Labels may be used once, more than once, or not at all.

card image

I A i

I B i

ii

ii, I A i, I B i, I A I B

28

Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?

a combination of polygenic inheritance and environmental factors

29

Which of the following inheritance patterns describes the ability of a single allele to have multiple phenotypic effects?

pleiotropy

30

Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes eye problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?

It is pleiotropic.

31

When a dominant allele coexists with a recessive allele in a heterozygote individual, how do they interact with each other?

They do not interact at all.

32

Quaking aspen trees usually reproduce by extending underground stems that then push aboveground and grow into trees. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?

38

33

Which of the following statements best describes homologous chromosomes?

They carry information for the same traits.

34

In a typical animal, mitosis produces _________, while meiosis produces____________.

two diploid daughter cells, four haploid daughter cells

35

Which of the following answers describes the phenomenon of crossing over in meiosis?

the exchange of homologous portions of nonsister chromatids

36

The two homologs of a pair move toward opposite poles of a dividing cell during

meiosis I

37
card image

How can you tell that the cell in the figure below is undergoing meiosis, not mitosis?

card image
38

During which of the following phases of meiosis do centromeres split and sister chromatids migrate to opposite poles of the cell?

anaphase II

39

Independent assortment of chromosomes is a result of which of the following processes?

the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

40

Two different species of protists living in a tide pool. Species A reproduces both sexually and asexually, and Species B reproduce only asexually. The pool gradually becomes infested with disease-causing viruses. Which species are more likely to survive in the changing environment?

Species A only

41

Two sister chromatids are joined at the centromere prior to meiosis. Which statement is correct?

Barring mutation, the two sister chromatids must be identical

42

In alternation of generations, what is the diploid stage of a plant that follows fertilization called?

sporophyte

43

What number and types of chromosomes are found in a human somatic cell?

44 autosomes and 2 sex chromosomes

44

Which of the following statements best describes homologous chromosomes?

They carry information for the same traits.

45

Which of the following statements correctly describes how sister chromatids and homologous chromosomes differ from each other?

Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.

46

In a typical animal, mitosis produces _________, while meiosis produces____________.

two diploid daughter cells, four haploid daughter cells

47

Meiosis II is similar to mitosis in that

sister chromatids separate during anaphase

48

Which of the following processes has just occurred when chiasmata can first be viewed under a microscope?

prophase I

49

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I?

The cells have half the number of chromosomes and one-fourth the amount of DNA.

50

For the following question, match the key event of meiosis with the stages listed below.

I.Prophase IV.Prophase IIII.Metaphase IVI.Metaphase IIIII.Anaphase IVII.Anaphase IIIV.Telophase IVIII.Telophase II
Homologous chromosomes are aligned at the middle of the spindle.

II

51

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes based on the independent assortment of chromosomes during meiosis?

about 8 million

52

Which of the following conditions is required for a target organ to respond to a particular hormone?

The target organ must have receptors that recognize and bind the hormone molecule

53

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule

54

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule

55

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

ligand-gated ion channel

56

Which of the following are among the most common second messengers?

calcium ions and cAMP

57

Which of the following statements best describes why phosphorylation cascades are useful in cellular signal transduction?

they amplify the original signal many times

58

Part completeWhat is the name of the region on duplicated chromosomes where the sister chromatids are most closely attached to each other?

the centromere

59

Which of the following occurs during S phase?

replication of the DNA

60

Which of the following statements describes a characteristic feature of metaphase?

alignment of chromosomes on the equator of the cell

61

Besides the ability of some cancer cells to over proliferate, which of the following situations is most likely to result in a tumor?

lack of appropriate cell death

62

Which of the following statements best describes a cleavage furrow?

a groove in the plasma membrane between daughter nuclei

63

A type of localized signaling in which a cell secretes a signal molecule that affects neighboring cells is best described as which of the following?

paracrine signaling

64

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because

intracellular receptors are present only in target cells

65

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

ligand-gated ion channel

66

Which of the sequences below best describes the sequential steps (numbered 1-5) in a signal transduction pathway that utilizes a G protein-coupled receptor?
1. The signal-receptor complex activates a G protein.
2. Protein kinases are activated.
3. A signal molecule binds to a receptor.
4. Target proteins are phosphorylated.
5. cAMP is produced.

3, 1, 5, 2, 4

67

What is apoptosis?

controlled cell suicide

68

Eukaryotic chromatin is composed of which of the following macromolecules?

DNA and proteins

69

Which of the following correctly matches a phase of the cell cycle with its description?

G1, follows cell division

70

Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in

G1

71

Which of the following statements best describes how cytokinesis differs between plant and animal cells?

Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow.

72

Which of the following statements describes a characteristic feature of metaphase?

alignment of chromosomes on the equator of the cell