Genetics Chapter 14

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1

Transcriptional regulation requires DNA-protein interactions that determines

(1) will transcription happen at all,
and

(2) in what amount?

2

Regulatory proteins often work as

dimers, trimers, or tetramers for interacting with DNA

3

“helix-turn-helix”

the most common structure in bacterial regulatory proteins

4

What does The Homodimer allow

It allows contact at inverted repeats, a common regulatory sequence

5

Bacterial Genomes

  • Circular
  • Compact
  • Small- necessary for quick reproduction and responses to environmental change.
6

Operon

A group of genes that are controlled by the same regulatory machinery

7

β-galactosidase

Cleaves lactose; converts some to allolactose

8

Permease

Facilitates passage of lactose into the cell

9

Transacetylase

Protects against damagin byproducts of lactose metabolism

10

What type of aneuploidy is responsible for Turner syndrome in humans?

A) trisomy 13

B) trisomy 18

C) trisomy 21

D) monosomy XO

E) monosomy YO

D) monosomy XO

11

When nondisjunction occurs early in embryogenesis rather than gametogenesis, what would you expect in the resulting karyotype?

A) monosomy

B) trisomy

C) mosaicism

D) uniparental disomy

E) random X-inactivation

C) mosaicism

12

Prader-Willi and Angelman syndromes are caused by which type of chromosomal mutations, both in connection with chromosome 15?

A) monosomy

B) trisomy

C) mosaicism

D) uniparental disomy

E) random X-inactivation

D) uniparental disomy

13

In an allopolyploid organism, what is true regarding the fertility of interspecies hybrids?

A) Interspecies hybrids are fertile due to nonhomology of chromosomes.

B) Chromosome doubling and nondisjunction in gametocytes can lead to homologous chromosome pairing, disjunction, and fertile hybrids.

C) Interspecies hybrids will be fertile so long as there is an even number of chromosomes in the offspring.

D) Mitotic nondisjunction results in haploid cells.

E) Meiotic nondisjunction produces three haploid gametes and one diploid gamete.

B) Chromosome doubling and nondisjunction in gametocytes can lead to homologous chromosome pairing, disjunction, and fertile hybrids.

14

If a plant is an autotetraploid with the genotype A1A1A2A2, what is the frequency of offspring with the genotype A1A1A1A1 following self-fertilization of the plant?

A) 1/2

B) 1/4

C) 9/16

D) 8/36

E) 1/36

E) 1/36

15

Which type of chromosome breakage results in very small deletions that are too small to identify on a karyotype?

A) acentric deletions

B) microdeletions

C) terminal deletions

D) partial deletions

E) interstitial deletions

B) microdeletions

16

Which type of chromosome deletions is caused by two concurrent chromosome breaks (rather than a single break)?

A) acentric deletions

B) microdeletions

C) terminal deletions

D) partial deletions

E) interstitial deletions

E) interstitial deletions

17

Heterozygous carriers of chromosome inversions or translocations

A) will be viable and completely fertile because no genes were deleted.

B) may or may not exhibit phenotypic abnormalities.

C) may be infertile due to complications during meiosis.

D) Both A and B are correct.

E) Both B and C are correct.

E) Both B and C are correct.

18

A region of a chromosome on spanning the centromere is broken and reattached in the reverse direction. This is an example of which type of chromosomal defect?

A) paracentric inversion

B) pericentric inversion

C) pericentric translocation

D) dicentric inversion

E) dicentric translocation

B) pericentric inversion

19

A chromosome has broken, and a piece of one chromosome is translocated to a nonhomologous chromosome. This is an example of what type of chromosomal alteration?

A) paracentric inversion

B) dicentric bridge

C) unbalanced translocation

D) Robertsonian translocation

E) inversion loop

B) dicentric bridge

20

Crossover suppression implies that

A) there are no crossovers between homologous chromosomes.

B) recombinant chromosomes are absent in the progeny.

C) small inversions have a high frequency of crossover.

D) nonreciprocal translocations prevent equal exchange of chromosomes, resulting in loss of chromosome fragments.

E) Both A and C are correct.

B) recombinant chromosomes are absent in the progeny.

21

A chromosome contains the following gene order:

A B C D • E F G H

Which of the following rearrangements represents a pericentric inversion?

A) A B C • D E F G H

B) A F G H • B C D E

C) A C B D • E F G H

D) A F D E • C B G H

E) A B C D • H G F E

D) A F D E • C B G H

22

A chromosome contains the following gene order:

A B C D • E F G H

Which of the following rearrangements represents a paracentric inversion?

A) A B C • D E F G H

B) A F G H • B C D E

C) A C B D • E F G H

D) A F D E • C B G H

E) A B C D • H G F E

C) A C B D • E F G H

23

If an organism is an inversion heterozygote,

A) homologous chromosomes align during meiosis through formation of an inversion loop at synapsis.

B) homologous chromosomes align during meiosis through formation of a Holliday junction at synapsis.

C) nonhomologous chromosomes pair during meiosis due to the translocation of genes between two different chromosomes.

D) it will experience normal chromosome synapsis during meiosis.

E) it will be unable to complete replication due to DNA damage, and the cell cycle will be arrested.

A) homologous chromosomes align during meiosis through formation of an inversion loop at synapsis.

24

Humans with the condition of familial Down syndrome exhibit which type of chromosomal aberration?

A) chromosome 21 duplication

B) chromosome 21 inversion

C) chromosome 14/21 Robertsonian translocation

D) chromosome 21 deletion

E) trisomy of chromosome 21

C) chromosome 14/21 Robertsonian translocation

25

An organism with a genome size of n = 23 experienced a Robertsonian translocation. How many chromosomes would you expect to see in the karyotype of a somatic cell in an affected individual?

A) 21

B) 25

C) 42

D) 44

E) 46

D) 44

26

In balanced translocation heterozygotes, which pattern of chromosome segregation produces viable gamets and progeny?

A) adjacent-1 segregation

B) adjacent-2 segregation

C) alternate segregation

D) Adjacent-1 and alternate segregation are both viable.

E) Adjacent-1, adjacent-2, and alternate segregation are all viable.

C) alternate segregation

27

In bacteria, what is contained within the IS elements?

A) transposase gene

B) short tandem repeats

C) inverted repeats

D) Both A and B are correct.

E) Both A and C are correct.

E) Both A and C are correct.

28

What sequences or structures within the DNA can be used to identify sites of transposition?

A) target site duplication and direct repeats

B) target site duplication and short tandem repeats

C) inverted loops

D) target site inversion and direct repeats

E) chromosome translocation and insertion of transposase gene

A) target site duplication and direct repeats

29

AluI is an example of which type of transposable element commonly found in the genome of humans?

A) LINE elements

B) SINE elements

C) P elements

D) Copia elements

E) Ty elements

B) SINE elements

30

During gametogenesis, what percentage of gametes would be aneuploid if the nondisjunction event occurs during meiosis I?

Answer: 100% (4/4)

31

During gametogenesis, what percentage of gametes would be trisomic if the nondisjunction event occurs during meiosis II?

Answer: 25% (1/4)

32

What is the name of the chromosomal region, located on region 21q22.2 that was identified by studying individuals with partial trisomy of chromosome 21?

Answer: DSCR (Down syndrome critical region)

33

In Drosophila and Lepidoptera, sex-chromosome mosaicism produces what type of sexually ambiguous phenotype?

Answer: gynandromorphy

34

Of the three mechanisms leading to autopolyploidy, which is the most rare event?

Answer: multiple fertilizations

35

"Seedless" fruits and vegetables have how many chromosomes and what type of chromosomal distribution?

Answer: odd-numbered allopolyploidy

36

How many possible genotypes will there be following self-fertilization of a plant with the B1B1B2B2B3B3 genotype?

Answer: 15

37

Cri-du-chat syndrome is a human disorder caused by which type of chromosomal defect?

Answer: terminal deletion

38

A partial chromosome deletion or duplication can be observed at prophase I homologous chromosome synapsis during meiosis by looking for what structure?

Answer: unpaired loop

39

Pseudodominance is used to map genes by using what method?

Answer: deletion mapping

40

What structure, seen during synapsis, is indicative of a chromosome inversion?

Answer: inversion loop

41

Gametes produced by inversion heterozygotes can produce no viable recombinant chromosomes due to what phenomenon?

Answer: crossover suppression

42

What effect does a Robertsonian translocation have on chromosome number?

Answer: reduction (2n - 2)

43

What are the two common patterns of chromosome segregation seen in the tetravalent structures found in translocation heterozygotes?

Answer: alternate and adjacent-1

44

Barbara McClintock identified corn mutants with the unstable mutant phenotype with what pattern of color?

Answer: colorless with purple spots

45

In McClintock's maize studies, which genetic element is found at the site of chromosome breakage?

Answer: dissociation (Ds) element

46

Which enzyme(s) is/are responsible for excising and copying transposable genetic elements from chromosomes and inserting them into new locations?

Answer: transposase

47

The phenomenon of ________ in allopolyploids consists of more rapid growth, increased fruit and flower production, and improved disease resistance.

Answer: hybrid vigor

48

________ is rare and occurs most commonly when repetitive regions of homologous chromosomes misalign, resulting in partial deletions and partial duplications.

Answer: Unequal crossover

49

________ is a genetic phenomenon that occurs when a normally recessive allele is "unmasked" and expressed in the phenotype because the dominant allele on the homologous chromosome has been deleted.

Answer: Pseudodominance

50

Chromosomal translocation involves chromosome breakage and reattachment of the broken segment to a ________.

Answer: nonhomologous chromosome