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Genetics > Chromosome Variation > Flashcards

Chromosome Variation Flashcards

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Biology 101 flashcards
1
Q

What is involved in karyotyping?

A

Chromosomes are prepared from actively dividing cells.

They are halted in metaphase.

Chromosomes are arranged according to size.

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2
Q

What is involved in chromosome painting?

A

The use of fluorescent-tagged chromosome specific DNA sequences to visualize specific chromosomes or chromosome segments by in situ DNA hybridization and fluorescence microscopy.

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3
Q

What are two types of chromosome mutations?

A

Aneuploidy

Polyploidy

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4
Q

You are examining the chromosomes taken from a developing embryo. You notice that a chromosome is missing. What kind of chromosome mutation is this?

A

Aneuploidy

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5
Q

What is polyploidy?

A

Organisms that contain more than two complete paired (homologous) sets of chromosomes.

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6
Q

You are studying the chromosomes of an organism and note that there is a duplication. What type of chromosome mutation is this?

A

Chromosome rearrangement

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7
Q

You are studying the chromosomes of an organism and note that there is a trisomy. What type of chromosome mutation is this?

A

Aneuploidy

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8
Q

You are studying the chromosomes of an organism and note that there is an autotriploid. What type of mutation is this?

A

Polyploidy

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9
Q

What occurs during chromosome duplication?

A

A segment of the chromosome is duplicated.

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10
Q

What occurs during chromosome inversion?

A

A segment of the chromosome is turned 180 degrees.

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11
Q

What occurs during chromosome deletion?

A

A segment of the chromosome is deleted.

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12
Q

What occurs during translocation?

A

A segment of a chromosome moves from one chromosome to a nonhomologous chromosome, or to another place on the same chromosome.

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13
Q

What occurs to a chromosome that is heterozygous for a duplication?

A

The duplicated chromosome loops out during pairing in prophase I.

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14
Q

What are three effects of deletions?

A

Imbalances in gene product

Expression of a normally recessive gene (pseudodominance)

Haploinsufficiency

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15
Q

When does a deletion loop form?

A

During prophase I.

In prophase I, the normal chromosome must loop out in order for the homologous sequences of the chromosomes to align.

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16
Q

What is a paracentric inversion?

A

An inversion in which the breakpoints are confined to one arm of a chromosome; the inverted segment does not span the centromere.

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17
Q

What is pericentric inversion?

A

An inversion in which the breakpoints occur on both arms of a chromosome. The inverted segment spans the centromere.

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18
Q

True or false: problems arise in meiosis for homozygous individuals who have inversions.

A

False

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19
Q

When do homologous sequences align in inversions?

A

Only if the two chromosomes form an inversion loop.

20
Q

What occurs in heterozygous individuals when they have an inversion in meiosis?

A

Individuals with para- or peri- centric inversion often have nonfunctional gametes due to loss of large amounts of genetic material during meiosis.

Homologous sequences align only if the two chromosomes form an inversion loop.

21
Q

In an individual heterozygous for a paracentric inversion, the chromosomes ….

A

Form an inversion loop during pairing in prophase I.

22
Q

What would occur to a heterozygote with one normal chromosome and one chromosome with an inverted segment during meiosis?

A

In prophase I of meiosis, the chromosomes form an inversion loop, which allows the homologous sequences to align.

23
Q

What occurs in a heterozygous individual in which there is a single crossover within a paracentric inversion?

A

Abnormal gametes

24
Q

What occurs in a heterozygous individual that has a single crossover within a pericentric inversion?

A

Abnormal gametes are formed

25
Q

A dicentric chromosome is produced when crossing over takes place in an individual heterozygous for which type of chromosome rearrangement?

A

Paracentric inversion

26
Q

What are the two types of translocations?

A

Nonreciprocal translocation

Reciprocal translocation

Robertsonian translocation

27
Q

What occurs during robertsonian translocation?

A

The short arm of one acrocentric chromosome is exchanged with the long arm of another, creating a large metacentric chromosome and a fragment that often fails to segregate and is lost.

28
Q

What can be concluded from translocations in meiosis?

A

Gametes resulting from adjacent-1 and adjacent-2 segregation are nonviable because some genes are present in two copies whereas others are missing.

29
Q

What occurs during a translocation in meiosis?

A

An individual heterozygous for one translocation possesses one normal copy of each chromosome and one translocated copy of each.

Because each chromosome has sections that are homologous in two other chrmosomes, a crosslike configuration forms in prophase I of meiosis.

In anaphase I, the chromosoems separate in one of three different ways.

30
Q

What is the outcome of a Robertsonian translocation?

A

One metacentric chromosome and one chromosome with two very short arms.

31
Q

What are 3 causes of aneuploidy?

A

Deletion of a centromere during mitosis and meiosis

Robertsonian translocation

Nondisjunction during meiosis and mitosis

32
Q

What are the 4 types of aneuploidy?

A

Nullisomy

Monosomy

Trisomy

Tetrasomy

33
Q

What is a nullisomy?

A

A loss of both members of a homologous pair of chromosmoes 2n - 2

34
Q

What is a monosomy?

A

A loss of a single chromosome 2n - 1

35
Q

What is a trisomy?

A

A gain of a single chromosome 2n + 1

36
Q

What is a tetrasomy?

A

The gain of two homologous chromosomes; 2n + 2

37
Q

A diploid organism has 2n = 36 chromosomes. How many chromosomes will be found in a trisomic member of this species?

A

2n + 1 = 36 + 1 = 37

38
Q

What are two examples of sex-chromosome aneuploids?

A

Turner syndrome, XO

Klinefelter syndrome, XXY

39
Q

What results from trisomy 18?

A

Edward syndrome

40
Q

What results from trisomy 13?

A

Patau syndrome?

41
Q

Why are sex-chromosome anueploids more common than autosomal aneuploids in humans and mammals?

A

There is no mechanism of dosage compensation for autosomal chromatids.

Autosomes carry more genes.

Most autosomal aneuploids are spontaneously aborted.

42
Q

Autopolyploidy occurs from ___

A

Single species

43
Q

Allopolyploidy occurs from ___

A

Two species

44
Q

What do most allopolyploids arise from?

A

Hybridization between two species followed by chromosome doubling.

45
Q

What is the significance of polyploidy?

A

It causes an increase in cell size.

It gives larger plant attributes

And it may give rise to new species.

46
Q

Species A has 2n = 16 chromosomes and species B has 2n = 14. How many chromosomes would be found in a allotriploid of the two species?

A

2a + b = 16 + 7 = 23

A + 2b = 8 + 14 = 22

47
Q

What are the four different chromosome morphologies?

A

Metacentric

Submetacentric

Acrocentric

Telocentric

Genetics (11 decks)

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