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Genetics > Chromosome Changes (Lec 11) > Flashcards

Chromosome Changes (Lec 11) Flashcards

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1
Q

Findings suggest that Down Syndrome is not due to a single gene but is caused by complex interactions among multiple genes that are affected when an extra copy of which chromosome is present?

A

21

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2
Q

Duplications, deletions, inversions, and translocations are all type of what?

A

chromosome rearrangements

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3
Q

True or False?

In a chromosome inversion, a segment of the chromosome is turned 180 degrees

A

true

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4
Q

Type of duplication in which the duplicated region is immediately adjacent to the original segment. Ex. AB*CDEFGefg

A

tandem duplication

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5
Q

Type of duplication in which the duplicated region is located some distance from the original segment, either on the same chromosome or on a different one. EX. AB*CDEFGab

A

displaced duplication

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6
Q

A duplication in which the duplicated region is inverted. Ex. ABba*CDEFG

A

reverse duplication

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7
Q

What causes unequal crossing over of wild type chromosomes and what is the result?

A

chromosomes that do not align properly; results in one chromosome containing a duplication and the other chromosome containing a deletion

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8
Q

What is the result of unequal crossing over between bar chromosomes (each have two copies of Bar)?

A

a chromosome with three Bar copies and a wild type chromosome

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9
Q

In regards to chromosome rearrangement, why can a large deletion be easily detected?

A

the chromosome is noticeably shortened and the normal chromosome must loop out during the pair of homologs

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10
Q

In regards to chromosomal rearrangements, what are the effects of deletions?

A

imbalances in gene product, expression of a normally recessive gene, haploinsufficency

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11
Q

This type of deletion is a series of X-linked wing mutations in drosophila that can act as a recessive lethal

A

Notch

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12
Q

In what phase of meiosis does the normal chromosome loop out in order to allow for correct pairing and alignment between chromosomes?

A

prophase I

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13
Q

What does Notch code for?

A

a receptor that transmits signals received from outside the cell to the cell’s interior

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14
Q

Loss of all copies of Notch gene prevents normal development, acting as what?

A

a recessive lethal

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15
Q

In regards to chromosome rearrangement, specifically inversion, what is the type of inversion that does not include the centromere?

A

Paracentric inversion

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16
Q

In regards to chromosome rearrangement, specifically inversion, what is the type of inversion that includes the centromere?

A

Pericentric inversion

note: “i” in pericentric is for “includes” centromere

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17
Q

ABCDEFG to ABCFEDG is an example of what type of chromosome rearrangement?

A

Paracentric inversion

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18
Q

ABCDEFG to ADCBEFG is an example of what type of chromosome rearrangement?

A

Pericentric inversion

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19
Q

ABCDEFG to ABCDEFGEFG is an example of what type of chromosome rearrangement?

A

Tandem duplication

20
Q

ABCDEFG to ABCDEFGAB is an example of what type of chromosome rearrangement?

A

Displaced duplication

21
Q

ABCDEFG to ABBACDEFG is an example of what type of chromosome rearrangement?

A

Reverse duplication

22
Q

How is translocation different from crossing over?

A

Crossing over is the exchange of genetic material between homologous chromosomes while translocation involves the transfer or movement of genetic material between non-homologous chromosomes.

23
Q

In regards to a pairing of a WT chromosome with a chromosome containing paracentric inversion in a heterozygous individual, formation of an inversion loop and thus crossing over with inversion results in an unusual structure. Describe the chromatids of this structure after this occurs

A

One of the four chromatids has two centromeres, one lacks a centromere

24
Q

In regards to a pairing of a WT chromosome with a chromosome containing paracentric inversion in a heterozygous individual, in anaphase I, the centromeres separate, stretching the dicentric chromatid which breaks. What happens to the chromosome lacking a centromere?

A

it is lost

25
Q

In regards to a pairing of a WT chromosome with a chromosome containing paracentric inversion in a heterozygous individual , what are the resulting gametes like after anaphase II?

A

two gametes contain nonrecombinant chromosomes: one WT and one with inversion; the other two chromosomes contain recombinant chromosomes that are missing some genes

26
Q

True or False?

The resulting recombinant gametes from inversion in a heterozygous individual are still viable.

A

false; they are nonviable due to missing genes

27
Q

In regards a pairing of a WT chromosome with a chromosome containing pericentric inversion in a heterozygous individual, describe the unusual structure that is formed, specifically the chromatids.

A

two of the resulting chromatids have too many copies of some genes and no copies of others

28
Q

In regards to inversions in meiosis, do homozygous individuals have problems during meiosis?

A

no, only heterozygous individuals

29
Q

Heterozygous individuals demonstrate reduced recombination in ____ inversion, as gametes formed result in nonviable offspring and have abnormal gametes formed in ___ inversion.

A

paracentric; pericentric

30
Q

_____ entails the movement of genetic material between non-homologous chromosomes

A

translocation

31
Q

This type of translocation is more common and involves the movement of material between non homologous chromosomes

A

reciprocal translocation

32
Q

This type of translocation involves the movement of genetic material from one chromosome to another without any reciprocal exchange

A

non-reciprocal translocation

33
Q

Robertsonian translocation results in what?

A

a large metacentric chromosome and a fragment that often fails to segregate and is lost

34
Q

In prophase I when alignment of chromosomes occurs, what kind of structure is formed for translocation

A

a crosslike configuration that allows homologous sections from one chromosome to match to two other chromosomes

35
Q

In regards to translocation segregation patterns, in anaphase I, the chromosomes separate in how many different ways?

A

one of three different ways:
alternate segregation
adjacent-1 segregation
adjacent-2 segregation (rare)

36
Q

Out of the three types of translocation segregation, which type produces viable gametes after anaphase II?

A

only alternate segregation; gametes resulting from adjacent-1 and adjacent-2 segregation are nonviable because some genes are present in two copies, whereas others are missing

37
Q

Fragile-X syndrome is named after a fragile site on the human X chromosome. What are some characteristics of the syndrome?

A

mental retardation; x-linked inheritance; 1 in 1250 male births; results from an increase in the number of repeats of a CGG trinucleotide

38
Q

What does G banding reveal?

A

bands rich in A-T base pairs

39
Q

What does Q banding reveal?

A

difference in relative amounts of C-G and A-T base pairs

40
Q

What does C banding reveal?

A

regions with centromeric heterochromatin

41
Q

What does R banding reveal?

A

bands rich in C-G base pairs

42
Q

What is the genetic basis of Cri-du-chat syndrome and what is the phenotype?

A

deletion on short arm of chromosome 5; infants often have a high-pitched cry, also characterized by intellectual disability and delayed development, small head size, low birth weight and weak muscle tone. Some children are born with a heart defect

43
Q

What is the genetic basis of Wolf-Hirschhorn syndromee and what is the phenotype?

A

chromosome deletion on short arm of chromosome 4; distinct craniofacial phenotype, growth and mental retardation, seizures, heart defects

44
Q

What is the genetic basis of Williams-Beuren syndrome and what is the phenotype?

A

deletion on short arm of chromosome 7; facial features, heart defects, mental impairment

45
Q

What is the genetic basis of Prader-Wili syndrome and what is the phenotype?

A

deletion on short arm of chromosome 15; feeding difficulty at early age, but becoming obese after 1 year

Genetics (15 decks)

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