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Genetics > Ch. 8 > Flashcards

Ch. 8 Flashcards

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1
Q

Difference between rearrangements and aneuploidy

A

Rearrangements: alter the structure of chromosomes

Aneuploidy: alter the number of chromosomes

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2
Q

Chromosome rearrangement is also called _______ and expressed by ____

A

duplication, part of one chromosome is duplicated

2n = 6

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3
Q

Aneuploidy is also called ________ and is expressed by _____

A

trisomy

2n + 1 = 7

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4
Q

Polyploidy is also called ______ and is expressed by _____

A

auto-triploid

3n = 9

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5
Q

Chromosome rearrangements often occur through what?

A
  1. Double stranded breaks occur in the DNA molecule within chromosome, these often cause cell death, so organisms have evolved to rejoin ends, but this can sometimes happen incorrectly
  2. Chromosome rearrangements can also arise through errors in crossing over or when crossing over occurs between repeated DNA sequences
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6
Q

Tandem Duplication

A

duplicated segment is adjacent to the original segment

AB:CDEF
AB:CDEDEF

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7
Q

Displaced Duplication

A

Duplicated segment is located some distance from the original segment

ABC: DEFGEF
ABC:DEFG

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8
Q

Reverse Duplication

A

Inverted Duplication

AB:CDEFG
AB:CDEFFEG

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9
Q

Segmental Duplications

A

Duplications greater than a thousand base pairs in length.

Most are intrachromosomal duplications (the 2 copies are found on the same chromosome).

Interchromosomal: two copies found on different chromosomes

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10
Q

How does chromosome Duplication alter the phenotype?

A

Imbalances in amounts of gene products (abnormal gene dosage)

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11
Q

Effects of deletions
Homo?
Hetero?

A

Phenotypically depends on location, many lethal in homozygous state

  1. Heterozygous produce imbalances in amounts of gene produces
  2. normally recessive mutations may be expressed when wild-type allele has been deleted.
  3. Some genes must have 2 copies for normal function
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12
Q

Pseudodominance

A

The expression of a normally recessive mutation, indicates that one of the homologous chromosomes has a deletion

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13
Q

Haploinsufficient

A

when a single copy of a gene is not sufficient to produce a wild-type phenotype

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14
Q

Chromosome Inversion

A

Chromosome segment turned 180 degrees

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15
Q

Paracentric inversion

A

Dose not include centromere

AB:CFEDG

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16
Q

Pericentric Inversion

A

ADC:BEFG

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17
Q

Position Effect

A

Result of inversion
Many genes regulated by position dependent manner. If positions are altered by an inversion, their expression may be altered, an outcome referred to as position effect

18
Q

Heterozygous inversion offspring: paracentric

A

2 non-recombinant gametes: 1 normal, 1 with paracentric inversion
2 nonviable recombinant gametes

19
Q

Heterozygous inversion offspring: pericentric

A

1 Normal nonrecombinant gamete
1 nonrecombinant gamete with pericentric inversion
2 nonviable recombinant gametes

20
Q

inversion: Chromosomes with 2 centromeres vs. no centromeres

A

Dicentric

Acentric

21
Q

What happens with dicentric chromosomes during anaphase 1?

A

Dicentric bridge, chromosome stretched across nucleus

22
Q

Translocation

A

Movement of genetic material between nonhomologous chromosomes

23
Q

Nonreciprocal translocation

A

Genetic material moves from one chromosome to another without any reciprocal exchange

24
Q

Reciprocal translocation

A

two way exchange of segments between chromosomes

25
Q

Effects of translocations

A
  1. Physically link genes that were once on different chromosomes
  2. Chromosome breaks that bring about translocation may take place within a gene and disrupt its function
26
Q

Robertsonian translocation

A

long arms of two acrocentric chromosomes become joined to a common centromere through a translocation, generating a metacentric chromosome with two long arms and another chromosome with two very short arms.

27
Q

Translocations in meiosis

A

Alternate segregation: viable, common. the 2 normal ones move together
Adjacent 1-segregation: nonviable, common. Matching (opposite) centromeres more together.
Adjacent 2-segregation: nonviable, rare, different centromeres move together.

28
Q

Fragile sites

A

Sites that develop constrictions or gaps when the cells are grown in culture and that are prone to breakage under certain conditions.

29
Q

Aneuploidy is the change in the number of individual chromosomes. How does this happen?

A
  1. Chromosome may be lost in the course of mitosis or meiosis if centromere is deleted
  2. small chromosome generated by Robertson translocation may be lost in mitosis or meiosis
  3. nondisjunction, failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis
30
Q

Aneuploidy: Nullisomy

A

Loss of both members of homologous pair of chromosomes. 2n-2

Humans = 44 chromosomes, 46 normal

31
Q

Aneuploidy: Monosomy

A

Loss of single chromosome. 2n-1

32
Q

Aneuploidy: Trisomy

A

Gain of single chromosome 2n +1

33
Q

Aneuploidy: Tetrasomy

A

Gain of 2 homologous chromosomes, 2n+2

34
Q

Effects of aneuploidy, assuming viable (not likely) are most likely due to

A

abnormal gene dosage

35
Q

Familial Down Syndrome

A

Part of 21 is on another chromosome. 1/3 down, 1/3 normal, 1/3 carrier. Others are aborted.

36
Q

Uniparental Disomy

A

Both copies, 1 parent (originally trisomy, but one gets deleted)

37
Q

Genetic Mosaicism

A

Nondisjunction that generates patches of cells in which every cell has a chromosome abnormality and other patches in which every cell has normal karyotype

38
Q

Gynandromorphs

A

XX/XO, mix of female and male traits

39
Q

Autopolyploidy

A

all chromosomes sets are from a single species

40
Q

Allopolyploidy

A

Chromosomes sets are from 2+ species

41
Q

Autopolyploidy gametes are

A

unbalanced

42
Q

Allopolyploid that consists of 2 combined diploid genomes

A

amphidiploid

Genetics (15 decks)

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