Chromosome Mutations Flashcards Preview

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Flashcards in Chromosome Mutations Deck (50)
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1
Q

Change from normal chromosome structure and or number.

  • Change in gene expression pattern if the organism is viable
  • detectable through karyotyping
A

Chromosomal aberrations

2
Q

Common occurrences of chromosome mutations:

A
  • 6/1000 live births
  • still births/miscarriages
  • embryonic lethal
  • if survive embryonic stage:
    • mental and developmental disorders and infertility
3
Q

Variations in chromosome number

A

Euploid

Aneuploid

4
Q

True ploidy level; # of chromosomes in the individual’s cells is a multiple of the normal haploid set.
ex. humans- haploid: 23; diploid: 46

A

Euploid

5
Q

Not a multiple of the normal haploid set; one or more extra or missing chromosomes.
ex. humans- haploid: 23; Turner Syndrome: 45,X
2n-1

A

Aneuploid

6
Q

Homologous chromosomes during anaphase I or sister chromatids during anaphase II don’t segregate properly.
-fertilzation of aneuploid gametes leads to aneuploid progeny.

A

Nondisjunction

7
Q

Aneuploid Conditions

A

Nullisomy
Monosomy
Trisomy
Tetrasomy

8
Q

Both homologous chromosomes are absent

-embryonic lethal

A

Nullisomy

9
Q

One chromosome is missing

-Turner Syndrome: 2n-1

A

Monosomy

10
Q

One extra chromosome

-2n+1

A

Trisomy

11
Q

Two extra chromosomes

-2n+2

A

Tetrasomy

12
Q

Example of aneuploidy: Trisomy 21

A

Down Syndrome in humans

-consequences: problem with gene dosage

13
Q

Trisomy 21 and Advance Maternal Age

A

Oocytes are arrested in prophase I

-each month, after puberty, meiosis continues in the one egg.

14
Q

Ploidy levels of somatic cells

A

monoploidy
diploidy
polyploidy

15
Q

One set

A

monoploidy

16
Q

Two sets

A

Diploidy

17
Q

At least two sets

A

Polyploidy

18
Q

Somatic cell; result from meitotic division.

A

Monoploidy

19
Q

Result from meiosis; germ-line cells which will fuse with other haploid cells

A

Haploidy

20
Q

Different Types of Polyploidy

A

Autopolyploidy
Allopolyploidy
Endopolyploidy

21
Q

Extra set of chromosomes is identical to the normal haploid set

A

Autopolyploidy

22
Q

Chromosomes come from two different species to produce a hybrid

A

Allopolyploidy

23
Q

When only certain cells within an organism are polyploidy.

A

Endopolyploidy

24
Q

Changes in chromosome structure (4 major types)

A
  1. Deletion
  2. Duplication
  3. Inversion
  4. Translocation
25
Q

How do changes in chromosomes occur?

A
  • Breaks in the chromosome

- General errors in recombination

26
Q

When part of a chromosome or a sequence of DNA is missing.

A

Deletion

27
Q

If deleted piece contains recessive allele

A

Normal phenotype

28
Q

If deletion of a dominant allele and unmasking of a recessive allele.

A

Pseudodominance

29
Q

Deletion reduces gene dosage

A

Haplosufficiency

30
Q

Deletion removes a centromere (nondisjunction–>aneuploidy)

A

Acentric chromosome

31
Q

Cri-du-chat
gene encoding telomerase is missing
46, 5P

A

Deletion

32
Q

when part of a chromosome is copied abnormally, resulting in extra genetic material from the duplicated segment.
-Slippage during S phase can also cause this to happen

A

Duplications

33
Q
  • Gene amplification; more gene product
  • Unequal crossing over can induce a deletion
  • Duplication loops
A

Consequences of duplication

34
Q

Reduced number of eye facets due to extra negatively influencing 16A allele.
-incomplete dominance

A

Bar allele in Fruit Flies; example of duplication

35
Q

Duplications might result in _______.

ex. hemoglobin subunits and rRNA genes

A

Multigene families

36
Q

Multiple genes with related functions near each other on the same chromosome

A

Multigene family

37
Q

Type of homolog, 2 or more genes in an organism that have similar or identical functions.

A

Paralogs

38
Q

when a segment of a chromosome is reversed from end to end. (breakage and rearrangement within itself)

A

Inversion

39
Q

Two types of inversions

A
  1. Paracentric

2. Pericentric

40
Q

Inversion that doesn’t include the centromere

A

Paracentric

41
Q

Inversion that does include the centromere

A

Pericentric

42
Q

What causes breakage for an inversion to happen

A

Inversion loop

43
Q

location of gene in chromosome can effect how much of that gene is transcribed
-over-expression of genes that are not meant to be silenced

A

Consequences of Inversions: Position effect

44
Q

Rearrangement of parts between nonhomologous chromosomes.

A

Translocation

45
Q

Occurs when the transfer of chromosome material is one way

A

Non-reciprocal translocation

46
Q

Occurs when chromosomes swap parts

A

Reciprocal translocation

47
Q

Consequences of Translocations

A
  • position effect

- Non- wild type gene order

48
Q

Philadelphia chromosome in chronic myelogenous leukemia (CML)

A

Example of a translocation

49
Q

Happen because of trinucleotide repeat expansion

  • Narrow sites of some chromosomes that are prone to breakage
  • breakage would cause a deletion
A

Fragile sites

50
Q

Fragile X

A
  • Male offspring have a 50% chance of receiving fragile X from a carrier mom (can result in mental retardation or transmitting male–normal)
  • Molecular basis: FMR-1 gene located at the fragile X site which contains 3 basepair (CGG) repeats in the 5’ UTR
  • FMR-1 encodes FMRP (RNA binding protein) that is active at synapses in the brain.