Chromosome Mutations Flashcards Preview

Bio 233 > Chromosome Mutations > Flashcards

Flashcards in Chromosome Mutations Deck (50):
1

Change from normal chromosome structure and or number.
-Change in gene expression pattern if the organism is viable
-detectable through karyotyping

Chromosomal aberrations

2

Common occurrences of chromosome mutations:

-6/1000 live births
-still births/miscarriages
-embryonic lethal
-if survive embryonic stage:
*mental and developmental disorders and infertility

3

Variations in chromosome number

Euploid
Aneuploid

4

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

Euploid

5

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

Aneuploid

6

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

Nondisjunction

7

Aneuploid Conditions

Nullisomy
Monosomy
Trisomy
Tetrasomy

8

Both homologous chromosomes are absent
-embryonic lethal

Nullisomy

9

One chromosome is missing
-Turner Syndrome: 2n-1

Monosomy

10

One extra chromosome
-2n+1

Trisomy

11

Two extra chromosomes
-2n+2

Tetrasomy

12

Example of aneuploidy: Trisomy 21

Down Syndrome in humans
-consequences: problem with gene dosage

13

Trisomy 21 and Advance Maternal Age

Oocytes are arrested in prophase I
-each month, after puberty, meiosis continues in the one egg.

14

Ploidy levels of somatic cells

monoploidy
diploidy
polyploidy

15

One set

monoploidy

16

Two sets

Diploidy

17

At least two sets

Polyploidy

18

Somatic cell; result from meitotic division.

Monoploidy

19

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

Haploidy

20

Different Types of Polyploidy

Autopolyploidy
Allopolyploidy
Endopolyploidy

21

Extra set of chromosomes is identical to the normal haploid set

Autopolyploidy

22

Chromosomes come from two different species to produce a hybrid

Allopolyploidy

23

When only certain cells within an organism are polyploidy.

Endopolyploidy

24

Changes in chromosome structure (4 major types)

1. Deletion
2. Duplication
3. Inversion
4. Translocation

25

How do changes in chromosomes occur?

-Breaks in the chromosome
-General errors in recombination

26

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

Deletion

27

If deleted piece contains recessive allele

Normal phenotype

28

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

Pseudodominance

29

Deletion reduces gene dosage

Haplosufficiency

30

Deletion removes a centromere (nondisjunction-->aneuploidy)

Acentric chromosome

31

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

Deletion

32

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

Duplications

33

-Gene amplification; more gene product
-Unequal crossing over can induce a deletion
-Duplication loops

Consequences of duplication

34

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

Bar allele in Fruit Flies; example of duplication

35

Duplications might result in _______.
ex. hemoglobin subunits and rRNA genes

Multigene families

36

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

Multigene family

37

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

Paralogs

38

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

Inversion

39

Two types of inversions

1. Paracentric
2. Pericentric

40

Inversion that doesn't include the centromere

Paracentric

41

Inversion that does include the centromere

Pericentric

42

What causes breakage for an inversion to happen

Inversion loop

43

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

Consequences of Inversions: Position effect

44

Rearrangement of parts between nonhomologous chromosomes.

Translocation

45

Occurs when the transfer of chromosome material is one way

Non-reciprocal translocation

46

Occurs when chromosomes swap parts

Reciprocal translocation

47

Consequences of Translocations

-position effect
-Non- wild type gene order

48

Philadelphia chromosome in chronic myelogenous leukemia (CML)

Example of a translocation

49

Happen because of trinucleotide repeat expansion
-Narrow sites of some chromosomes that are prone to breakage
*breakage would cause a deletion

Fragile sites

50

Fragile X

-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.