Chromosome Mutations

Question 1

Change from normal chromosome structure and or number.

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

Answer 1

Chromosomal aberrations

Question 2

Common occurrences of chromosome mutations:

Answer 2

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

Question 3

Variations in chromosome number

Answer 3

Euploid

Aneuploid

Question 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

Answer 4

Euploid

Question 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

Answer 5

Aneuploid

Question 6

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

Answer 6

Nondisjunction

Question 7

Aneuploid Conditions

Answer 7

Nullisomy
Monosomy
Trisomy
Tetrasomy

Question 8

Both homologous chromosomes are absent

-embryonic lethal

Answer 8

Nullisomy

Question 9

One chromosome is missing

-Turner Syndrome: 2n-1

Answer 9

Monosomy

Question 10

One extra chromosome

-2n+1

Answer 10

Trisomy

Question 11

Two extra chromosomes

-2n+2

Answer 11

Tetrasomy

Question 12

Example of aneuploidy: Trisomy 21

Answer 12

Down Syndrome in humans

-consequences: problem with gene dosage

Question 13

Trisomy 21 and Advance Maternal Age

Answer 13

Oocytes are arrested in prophase I

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

Question 14

Ploidy levels of somatic cells

Answer 14

monoploidy
diploidy
polyploidy

Question 15

One set

Answer 15

monoploidy

Question 16

Two sets

Answer 16

Diploidy

Question 17

At least two sets

Answer 17

Polyploidy

Question 18

Somatic cell; result from meitotic division.

Answer 18

Monoploidy

Question 19

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

Answer 19

Haploidy

Question 20

Different Types of Polyploidy

Answer 20

Autopolyploidy
Allopolyploidy
Endopolyploidy

Question 21

Extra set of chromosomes is identical to the normal haploid set

Answer 21

Autopolyploidy

Question 22

Chromosomes come from two different species to produce a hybrid

Answer 22

Allopolyploidy

Question 23

When only certain cells within an organism are polyploidy.

Answer 23

Endopolyploidy

Question 24

Changes in chromosome structure (4 major types)

Answer 24

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

Question 25

How do changes in chromosomes occur?

Answer 25

- Breaks in the chromosome | - General errors in recombination

Question 26

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

Answer 26

Deletion

Question 27

If deleted piece contains recessive allele

Answer 27

Normal phenotype

Question 28

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

Answer 28

Pseudodominance

Question 29

Deletion reduces gene dosage

Answer 29

Haplosufficiency

Question 30

Deletion removes a centromere (nondisjunction-->aneuploidy)

Answer 30

Acentric chromosome

Question 31

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

Answer 31

Deletion

Question 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

Answer 32

Duplications

Question 33

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

Answer 33

Consequences of duplication

Question 34

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

Answer 34

Bar allele in Fruit Flies; example of duplication

Question 35

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

Answer 35

Multigene families

Question 36

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

Answer 36

Multigene family

Question 37

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

Answer 37

Paralogs

Question 38

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

Answer 38

Inversion

Question 39

Two types of inversions

Answer 39

1. Paracentric | 2. Pericentric

Question 40

Inversion that doesn't include the centromere

Answer 40

Paracentric

Question 41

Inversion that does include the centromere

Answer 41

Pericentric

Question 42

What causes breakage for an inversion to happen

Answer 42

Inversion loop

Question 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

Answer 43

Consequences of Inversions: Position effect

Question 44

Rearrangement of parts between nonhomologous chromosomes.

Answer 44

Translocation

Question 45

Occurs when the transfer of chromosome material is one way

Answer 45

Non-reciprocal translocation

Question 46

Occurs when chromosomes swap parts

Answer 46

Reciprocal translocation

Question 47

Consequences of Translocations

Answer 47

- position effect | - Non- wild type gene order

Question 48

Philadelphia chromosome in chronic myelogenous leukemia (CML)

Answer 48

Example of a translocation

Question 49

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

Answer 49

Fragile sites

Question 50

Fragile X

Answer 50

- 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.