Chromosome Mutations

Chromosomal mutations involve changes in what 2 things

Changes in structure

Changes in number

Changes in chromosome structure are called

Rearrangements

Changes in structure of chromosome includes what 4 things

Duplication

Deletions

Inversion

Translocation

Changes in number includes what 2 things

Aneuploidy

Polyploidy

Chromosomal duplication

a segment of a chromosome is repeated

chromosome deletion mutation

Segment of chromosome is deleted

Chromosome Inversion Mutation

the detachment, 180° rotation, and reinsertion of a chromosome arm

chromosome translocation mutation

Segment of chromosome is removed and moves to a non homologous chromosome or another place on the same chromosome

What causes chromosome rearrangements(2)

Errors in crossing over

DNA breakage and errors in rejoining

Why do chromosomal rearrangements result in a mutant phenotype

Change the number of genes in a cell or expression of genes

The Bar phenotype in drosophila results from

X linked duplication

Bar mutation in Drosophila

Changes size of eye

Unbalanced gene dosage

Changes in amount of gene products or ratio of the gene product to others

Unbalanced gene dosage leads to

Developmental problems

What causes unbalanced gene dosage?

duplications

What is lost if the centromere is deleted

Chromosome is lost

pseudodominance

Expression of a normally recessive gene

What causes pseudodominance

Deletion in one chromosome of a homologous pair

Haploinsufficiency

The appearance of a mutant phenotype in an individual cell or organism that is heterozygous for a normally recessive trait(one copy isn't enough to make a wild type)

NN= normal

N__ = mutant

N__ = dead

Inversions leads to alteration in

The order of chromosome segments

Position effect

Gene is repositioned in a way that alters its expression

Robertsonian translocation

Fusion of two acrocentric chromosomes

Robertsonian translocation causes

Down syndrome

Chromosomal rearrangements often have drastic effects on

The phenotype

Aneuploidy

Increase or decrease of number of individual chromosomes within a set

Nullisomy

Loss of 2 homologous chromosomes(2n -2)

Monosomy

Loss of a single chromosome(2n-1)

Trisomy

gain of a single chromosome (2n+1)

Tetrasomy

gain of two homologous chromosomes (2n+2)

Polyploidy

Presence of more than 2 sets of chromosomes

Autopolyploidy

multiple sets of chromosomes from the same species

allopolyploidy

multiple sets of chromosomes derived from different species(hybrids)

3 causes of aneuploidy

Deletion of centromere during mitosis or meiosis

Robertsonian translocation

Nondisjunction during meiosis or mitosis

Nondisjunction

Failure of chromosomes to separate during meiosis.

nondisjunction in meiosis I produces what cells

Produces 2 trisomic(extra chromosome)

Produces 2 monosomic cells(missing chromosome)

Nondisjunction in meiosis II produces what cells(3)

2 normal diploid cells

One trisomic cell(extra chromosome)

One monosomic cell(missing chromosomal)

Nondisjunction in mitosis produces what 2 cells

1 monosomic cell

1 trisomic cell

Trisomy 21

Down syndrome(1/700 births)

There is a drastic decrease in frequency of trisomic syndrome from chromosome

21 to 8

Turner Syndrome

(XO) Only example of monosomy in humans

Klinefelter syndrome

XXY

Polyploidy is common in

Plants but not animals

Why is polyploidy important in plant cells(3)

Increases cell size

Larger plant attributes

May give rise to new species

Autopolyploidy through mitosis

Chromosomes replicate but cell does not divide

Autopolyploidy through meiosis

In meiosis 1, nondisjunction produces a 2n gamete that fuses with a 1n gamete to produce an autotriploid

Autopolyploids that have extra chromosome sets from the same species(autotriploid) are usually

Sterile

Autotriploids produce highly

Unbalanced gametes

Why do autotriploids produce highly unbalanced gametes

Unequal separation of homologous chromosomes in anaphase 1

Why is sterility agriculturally desirable?

It produces seedless fruits

Hybridization is a fusion between

2 diploid species