Ch. 17 Large-Scale Chromosomal Changes

Front 1

What are chromosome mutations?

Back 1

Any type of change in chromosome structure or number. Unlike DNA mutations, they can be seen microscopically.

Front 2

What is a cytogeneticist?

Back 2

Someone who studies chromosomes, chromosome mutations, and who typically works in a hospital setting.

Front 3

What are the three ways chromosomes are classified and identified?

Back 3

1. Location of centromere

2. Size of chromosome with #1 chromosome typically being the largest.

3. Banding patterns of chromosomes after staining.

Front 4

What are the four different centromere placements?

Back 4

1. Metacentric (centered)

2. Submetacentric (slightly off center)

3. Acrocentric (more significantly off center)

4. Telocentric (off to one end)

Front 5

What are the two basic ways chromosome mutations can be grouped?

Back 5

1. Changes in chromosome number

2. Changes in chromosome structure

Front 6

What does euploidy mean?

Back 6

That the chromosome number is an exact multiple if a chromosome set for a normal individual (eg, haploid is n and diploid is 2n).

Front 7

What is monoploidy?

Back 7

It means there is only one chromosome set (n). Haploids are naturally monoploid.

If the organism would typically be diploid but has only one chromosome set, then it has an aberrant euploidy. Meaning the wrong # of chromosomes.

Front 8

What does aberrant euploidy mean?

Back 8

It means a cell or organism has a different number off chromosomes in its set compared to the wild type.

Front 9

What is polyploidy?

Back 9

When a cell or organism has 3 or more chromosome sets. Ex: triploid (3n), terraploid (4n), pentaploid (5n), etc. Common in plants, but rate in most animals.

Front 10

What does aneuploidy mean?

Back 10

The chromosome set is not an exact multiple of n. The presence of an abnormal number of chromosomes in a cell.

Front 11

What does Nullisomic mean?

Back 11

A type of aneuploidy.

The loss if a chromosome pair (2n-2)

Front 12

What does Tetrasomy mean?

Back 12

A type of aneuploidy.

The gain of a chromosome pair (2n+2).

Front 13

What does Monosomy mean?

Back 13

A type of aneuploidy.

The loss of one chromosome (2n-1). Autosomal gene expression will be 50% rather than 100%.

Front 14

What is Trisomy?

Back 14

A type of aneuploidy

The gain if one chromosome. (2n+1).

Autosomal gene expression is 150% instead of 100%.

Front 15

What does nondisjunction mean?

Back 15

The failure of homologs (at meiosis) or sister chromatids (at mitosis) to separate properly to opposite poles. This is the cause of most aneuploidy.

In meiosis, can fail to separate during anaphase I or anaphase II.

Front 16

What happens when meiotic nondisjunction happens during anaphase I?

Back 16

In the first cell division, the homologous pairs won't separate. This will leave you with two n+1 gametes and two n-1 gametes at the end of meiosis.

Front 17

What happens if meiotic nondisjunction occurs in anaphase II?

Back 17

The homologous pairs separate properly in anaphase I. However, in at least one of the resulting two cells, the sister chromatids fail to separate. This leaves you with one n+1 gamete, one n-1 gamete, and two normal n gametes (if only one set of sister chromatids failed to separate properly).

Front 18

In a diploid species, complete nondisjunction during meiosis I may produce a viable cell that is what? Why?

Back 18

Trisomic. This is because when the maternal and paternal gametes unite, one is a normal n gamete, but the other is an n+1 gamete, meaning it has two copies of the same chromosome. This leaves you with offspring that has 3 copies of the same chromosome.

Front 19

What happens if the autosomal cells are monosomic?

Back 19

It is lethal. An n-1 x n gametic union results in autosomal monosomy.

Front 20

What may attribute to the characteristics of sex chromosomal aneuploidy?

Back 20

Expression of X-linked genes prior to embryonic X inactivation or expression of a few genes on the inactivated X chromosome.

Front 21

What is Patau syndrome?

Back 21

Trisomy 13. Can also be written as (47, +13). Shows the child has 47 chromosomes, and the additional chromosome is #13.

Front 22

What is Edwards syndrome?

Back 22

Trisomy 18. Can also be written as (47, +18).

80% of those affected are female.

Front 23

What is Down Syndrome?

Back 23

Trisomy 21. Can also be written as (47, +21). These children can reach adulthood and live to roughly 50.

Front 24

What is Klinefelter syndrome?

Back 24

XXY. Can also be written as (47, XXY).

Most cases arise by mitotic errors after fertilization.

XXY is considered male.

Front 25

What is Jacob's syndrome?

Back 25

XYY. Can also be written as (47, XYY).

Those affected are considered male.

Front 26

What is Triple X syndrome?

Back 26

XXX. Can also be written as (47, XXX). Those affected are considered female.

Front 27

What is Turner syndrome?

Back 27

XO. Can also be written as (45, XO). Those affected are considered female. The "O" represents the missing X chromosome. It is the only viable form of monosomy in humans.

Front 28

What is gene balance?

Back 28

The idea that a normal phenotype requires a 1:1 relative proportion of genes in the genome.

Front 29

What does homologous mean as it relates to ancestry?

Back 29

Two or more genes were derived from one ancestral gene.

Front 30

What does paralogous mean?

Back 30

Homologous genes within a single species.

Front 31

What does orthologous mean?

Back 31

Homologous genes in different species due to divergence.

Front 32

What do chromosomal structural change consequences depend on?

Back 32

How much of the chromosome was involved and where it took place. Known as the positional effect.

Front 33

What are the four types of changes in chromosome structure?

Back 33

1. Deletions

2. Duplications

3. Inversions

4. Translocations

Front 34

What are chromosomal deletions?

Back 34

The loss of a chromosome segment. There are two types.

1. Interstitial: within the chromosome

2. Terminal: at the end of the chromosome

Front 35

What is Cri du chat syndrome?

Back 35

A heterozygous terminal deletion of the p (short) arm of the 5 chromosome. Also called Lejuene's syndrome.

Written as 5p- or 46, del(5p).

Front 36

What type of chromosome structural change causes Angelman syndrome and Prader-Willi syndrome?

Back 36

It's a heterozygous interstitial deletion on the q (long) arm of chromosome 15. Written as 46, del(15q).

Front 37

What are chromosomal duplications?

Back 37

The doubling of a chromosomal segment. There are three types.

1. Tandem: the copy is right next to the original (ex: BCBC)

2. Reverse tandem: the copy is right next to the original but is inverted (ex: BCCB)

3. Terminal tandem: the copy is located at the end of the chromosome.

Front 38

What type of chromosome structure change can lead to the formation of gene families?

Back 38

Duplications. They can provide more genes into a specie's genome. After many generations, gene families can form.

Front 39

What is a gene family?

Back 39

Two or more genes that are similar to one another, but differ due to accumulation of different mutations.

Front 40

What are the human Myoglobin and Hemoglobin genes in relation to each other?

Back 40

Paralogs.

Front 41

What does the Psi symbol (looks like a trident) represent?

Back 41

Pseudogenes. These are genes that don't do anything.

Front 42

What are chromosomal inversions?

Back 42

A 180°rotation of a chromosomal segment. There are two kinds.

1. Paracentric: the inversion happens next to the centromere and doesn't include it

2. Pericentric: Does include the centromere

Inversions don't change the amount of genomic material.

Front 43

What is an example of a disorder caused by an inversion?

Back 43

Hemophilia A. It is caused by an X-linked inversion. Breaks the F8 gene (exons 1-22), thereby inactivating it.

Front 44

What is a chromosomal translocation?

Back 44

A change in a chromosomal segment location. There are three types.

1. Nonreciprocal INTRAchromosomal translocation: occurs within the chromosome.

2. Nonreciprocal INTERchromosomal translocation: happens between two nonhomologous chromosomes. One chromosome donates a piece, and the other receives that piece.

3. Reciprocal INTERchromosomal translocation: happens between two nonhomologous chromosomes and both receive a piece from the other.

Front 45

What causes chronic myelogenous leukemia?

Back 45

A reciprocal translocation between chromosomes 9 and 22. Written as 46, t(9:22).

90% of the time caused by a Philadelphia chromosome, a product of the translocation.

Front 46

What is familial Down syndrome caused by?

Back 46

Unbalanced translocation. Not to be confused with trisomy 21. Occurs when the p arms of chromosomes 14 and 21 are deleted, and the q arm of 21 undergoes a reciprocal translocation with chromosome 14.

Front 47

What is balanced translocation?

Back 47

When no genetic material is gained or lost. This is what typically happens.

Front 48

What is unbalanced translocation?

Back 48

When genetic material is deleted and/or duplicated along with a translocation.

Front 49

How many Barr bodies would you expect to see in the following? What is the gender of each?

XXY

XYY

XXX

X

Back 49

1. One (male. Klinefelter syndrome)

2. None (male. Jacob's syndrome)

3. Two (female. Triple X syndrome)

4. None (female. Turner syndrome)

Front 50

If the diploid # of chromosomes is 2n=12, how many chromosomes would be found in the diploid cells of the following plants?

A tetraploid

Monosomy 3

Nullisomy 4

Back 50

1. Find haploid #, then multiply. N=6, so 4n=24

2. 2n-1=12. Subtract 1 to get 11.

3. 2n-2=12. Subtract 2 to get 10.