Chapter 8

Question 1

Define Euploidy

Answer 1

Normal amount of chromosomes (46)

Question 2

Define Aneuploidy

Answer 2

Abnormal amount of chromosomes

Question 3

Define monosomy

Answer 3

Missing 1 chromosome

Question 4

Define trisomy

Answer 4

Having 1 extra chromosome (tri = 3)

Question 5

Generally, what occurs when a fetus has autosomal aneuploidy?

Answer 5

Death of the offspring in utero

Question 6

What are the examples in which trisomy in autosomes survive?

Answer 6

Trisomy 21 (Down syndrome)
Trisomy 13 (Patau Syndrome)
Trisomy 18 (Edwards Syndrome)

Question 7

Which type of chromosome tolerates aneuploidy better? What happens?

Answer 7

Sex chromosomes
Abnormal sexual development occurs but is not usually lethal.

Question 8

What sex chromosome tolerates aneuploidy better and why?

Answer 8

X-chromosome as they can have X-inactivation occur.

Question 9

How does aneuploidy occur?

Answer 9

During nondisjunction when chromosomes/chromatids don’t separate properly in meiosis I or II

Question 10

Define deletion

Answer 10

When part of a chromosome is lost/deleted

Question 11

Define terminal deletion

Answer 11

When deletion occurs at te end of the chromosome

Question 12

Define intercalary deletion

Answer 12

When center of chromosome is deleted

Question 13

How does intercalary deletion occur (3 steps)

Answer 13

1. DNA forms a loop
2. Edges of the loop breaks (dsDNA breaks)
3. Broken edges are sealed back together

Question 14

Define duplication

Answer 14

When part of the chromosome is present twice.

Question 15

How does duplication occur?

Answer 15

Unequal crossing over in prophase I. It happens when homologous chromosomes don’t line up properly.

Question 16

How many copies of ribosomal DNA and tRNA genes do humans have?

Answer 16

~450 copies of ribosomal DNA gene
~600 copies of tRNA genes
Many genes have multiple copies in the genome due to past duplication events.

Question 17

What happens to the duplicated copy?

Answer 17

Since the organism doesn’t need the extra copy, the copy is inactive allowing for mutations to accumulate.
This copy is not under selective pressure, so there is nothing preventing the accumulation of mutations

Question 18

Define neofunctionalization

Answer 18

When the duplicate gene gains a new function

Question 19

Define pseudogene

Answer 19

AKA nonfunctionalization. Duplicate gene loses its function “false gene”

Question 20

Define conservation

Answer 20

Duplicated gene does not change function

Question 21

Define subfunctionalization

Answer 21

Duplicated gene does part of the function, and the original gene does other part of the function. The other half of each gene has no function
(each does half of the function)

Question 22

Define specialization

Answer 22

Each gene does half the original function, working together. The other half of each gene does a new function.

Question 23

Define gene families

Answer 23

Past duplications of genes and subsequent mutations create genes that have similar functions but do different things.

Question 24

What is an example of a gene family?

Answer 24

hemoglobin gene family.
Multiple hemoglobin genes, each for a different part of development: fetal, embryo, and adult.

Question 25

Define hemoglobin

Answer 25

Protein that carries oxygen in blood

Question 26

Define inversion

Answer 26

When part of a chromosome is inverted - preventing chromosomes from aligning properly.

Question 27

How do inversions occur?

Answer 27

1. DNA forms a loop 2. DNA break occurs 3. Breaks are re-ligated incorrectly

Question 28

What is the issue with inversions?

Answer 28

They prevent homologous chromosomes from properly aligning in prophase I. This causes the other chromosome to loop around to match, and these inverted chromosomes can still undergo crossing over (causing other issues)

Question 29

What issues would crossing over after an inversion cause?

Answer 29

Half of each chromosome is now backwards, and some genes are duplicated while others are deleted

Question 30

Define dicentric chromatid

Answer 30

2 centromeres caused by inversion

Question 31

Define acentric chromatid

Answer 31

no centromeres due to inversion

Question 32

Define paracentric inversion

Answer 32

When an inversion happens in a region that doesn't include the centromere

Question 33

Define pericentric inversion

Answer 33

When an inversion happens and DOES include the centromere

Question 34

Define translocation

Answer 34

When part of one chromosome is transferred to the other. Swapping of DNA between NONHOMOLOGOUS chromosomes.

Question 35

Define reciprocal translocation

Answer 35

Each nonhomologous chromosome breaks and connects with the opposite chromosome.

Question 36

Define nonreciprocal translocation

Answer 36

Only one chromosome breaks and adds onto another nonhomologous chromosome.

Question 37

How does translocation occur?

Answer 37

1. 2 chromosomes become near each other 2. they experience dsDNA beaks 3. they are re-ligated incorrectly. 4. All 4 of these chromosomes involved synapse (join together) in meiosis, influencing chromosome segregation

Question 38

What type of gametes can be formed after translocation?

Answer 38

- Normal - Have one of each gene - Be missing one gene and having an extra of another

Question 39

Define alternate segregation

Answer 39

When the gamete has one of each gene

Question 40

Define adjacent segregation

Answer 40

When a gamete is missing one gene and has an extra of another

Question 41

Define fragile sites

Answer 41

Thin areas of chromosomes that are more likely to break

Question 42

What makes chromosomes more likely to break?

Answer 42

Caused by lower chromatin compaction in the region.

Question 43

What is an example of a fragile site

Answer 43

FRA3B on chromosome 3. It often undergoes deletion and causes lung cancer.