Chromosomal Mutations

Question 1

Chromosomal Mutations

Answer 1

1. Variation in the structure
2. Number of chromosomes

Question 2

Chromosomic mutations

Answer 2

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

Question 3

Deletion

Answer 3

Consists of a deletion of a part of a chromosome

Question 4

2 types of deletions

Answer 4

1. Terminal deletion: consists of a single break in the terminal part of a chromosome
2. Interstitial deletion: consists of the breakage of the chromosome in the middle of one arm: chromosome without centromere is generated and so is lost during replication

Question 5

Cri-di-chat syndrome

Answer 5

Deletion of chromosome 5

Question 6

Dangerous consequence of deletion

Answer 6

Loss of heterozygosity: copy of genes reduced from 2 to 1 which leads to protein insufficiency

Question 7

Duplication

Answer 7

Duplicates a region of the chromosome

Question 8

How is duplication caused?

Answer 8

Due to crossing over in which there is unequal pairing of repeated regions due to misalignment

Question 9

Can duplication be advantageous?

Answer 9

Yes and it can be fixed and favoured in the genome i.e. alpha and beta globin of hemoglobin

Question 10

A dangerous consequence of duplication

Answer 10

Certain regions are overexpressed

Question 11

Inversion

Answer 11

Occurs when a part of a chromosome breaks and is rejoined with a rotation of 180 degrees of the sequence

Question 12

Paracentric inversion

Answer 12

Does not involve the centromere

Question 13

Pericentric inversion

Answer 13

Includes the inverted region and the centromere

Question 14

Where does the issue arise in inversion?

Answer 14

When there is a pairing of homologous chromosomes: the pairing occurs in a loop to have the gene’s sequences matching

Question 15

Acentric chromosome

Answer 15

No centromere

Question 16

What happens to acentric chromosomes?

Answer 16

Lost due to the lack of centromere

Question 17

Dangerous consequence of inversion

Answer 17

Silencing, some genes may be replaced in different chromatin context

Question 18

Translocation

Answer 18

The breakage within a chromosome, after which the genetic material is joined in a different chromosome

Question 19

Direct translocation

Answer 19

Part of a chromosome is directly translocated into another one

Question 20

Reciprocal translocation

Answer 20

An exchange of genetic material, meaning both chromosomes are involved in translocating their genetic material from one another

Question 21

What does translocation not lead to?

Answer 21

To the loss of how DNA is transcribed

Question 22

What is nonreciprocal intrachromosomal translocation?

Answer 22

Goes from the region of one chromosome into another region of the same chromosome

Question 23

What is nonreciprocal interchromosomal translocation?

Answer 23

A region of a chromosome moved into another chromosome

Question 24

What is reciprocal interchromosomal translocation?

Answer 24

exchange of genetic material between different chromosomes

Question 25

What does the short arm consist of?

Answer 25

Satellite DNA= non-coding repetitive sequences + genes for RNA

Question 26

Metacentric

Answer 26

When the centromere is located exactly in the middle

Question 27

Acrocentric

Answer 27

When the centromere is moved towards the ends of the chromosome

Question 28

When can Robertsonian translocation occur?

Answer 28

When the centromere is moved towards the ends of the chromosome

Question 29

5 acrocentric chromosomes in our genome

Answer 29

13 14 15 21 22

Question 30

Down syndrome

Answer 30

Due to trisomy 21 or Robertsonian translocation between chromosomes 14 and 21

Question 31

Reciprocal translocation between acrocentric chromosomes

Answer 31

could form one chromosome with 2 long arms and a centromere and 2 short arms which is then lost

Question 32

Nullisomic

Answer 32

Lack of a pair of homologous chromosomes of one chromosome LETHAL

Question 33

Monosomy

Answer 33

one of the 2 homologous chromosome is missing LETHAL

Question 34

Double monosomy

Answer 34

two chromosomes are missing, but in 2 different pairs of homologus chromosomes

Question 35

Trisomy

Answer 35

one extra chromosome only non-lethal is trisomy 21

Question 36

Tetrasomy

Answer 36

2 extra homologous chromosomes

Question 37

Double tetrasomy

Answer 37

2 extra chromosomes on 2 different homologous chromosomes

Question 38

Triploidy

Answer 38

A condition which there are 3 copies of chromosomes [XXX or YYY] LETHAL

Question 39

Why are sex chromosome mutations more likely to be compatible with life?

Answer 39

Because of chromosome X inactivation

Question 40

Turner Syndrome

Answer 40

Women who lack one X chromosome

Question 41

Human aneuploidy

Answer 41

abnormally high number of chromosomes

Question 42

Anaphase lagging

Answer 42

One chromosome is left behind during separation and is lost during cell division

Question 43

Non-disjunction in meiosis I

Answer 43

All of the 4 daughter cells will be chromosomally abnormal

Question 44

Non-disjunction in meiosis II

Answer 44

2 will be normal and 2 daughter cells will present aneuploidy