Molecular Biology Week 5

Question 1

What are the two types of numerical abnormalities called chromosome abnormalities?

Answer 1

Aneuploidy and Polyploidy.

Question 2

What is aneuploidy and give an example:

Answer 2

Aneuploidy occurs due to abnormalities in meiosis. This is where an individual is missing either a chromosome from a pair or has more than two individual chromosomes of a pair (trisomy) ex: Down Syndrome Trisomy 21

Question 3

Give an example of monosomy:

Answer 3

Turner Syndrome, a female born with one sex chromosome, an X

Question 4

What is polyploidy and give an example:

Answer 4

This occurs in cells and organisms where are two sets of chromosomes +. Most organisms are diploid. Polyploidy may occur due to abnormal cell division during metaphase I in meiosis. Mainly plants and amphibians.

Question 5

What are deletions and give an example:

Answer 5

Deletions are when a portion of the chromosome is missing or deleted. Terminal or interstitial. This leads to insufficient gene products which unmask mutant alleles on normal chromosomes ex: Cri de Chat

Question 6

What are duplications?

Answer 6

This is where a portion of the chromosome is duplicated, resulting in extra genetic material.

Question 7

What are inversions and explain the two variations of this type:

Answer 7

Inversions occur when a portion of the chromosome has broken off, turned upside down, and reattached, therefore the genetic material is inverted there are two different types Pericentric (both arms) and Paracentric (just one arm).

Question 8

Epilepsy and mental retardation are caused by what forming?

Answer 8

Rings, when a portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material.

Question 9

What is translocation? What are the two types called?

Answer 9

This is when a portion of one chromosome is transferred to another chromosome. The two main types are reciprocal translocation and Robertsonian translocation.

Question 10

What is Reciprocal translocation?

Answer 10

This is when segments from two chromosomes have been exchanged.

Question 11

What is Robertsonian translocation?

Answer 11

This is when an entire chromosome has attached to another at the centromere in humans these occur with chromosomes 13, 14, 15, 21, and 22.

Question 12

What is mosaicism?

Answer 12

This occurs after conception, resulting in mosaicism where some cells have an abnormality and some do not.

Question 13

What does de novo mean?

Answer 13

New to the individual.

Question 14

There are two different types of interphase chromatin, what are they?

Answer 14

Euchromatin; active DNA. Heterochromatin; mostly inactive DNA. (constitutive - never expressed, near centromere mostly repetitive DNA.) (facultative (sometimes expressed)

Question 15

Which is the lighter/darker stained chromatin in the interphase nucleus?

Answer 15

Lighter: Euchromatin, Darker: Heterochromatin

Question 16

What shape is the chromosome in bacterial cells?

Answer 16

Small and circular.

Question 17

Describe Metaphase Chromatin:

Answer 17

This is when a cell is in the process of dividing after the chromosome has been replicated into identical double structures known as sister chromatids.

Question 18

Which is the short and the long arm in the two identical chromatids?

Answer 18

p arm - short arm, q arm -long arm. The centromere is the constricted point of the chromosome.

Question 19

There are four different chromosome morphological types (MAST) name them. Based on the position of the centromere.

Answer 19

Metacentric, Acrocentric, Submetric and Telocentric.

Question 20

What is a metacentric?

Answer 20

This is when the centromere is close to the midpoint.

Question 21

What is acrocentric?

Answer 21

This is when the centromere is near the end and the short arm can only just be seen.

Question 22

What is submetric?

Answer 22

This is when the centromere is removed from the midpoint so a short arm (p-arm) and long arm (q-arm) can be seen

Question 23

What is telemetric?

Answer 23

This is when the centromere is at the end and only one arm can be seen.

Question 24

What is a karyotype?

Answer 24

This is in any species where the complete set of diploid chromosomes is known as a karyotype. In humans, there are 22 matched pairs/autosomes.

Question 25

How are karyotypes constructed?

Answer 25

Karyotypes are constructed when cells are synchronized. A photograph of the metaphase chromosomes is taken and the chromosomes are arranged by size from the largest to the smallest pairs.

Question 26

Which staining can aid in discriminating between the chromosomes?

Answer 26

Giemsha Staining