GENOMICS Numerical Chromosomal Abnormalities

Question 1

What happens in G1 of cell cycle?

Answer 1

Cellular contents, excluding the chromosomes are duplicated

Question 2

What happens in S phase of cell cycle?

Answer 2

Each of the 46 chromosomes is duplicated by the cell

Question 3

What happens in G2 phase of the cell cycle?

Answer 3

The cell ‘double checks’ the duplicated chromosomes for error, making any needed repairs

Question 4

What is a genetic locus?

Answer 4

A genetic locus is the location of a particular gene on a chromosome

Question 5

What does an individual have at each genetic locus?

Answer 5

At each genetic locus, an individual has 2 alleles, one on each homologous chromosome

Question 6

What happens during interphase in mitosis?

Answer 6

Chromosomes duplicate and the copies remain attached to each other

Question 7

What happens in prophase in mitosis?

Answer 7

In the nucleus, chromosomes condense and become visible.
In the cytoplasm, the spindles form

Question 8

What happens in prometaphase in mitosis?

Answer 8

The nuclear membrane breaks apart, and the spindle starts to interact with the chromosomes

Question 9

What happens in metaphase in mitosis?

Answer 9

The copied chromosomes align in the middle of the spindle

Question 10

What happens in anaphase in mitosis?

Answer 10

Chromosomes separate into 2 genetically identical groups and move to opposite ends of the spindle

Question 11

What happens in telophase in mitosis?

Answer 11

Nuclear membrane form around each of the 2 sets of chromosomes, and the chromsomes begin to spread out, and the spindle begins to break down

Question 12

What happens in cytokinesis in mitosis?

Answer 12

The cell splits into 2 daughter cells each with the same number of chromosomes as the parent. This forms a diploid.

Question 13

What are the steps involved in meiosis?

Answer 13

1. DNA replication
2. Pairing of duplicated homologues and recombination
3. Homologue pairs line up on the spindle
4. Separation of homologues at anaphase 1
5. Completion of cell division 1
6. Separation of sister chromatids at anaphase 2
7. Cell division 2 occurs which leaves us with haploid gametes

Question 14

What happens in bivalents and recombination?

Answer 14

-Homologous chromosomes align
-Form a bivalent structure
-Exchange genetic material(Recombine)

Question 15

What is crossing over of chromosomes?

Answer 15

Reciprocal breaking and rejoining of the homologous chromosomes in meiosis

Question 16

What does crossing over of chromosomes result in?

Answer 16

Results in exchange of chromosomal segments and new allele combinations

Question 17

What are the 2 phases of meiosis?

Answer 17

meiosis I and meiosis II

Question 18

What occurs in meiosis 1?

Answer 18

• Chromosomes Align as 23 bivalents
• Allows for chiasma formation (i.e. recombination)
• Pulls apart homologues from one another
• Daughter cells have 23 chromosomes (each with 2 chromatids)

Question 19

What occurs in meiosis 2?

Answer 19

• Align as independent chromosomes
• Sister chromatids pulled apart
• Daughter cells have 23 chromosomes (each of 1 chromatid)

Question 20

What does meiosis introduce?

Answer 20

introduce natural variation via independent assortment of chromosomes and recombination

Question 21

How can numerical chromosomal changed be detected?

Answer 21

Can detect through traditional karyotyping, FISH, QF-PCR, NGS

Question 22

What is polyploid?

Answer 22

multiple of the haploid number (e.g. 4n=92)

Question 23

What is aneuploid?

Answer 23

chromosome number which is not an exact multiple of haploid number - due to extra or missing chromosome(s) (e.g. 2n+1=47) (trisomy, monosomy)

Question 24

What is the primary mechanism by which aneuploidy arises?

Answer 24

Non-disjunction

Question 25

What does trisomy 13 cause?

Answer 25

Patau’s sydrome

Question 26

What does trisomy 18 cause?

Answer 26

Edwards syndrome

Question 27

What does trisomy 21 cause?

Answer 27

Downs syndrome

Question 28

What aneuploidies is turners syndrome?

Answer 28

(45,X)

Question 29

What aneuploidies is triple X syndrome?

Answer 29

(47,XXX)

Question 30

What aneuploidies is Klinefelter’s?

Answer 30

(47,XXY)

Question 31

What is mosaicism?

Answer 31

The presence of two or more genetically different cell lines derived from a
single zygote

Question 32

What is an example of chromosomal mosaicism?

Answer 32

Two types of cells in the body
-One with normal cell with 46 chromosomes
-One with cells missing a chromosome

Question 33

What is the severity like for mosaic phenotype?

Answer 33

Mosaic phenotype thought to be less severe

Question 34

Why is mosaicism difficult to assess?

Answer 34

• What are the proportions of different cell types?
• Which tissue/organs are affected?

Question 35

What does full monosomy arise by?

Answer 35

Full monosomy arises by non disjunction