Cytogenetics

Question 1

What is cytogenetics

Answer 1

The study of chromosomes and chromosomal abnormalities

Question 2

A lot of fertility issues linked to…

Answer 2

Chromosomal abnormalities

Question 3

Most chromosomal abnormalities are…

Answer 3

Not compatible with. Survival

Question 4

Chromosomal abnormalities related to… (3)

Answer 4

– Infertility
– Embryonic loss
– Growth and developmental abnormalities

Question 5

What is a karyotype

Answer 5

general appearance of the complete set of chromosomes in an animal

(Anki shows what it looks like)

Question 6

Chromosomes made up of…

Answer 6

Proteins, DNA wrapped. Around histone octamers to form nucleosides which are compacted into chromatin fibre

Question 7

What are autosomes & what do they determine

Answer 7

Non sex chromosomes
Determine somatic characteristics

Question 8

What are allosomes
-role

Answer 8

Sex chromosomes
-sex determination

Question 9

-Female sex chromosomes
-Male sex chromosomes
-Birds/moths/butterflies male and female

Answer 9

XX
XY
ZW female, ZZ male

Question 10

How are karyotype images ordered

Answer 10

Largest to smallest & sex chromosomes at the end

Question 11

Describe process of preparation of Karyotypes

Answer 11

• Nucleated cells are isolated from animal e.g. White blood cells, amniotic fluid
• Cells are grown in culture -mitogens to stimulate cell division
• Cells are ‘arrested’ in metaphase-disruption of the mitotic spindle
• Cells are dropped onto slides and stained- dropping from a short height allows chromosomes to spread; ‘chromosome spreads’

Question 12

Name staining technique used to view chromosomes

Answer 12

Fluorescent/light microscopy

Question 13

Staining patterns are unique for each chromosome which aids in…

Answer 13

Chromosome identification

Question 14

Why are chromosomes arrested in metaphase in karyotype preparation

Answer 14

During metaphase they are most replicated and condensed

Question 15

Sister chromatid is…

Answer 15

An arm of a chromosome

Question 16

Name each component of chromosome.

Answer 16

On anki

Question 17

position of the centromere also aids identification of chromosomes. Name the 3 different positions that exist

Answer 17

Acrocentric- just off centre (common in cows)
Metacentric- in the middle
Telocentric- at edge

Question 18

What is chromosomal painting
-probes can be…
-advantage

Answer 18

Use of fluorescent probes to help identify specific chromosomes
-can be specific to specific chromosome eg X specific probe paints the X chromosome a different colour
-doesn’t rely on position of centromere and rapid way of identifying

Question 19

2 Types of chromosomal abnormalities

Answer 19

1. Numerical- Changes in chromosomal number
2. Structural

Question 20

Changes in chromosomal number
—aneuploidy
-definition
-usually affects…

Answer 20

Presence or absence of one or more chromosomes
-X chromosome

Question 21

Euploidy meaning

Answer 21

Normal diploid set of chromosomes

Question 22

-Trisomy
-Monosomy

Answer 22

-47XXX—> 1 extra X ch.
-45XO—> only 1 X ch.

Question 23

What type of chromosomal abnormality causes Down syndrome

Answer 23

47XX + 21–> 1 extra ch. 21

Question 24

Gene dosage effect meaning

Answer 24

3 sets or 1 set of chronometer expressed (abnormal amount)

Question 25

The less that gene is disrupted by chromosomal abnormalities, the more likely it is…

Answer 25

To be compatible with animal

Question 26

What are numerical chromosome abnormalities caused by?

Answer 26

Failure of chromosomes to separate properly

Question 27

Name a type of chromosome failure to separate properly

Answer 27

Nondisjunction

Question 28

Describe what occurs in nondisjunction

Answer 28

Either: abnormality in meiosis 1 causing both chromosomes to stay together and not divide or abnormality in meiosis II (Diagram on anki)

Question 29

What types of aneuploidy occurs in end product during nondisjunction of meiosis I & meiosis II

Answer 29

-Trisomy and monosomy -trisomy, monosomy & diploid

Question 30

Animals with two or more cells derived from a single zygote (2 different Karyotypes that exist within animal)

Answer 30

Mosaic

Question 31

What are Chimeras

Answer 31

Animals with 2 or more cell lines derived from 2 zygotes (fusion of 2 different Karyotypes)

Question 32

What is placental anastomosis

Answer 32

Fusion of placenta

Question 33

How can a vet check whether an animal is chimera?

Answer 33

Looks for XX and XY Karyotypes present in karyotype image

Question 34

What is the most common chromosomal disorder in horses?

Answer 34

Monosomy ch.63 (XO)

Question 35

What does monosomy X ch. 63 cause in horses?

Answer 35

Infertility

Question 36

What is male to female sex reversal syndrome: what causes is

Answer 36

Female XY Animals have a male karyotype; can display external genitlalia; usually have no uterus, US often shows testicles in abdomen Causes infertility -caused by lack of SRY gene on Y chromosome; this means they lack processes that cause a foetus to develop male gonads and prevent development of female reproductive structures

Question 37

XXY chromosomal abnormalities in animals -affected animals show… -causes…

Answer 37

-males with extra X chromosome -show male phenotype; underdeveloped male sexual characteristics -causes infertility

Question 38

Changes in chromosome structure arises when… -2 types and their meeanings

Answer 38

chromosomes break and are not restored to the original structure -genetically balanced- All genetic information retained but in different order -genetically unbalanced- Some genetic information missing or present in more than one copy

Question 39

Main types of chromosome structural abnormalities

Answer 39

Deletion Duplication Inversion- reverses segment within chromosome Translocation- moves segment from one chromosome to another

Question 40

What is the robertsonian translocation -what does this mean for cell -what does it cause in cell

Answer 40

Centromere of two acrocentric chromosomes fuse together to give one large metacentric chromosome -can’t undergo mitosis -embryonic loss

Question 41

Causes of structural chromosomal abnormalities

Answer 41

• Some may be inherited • Others occur as random events in the formation of reproductive cells – Unequal crossing over in meiosis – Breakage of chromosomes (e.g. Chemical mutagens, Radiation)