Chromosomal Abnormalities

Question 1

What are gametes derived from?

Answer 1

Primordial germ cells (PGCs)

Question 2

When are PGCs formed?

Answer 2

The second week of development

Question 3

Where do PGCs migrate to and through what?

Answer 3

The migrate through the primitive streak to the wall of the yolk sac

Question 4

What is gametogenesis?

Answer 4

The process by which sex cells (gametes) are developed

Question 5

What is cytodifferentiaition?

Answer 5

The development of specialized cells (eg nerve cells) from undifferentiated precursors.

Question 6

What are tetratomas?

Answer 6

These are tumors that contain a variety of tissues that are formed by the germ layers including Hair, muscle, gut epithelia and bone etc

Question 7

How many chromosomes do normal humans have?

Answer 7

46 chromosomes, 44 of which are autosomes and 2 of which are sex chromosomes that determines an individuals sex

Question 8

What do we call genes on the same chromosome?

Answer 8

Linked genes

Question 9

What does fertilization do in terms of chromosomes?

Answer 9

Restores the diploid number of 46 due to the fact that gametes only have 23

Question 10

What is synapsis?

Answer 10

Process by which homologous chromosomes align themselves in pairs

Question 11

What is crossing over/crossover?

Answer 11

This is the interchange of chromatid segments between paired homologous chromosomes.

Question 12

What is chiasma?

Answer 12

X - like structure formed by chromosomes

Question 13

How is genetic variability enhanced?

Answer 13

Crossover and random distribution of homologous chromosomes

Question 14

What is a polar body?

Answer 14

A daughter cell of a primary oocyte that didn’t mature into a gamete

Question 15

What are the most common chromosomal abnormalities?

Answer 15

45,X (Turner Syndrome), Triploidy and Trisomy 16

Question 16

What are the two types of chromosomal abnormalities ?

Answer 16

Numerical and Structural

Question 17

What does Euploid mean?

Answer 17

Exact multiple of n

Question 18

Aneuploid meaning?

Answer 18

When the chromosome number isn’t a multiple of n so like an extra chromosome for example

Question 19

What is the term used to describe an extra chromosome?

Answer 19

Trisomy

Question 20

What is monosomy?

Answer 20

Where a chromosome is missing

Question 21

What are some causes for Numerical abnormalities?

Answer 21

Nondisjunction and translocation

Question 22

Describe the process of nondisjunction.

Answer 22

Nondisjunction refers to the failure of chromosomal division during meiosis. Which results in two daughter cells having an extra chromosome while two have one less

Question 23

What increases with age?

Answer 23

The incidence of chromosomal abnormalities

Question 24

What is translocation?

Answer 24

The process by which chromosomes break and pieces of one chromosome, may attach to another.

Question 25

What type of translocation doesn’t result in chromosomal abnormality?

Answer 25

Balanced

Question 26

What translocation can cause Down syndrome?

Answer 26

Translocation of 14 and 21 that produces an extra copy of chromosome 21

Question 27

What causes Down Syndrome?

Answer 27

Trisomy 21 - an extra copy of chromosome 21

Question 28

What are the features of Down Syndrome?

Answer 28

Growth retardation, intellectual disability, cardio facial abnormalities, upward slanting eyes, small ears, cardiac defects and hypotonia

Question 29

What diseases are individuals with Down syndrome prone to?

Answer 29

Leukemia, infections, premature aging and increased risk/frequency of earlier onset Alzheimer’s disease.

Question 30

What are features of trisomy 18?

Answer 30

Intellectual Disability, Congenital heart defects, low set ears and Flexion of fingers and hands (), Micrognathia, syndactlyly and malformation of the skeletal system

Question 31

What are the features of trisomy 13?

Answer 31

Cleft lip and palate, Deafness, Congenital heart defects, microphthalmia, anophthalmia and Coloboma

Question 32

What is Klinefelter Syndrome?

Answer 32

Where males have 47 chromosomes with a sex complement of XXY or 48 with a sex compliment of XXXY

Question 33

What is Turner Syndrome?

Answer 33

45, X karyotope

Question 34

What is a unique feature of turner syndrome?

Answer 34

It is the only monosomy compatible with life.

Question 35

What are common features of Turner Syndrome?

Answer 35

Webbed Neck, broad chest, widely set nipples, gonadal dysgenesis in females etc

Question 36

What is Triple X Syndrome?

Answer 36

47, XXX normally undiagnosed and characterized with problems with speech and self esteem

Question 37

Name some structural abnormalities.

Answer 37

Angelman Syndrome and Prader-Willi syndrome and Cri-du-chat syndrome

Question 38

What are structural abnormalities caused by?

Answer 38

Chromosome breakage and lost also known as deletion

Question 39

What are sites of Microdeletions called?

Answer 39

Contiguous gene complexes

Question 40

What are contiguous gene complexes incentivized with?

Answer 40

Fluorescence in situ hybridization

Question 41

What does FISH stand for?

Answer 41

Fluorescence in situ hybridization

Question 42

What is Angelman Syndrome caused by?

Answer 42

The microdeletion of the long arm of chromosome 15 so 15q11 - 15q13 is gone

Question 43

“q” means?

Answer 43

long arm

Question 44

“p” means ?

Answer 44

Short arm

Question 45

Features of Angelman syndrom?

Answer 45

Intellectual disability, can’t speak , poor motor development, prolonged unprovoked periods of laughter… on maternal chromosome btw

Question 46

What is the name of Trisomy 18?

Answer 46

Edward’s Syndrome

Question 47

What is the name of Trisomy 16?

Answer 47

Mosaic

Question 48

What is the name of Trisomy 13?

Answer 48

Patau Syndrome

Question 49

What are features of Klinefelter Syndrome?

Answer 49

Smaller testicles, lower testosterone production, less muscle mass, reduced body and facial hair, enlarged breast tissue

Question 50

What is the cause of cri-du-chat syndrome?

Answer 50

Partial deletion of short arm of chromosome 5

Question 51

Features of cri-du-chat syndrome?

Answer 51

Cat like cry, microcephaly, intellectual disability, congenital heart disease

Question 52

What causes Prada-Willi syndrome?

Answer 52

Microdeletion of chromosome 15; on the paternal chromosome

Question 53

What are fragile sites?

Answer 53

Regions of chromosomes that demonstrate a propensity to separate or break under certain cell manipulations.

Question 54

What do fragile sites consist of ?

Answer 54

CGG repeats

Question 55

In which gene do fragile sites end in altered phenotype?

Answer 55

FMRI gene

Question 56

What is the name of syndrome of the long arm of chromosome X- Xq27?

Answer 56

Fragile X syndrome

Question 57

What are recessive mutations?

Answer 57

If both alleles have to be abnormal or X linked and occurs in males to cause an abnormality

Question 58

What are dominant mutations?

Answer 58

If a mutant gene produces abnormality in a single dose despite the presence of a normal allele.

Question 59

What is mosaicism?

Answer 59

When an individual has one more than one genetically distinct cell line

Question 60

What can happen in germ line mosaicism?

Answer 60

A parent may not express the abnormality but can pass it on to their offspring

Question 61

What is cytogenetic analysis used to do?

Answer 61

Assess chromosome number and integrity?

Question 62

How are chromosomes stained?

Answer 62

Giemsa-stained

Question 63

What is exome sequencing ?

Answer 63

Approach to find mutations and polymorphisms in which coding regions (exons) in the genome are sequenced?