Genetics

Question 1

What is a Genotype?

Answer 1

the genetic makeup of a person

Question 2

What is a Phenotype?

Answer 2

the physical manifestation of an inherited trait or disease

Question 3

When do you consider a referral to genetics? (6)

Answer 3

• developmental delay
• dysmorphic features
• congenital malformations
• a positive family history of a genetic disorder
• recurrent miscarriages/still births
• consanguinity

Question 4

What are some disorders that become more common due to founder effect/consanguinity? (6)

Answer 4

• Ashkenazi Jewish: Tay-Sachs, BRCAI
• Mediterranean: beta-thalassemia
• Southeast Asian: alpha-thalassemia
• Amish/Mennonite and Arab: various rare disorders
• African: sickle cell anemia
• Caucasian: cystic fibrosis

Question 5

What are G/Giemsas?

Answer 5

Banded Chromosomes

Question 6

What are the largest chromosome pairs?

Answer 6

Number 1

Question 7

What are the smallest chromosome pairs?

Answer 7

Number 2

Question 8

Which chromosomes determine sex?

Answer 8

Chromosome 23

Question 9

What are the different Chromosomal Disorders?

Answer 9

• Numerical Chromosome Anomaly
• Structural Anomaly

Question 10

What is Numerical Chromosome Anomaly?

Answer 10

Error which occurs in Meiosis (1 or 2), resulting in aneuploidy (monopsony or trisomy) or triploidy

Question 11

What is Structural Anomaly?

Answer 11

Error of recombination

Question 12

What is the most common cause of Trisomy 21?

Answer 12

Nondisjunction

Question 13

What is Trisomy 21?

Answer 13

When a person has an extra chromosome 21
Results in Down syndrome

Question 14

What are the characteristics of Down Syndrome?

Answer 14

• distinct facial features
• developmental delay
• heart defects

Question 15

In which population is Trisomy 21 most common? (3)

Answer 15

• Mothers of advanced maternal age
• due to cell division completing in mothers after ovulation and further after fertilization
• with time, those chromosomes become very sticky as the age of the egg advances

Question 16

What are the different ways Trisomy 21 can occur? (3)

Answer 16

• nondisjunction
• Translocation
• Mosaic

Question 17

What are Structural Chromosome Anomalies? (3)

Answer 17

• Caused by error of recombination
• May be balanced - translocation (reciprocal or robertsonian) or inversion
• may be unbalanced - deletion, duplication, translocation, inversion

Question 18

What are the different Chromosome Disorders? (4)

Answer 18

• Trisomy 13
• Trisomy 18
• Turner Syndrome (45x)
• Klinefelter Syndrome 47, XXY

Question 19

What is Trisomy 13? (5)

Answer 19

• also known as Palau Syndrome
• Midline defects are common
• extra fingers
• 80-90% die in first year
• Severe developmental delay

Question 20

What is Trisomy 18? (5)

Answer 20

• also known as Edward Syndrome
• Most are female (5:1)
• Frequent cardiac defects
• 80-90% die in first year of life
• Marked developmental delay

Question 21

What is Turner Syndrome? (7)

Answer 21

• disorder in which there is only one X chromosome
• puffy hands and feet at birth
• webbed neck
• coarctation of aorta
• short stature
• primary amenorrhea and infertility (streak ovaries)
• Normal intelligence

Question 22

What is Klinefelter Syndrome? (7)

Answer 22

• disorder in which there is an extra X chromosome XXY
• Tall stature
• Excess breast development
• small testes
• infertility
• normal appearance
• may have learning disabilities

Question 23

Who is the father of Genetics?

Answer 23

George Mendel

Question 24

What did George Mendel do?

Answer 24

He worked with seven characteristics of pea plants, and crossed them to see what he could get, looking at the genetics

Question 25

What is Autosomal Dominant? (5)

Answer 25

- Diseases/disorders that run in families - usually present in every generation - not tied to a X chromosome - Males and females are affected equally - about 50% transmission

Question 26

What is an example of an Autosomal Dominant Disease?

Answer 26

Polycystic Kidney disease

Question 27

What is Autosomal Recessive? (4)

Answer 27

- diseases/disorders in which the person inherits two changed genes - majority of people are carriers, but it does not affect their health - Males and females are effected equally - Consanguinity increase the number of individuals affected

Question 28

What is an example of Autosomal Recessive Disease?

Answer 28

Cystic Fibrosis

Question 29

What is Cystic Fibrosis? (3)

Answer 29

- When we have mutations or changes in the gene CFTR - It codes for the CFTR protein which is responsible for chloride channels - it starts to affect the mucus and motility of the cilia

Question 30

What are the characteristics of an X-linked Inheritance? (4)

Answer 30

- Males affected almost exclusively - the gene alteration can be transmitted from female carriers to sons, but the females are often asymptomatic - affected males cannot transmit the condition to their sons - carrier females may be mildly affected or fully affected due to skewed X inactivation

Question 31

Why are males affected by X-linked disorders?

Answer 31

- only 1 X chromosome - must express all x-linked genes - hemizygous

Question 32

What is Duchenne Muscular Dystrophy? (5)

Answer 32

- X-linked disorder that impacts the gene called DMG - this gene codes for dystrophin, which is important in the muscles - affected males die in their early 20s due to cardiomyopathy - mutation may be inherited from mother or new mutation - high spontaneous mutation rate

Question 33

What occurs in boys who have Duchenne Muscular Dystrophy?

Answer 33

- They will present early on with progressive breakdown of muscles - One of the signs is hypertrophy, fatty tissue as opposed to muscle - progressive muscle weakness

Question 34

What are the characteristics of Mitochondrial DNA Disorders? (4)

Answer 34

- all mitochondria are inherited from the mother through the egg - mitochondria have their own circular DNA - expectation is to have maternal inheritance, and all her offspring will have it/carry it - severity depends on the abnormality of the mitochondria genetic material

Question 35

What are the Symptoms of Mitochondrial Multi-systemic Disorders? (6)

Answer 35

- Muscle = fatigue and low tone - Brain = cognitive dysfunction - Digestive = feeding difficulties, constipation - Cardiac = cardiomyopathy - Eye = limited eye movement - Diabetes