Genetics week 6 + clinical info

Question 1

What is another way to write mitochondrial DNA

Answer 1

• mtDNA

Question 2

Where is mitochondrial DNA inheritied from

Answer 2

• Maternal line

Question 3

What does the mitochondrial encode and why

Answer 3

• 13 polypeptides
• 2 rRNAS
  -22 tRNAs
  For oxidative phosphorylation

Question 4

What are key features of mtDNA(mitochondrial DNA)

Answer 4

• lacks introns
• Has mutation rate 10x higher than nucler DNA
  -Susceptible to damage

Question 5

Why is the mitochondrial DNA susceptible to damage?

Answer 5

• Due to fewer repair mechanisms
• Exposure to free radicals during oxidative phosphorylation

Question 6

What is heteroplasmy? (in relation to mitochondrial DNA)

Answer 6

• Where cells may contain a mix of normal and mutant mTDNA molecules
• The amount/porportion of mutant mtDNA detrmines the severity of mitochondrial diseases

Question 7

What type of organs are more severly affected by mtDNA molecules

Answer 7

• Organs with high ATP demands

Question 8

Name the types of mitochindrial mutations

Answer 8

• Misense mutations
• Single base mutations in tRNA genes
  -Duplication and deletions

Question 9

What does misense mutations lead to

Answer 9

LHON

Question 10

What does LHON lead to

Answer 10

• Rapid loss of vision in the central field

Question 11

What does single base mutations lead to

Answer 11

• MERRF
• MELAS

Question 12

What does duplications and deletions lead to

Answer 12

-Kearns-sayre disease
- Pearson syndrome
- CPEO

Question 13

What does kearns-sayre disease lead to

Answer 13

• Muscle weakness and heart failure

Question 14

What is genetic imprinting?

Answer 14

• It is a form of gene silencing, where only 1 allele of a gene is transcriptionally active, depending on the parent of origin

Question 15

Describe the mechanism for geneomic imprinting

Answer 15

-The transcriptionally inactive alleles is refered to as imprinted.
-The imprinted genes are transcriptionally silent due to epigenetic modifications such as:
- DNA methylation
- Histone hypoacetylation
- Chromatin condensation(preventing transcription factor binding)

Question 16

What does chromatin condensation do

Answer 16

• Prevent trasncription fators from binding

Question 17

What is prader willi and angelman syndrome caused by

Answer 17

-Deletion of several megabases(Mb) on the long arm of chromosome 15

Question 18

How is prader willi syndrome inherited

Answer 18

-Deletion inhertied from the father

Question 19

How is Angelman syndrome inherited

Answer 19

• Deletion inherited from the mother

Question 20

What are features of someone with Prader willi syndrome

Answer 20

• Obesity,
• small hands and feet
• Short stature
• poor muscle tissue(hyptonia)

Question 21

What are the features of someone with Angelman syndrome

Answer 21

• Seizures
• Intelectual disability

Question 22

What is Mosaicism

Answer 22

• Refers to the presence of 2 or more genetically distinct cell lines within an individual.This can occur do to several mechanism

Question 23

What are the mechanisms that can cause mosaicism

Answer 23

• Chromosomal nondisjunctions during mitosis
• Gene mutations during development
• Chromosome inactivation in females

Question 24

What happens in chromosomal nondisjunction during mitosis

Answer 24

• When a chromosome does not separate properly during cell division therefore the daughter cell will have an abnormal number of chromosomes

Question 25

What are the types of mosaicism?

Answer 25

- Germaline - Somatic - Confined placental mosaicism

Question 26

When does germlin mosaicism occur

Answer 26

- Occurs when a mutation is present in the germ cells(sperm and egg) but not the somatic cells

Question 27

When does somatic mosaicims occur

Answer 27

= Occurs when there is mutations in some of the body cells but not the germline cells

Question 28

When does confined placental mosaicism occur

Answer 28

When chromosomal abnormalities are present in the placenta

Question 29

What are triplet repeats

Answer 29

Sequences of 3 nucleotides that are repeated in tandem within a gene

Question 30

Explain the concept of normal variation in triplet repeats

Answer 30

- A certain number of triplet repeats is considered normal , but expansions beyond this range can lead to disease

Question 31

Explain the concept of disease mechanisms in triplet repeats

Answer 31

- The expansion of triplet repeats can disrupt gene function in several ways depending on the location of the repeats within the gene

Question 32

What is osteogensis imperfecta caused by

Answer 32

- Defects in Type 1 collagen which leads to weakened bone strength

Question 33

Whats the most common substitution leading to OI

Answer 33

Sub of glycine in the collagen triple helix

Question 34

What are they symptoms of OI

Answer 34

- Short stature - Blue sclerae - Hearing loss - Bone deformitites - Dental issues

Question 35

What is the most severe type of OI What is the midelst type of OI

Answer 35

- Type 2 - Type 1

Question 36

How many different types of OI are there

Answer 36

1,2,3,4,5,6,7,

Question 37

What is cystic Fibrosis(CF) caused by

Answer 37

- Mutations in the CFTR gene, which encodes chlorine ion channels involved in fluid transport

Question 38

Whats the most common mutation in CF and its effect

Answer 38

-F508 - Deletion of 3 nucleotides resulting in the loss of the amino acid phenylalanine

Question 39

What type of disorder is cystic fibrosis

Answer 39

- Autosmal recessive disorder

Question 40

What is retinoblastoma

Answer 40

- Malignant tumor of the retina

Question 41

What is retinblastoma caused by?

Answer 41

- Mutations in the RB1 gene which is a tumor suppressor gene located on chromosome 13

Question 42

What is the function of the TSG

Answer 42

regulates cell growth

Question 43

What type of inheritance pattern is Huntingtons disease

Answer 43

- Autosomal dominant

Question 44

What is the role of the HTT gene in Huntington's disease

Answer 44

It encodes for the Huntington protein

Question 45

What is Huntington's disease?

Answer 45

- Neurodegenerative disorder characterised by motor, cognitive and psychiatric

Question 46

What is huntingtions disease caused by

Answer 46

- Expansions of a CAG trinucleotide repeat in the HTT gene that codes for Huntington protein

Question 47

What does neurofibromatosis effect

Answer 47

- Effects the development and growth of nerve cells

Question 48

What is neurofibromatosis caused by?

Answer 48

- Caused by mutations in the NF1 gene which encodes a protein called neurofibromin that acts as a tumor suppressor gene

Question 49

What is Marfan syndrome

Answer 49

- A connective tissue disorder, that affects multiple organ systems

Question 50

What is the most common form of marfan syndrome

Answer 50

- Marfan syndrome type 1

Question 51

What is marfan syndrome caused by

Answer 51

- Mutations in the FBN1 gene which encodes the protein fibrillin-1 . This weakens the connective tissues

Question 52

What are symptoms of marfan syndrome

Answer 52

- Tall stature - Long limbs - Scoliosis - Cardiovascular abnormalities

Question 53

What are the symptoms of duchenne muscular dystrophy

Answer 53

- leads to muscle weakness and degradation

Question 54

What is duchenne muscular dystrophy caused by

Answer 54

- Mutation in the DMD gene which encodes dystrophin, which is a protein that is essential for the structure of the muscle fibers

Question 55

What is Hemophilia A

Answer 55

- A bleeding disorder in the f8 gene which encodes clotting factor V111

Question 56

What are the symptoms of the Hemophilia A

Answer 56

- Severe bleeding - Blood clots - Easy bruising

Question 57

What type of inheritance is retinoblastoma

Answer 57

Autosomal recessive inheritance

Question 58

What type of inheritance is Marfan syndrome

Answer 58

Autosomal dominant