Unit 1

Question 1

What are the three laboratory sciences in medical genetics?

Answer 1

Cytogentics, Molecular and Biochemical genetics

Question 2

How is the sickle cell trait a positive mutation?

Answer 2

Having the sickle cell trait can protect individuals from malaria where the disease is endemic

Question 3

What is a syndrome?

Answer 3

core group of symptoms together having a common cause

Question 4

If tyrosine oxidase is blocked, what condition will result in an animal?

Answer 4

Albinism (loss of melanin and pigment A)

Question 5

How can toxicity from over-accumulation of precusors be avoided?

Answer 5

Salvage pathways can use up the precursors.

Question 6

Detection of which substance in the urine is indicative of Phenylketonuria?

Answer 6

Phenylpyruvic Acid–> formed wen Phe accumulates

Question 7

Why is is crucial for mothers with Phenylketonuria to maintain a low Phe diet?

Answer 7

Because Phe can cross the placenta and damage baby

Question 8

How is the BH4 defect an example of locus heterogeneity?

Answer 8

Because BH4 can be knocked out through several mutations in different steps of the BH4 pathway.

Question 9

What is wrong with putting a patient that is BH4 defective on a low Phe diet?

Answer 9

It wont help much and the patient will develop neurological defects because of BH4’s involvement in other pathways (serotonin and dopamine). Must supplement with l-dopa and OH-trp

Question 10

What is the total cell chromosome number and DNA content in metaphase of mitosis?

Answer 10

2N/4C

Question 11

During reduction division, what is the change in chromosome number?

Answer 11

2N->N

Question 12

When does reduction division during meiosis occur?

Answer 12

Anaphase I

Question 13

What stage of meiosis is completed once ovulation begins?

Answer 13

Meiosis I

Question 14

What stage is a primary spermatocyte in?

Answer 14

Meiosis I

Question 15

What is the transition between the primary and secondary spermatocyte?

Answer 15

Reduction division in meiosis I.

Question 16

Herpes, smallpox and papilloma are viruses containing which type of genome?

Answer 16

dsDNA

Question 17

Why do viruses often have RNA as their genome?

Answer 17

Because RNA is less stable and more prone to mutations that DNA, the genome can more easily adapt to the environment

Question 18

On which carbons of the deoxyribose sugar base is the phosphate group attached?

Answer 18

C-3 and C-5

Question 19

Demethylation of thymine will convert it in which base?

Answer 19

Uracil

Question 20

In the following RNA sequence- CCGAU- a point mutation occurs removing the amine group from cytosine. What would be the complement of this sequence?

Answer 20

AACUA

Question 21

What is the significance of dNTPs?

Answer 21

nucleoside triphosphates are the immediate precursors for RNA/DNA synthesis

Question 22

How many helical turns are there in a 315 bp A/B/Z- DNA conformation?

Answer 22

A-DNA: 28.6 B-DNA: 30 Z-DNA: 26.25

Question 23

In a dehydrated sample, what form will DNA favor?

Answer 23

A-DNA (shorter form)

Question 24

What change will 5-hydroxymethylcytosine cause in the following DNA sequence: AGCTA

Answer 24

AGCUA (demethylation of thymine to form uracil)

Question 25

What are hoogsteen base pairs?

Answer 25

when purine bases flip from anti to syn, they form different bonds (perhaps because of gene regulation)

Question 26

What is a chromosome made of?

Answer 26

Nucleosome + histone

Question 27

What is a nucleosome made of?

Answer 27

Eight histones which DNA wrapped around

Question 28

How are RNA unstable?

Answer 28

They are vulnerable to base-catalyzed hydrolysis thanks to their C-2 OH

Question 29

What changes in the nuclear envelope take place right before mitosis?

Answer 29

It dissolves into vesicles as lamins get modified.

Question 30

Why does RanGDP concentrate on cytoplasmic side while RanGTP concentrates on the nucleus side?

Answer 30

The concentration gradient of RanGAP1 (more on the cytoplasm side) and RanGEF1 (more on the nucleus side)

Question 31

Where is the nucleolus formed?

Answer 31

On rDNA sequences on 10 chromosomes

Question 32

Which rRNA pieces are part of the large ribosomal subunit?

Answer 32

28S, 5.8S + (5S from RNA pol III)

Question 33

Where is the ribosomal biogenesis pathway completed?

Answer 33

outside the nucleus (the subunits leave the nucleus after being formed)

Question 34

What are the 5 kinds of major histones?

Answer 34

H1, H2A, H2B, H3, H4

Question 35

What does a histone octamer consist of?

Answer 35

Two of each of the H2A, H2B, H3, H4

Question 36

What is the significane of the H1 histone?

Answer 36

It coils nucleosomes to form the 30nm chromatin fiber---important in chromosome condensation?

Question 37

If your patients bloodwork shows that she is producing antibodies against nuclear antigen, what disease could this be?

Answer 37

Lupus

Question 38

What structure of the chromosome can we use to distinguish one pair from another?

Answer 38

The banding pattern of the chromosome

Question 39

Name three ways to identify chromosomal abnormalities?

Answer 39

Size, banding patterns and centromere position

Question 40

How can one trace a defective gene through a family tree if there is also chromosomal polymorphism in the family?

Answer 40

The defective gene and the polymorphism will often co-segregate and we can follow the mutation by following the polymorphism

Question 41

How can you distinguish dispermy vs. meiotic non-disjunction leading to triploidy?

Answer 41

Fetuses that result in triploidy due to dispermy will often have a partial hydatiform mole

Question 42

A child born with the following crossed fingers was born. What aneuploidy does this point towards?

Answer 42

Trisomy 18, Edwards Syndrome

Question 43

What can we predict about the frequency of cells with trisomy in a person whose cells have experiences mitotic non-disjunction very early on in the process?

Answer 43

There will be a higher frequency of cells affected with trisomy in this person

Question 44

Can mosacism be inherited?

Answer 44

Absolutely not, it is ONLY acquired

Question 45

What is the function of the TDF in the male Y chromosome?

Answer 45

If produces testis, which inhibit mullerian ducts and activate wollfian ducts

Question 46

A patient is about to get a bone marrow transplant from a female donor. He is apprehensive because he is afraid that he will develop female characteristics due to the transplant. Is he correct in assuming this?

Answer 46

No, because sex deter

Question 47

What is the critical point in the development of a female?

Answer 47

The point at which one of the Xs is inactivated in a female to become a Barr Body (3-7 days after fertilization).

Question 48

Why would it be dangerous to have DNA replicate multiple times in one cell cycle?

Answer 48

This would cause there to be a risk of aneuploidy developing

Question 49

What is the name of the protein complex marking the origin of replication?

Answer 49

Origin recognition complex

Question 50

What causes the accumulation of mutations in Hereditary Non-polyposis Colon cancer?

Answer 50

Deficiency in DNA mismatch repair causing the mutator phenotype

Question 51

How does the FEN1 gene contribute to autoimmune reactions in affected patients?

Answer 51

It causes recognization of the patient's own DNA as an antigen and attacks

Question 52

If the DNA polymerase chose to go ahead with translesion synthesis, rather than lesion avoidance, what result would we see in the newly synthesized DNA?

Answer 52

The newly synthesized DNA would tend to be error prone.

Question 53

What are the 2 main stressors on DNA replication?

Answer 53

1. Shortage of nutrients and DNA damage

Question 54

Describe the mechanism of Azidothymidine (AZT)

Answer 54

Premature chain termination in DNA replication (missing 'OH group), so virus disrupted in growing.

Question 55

After taking into account the activity of correcting steps such as mismatch repaire and exonuclease proofreading, what is the total error rate in DNA synthesis?

Answer 55

one nucleotide per 10^9 nucleotide

Question 56

Mutations in what structure is the underlying cause of progeria?

Answer 56

Progeria is a disorder of Lamin A, which is composed of intermediate filaments.

Question 57

A patient with gout is being treated with the anti-microtubule drug Colchicine. Why is this drug effective?

Answer 57

Gout causes the crystals to form in joints of the patients. Colchicine can disrupt these crystals by disrupting the mitotic spindles (made of microtubules) of divinding cells forming crystals.

Question 58

Which end (+/-) of the microtubule is usually associated with the organizing center?

Answer 58

-

Question 59

What roles do centrioles play in cilia assembly?

Answer 59

They act as nucleating sites

Question 60

An enzyme involved in the early stages of processing of a lipid from the ER will be found in which section of the Golgi?

Answer 60

The cis section

Question 61

Hirschsprung disease is caused by a loss of function mutation on chromosome 10. Multiple endocrine neoplasia type II also involes a mutation on the same gene on chromosome 10. This is an example of which type of heterogeneity?

Answer 61

Phenotypic (clinical) hetergeneity

Question 62

In three generations of a family, with many offsprings in each generation, all males, and only males are affected by a disease. What is the possible MOI of this disease?

Answer 62

Y-linked likely

Question 63

Why is a drug that causes a prolonged block in mitosis useful in anti-cancer therapy?

Answer 63

A cell stuck without progression to mitosis for a long time will evenually apoptose.

Question 64

What is the role of the replication origin complexes in controlling DNA replication during S phase of each cell cycle?

Answer 64

They are modified by the replication forks and can only reform on the next cell cycle, thereby preventing DNA from replication more than once.