Lecture 30. Mapping Mendelian Traits

Question 1

Talk about dominant inheritance.

Answer 1

The affected individual usually has at least one affected parent. The disease can be transmitted by either parent. Usually 50% of siblings have the disease

Question 2

Talk about recessive inheritance ?

Answer 2

Affected people are usually born to unaffected parents who are both carriers. Children from these matings have a 25% chance of being affected

Question 3

Talk about x-linked inheritance.

Answer 3

Usually males are affected. The mother is an unaffected carrier. 50% of male children are affected and there is no male to male transmission.

Question 4

How many versions of each autosome do we have ?

Answer 4

2

Question 5

What is female deactivation ?

Answer 5

Rendering transcriptionally silent one of the x-chromosomes by highly condensing it

Question 6

What is the law of segregation ?

Answer 6

Alternative forms of the same genes at the same position/locus on homologous chromosomes

Question 7

What is mitosis ?

Answer 7

Somatic cell division

Question 8

By what stage have all 46 chromosomes replicated ?

Answer 8

Late prophase

Question 9

What are replicated chromosomes held together by ?

Answer 9

The centromere

Question 10

What has occurred by metaphase ?

Answer 10

The nuclear membrane has disappeared and all 46 chromatids are drawn to opposite poles of the cell, and two daughter cells are generated

Question 11

What does the formation of germ cells require ?

Answer 11

Reductive division or meiosis

Question 12

How are chromosomes prepared ?

Answer 12

1. A small blood sample is removed.
2. White cells are recovered and place in a culture
3. An agent is added which arrests cell replication
4. The cells are lysed and chromosomes are stained

Question 13

What is the agent that is often added to prepare chromosomes ?

Answer 13

Colchicine

Question 14

What are metacentric chromosomes ?

Answer 14

Centromere divides chromosome into equal halves

Question 15

What are sub-metacentric ?

Answer 15

P arm is shorter than q arm

Question 16

What is acrocentric chromosomes ?

Answer 16

No short arm

Question 17

What does SRY stand for ?

Answer 17

Sex determining gene

Question 18

What does the SRY encode ?

Answer 18

A transcription factor which controls the expression of testis determining genes

Question 19

What does chronic myeloid leukaemia display on an ideogram ?

Answer 19

A chromosomal translocation - small pieces of chromosome 9 and 22 exchange places

Question 20

What is the chromosomal translocation in chronic myeloid leukaemia called ?

Answer 20

The Philadelphia translocation

Question 21

What is a treatment option for a chronic myeloid leukaemia which is not caused by translocation ?

Answer 21

Gleevac

Question 22

What is a method of chromosome analysis ?

Answer 22

Multi-colour special karyotyping (SKY)

Question 23

What tissue has the highest oxygen consumption per unit gram in the human body ?

Answer 23

Retina

Question 24

What are cones required for in eyes ?

Answer 24

Day time vision

Question 25

Where are cones found ?

Answer 25

Foveal pit

Question 26

What are rods required for ?

Answer 26

Night time vision

Question 27

What are some clinical manifestations of renitis pigmentosa ?

Answer 27

1. Night blindness 2. Loss of rod photoreceptors 3. Tunnel vision 4. Eventual complete vision loss

Question 28

Where is the mutation that forms the disease retinitis pigmentosa ?

Answer 28

Chromosome 3

Question 29

What does the mutated gene for retinitis pigmentosa encode ?

Answer 29

Rhodopsin

Question 30

What is rhodopsin ?

Answer 30

A light sensitive pigment of rod photoreceptor cells

Question 31

What is the mutation of rhodopsin for retinitis pigmentosa ?

Answer 31

A single point mutation within one allele of the gene, proline is changed to histidine at position 23 of the polypeptide.

Question 32

What is the coefficient of relationship ?

Answer 32

The proportion of alleles shared by 2 people as a result of a common genetic descent

Question 33

What is leber congenital amaurosis ?

Answer 33

The most prevalent form of congenial blindness. Photoreceptors are non-functional but remain alive within the retina

Question 34

Signs and symptoms of Alzheimer's ?

Answer 34

1. Memory loss for recent events - progresses into dementia 2. Inability to converse, loss of language ability 3. Affective/personality disturbance - hostile 4. Death from opportunistic infections

Question 35

How can you confirm Alzheimer's disease ?

Answer 35

1. Neuronal (amyloid, beta amyloid, Abeta amyloid) plaques 2. Neurofibrillary tangles 3. Bain atrophy

Question 36

How can you classify Alzheimer's disease ?

Answer 36

1. Familial verses sporadic | 2. Early verses late onset

Question 37

Which locus segregates with familial alzheimer's disease ?

Answer 37

Chromosome 21

Question 38

What is the linkage analysis test statistic ?

Answer 38

The LOD score

Question 39

What is the LOD score ?

Answer 39

Based on the log of the ration of the probability of a segregation occurring under the assumption of linkage and the probability of it occurring under the assumption of independent segregation

Question 40

What is linkage ?

Answer 40

The relationship between two or more loci

Question 41

What is association ?

Answer 41

The relationship between the alleles of two or more loci

Question 42

What is association mapping ?

Answer 42

The coincidence of trait and marker allele in populations

Question 43

Why is association mapping a good technique for candidate gene testing ?

Answer 43

Resolution is high but coverage is low