human genetics 2 (disorders)

Question 1

overall facts

Answer 1

• 5,000 human disorders are known to have genetic origins

Question 2

recessive gene + single dominant gene

Answer 2

RG: PKU, sickle-cell anemia, tay sachs, cystic fibrosis
SDG: Huntington’s disease, neurfibromatosis

Question 3

polygenic inheritance +sex-linked inheritance

Answer 3

PI: cancer, heart disease, asthma, psychiatric, behvaior disorders
SLI: red-green colour blindness, fragile-X syndrome

Question 4

regulator gene defects, chromosomal abnormalities

Answer 4

RGD: genetic male with female genatalia
CA: downsyndrome, Klinefelter syndrome, turner syndrome

Question 5

Tay- Sachs disease

Answer 5

• fatal, autosomal recessive neurodegenerative disease of infancy and early childhood
• gene tells the body to stop producing Hex-a enzyme needed to break down fatty subsance
• caused by mutations of Hex A gene chromosome

Question 6

Huntington’s disease

Answer 6

progressive neurodegenerative disorder, autosimal dominate.
>40 repreats of cytosine, adenine and guanine in coding region of gene
- onset= 4oy/o 12-15 yrs afterwards= death

Question 7

symptoms of HD

Answer 7

cognitive deterioration, personality change, memory loss, depression, slow movement

Question 8

invoulantary movement characteristic of HD

Answer 8

invoulantary ‘dance like’ movement
- abates in advance stages of disease, when akinetic and bradykinetic movements become clear

Question 9

voulantary characterise movement in HD

Answer 9

• Bradykinetic
• inconsistent and inefficient movement
• abnormal co-contractions of muscles
• prolonged EMG bursts
• less efficient and more variable movements in handwriting
• sequential and simultaneous movement difficulties

Question 10

broad sub-cortical and cortical damage

Answer 10

• neuronal and astrocyte loss in basal ganglia
• selective degeneration of GABAergic neurons of striatum
• as disease progresses, greater cortical atrophy occurs

Question 11

HD cont.

Answer 11

• gene contains expanded trinucleotide repeat that ranged from 9-35 in healthy adults but 36-190 for HD
• allels with 36-39 repeat how ‘reduced penetrance’- only some individuals will develop clinical symptoms
• young patiesnts= >55 repeats and develop HD before 20 y/o
• onset earlier if transmitted by father

Question 12

polygenetic inheritance

Answer 12

• when traits are governed than more than one gene
• shifts from focusing on single gene mutation to examining the combination of many genes working together

Question 13

schizo

Answer 13

• young adulthood= onset
• 0.5% pop affected, can be continuous or episodic
• more likley to be continuous than categorical
• genetic risk of schizo= largely polygenenic

Question 14

fragile X syndrome

Answer 14

• FXS= most common intellectual diability
• expansion mutation of CGG repeat sequence in the FMR1 gene at the locus
• leads to the silencing of the gene and absence of the gene product
• protein is essential for brain development- brain synaptic plasticity, development
• boys= more affected than girls

Question 15

Phenylketonuria

Answer 15

• children w PKU are unable to metabolize phenylalanine
• phenylalanine is a amino acid found in high protein food
• PKU is a disorder that is related to a defective gene on chromosome 12, which the body cannot break down and may cause damages w brain development
• early diagnosis= restricted diet can stop menta retardation.

Question 15

phenotype and genotype

Answer 15

• development will only occur if a given gene is turned on and off at the correct time, in the right place and for the right length of time
• some genes are only turned on in a few cells and for only a few hours and then switched off permanently
• other genes= basic functioning of almost all cells
  regulator genes control the switching on switching off of genes

Question 15

phenotype acnd genotype

Answer 15

external factors= can affect the switching on and off of genes
- there is a continuous interaction between the environment and the genotype

Question 15

the range (norm) of reaction

Answer 15

refers to all the phenotypes that could theoretically result from a given genotype, given all the envuronemnts in which it would survive and develop

Question 16

range of norm- plants

Answer 16

three cuttings (genetically identical) taken from 7 plants, planted at different elevations.
- the phenotype is the unique consequence of a particular genotype in a particular environemnt

Question 17

phenotype and genotype

Answer 17

• a child with a given genotype develops differently in a loving gamily compared to abusive
• the child actively creates and explores the environment where they live
• by virtue of nature, they evoke different responses

Question 18

epigenetics

Question 19

genome

Answer 19

recors of the genetic material of an organism encoded in DNA

Question 20

epigenome

Answer 20

record of the chemical changes to the DNA and histone proteins of an organism

Question 21

heritable

Answer 21

but reversible changes in gene expression that are not coded in the DNA sequence but by post-translational modifications in DNA< histone proteins are in micro RNA

Question 22

autoimmune disorders

Answer 22

they affect 7% of the population, it is not completely genetic so there is a role in the environment because some twins will have the disease while others wont.
- more females are affected than males and more likely away from equator.