Genetics: modes of inheritance Flashcards

1
Q

What is human genetic material encoded on?

A

chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How many chromosomes do humans have?

A

46
23 pairs
22 autosomal pairs + sex chromosomes (XX or XY)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What other DNA do we inherit other than chromosomal?

A

mitochondrial DNA
16500 bp, encodes 15 proteins, rRNA and some tRNAs

most mitochondrial proteins are encoded by cell genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where is the mitochondrial DNA derived from?

A

the mother

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Homozygous for a gene?

A

contains 2 identical copies of an allele

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Heterozygous for a gene?

A

contains 2 different alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a locus?

A

the position of the gene on a chromosome?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are single gene disorders?

A

affect all body systems
(most common)
cause a large health burden

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are chromosomal disorders?

A

occur when the chromosome are damaged during the formation of the sperm or egg or during early development of the embryo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are complex disorders?

A

result from a combination of genetic and environmental factors interacting

eg. obesity, type II diabetes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is autosomal dominant?

A

A characteristic is dominant if it manifests in a heterozygote (ie two different alleles at a locus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are we referring to when talking about dominance?

A

phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What gene is responsible for eye colour?

A

OCA-2
active OCA-2 –> melanocytes full of melanin (brown)

inactive OCA-2 –> melanocytes no melanin (blue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Dominant autosomal disease?

A

single gene/allele

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is an autosomal dominant disease passed down?

A

Each child of an affected person has a 1 in 2 chance of being affected

Males and females are equally affected and equally likely to pass on the condition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What pedigree diagram represents the autosomal dominant disease?

A

Vertical pedigree pattern

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is huntingtons disease?

A

Symptoms usually start 30-50 years of age

Difficulty concentrating, depression, stumbling, involuntary jerking, problems swallowing

Abnormal intracellular Huntington protein aggregate gains a pathological function and is toxic to neurons resulting in cell death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is brittle bone disease?

Osteogenesis imperfecta

A

Bones break easily

Weakening connective tissue particularly bone

19
Q

What is the “gain of function” dominant autosomal disorder?

A

gene now makes a protein with a new function

eg longer lifespan/new location thus increasing their effect

20
Q

What is the “dominant negative effect” dominant autosomal disorder?

A

the mutated form interferes with the activity of proteins it binds

eg dimers or multimers which reduces activity

21
Q

What is the “Insufficient” dominant autosomal disorder?

A

mutant in one gene results in ½ the amount of a protein that is not enough for normal function (rare)

22
Q

What are autosomal recessive disorders?

A

two copies of the abnormal (non-working) gene must be present in order for the disease or trait to develop

Tend to be ‘loss of function’ mutations (eg deletions)

23
Q

Who are “carriers” of autosomal recessive diseases?

A

They have lost a single copy of a gene but the normal one is sufficient to maintain normal function

24
Q

What pedigree chart is used for an autosomal recessive disease?

A

A horizontal pedigree pattern

25
What pedigree chart is used for an autosomal recessive disease?
A horizontal pedigree pattern
26
What is Cystic Fibrosis?
Defective chloride ion channel Results in impaired airway defense Prone to respiratory infections Digestive issues eg meconium ileus
27
What mutations give rise to cystic fibrosis?
Various mutation in gene encoding chloride ion channel (CFTR gene on chromosome 7)
28
What are the sex chromosomes?
Consist of an X and a Y chromosome | Determine the sex
29
How many genes do the X and Y chromosomes contain?
- X-chromomsome 1000- 1300 genes (~850 protein coding) | - Y-chromosome 150 genes (50-70 protein coding)
30
What are X-linked recessive disorders?
- Affects mainly males – effectively dominant - Females can be carriers - Females who are homozygous for the mutation (two copies) have the disorder
31
What are the chances of being affected by having an unaffected father and carrier mother?
boys- 1/2 | girls- 1/2 of being a carrier
32
What is an example of an x-linked recessive disorder?
Haemophilia | - In some cases female carriers exhibit subtle signs of the disease
33
What are X-linked dominant disorders?
- Similar to autosomal dominant pattern - all daughters and no sons of an affected father are affected (Condition often milder and more variable in females than in males)
34
What is an example of an X-linked dominant disorder?
hypophosphatemia | Results in vitamin D-resistance rickets
35
What are Y-linked disorders?
- Affects only males - All sons of an affected father very few- bc only a few genes are encoded on Y chromosome
36
What is an example of a Y-linked disorder?
Retinitis Pigmentosa | Cells of retina produce a defective protein
37
What pedigree chart is used for a Y-linked disease?
vertical pedigree
38
What are mitochondrial inherited disorders?
caused by mutations in Mitochondrial DNA
39
How are mitochondrial disorders inherited?
Are maternally inherited - All children of an affected woman may be affected - Children of affected men are never affected
40
Mitochondrial disease variability
- Mitochondria have multiple copies genome some normal some mutant (heteroplasmy) - Only express disease effects above a threashold
41
How else are mitochondrial diseases caused?
by mutations in cell genome and have mendalian or sex chromosome linked inheritance
42
How does a mitochondrial disease develop?
- Random segregation - Number of affected mitochondria - Symptoms develop once threshold reached - Cells different number mutant mitochondria can change with time
43
When do mitochondrial diseases develop?
with age due to accumulation of mutant mitochondria
44
What is an example of mitochondrial disease?
Motor and nerve function commonly affected Leber’s hereditary optic neuropathy (Visual loss in young adulthood)