Genetics

Question 1

Define the following terms:

1. Gene
2. Locus
3. Allele
4. Genotype
5. Phenotype

Answer 1

1. Basic unit of inheritance
2. Physical location of a gene on a chromosome
3. Alternative forms of a gene at a given locus
4. Genetic constitution of an individual
5. Observed expression of a gene (genotype and environment both play a role)

Question 2

Homozygous vs heterozygous?

Answer 2

Homo= identical alleles at a single locus
Hetero= different alleles at a single locus

Question 3

Dominant vs recessive in expression?

What is mutant allele mean?

Answer 3

Dominant= only one copy of mutant allele is necessary for phenotypic expression 
Recessive= seen only in homozygotes (requires 2 copies of mutant allele)

Allele associated with a disease condition

Question 4

Define the following?

1. Autosome
2. Diploid
3. Haploid

Answer 4

1. A nonsex chromosome
2. 2 copies of each chromosome
3. 1 copy of each chromosome

Question 5

1. How many autosomes do humans have?

2. Somatic cells are always __; gametes are always __

Answer 5

1. 22

2. Diploid; haploid

Question 6

1. Define single gene disorder

2. 3 subsections of single gene disorders

Answer 6

1. Produced by the effect of a single gene (or gene pair)

2. Autosomal dominant, autosomal recessive, X linked

Question 7

Reading a pedigree:

1. Circle
2. Square
3. Colored in?
4. Half colored in?
5. Small circle
6. Line through it

Answer 7

1. Female
2. Male
3. Affected
4. Carrier of an autosomal recessive
5. Stillborn/abortion
6. Dead

Question 8

Autosomal dominant:

1. How many mutant alleles are needed for disease to be phenotypic?
2. How many parents need to be affected ?
3. What sex does it affect?
4. Can male to male transmission occur?
5. Often involve what kind of proteins?
6. Can you be a carrier?

Answer 8

1. One
2. At least one
3. Both
4. Yes
5. Non-catalytic
6. No

Question 9

The following autosomal dominant diseases have what defect:

1. Familial hypercholesterolemia
2. Huntington disease
3. Myotonic dystrophy
4. Neurofibromatosis type 1
5. Osteogenesis imperfecta
6. Marfan syndrome

Answer 9

1. LDL receptor deficiency
2. Tri-nucleotide repeats
3. Muscular atrophy and wasting
4. Nerve tissue tumors
5. Collagen mutation
6. Connective tissue defect

Question 10

Autosomal dominant diseases have a recurrence risk - what does that mean?

Answer 10

Probability that offspring of a couple will have the genetic disease to

Question 11

Autosomal recessive:

1. How many mutant alleles are required for disease to be expressed
2. Parents of an affected child are usually?
3. Which sex can be affected; meaning?
4. Can male to male transmission occur? Why
5. Usually involves what kind of proteins? Meaning
6. Recurrence risk?

Answer 11

1. 2
2. Unaffected (carrier population is bigger)
3. Both (not X linked)
4. Yes - not X linked
5. Catalytic - one functional allele can usually compensate for mutant allele
6. Yes

Question 12

4 autosomal recessive diseases?

Answer 12

Tay sachs, sickle cell anemia, cystic fibrosis, PKU

Tall surfers catch pussy

Question 13

In autosomal recessive disorders, which allele is the mutant allele?

Answer 13

The recessive one (lower case)

Question 14

1. Is X linked dominant common or rare?
2. When you see just “X-linked” that is always referring to
3. Some sources consider what disease to be X linked dominant?

Answer 14

1. Very rare - no high yield diseases
2. X-linked recessive
3. Fragile X

Question 15

X-linked (recessive)

1. Affects which sex
2. Affected males parents are usually
3. Is there male to male transmission

Answer 15

1. Usually only males (females usually have a normal X)
2. Unaffected (mom is usually a carrier)
3. No because males only get the Y from dad

Question 16

5 X linked recessive diseases

Answer 16

Duchenne and becker muscular dystrophy, lesch-nyhan syndrome, glucose 6 phosphate dehydrogenase deficiency, hemophilia A and B

Question 17

What is unique about mitochondria compared to other organelles

Answer 17

Only organelles that contain their own DNA

Question 18

Mitochondrial inheritance:

1. Inherited from which parent
2. Effects which sex?
3. How does it affect males vs females specifically
4. Recurrence risk?
5. Causes what 2 general conditions

Answer 18

1. Mother
2. Both
3. Males- no offspring of an affected male are affected
   Females- all offspring of an affected female are affected
4. No
5. Neuropathies and cardiomyopathies

Question 19

3 mitochondrial inheritance diseases

Answer 19

Leber hereditary optic neuropathy (LHON), hereditary blindness, optic atrophy