Genetic Disorders - Basics

Question 1

What are 3 categories of human genetic disorders?

Answer 1

1. Single gene mutation - Mendelian disorders
2. Chromosomal Disorders
3. Complex Multigenic Disorders

Question 2

What are the 3 categories of human genetic disorders?

Answer 2

1. Single gene mutation - Mendelian disorders
2. Chromosomal Disorders
3. Complex Multigenic Disorders

Question 3

Single gene mutations are common or uncommon and what type of penetrance do they have?

Answer 3

UNcommon

High penetrance

Question 4

Chromosomal Disorders are common or uncommon and what type of penetrance do they have?

Answer 4

UNcommon

High penetrance

Question 5

Complex Multigenic Disorders are common or uncommon and what type of penetrance do they have?

Answer 5

COMMON

LOW penetrance

Question 6

What are Complex Multigenic Disorders?

Answer 6

Environment and multiple gene variants that interact

Question 7

Is a single gene sufficient to produce disease with complex multigenic disorders?

Answer 7

No - need multiple and environmental factors

Question 8

Permanent change in DNA

Answer 8

Mutation

Question 9

Point mutation within a coding sequence changes?

Answer 9

A single base

Question 10

What are the 2 types of point mutations and what do they do?

Answer 10

Missense - alters meaning of protein

Nonsense - stop codon

Question 11

Point mutations with NON-coding sequences can be found where?

Answer 11

Promoter/enhancer sequences

Defective splicing

Question 12

Point mutations with NON-coding sequences fail to form?

Answer 12

mRNA - no translation

Question 13

If a deletion or insertion is a multiple of____ it will be an abnormal protein

Answer 13

multiple of 3

Question 14

If a deletion or insertion is NOT a multiple of 3 it will be a ______ mutation

Answer 14

Frameshift mutation

Question 15

What is a Trinucleotide repeat?

Answer 15

Amplification of a sequence of 3 nucleotides

Question 16

Trinucleotide repeats are usually which bases?

Answer 16

C and G

Cytosine and Guanine

Question 17

Common thing that happens with Trinucleotide repeats?

Answer 17

Anticipation

Question 18

What is Anticipation?

Answer 18

• Seen with Trinucleotide repeats

= Genetic disorders passed on to next generation and symptoms become apparent earlier and are more severe

Question 19

Genetic disorders become apparent at an earlier age with each generation and are more severe

Answer 19

Anticipation

Question 20

Codominance

Answer 20

Both alleles contribute to phenotype

Question 21

Pleiotropism

Answer 21

Single mutant gene creates many end effects

Question 22

Genetic heterogeneity

Answer 22

Mutations at several loci may produce the same trait

Question 23

2 Autosomal Dominant disorders that affect the nervous system?

Answer 23

Huntington Disease

Neurofibromatosis

Question 24

3 Autosomal Dominant disorders that affect the skeletal system?

Answer 24

Marfan Syndrome
Ehler-Danlos Syndrome
Osteogenesis Imperfecta

Question 25

1 Autosomal Dominant disorder that affects the metabolic system?

Answer 25

Familial Hypercholesterolemia

Question 26

Familial Hypercholesterolemia has a _____ mutation

Answer 26

Loss of function

Question 27

Huntington Disease has a _____ mutation

Answer 27

Gain of function

Question 28

For Autosomal Dominant Disorders, is a parent usually affected and how many kids are usually affected?

Answer 28

Yes a parent is usually affected | 50% of kids

Question 29

For Autosomal Dominant Disorders, when do new mutations occur?

Answer 29

In germ cells of older fathers | -- Unless disease decreases reproductive fitness then there will be new mutations

Question 30

Incomplete pentrance

Answer 30

Mutation is present but normal phenotype

Question 31

Variable expressivity

Answer 31

Trait is present but expressed differently

Question 32

2 patterns of disease for Autosomal Dominant disorders?

Answer 32

1. Regulation of metabolic pathways | 2. Key structural proteins

Question 33

Autosomal Dominant and Recessive - expressivity?

Answer 33

Dominant - variable expressivity | Recessive - uniform

Question 34

Autosomal Dominant and Recessive - penetrance?

Answer 34

Dominant - incomplete penetrance | Recessive - complete penetrance

Question 35

Autosomal Dominant and Recessive - age of onset?

Answer 35

Dominant - LATER | Recessive - EARLY

Question 36

Autosomal Dominant and Recessive - new mutations?

Answer 36

Dominant - possible | Recessive - rare

Question 37

What are almost all of Autosomal Recessive Disorders?

Answer 37

Inborn Errors of Metabolism

Question 38

What is the inheritance of Cystic Fibrosis and Phenylketonuria?

Answer 38

Autosomal Recessive | -- IEM

Question 39

What chromosome has the mutation for Cystic Fibrosis?

Answer 39

7q31.2

Question 40

What is the most common lethal genetic disease of caucasions?

Answer 40

Cystic Fibrosis

Question 41

Do heterozygotes for cystic fibrosis have any symptoms?

Answer 41

They show an increased incidence of respiratory and pancreatic disease

Question 42

Can other genes besides the CFTR gene manifest symptoms?

Answer 42

Yes - organ specific

Question 43

Meconium ileus, male infertility, pancreas and lung disease is probably?

Answer 43

Cystic Fibrosis

Question 44

What population is usually affected with phenylketonuria?

Answer 44

Scandinavian descent Caucasians

Question 45

Phenylketonuria has a defect in? What reaction does not take place?

Answer 45

Defect in Phenylalanine Hydroxylase - Cannot convert Phenylalanine to Tyrosine (- Or Tyrosine to Melanin since there is no tyrosine!)

Question 46

Symptoms of Phenylketonuria?

Answer 46

Hypopigmentation, intellectual disability and a musty/mousy odor to urine and sweat

Question 47

With Autosomal Recessive disorders is a parent usually affects and what percentage of kids are likely to be affected?

Answer 47

NO parent is usually affected | - 25% of kids

Question 48

If a mutation has low frequency it is likely due to?

Answer 48

Consanguineous marriage

Question 49

X-linked Recessive Blood disorder?

Answer 49

Glucose - 6 - phosphate dehydrogenase deficiency

Question 50

X-linked Recessive Nervous system disorder?

Answer 50

Fragile X Syndrome

Question 51

X-linked recessive disorders affect who?

Answer 51

MALES

Question 52

Daughters of affected males with X-linked recessive disorders are?

Answer 52

CARRIERS

Question 53

With mitochondrial inheritance, affected females cause how many children to be affected?

Answer 53

ALL OF THEM

Question 54

With mitochondrial inheritance, affected males cause how many children to be affected?

Answer 54

NONE