Inheritance Patterns 1

Question 1

Allele Def

Answer 1

Each gene copy across a pair of chromosomes. Alleles can vary across chromosome pair (DNA base sequences variation)

Question 2

Genotype Def

Answer 2

Organism’s genetic constitution

Question 3

Phenotype Def

Answer 3

Organism’s observable appearance

Question 4

Homozygous alleles outline

Answer 4

Base pair sequences are identical in gene across chromosomes

Question 5

Heterozygous Alleles Outline

Answer 5

Base pair seequences are different in genes across chromosome

Question 6

5 Mendelian Inheritance Patterns

Answer 6

Autosomal dominant, autosomal recessive, Y-linked, X link dominant, X link recessive

Question 7

Consanguineous Def

Answer 7

People closely genetically related (eg cousins, siblings) reproducing

Question 8

Autosomal Dominant Inheritance

Answer 8

Expressed in heterozygotes and homozygous dominant. Homozygous disease transmission tends to have more severe symptoms and shorter life expectancy (lower chance of passing on)

Question 9

Familial Hypercholesterolemia Outline

Answer 9

Autosomal dominant inheritance. Heterozygous; damage to LDL receptors to extent of x2 ‘healthy’ LDL plasma levels. Homozygous; damage to LDL receptors to extent of x10 ‘healthy’ LDL plasma levels (high risk of myocardial infarction in childhood).

Question 10

Examples of Disease Autosomal Dominance Inheritence

Answer 10

Familial Hypercholesterolemia, neurofibromatosis and familial adenomatous polyposis

Question 11

Autosomal Dominance Inheritance Pedigree

Answer 11

50% chance of passing allele to offspring (disease presenting, no carriers), effects both sexes equally

Question 12

Autosomal Dominance Inheritance Exceptions

Answer 12

Mutation (de novo mutations, random start), Reduced Penetrance, Variable Expressivity (in phenotype)

Question 13

Reduced Penetrance Outline

Answer 13

Individual has allele but doesn’t clearly express condition. Causes; protective mutations, enviornmental/lifestyle factors, epigenetics

Question 14

Haploinsufficiency Def

Answer 14

Loss of 50% of ‘normal’ protein results in disease

Question 15

Dominant Negative Effect

Answer 15

Abnormal protein produced prevents/reduces action of normal protein

Question 16

Autosomal Recessive Inheritance Outline

Answer 16

Recessive homozygotes present disease, heterozygous are carriers. Autosomal recessive diseases are more prevalent in population (higher survival rates)

Question 17

Autosomal Recessive Diseases

Answer 17

Sickle Cell Anemia, Cystic fibrosis, classical Galactosemia and phenylketonuria

Question 18

Autosomal Recessive Pedigree Charts

Answer 18

25% offspring disease presentation, 50% offspring carriers. Effects both sexes equally, skips generation

Question 19

Challenges Identifying Autosomal Recessive Inheritence

Answer 19

Small family size (hard comparison), random gene segragation, unknown parentage,

Question 20

Clinical Aspects of Autosomal Recessive

Answer 20

Pedigree analysis, molecular genetic analysis (sequencing) and genetic counselling (family history)

Question 21

Punnett Square Outline

Answer 21

Graphical tool used to predict expected outcomes of a genetic cross between 2 individuals showing all possible outcomes