12 Questions
What is the primary purpose of a pedigree chart?
To study the transmission of hereditary conditions
Which of the following is an example of an autosomal dominant trait?
Huntington's disease
In autosomal recessive inheritance, what is required for the trait to be expressed?
Two copies of the affected allele
Which of the following is an example of an acquired trait?
Calluses on the hands
What is the relationship between genetics and heredity?
Genetics is the study of how traits are passed from parent to offspring
What is the primary difference between autosomal dominant and autosomal recessive inheritance?
Autosomal dominant traits are expressed in the presence of a single copy of the affected allele, while autosomal recessive traits require two copies
What is the principle that states that pairs of alleles are separated when gametes are formed?
Segregation
Which of the following is an example of a condition caused by an X-linked recessive trait?
Colorblindness
What is the pattern of inheritance for Y-linked traits?
No affected females, and all sons of affected males are affected.
What is the term used for genes that are controlled by more than two alleles?
Multiple Alleles
Which of the following is an example of a condition caused by a mitochondrial inheritance pattern?
Leigh Syndrome
What is the term used when both alleles contribute to the expressed phenotype?
Codominance
Study Notes
Inheritance and Pedigree Charts
- Inheritance is the passing of traits from parents to offspring
- A pedigree chart is a record of an individual's family to study the transmission of a hereditary condition
- Goals of pedigree charts: determine the mode of inheritance and probability of an affected offspring
Modes of Inheritance
Autosomal Dominant
- A single copy of an allele is sufficient to cause a trait
- Examples: Huntington's Disease, Progeria, Marfan Syndrome, Hereditary Hemorrhagic Telangiectasia (HHT), Neurofibromatosis (NF)
Autosomal Recessive
- Two recessive alleles result in a trait being expressed
- Examples: Albinism, Tay Sachs Disease
Mendelian Principles
- Segregation: pairs of alleles are separated when gametes are formed
- Independent Assortment: pairs of alleles will be sorted independently of one another when gametes are formed
- Principle of Dominance: one allele masks the effect of another allele
Non-Mendelian Genetics
- Incomplete Dominance: partial dominance or blending when one allele is not completely dominant over another
- Codominance: both alleles contribute to the expressed phenotype
- Multiple Alleles: genes that are controlled by more than two alleles
Blood Typing
- Blood type is determined by the genotype of an individual
- ABO blood types: A, B, AB, O
Sex-linked Traits
X-Linked Recessive
- Both males and females can be affected, but the trait is much more common in males
- Examples: Colorblindness, Hemophilia, Fabry Disease, Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency, Lesch Nyhan
X-Linked Dominant
- Both sexes are affected
- Examples: Enamel Hypoplasia, Rickets, Rett Syndrome, Incontinentia Pigmenti, Fragile X Syndrome
Y-Linked
- No affected females
- Example: Auricular Hypertrichosis
Mitochondrial
- Both sexes are affected
- Example: Leigh Syndrome
Test your knowledge on inheritance and pedigree charts. Explore the modes of inheritance, determine the probability of affected offspring, and learn about different symbols used in pedigree charts.
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