Lecture 6: Autosomal Inheritance and Disorders

Exam 2 (Midterm)

What is nondisjunction?

An error during meiosis that results in an altered chromosome number in gametes or offspring.

What is translocation in genetics?

A mistake during crossing over where pieces of chromosomes are exchanged between non-homologous chromosomes.

What is the difference between reciprocal and Robertsonian translocation?

Reciprocal translocation involves the exchange of segments between non-homologous chromosomes, while Robertsonian translocation involves the fusion of two acrocentric chromosomes.

What are the potential consequences of translocations during gametogenesis?

Translocations can lead to difficulties in gamete formation and may result in aneuploidy in the zygote.

What is a trisomy?

A condition where there is an extra copy of a chromosome, often leading to developmental issues.

Which trisomies are considered survivable?

Trisomy 13, 18, and 21.

What are common phenotypes associated with Down syndrome (Trisomy 21)?

Single palmar crease, epicanthal folds, flat face, and health issues like heart defects and sleep apnea.

What is the life expectancy for individuals with Down syndrome?

Approximately 50-60 years as of the 2010s.

What is Edward syndrome (Trisomy 18)?

A condition with a high mortality rate, where most affected individuals do not survive past the first year.

What are common features of Patau syndrome (Trisomy 13)?

Fusion of brain hemispheres, seizures, cleft palate, and a high rate of stillbirth.

What is the significance of chromosome 15 in Angelman and Prader-Willi syndromes?

Both syndromes result from deletions on chromosome 15 but have different phenotypes due to genetic imprinting.

What is genetic imprinting?

A process where maternal and paternal DNA is marked for regulation, often involving methylation.

What is mosaicism in genetics?

The presence of two or more different karyotypes in a single individual, leading to variable phenotypes.

What are common health issues associated with Down syndrome?

Sleep apnea, heart defects, delayed intellect, and a low-functioning immune system.

What is the common appearance of individuals with Edward syndrome?

Small, strawberry-shaped head, clenched fists, and rocker bottom feet.

What are the characteristics of Cri Du Chat syndrome?

Microcephaly, cleft palate, severe intellectual disability, and a distinctive cry that sounds like a cat.

What is the typical karyotype notation for trisomy 21?

47, XX, +21.

What is Turner Syndrome?

A condition where one sex chromosome is missing, leading to various developmental issues.

What are the common phenotypes of Angelman syndrome?

Developmental delays, reduced cognition, clumsy gait, and hand flapping.

What is the main cause of miscarriages related to chromosomal abnormalities?

Nondisjunction leading to an abnormal number of chromosomes.

What is the role of crossing over during meiosis?

It allows for the exchange of corresponding allele segments between non-sister homologous chromosomes.

What is the significance of the Barr body?

It indicates the presence of an extra X chromosome in females.

What are the implications of duplications in genetic material?

They can amplify gene expression, potentially leading to disorders.

What are deletions in genetics?

Missing segments of DNA that can reduce gene expression.

What is the typical outcome for most individuals with Patau syndrome?

Most are stillborn or die within the first year of life.

How does maternal age affect the likelihood of trisomies?

Advanced maternal age is a significant risk factor for trisomy conditions.