Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

6. Chromosomal Variation

Chromosomal Mutations: Aneuploidy

Genetics

6. Chromosomal Variation

Chromosomal Mutations: Aneuploidy

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3:03 minutes

Problem B.11a

Textbook Question

The most common reason a physician might recommend that a woman have maternal serum screening and a karyotype analysis is concern that her fetus may have Down syndrome. Go to the OMIM website at www.ncbi.nlm.nih.gov/omim and look up Down syndrome (OMIM 190685).
List the main symptoms of Down syndrome.

Verified step by step guidance

Understand that Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21, also known as trisomy 21.

Go to the OMIM website at www.ncbi.nlm.nih.gov/omim and enter the OMIM number 190685 or search for 'Down syndrome' to access detailed genetic and clinical information.

Locate the section on the OMIM page that describes the clinical features or main symptoms associated with Down syndrome.

Identify and list the common symptoms, which typically include intellectual disability, characteristic facial features, hypotonia (low muscle tone), and congenital heart defects, among others.

Summarize the main symptoms clearly, ensuring you capture both physical and developmental characteristics as described in the OMIM entry.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Down Syndrome and Its Genetic Basis

Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21 (trisomy 21). This chromosomal abnormality leads to developmental and physical changes, including intellectual disability and characteristic facial features. Understanding its genetic cause is essential for interpreting karyotype results.

Maternal Serum Screening

Maternal serum screening is a prenatal test that measures specific proteins and hormones in a pregnant woman's blood to assess the risk of chromosomal abnormalities like Down syndrome. It is a non-invasive method used to identify pregnancies that may require further diagnostic testing.

Karyotype Analysis

Karyotype analysis is a laboratory technique that visualizes an individual's chromosomes under a microscope to detect numerical or structural abnormalities. In prenatal diagnosis, it confirms the presence of trisomy 21 by identifying the extra chromosome responsible for Down syndrome.

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