GEN 6 Biotechnology- Pre AP Biology Study Notes - New Syllabus.

Using Data to Examine Inheritance and Chromosomal Disorders

🌿 Introduction

Genetic inheritance and chromosomal disorders can be identified by analyzing biological data.
Scientists do not guess.
They examine:

• Chromosome number
• Chromosome structure
• Family inheritance patterns
• Visual chromosome models

One of the most important tools for this is the: Karyotype

🧠 What Is a Karyotype?

A karyotype is:

• A visual display of chromosomes
• Organized into homologous pairs
• Arranged by size, shape, and centromere position

Human somatic cells normally contain:

• 46 chromosomes
• 23 homologous pairs

The final pair determines sex:

• XX → female
• XY → male

Karyotypes allow scientists to examine chromosomal inheritance and detect abnormalities.

🔬 Using Data from a Karyotype

Step 1 – Count the Chromosomes

Normal human diploid number = 46

If total count is:

• 47 → possible trisomy
• 45 → possible monosomy

This indicates altered chromosome number.

Step 2 – Check Homologous Pairs

Each chromosome should appear in pairs.

If one pair has:

• Three copies → trisomy
• One copy → monosomy

That reveals a chromosomal disorder.

Step 3 – Examine Sex Chromosomes

Normally:

• Female → XX
• Male → XY

If abnormal combinations appear:

• XXY
• XO
• XXX

This indicates sex chromosome variation.

Step 4 – Look for Structural Abnormalities

Besides number changes, structural differences may include:

• Missing segments
• Extra segments
• Rearranged segments

These structural alterations can affect gene expression.

🧬 Types of Chromosomal Disorders Identified from Data

A) Trisomy

Three copies of a chromosome instead of two.

Result:

• Extra gene dosage
• Increased gene expression
• Developmental disruption

Detected when karyotype shows 47 chromosomes.

B) Monosomy

Only one copy of a chromosome instead of two.

Result:

• Missing gene dosage
• Reduced protein production
• Often more severe effects

Detected when karyotype shows 45 chromosomes.

🧠 Why Chromosome Number Matters

Each chromosome carries hundreds to thousands of genes.

Cells are designed to function with:

• Two copies of each gene

When chromosome number changes: Gene dosage becomes unbalanced.

This imbalance may:

• Disrupt normal development
• Affect organ systems
• Reduce viability

Analyzing chromosome number helps predict severity of disorder.

🧬 Using Data to Examine Inheritance Patterns

Karyotype data can also help determine:

• Whether disorder arose from nondisjunction
• Whether it may recur in future offspring

If abnormal chromosome number appears:

It suggests an error during meiosis.

Understanding this helps assess inheritance risk.

🧠 Data Interpretation Strategy

When given chromosome data:

• Identify total chromosome count
• Compare to normal diploid number
• Determine if extra or missing chromosome exists
• Identify which chromosome is affected
• Predict potential gene dosage imbalance

This step-by-step reasoning is essential for exam questions.

📊 Summary Table

📦 Quick Recap 
Karyotype = chromosome model
Normal human cells = 46 chromosomes
47 → trisomy
45 → monosomy
Extra chromosome → too much gene product
Missing chromosome → too little gene product
Data analysis = count → compare → predict