GeneticsLesson 1 of 1 in the course Development and Inheritance

Alleles, Inheritance Patterns, and Chromosomal Variation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces how genetic information is organized and how inherited alleles contribute to an individual’s characteristics.

Most human body cells contain 23 pairs of chromosomes: one chromosome in each pair comes from each genetic parent. A karyotype is a systematic display of an individual’s chromosomes. Twenty-two pairs are autosomes; the remaining pair consists of sex chromosomes, typically XX in females and XY in males.

All flashcards

What is the law of segregation?
The two alleles for a gene separate during gamete formation, so each gamete receives one allele.
What is a carrier of an autosomal recessive condition?
A person with one disease-associated recessive allele who usually does not show the condition.
What is codominance?
An allele relationship in which both alleles are expressed distinctly in a heterozygote.
What is independent assortment?
The principle that alleles of different gene pairs generally sort independently into gametes.
What is nondisjunction?
Failure of chromosomes to separate properly during cell division.

Quiz questions

  1. In a Tt × Tt cross with complete dominance, what is the probability that an offspring will have genotype Tt?Answer: 50 percent
  2. An affected father has an X-linked dominant allele. Which children inherit his X chromosome and therefore that allele?Answer: All daughters and none of his sons
  3. What blood type results from genotype I^A I^B in the ABO system?Answer: Type AB, with both A and B antigens expressed
  4. A mutation occurs in a reproductive cell and is passed to an offspring. What is a key consequence?Answer: The DNA change can be inherited by the offspring.
  5. Which chromosome-number change commonly causes Down syndrome?Answer: Three copies of chromosome 21

Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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