Genetics and Human Inheritance - Chapter 20
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Questions and Answers

What does it mean for an individual to be homozygous?

  • They possess one dominant and one recessive allele.
  • They have two different alleles for a gene.
  • They have two identical alleles for a gene. (correct)
  • They only express dominant traits.

Which of the following correctly defines a dominant allele?

  • An allele that must be paired with another dominant allele to show effects.
  • An allele that has no effect in the heterozygous condition.
  • An allele that can be expressed regardless of the presence of another allele. (correct)
  • An allele that only affects the phenotype in homozygous individuals.

What is the relationship between genotype and phenotype?

  • Genotype refers to observable traits, while phenotype refers to genetic composition.
  • Genotype is the external appearance, while phenotype is the internal genetic makeup.
  • Genotype comprises the alleles present, whereas phenotype includes observable traits. (correct)
  • Genotype can change over time, while phenotype remains constant.

Which of these pairs of alleles would be considered heterozygous?

<p>Tt (B)</p> Signup and view all the answers

What is the total number of possible combinations of alleles that can be formed in the resulting gametes after Meiosis II, according to the figure?

<p>4 (A)</p> Signup and view all the answers

In the context of the figure, which allele combination represents a homozygous dominant genotype?

<p>FF (C)</p> Signup and view all the answers

What type of cell is indicated before the process of meiosis begins in the figure?

<p>Diploid reproductive cell (A)</p> Signup and view all the answers

, which pair of alleles shows complete dominance?

<p>F and f (D)</p> Signup and view all the answers

What is the phenotypic ratio for the offspring in a monohybrid cross where both parents are heterozygous for a single trait?

<p>3 : 1 (A)</p> Signup and view all the answers

Which statement correctly describes Mendel's law of independent assortment?

<p>The segregation of alleles for one trait does not affect the segregation of alleles for another trait. (A)</p> Signup and view all the answers

In a dihybrid cross, what is the expected phenotypic ratio of the offspring?

<p>9 : 3 : 3 : 1 (C)</p> Signup and view all the answers

Which of the following terms refers to a cross where both parents are heterozygous for one trait?

<p>Monohybrid cross (A)</p> Signup and view all the answers

In terms of genotype, what is the expected ratio of offspring from a monohybrid cross between two heterozygous parents?

<p>1 homozygous dominant : 2 heterozygous : 1 homozygous recessive (C)</p> Signup and view all the answers

What is pleiotropy?

<p>One gene having many effects (A)</p> Signup and view all the answers

Which of the following is an example of pleiotropy?

<p>Sickle-cell anemia affecting multiple body functions (C)</p> Signup and view all the answers

What happens to red blood cells in individuals with sickle-cell anemia?

<p>They become sickle shaped and may clog blood vessels (C)</p> Signup and view all the answers

Which organs can be affected by the sickled cells in sickle-cell anemia?

<p>A variety of organs including the brain and kidneys (C)</p> Signup and view all the answers

What is a consequence of the sickled cells clogging blood vessels?

<p>Decreased blood flow leading to local failures (D)</p> Signup and view all the answers

What can physical weakness and anemia in sickle-cell patients be attributed to?

<p>Insufficient blood flow and cell breakdown (D)</p> Signup and view all the answers

Which of the following is NOT a consequence of sickle-cell anemia?

<p>Delayed wound healing (D)</p> Signup and view all the answers

When do red blood cells become sickle shaped in sickle-cell anemia?

<p>When the oxygen content of the blood is low (D)</p> Signup and view all the answers

What is the probability of obtaining an aa individual from a cross between two heterozygous individuals (Aa)?

<p>1/4 (B)</p> Signup and view all the answers

When is the product rule applied in probability calculations?

<p>When both events must occur independently (D)</p> Signup and view all the answers

Which statement best describes the rule of addition in probability?

<p>It determines the likelihood of mutually exclusive events occurring. (C)</p> Signup and view all the answers

In a six-sided die roll, what is the result of applying the rule of addition?

<p>The chance of rolling any number is 1/6. (B)</p> Signup and view all the answers

What does a Punnett square represent in genetics?

<p>The possible gamete combinations from parents (B)</p> Signup and view all the answers

If two independent events have probabilities of 1/4 and 1/3, what is the probability of both events occurring?

<p>1/12 (A)</p> Signup and view all the answers

In a genetics problem, when calculating the likelihood of rolling a six-sided die to get a two or a five, you apply which probability rule?

<p>Sum rule (B)</p> Signup and view all the answers

What occurs during meiosis according to Mendel's Law of Segregation?

<p>Each allele for a trait is packaged into separate gametes. (A)</p> Signup and view all the answers

Which allele is represented by the letter 'ff'?

<p>Homozygous recessive (B)</p> Signup and view all the answers

What is the outcome for gametes produced from a homozygous recessive individual?

<p>All gametes contain a recessive allele. (C)</p> Signup and view all the answers

During Meiosis I, what primarily separates?

<p>Homologous chromosomes (A)</p> Signup and view all the answers

What is the significance of polar bodies during meiosis?

<p>They are formed when gametes divide but do not function as gametes. (D)</p> Signup and view all the answers

How are alleles segregated during meiosis according to Mendel's Law?

<p>Alleles separate such that each gamete receives one allele for each trait. (C)</p> Signup and view all the answers

Flashcards

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Dominant allele

An allele whose effect is always seen, even if only one copy is present.

Recessive allele

An allele whose effect is only seen if two copies are present.

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Genotype

The combination of alleles an organism has for a particular gene.

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Monohybrid cross

A cross between two heterozygous individuals for one trait.

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Dihybrid cross

A cross between two heterozygous individuals for two traits.

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Law of independent assortment

Alleles of different genes segregate independently during gamete formation.

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Mendel's Law of Segregation

During meiosis, alleles for a trait separate into different gametes.

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Alleles

Different forms of a gene for a trait.

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Meiosis

Cell division that produces gametes (sperm/egg).

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Gamete

Sex cell (sperm or egg).

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Homologous chromosomes

Pairs of chromosomes that carry genes for the same traits, one from each parent.

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Pleiotropy

One gene affecting multiple traits or characteristics.

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What is pleiotropy?

A genetic phenomenon where a single gene influences various traits or characteristics of an organism.

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Sickle-cell anemia

A genetic disorder caused by a mutation in the gene for hemoglobin, leading to misshapen red blood cells.

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What happens to red blood cells in sickle-cell anemia?

The red blood cells become sickle-shaped due to an abnormal hemoglobin molecule, leading to various health issues.

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Effects of sickle-cell anemia

The sickled red blood cells can damage various organs and tissues, leading to complications like heart failure, lung damage, and kidney failure.

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What is the genotype for sickle-cell anemia?

The genotype for sickle-cell anemia is homozygous recessive, meaning two copies of the sickle-cell allele are present.

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How does pleiotropy relate to sickle-cell anemia?

Sickle-cell anemia demonstrates pleiotropy because the single gene mutation affects multiple aspects of the body.

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How does sickle-cell anemia affect the body?

The sickle-shaped red blood cells block blood flow, causing damage to various organs, leading to complications like heart failure, lung damage, and kidney failure.

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Product Rule of Probability

Used to calculate the probability of an event occurring when two independent events MUST happen. It involves multiplying the probabilities of each individual event.

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Independent Events

Events whose occurrence doesn't affect the likelihood of the other event happening.

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Applying the Product Rule

To find the probability of an offspring inheriting a specific genotype, multiply the probabilities of each parent contributing the necessary allele.

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Sum Rule of Probability

Calculates the probability of an event occurring when it can happen in multiple, mutually exclusive ways. It involves adding the probabilities of each individual way.

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Mutually Exclusive Events

Events that cannot happen simultaneously.

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Applying the Sum Rule

To find the probability of at least one of several mutually exclusive events happening, add the probabilities of each individual event.

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Punnett Square

A visual representation of possible allele combinations in offspring. It aids in calculating probabilities of genotypes and phenotypes.

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Probability and Genetics

Probability rules like the product rule and sum rule help predict the likelihood of inheriting specific traits. Punnett squares aid in visual representation.

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Study Notes

Chapter 20: Genetics and Human Inheritance

  • Heredity: Transmission of traits from one generation to the next.
  • Allele: Variant form of a gene. Some genes have multiple alleles.
  • Genetics: Scientific study of heredity, beginning with Gregor Mendel's experiments using pea plants.
  • Mendel traced traits through generations and hypothesized alternative versions of genes (alleles).
  • Homozygous: Individuals with two copies of the same allele.
  • Heterozygous: Individuals with different alleles of a given gene.
  • Dominant allele: Allele whose effects can be detected regardless of the alternative allele. Dominant alleles use upper case letters (e.g., "A").
  • Recessive allele: Allele whose effect is masked in the heterozygous condition. Recessive alleles use lower case letters (e.g., "a").
  • Genotype: An organism's complete set of alleles.
  • Phenotype: Observable physical traits of an organism.
  • Monohybrid cross: Cross between two heterozygotes for a single trait.
  • Dihybrid cross: Cross between two heterozygotes for two traits.
  • Mendel's law of segregation: During meiosis, allele pairs separate. Each allele is packaged into a separate gamete.
  • Mendel's law of independent assortment: Alleles of one gene segregate independently of alleles from other genes.
  • Punnett square: Matrix used to predict the genetic makeup of offspring from known parental genotypes.
  • Probability and Genetics: Calculating the chances of offspring inheriting traits.
  • Rule of addition: Probability of an event occurring in multiple ways is the sum of the individual probabilities.
  • Rule of multiplication: Probability of two independent events occurring together is the product of the individual probabilities.
  • Genetic disorders: Often caused by recessive alleles, occasionally by mutations, deletions or duplications in genes or chromosomes.
  • Carrier: Someone who displays the dominant trait but carries a recessive gene, and can pass on the recessive allele to their offspring.
  • Cystic Fibrosis: Recessive disorder, causing thick mucus accumulation in lungs and intestines.
  • Sickle-cell anemia: Co-dominant trait, producing both normal and sickle-shaped red blood cells; causes symptoms such as pain and anemia.
  • Duchenne Muscular Dystrophy: Recessive sex-linked disorder impacting muscle strength that progressively deteriorates over time.
  • Hemophilia: Recessive sex-linked disorder where blood does not clot properly due to a missing clotting factor.
  • Down syndrome: Extra copy of chromosome 21; resulting in unique facial features, intellectual delays and other characteristics.
  • Diagnostic Tests: Chorionic villus sampling (CVS), amniocentesis, used prenatally to identify genetic disorders.

Types of Inheritance

  • Complete dominance: Heterozygote exhibits the dominant phenotype.
  • Codominance: Both alleles are expressed in the heterozygote.
  • Incomplete dominance: Heterozygote exhibits an intermediate phenotype between the homozygous dominant and homozygous recessive phenotypes.
  • Multiple alleles: More than two alleles exist for a particular gene.

Other Concepts of Inheritance

  • Polygenic inheritance: Varying traits, such as height or skin color.
  • Sex-linked inheritance: Genes located on sex chromosomes.
  • Sex-influenced inheritance: Autosomal genes where expression differs between sexes. (example: pattern baldness)
  • Chromosomal breaks: Changes in chromosome structure; causes of changes in structure include chemicals, radiation, or viruses. Types of effects include deletion and duplication of chromosome pieces.

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Description

This quiz focuses on Chapter 20, which covers the principles of genetics and human inheritance. Key concepts such as alleles, genotype, phenotype, and Mendel's contributions are explored. Test your understanding of heredity and genetic terminology with this quiz!

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