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Questions and Answers
In a pedigree analysis, what distinguishes individuals expressing a recessive trait from those who are carriers?
In a pedigree analysis, what distinguishes individuals expressing a recessive trait from those who are carriers?
- Individuals expressing the trait are homozygous recessive, while carriers are heterozygous. (correct)
- Individuals expressing the trait are heterozygous, while carriers are homozygous recessive.
- Individuals expressing the trait are homozygous dominant, while carriers are heterozygous.
- Individuals expressing the trait are heterozygous, while carriers are homozygous dominant.
Monogenic traits, governed by multiple genes, exhibit a wide range of phenotypes due to the additive effects of each gene.
Monogenic traits, governed by multiple genes, exhibit a wide range of phenotypes due to the additive effects of each gene.
False (B)
What is the likelihood that a child will inherit Huntington's disease if one parent is heterozygous for the dominant Huntington's allele and the other parent does not have the allele?
What is the likelihood that a child will inherit Huntington's disease if one parent is heterozygous for the dominant Huntington's allele and the other parent does not have the allele?
50%
In genetic terms, the observable expression of a trait, such as eye color or height, is referred to as the ______.
In genetic terms, the observable expression of a trait, such as eye color or height, is referred to as the ______.
Match each genetic term with its correct definition:
Match each genetic term with its correct definition:
If a plant has a genotype of Tt for plant height, where 'T' is the dominant allele for tallness and 't' is the recessive allele for dwarfism, what would be the most accurate description of what occurs during gamete formation according to Mendel's Law of Segregation?
If a plant has a genotype of Tt for plant height, where 'T' is the dominant allele for tallness and 't' is the recessive allele for dwarfism, what would be the most accurate description of what occurs during gamete formation according to Mendel's Law of Segregation?
A recessive allele will always express its phenotype, regardless of whether an individual is homozygous or heterozygous for that gene.
A recessive allele will always express its phenotype, regardless of whether an individual is homozygous or heterozygous for that gene.
Explain how the process of gamete formation contributes to genetic variation in offspring, referencing Mendel's Law of Segregation.
Explain how the process of gamete formation contributes to genetic variation in offspring, referencing Mendel's Law of Segregation.
The specific location of a gene on a chromosome is referred to as its ______.
The specific location of a gene on a chromosome is referred to as its ______.
Match each term with its correct description:
Match each term with its correct description:
In a scenario where a scientist discovers a new gene with three possible alleles (A, B, and O), how many different genotypes are possible in a population?
In a scenario where a scientist discovers a new gene with three possible alleles (A, B, and O), how many different genotypes are possible in a population?
Haploid cells contain two sets of chromosomes, one from each parent, similar to somatic (body) cells.
Haploid cells contain two sets of chromosomes, one from each parent, similar to somatic (body) cells.
Describe a situation where knowing the genotype of an individual is crucial for predicting the potential phenotypes of their offspring, even if the trait in question isn't expressed in the parent.
Describe a situation where knowing the genotype of an individual is crucial for predicting the potential phenotypes of their offspring, even if the trait in question isn't expressed in the parent.
In a dihybrid cross (AaBb x AaBb), assuming independent assortment, what proportion of the offspring would be expected to have the genotype aabb?
In a dihybrid cross (AaBb x AaBb), assuming independent assortment, what proportion of the offspring would be expected to have the genotype aabb?
A mutation in a somatic cell will be passed on to the organism's offspring.
A mutation in a somatic cell will be passed on to the organism's offspring.
Define the term 'allele' and provide an example.
Define the term 'allele' and provide an example.
The observable characteristics or traits of an organism, resulting from the interaction of its genotype and the environment, are referred to as its ______.
The observable characteristics or traits of an organism, resulting from the interaction of its genotype and the environment, are referred to as its ______.
Match each type of mutation with its description:
Match each type of mutation with its description:
Which of the following statements best describes the Law of Independent Assortment?
Which of the following statements best describes the Law of Independent Assortment?
A haploid cell contains two complete sets of chromosomes.
A haploid cell contains two complete sets of chromosomes.
Explain the difference between a monohybrid cross and a dihybrid cross.
Explain the difference between a monohybrid cross and a dihybrid cross.
In genetics, the term ______ refers to the genetic makeup of an individual, specifically the alleles they possess for a particular gene.
In genetics, the term ______ refers to the genetic makeup of an individual, specifically the alleles they possess for a particular gene.
What is the primary function of a Punnett square?
What is the primary function of a Punnett square?
Recessive alleles are expressed in the phenotype only when present in a heterozygous condition.
Recessive alleles are expressed in the phenotype only when present in a heterozygous condition.
Describe how a point mutation can lead to a condition like sickle cell anemia.
Describe how a point mutation can lead to a condition like sickle cell anemia.
A protein that has been altered due to a mutation, which may cause it not to work correctly or to have a new function, is called a ______ protein.
A protein that has been altered due to a mutation, which may cause it not to work correctly or to have a new function, is called a ______ protein.
In a cross where one parent is homozygous dominant (DD) and the other is homozygous recessive (dd) for a particular trait, what is the probability that their offspring will have a heterozygous genotype?
In a cross where one parent is homozygous dominant (DD) and the other is homozygous recessive (dd) for a particular trait, what is the probability that their offspring will have a heterozygous genotype?
If a person has the genotype Bb for eye color, where B is for brown eyes (dominant) and b is for blue eyes (recessive), their phenotype will be blue eyes.
If a person has the genotype Bb for eye color, where B is for brown eyes (dominant) and b is for blue eyes (recessive), their phenotype will be blue eyes.
Flashcards
Gene
Gene
A segment of DNA that codes for a protein and determines a trait.
Allele
Allele
A variant form of a gene; individuals inherit two for each gene.
Genotype
Genotype
The genetic makeup of an organism for a specific gene (e.g., DD, Dd, dd).
Phenotype
Phenotype
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Dominant Allele
Dominant Allele
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Recessive Allele
Recessive Allele
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Homozygous
Homozygous
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Heterozygous
Heterozygous
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Pedigree Analysis
Pedigree Analysis
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Recessive Trait (Pedigree)
Recessive Trait (Pedigree)
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Monogenic Traits
Monogenic Traits
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Polygenic Traits
Polygenic Traits
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Dominant Disorder
Dominant Disorder
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Independent Assortment
Independent Assortment
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Mutation
Mutation
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Point Mutation
Point Mutation
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Chromosomal Mutation
Chromosomal Mutation
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Mutant Protein
Mutant Protein
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Gene Variants
Gene Variants
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Diploid
Diploid
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Haploid
Haploid
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Inheritance of Alleles
Inheritance of Alleles
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Monohybrid Cross
Monohybrid Cross
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Study Notes
- Mendelian genetics explains how traits are passed down through generations
Key Terminology
- A gene is a DNA segment that contains instructions for building proteins and determining traits
- For example, a gene determines eye color
- Alleles are specific variants of a gene, with individuals inheriting two alleles for each gene, one from each parent
- For example, eye color genes have a dominant allele (D) for brown eyes and a recessive allele (d) for blue eyes
- Genotype refers to the genetic makeup of an organism for a specific gene, represented by allele combinations
- DD is homozygous dominant
- Dd is heterozygous
- dd is homozygous recessive
- Phenotype is the observable characteristic resulting from the genotype
- An individual with the Dd genotype for eye color will have a brown eyes phenotype, as D (brown eyes) is dominant
- Dominant alleles mask the effects of recessive alleles, which are represented by capital letters
- For example, D
- Recessive alleles only show if an individual has two copies, represented by lowercase letters
- For example, d
- Homozygous is when an organism has two of the same alleles
- DD (homozygous dominant)
- dd (homozygous recessive)
- Heterozygous is when an organism has two different alleles for a gene
- Dd
- Gametes are haploid reproductive cells (sperm and egg) carrying one allele for each gene
- Gametes combine during fertilization to form a diploid zygote
- Diploid (2n) cells contain two sets of chromosomes, one from each parent
- Human body (somatic) cells are diploid
- Haploid (n) cells contain one set of chromosomes
- Gametes are haploid
- A locus is the specific location of a gene on a chromosome
Mendel’s Laws of Inheritance
- Mendel's pea plant experiments were the basis for understanding how traits are passed from one generation to the next
- This work is the basis of Mendelian genetics
Law of Segregation (First Law)
- Individuals have two alleles for each gene inherited from each parent
- During gamete formation, these alleles separate, so each gamete gets one allele per gene
- During fertilization, the offspring receives one allele from each parent
- For example, an individual with a Dd genotype will produce gametes with either the D or d allele
- After fertilization, a child will then have two alleles (one from each parent)
Law of Independent Assortment (Second Law)
- Genes on different chromosomes are inherited independently of each other
- During gamete formation, alleles for one gene do not affect the inheritance of alleles for other genes if they're on different chromosomes
- When crossing AaBb with AaBb, the alleles for A and B assort independently
Phenotype
- Phenotype refers to the observable characteristics of an organism
- Examples include eye color, height and skin color
- Phenotypes are determined by an individual’s genotype and environment
- Someone with a Bb genotype for eye color with B being brown, their phenotype will be brown eyes
Mutation
- Mutation refers to any change in the DNA sequence
- This change can cause a difference in the expressed protein, possibly changing the phenotype
Point Mutation
- A point mutation is a single base pair change in DNA
- This small change can have big effects on a gene’s function
- Sickle cell anemia is caused by a point mutation in the hemoglobin gene
- A single base change leads to a misfolded protein that causes red blood cells to sickle
Chromosomal Mutation
- Chromosomal mutations involve larger changes in chromosome structure/number
- These mutations can be significant, potentially causing diseases/abnormalities
- Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21)
Mutant Protein
- A mutant protein is altered due to a mutation which affects the protein's function
- The CFTR protein in cystic fibrosis patients is mutated, leading to thick mucus buildup
Allele
- An allele is a variant form of a gene, with a gene having multiple alleles that result in different traits
- Includes B for brown eyes, b for blue eyes and G for green eyes
Gene Variants
- Genes can have multiple variants (alleles) due to mutations
- These mutations cause the gene to produce different proteins or traits
- For eye color, mutations produce different shades of brown or types of blue
Diploid vs Haploid
- Diploid is having two complete sets of chromosomes (one set from each parent)
- Examples include human somatic cells with 46 chromosomes (23 from each parent)
- Haploid is having only one set of chromosomes
- Gametes (egg and sperm cells) are haploid
- Examples include a human egg or sperm cell containing 23 chromosomes
Inheritance of Alleles
- Offspring inherit one allele from each parent for each gene in sexual reproduction
- Somatic cells are diploid, having two alleles for each gene
- Gametes are haploid, having one allele for each gene
- If both parents have the genotype Dd, offspring could inherit DD, Dd, or dd
Dominant vs. Recessive Alleles
- Dominant alleles are expressed when present
- The dominant trait shows (phenotype) if one dominant allele is inherited
- Brown eye color (B) is dominant
- Inheriting both B and b will result in the individual having brown eyes
- Recessive alleles are only expressed when two copies are inherited
- The dominant allele masks the recessive allele if only one is inherited
- Blue eyes (b) are recessive
- A person with Bb (brown eyes) would carry the blue eye allele without it being expressed
Genotype vs Phenotype
- Genotype refers to the genetic makeup of an individual
- Includes Bb, BB, or bb for eye color
- Phenotype refers to the observable trait
- A person with the genotype Bb will have brown eyes
Monohybrid and Dihybrid Crosses
- A monohybrid cross is between two individuals differing in one trait
- A cross between Bb and Bb will have possible combinations of BB, Bb, and bb
- A dihybrid cross is between two individuals differing in two traits
- A cross between BbRr and BbRr for eye color (B/b) and seed shape (R/r) results in a 16-square Punnett square
Punnett Square
- A Punnett square diagram predicts the genetic outcomes of a cross
- Write the alleles from one parent across the top and the alleles from the other parent down the side, then fill in the boxes to show the possible combinations of alleles
- Example of a Bb x Bb monohybrid cross:
- B b B BB Bb b Bb bb
Pedigree Analysis
- Pedigree analysis tracks the inheritance of traits through generations in a family tree
- Recessive traits show up only in homozygous recessive individuals
- Parents who are heterozygous carriers can pass it to their children
- Recessive traits show up only in homozygous recessive individuals
Polygenic vs. Monogenic Traits
- Monogenic traits are controlled by a single gene that follow Mendel’s laws of inheritance
- Examples include flower color and seed shape
- Polygenic traits are controlled by multiple genes and contribute to the final phenotype
- Examples include human height and skin color
Single-Gene Disorders
- Dominant disorders need only one copy of the mutated allele to appear
- Example includes Huntington’s disease
- Recessive disorders need two copies of the mutated allele to appear
- Example includes cystic fibrosis
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Description
Explore genetics: distinguish recessive trait expression from carriers, understand polygenic traits, and calculate Huntington's inheritance risk. Learn about phenotypes, genotype combinations, and Mendel's Law of Segregation in heredity.
