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Questions and Answers
What happens during prophase one of meiosis?
What happens during prophase one of meiosis?
- Sister chromatids move apart to opposite poles
- Homologous chromosomes condense and line up (correct)
- Nuclear envelopes form around haploid cells
- Replication of DNA occurs for the first time
What is the main consequence if meiosis does not occur during gamete formation?
What is the main consequence if meiosis does not occur during gamete formation?
- The genetic variation among offspring increases.
- The chromosome number doubles with each generation. (correct)
- The chromosome number remains stable.
- All offspring will exhibit dominant traits.
Which process introduces genetic variation during meiosis?
Which process introduces genetic variation during meiosis?
- Crossing over during prophase one (correct)
- Separation of sister chromatids in meiosis two
- Independent assortment during anaphase one
- Replication of chromatids before meiosis
In terms of susceptibility to malaria, how does CLE cell disease affect an individual?
In terms of susceptibility to malaria, how does CLE cell disease affect an individual?
How do the daughter cells produced by meiosis compare to those produced by mitosis?
How do the daughter cells produced by meiosis compare to those produced by mitosis?
What genetic condition is associated with the presence of three copies of chromosome 21?
What genetic condition is associated with the presence of three copies of chromosome 21?
What effect does phenotypic plasticity have on individuals with the same genotype?
What effect does phenotypic plasticity have on individuals with the same genotype?
What is a key difference between the metaphase of mitosis and the metaphase of meiosis?
What is a key difference between the metaphase of mitosis and the metaphase of meiosis?
Which statement accurately describes telophase in meiosis?
Which statement accurately describes telophase in meiosis?
Which disease has an autosomal dominant inheritance pattern and is neurodegenerative?
Which disease has an autosomal dominant inheritance pattern and is neurodegenerative?
What type of inheritance is characterized by the mother passing the trait to all offspring if she has the trait?
What type of inheritance is characterized by the mother passing the trait to all offspring if she has the trait?
What does the presence of two unaffected parents and one affected child indicate about the child's inheritance pattern?
What does the presence of two unaffected parents and one affected child indicate about the child's inheritance pattern?
Which statement best describes the law of independent assortment?
Which statement best describes the law of independent assortment?
Which type of inheritance would likely produce an affected offspring when both parents are unaffected?
Which type of inheritance would likely produce an affected offspring when both parents are unaffected?
What characteristic defines linked genes?
What characteristic defines linked genes?
What ratio is observed in complete dominance for a monohybrid cross?
What ratio is observed in complete dominance for a monohybrid cross?
Which scenario describes co-dominance?
Which scenario describes co-dominance?
How does incomplete dominance differ from co-dominance?
How does incomplete dominance differ from co-dominance?
Which of the following traits result from autosomal inheritance?
Which of the following traits result from autosomal inheritance?
What is a key characteristic of dihybrid inheritance?
What is a key characteristic of dihybrid inheritance?
What is the significance of crossing over during prophase one of meiosis?
What is the significance of crossing over during prophase one of meiosis?
During which phase of meiosis are homologous chromosomes arranged on the metaphase plate?
During which phase of meiosis are homologous chromosomes arranged on the metaphase plate?
How does meiosis differ from mitosis in terms of daughter cells produced?
How does meiosis differ from mitosis in terms of daughter cells produced?
What role do independent assortment and crossing over play during meiosis?
What role do independent assortment and crossing over play during meiosis?
Which of the following accurately characterizes the end products of meiosis?
Which of the following accurately characterizes the end products of meiosis?
What is the primary effect of being homozygous recessive for CLE cell disease with respect to malaria susceptibility?
What is the primary effect of being homozygous recessive for CLE cell disease with respect to malaria susceptibility?
Which of the following conditions is an example of non-disjunction leading to the presence of an extra chromosome?
Which of the following conditions is an example of non-disjunction leading to the presence of an extra chromosome?
How does phenotypic plasticity influence individuals with the same genotype?
How does phenotypic plasticity influence individuals with the same genotype?
What determines whether an individual with Huntington's disease expresses symptoms?
What determines whether an individual with Huntington's disease expresses symptoms?
What is the effect of an acidic versus alkaline environment on hydrangea flowers?
What is the effect of an acidic versus alkaline environment on hydrangea flowers?
What is the expected phenotypic ratio resulting from a dihybrid cross demonstrating complete dominance?
What is the expected phenotypic ratio resulting from a dihybrid cross demonstrating complete dominance?
In the context of genetics, how does maternal inheritance differ from standard inheritance patterns?
In the context of genetics, how does maternal inheritance differ from standard inheritance patterns?
What pattern of inheritance is associated with blending traits, as seen when two colors create a third?
What pattern of inheritance is associated with blending traits, as seen when two colors create a third?
What does the term 'autosomal inheritance' refer to?
What does the term 'autosomal inheritance' refer to?
Which of the following statements best describes co-dominance?
Which of the following statements best describes co-dominance?
What type of inheritance is indicated when offspring inherit a trait exclusively from their mother, regardless of the father's status?
What type of inheritance is indicated when offspring inherit a trait exclusively from their mother, regardless of the father's status?
Which scenario would most likely indicate an autosomal recessive inheritance pattern?
Which scenario would most likely indicate an autosomal recessive inheritance pattern?
In the context of genetic linkage, what does a higher recombination percentage between two genes indicate?
In the context of genetic linkage, what does a higher recombination percentage between two genes indicate?
What does the law of segregation state regarding allele inheritance?
What does the law of segregation state regarding allele inheritance?
Which inheritance pattern is suggested by observing an equal number of affected males and females in a pedigree?
Which inheritance pattern is suggested by observing an equal number of affected males and females in a pedigree?
Flashcards
Crossing Over
Crossing Over
The process of homologous chromosomes exchanging genetic information during prophase I of meiosis.
Anaphase II
Anaphase II
Sister chromatids are pulled apart to opposite poles of the cell, resulting in four haploid daughter cells. This occurs during meiosis II.
Prophase I
Prophase I
The first stage of meiosis where homologous chromosomes pair up and exchange genetic information.
Independent Assortment
Independent Assortment
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Meiosis
Meiosis
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Codominance
Codominance
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Incomplete Dominance
Incomplete Dominance
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Autosomal Inheritance
Autosomal Inheritance
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Sex-linked Inheritance
Sex-linked Inheritance
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Maternal Inheritance
Maternal Inheritance
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Linkage
Linkage
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Law of Segregation
Law of Segregation
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Law of Independent Assortment
Law of Independent Assortment
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Sickle Cell Trait
Sickle Cell Trait
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Tay-Sachs Disease
Tay-Sachs Disease
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Huntington's Disease
Huntington's Disease
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Down Syndrome
Down Syndrome
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Phenotypic Plasticity
Phenotypic Plasticity
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Meiosis II
Meiosis II
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Linked Genes
Linked Genes
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Sickle Cell Disease
Sickle Cell Disease
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Non-Disjunction
Non-Disjunction
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Study Notes
Meiosis
- Meiosis is similar to mitosis initially, with prophase I.
- Chromatin condenses; sister chromatids and homologous chromosomes pair up.
- Crossing over occurs: Non-sister chromatids from maternal and paternal chromosomes exchange genetic material.
- Parental chromosomes (outer ones) vs. recombinant chromosomes (inner, with crossing over). Crossing over produces genetically distinct chromatids.
- Prophase prepares for division.
- Metaphase I: Homologous chromosomes line up on metaphase plate. This differs from mitosis where sister chromatids line up.
- Independent assortment: Maternal and paternal chromosomes align independently on metaphase plate, contributing to genetic variation.
- Anaphase I: Homologous chromosomes move to opposite poles.
- Two haploid cells result from Meiosis I (cytokinesis).
- No DNA replication between Meiosis I and II.
- Meiosis II: Similar steps to Meiosis I (prophase II, metaphase II, anaphase II, telophase II). Sister chromatids separate.
- Four haploid cells result.
- Meiosis I deals with homologous chromosomes; Meiosis II with sister chromatids.
- Mitosis vs. Meiosis:
- Both start as diploid (2n).
- Mitosis replicates and divides once (2n → 2n). Daughter cells identical to parent.
- Meiosis replicates and divides twice (2n → 4n →4 haploid cells). Daughter cells genetically distinct due to crossing over and independent assortment.
- Crossing over and independent assortment in prophase I and metaphase I are critical for genetic variation.
Inheritance Patterns
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Complete dominance: Dominant trait masks recessive. Functional vs. nonfunctional proteins. Homozygous dominant and heterozygous are indistinguishable.
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Codominance: Both traits are expressed independently. AB blood type, example of both A and B glycoproteins.
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Incomplete dominance: Traits blend. Heterozygous exhibits a blended phenotype (e.g., blue + yellow = green).
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Monohybrid: Heterozygous for one trait. Ratios can be calculated with Punnett Squares (3:1).
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Dihybrid: Heterozygous for two traits. 9:3:3:1 ratio (complete dominance).
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Dominance vs. Prevalence: Dominant doesn't equal common. Five fingers = homozygous recessive example; six fingers = a dominant trait.
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Autosomal inheritance: On non-sex chromosomes.
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Sex-linked inheritance: On sex chromosomes (X or Y).
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Maternal inheritance: Inherited from mitochondria or chloroplasts (passed from mother).
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Linkage: Genes located on the same chromosome tend to be inherited together.
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Recombinant frequencies: Used to determine the physical distance between linked genes (map units). The % of recombinant offspring indicates the distance between linked genes.
Pedigree Analysis
- Autosomal recessive: Two unaffected parents + affected child. Equal frequency of affected males and females.
- Sex-linked recessive: Affected males only have one X chromosome. More males than females affected. Affected males inherit the trait from heterozygous mothers.
- Autosomal dominant: Affected individuals present in every generation.
- Maternal inheritance: All offspring of an affected mother have the trait.
Genetic Disorders
- Sickle cell disease: Autosomal recessive. Heterozygous: increased resistance to malaria.
- Tay-Sachs: Autosomal recessive. Lipid buildup in brain.
- Huntington's disease: Autosomal dominant. Neurodegenerative, symptoms appear later in life.
- Down syndrome: Trisomy 21 (three copies of chromosome 21), non-disjunction.
- Cri du chat: Deletion of a portion of chromosome 5.
- Klinefelter syndrome: XXY (extra X chromosome).
- Turner syndrome: XO (lack of second sex chromosome).
- Phenotypic plasticity: Environment influences phenotype. Examples include rabbit fur color, bird plumage, hydrangea flower color.
Meiosis and Inheritance (Specific Examples)
- Effect of non-occurrence of meiosis: Chromosome number doubles each generation if meiosis does not occur.
- Independent Assortment and crossing over: Data showing crossing over between genes leads to recombinant phenotypes.
- Test crosses: Predictions for offspring phenotypes when crossing with homozygous recessive.
- Pedigree analysis: Determining genotypes and inheritance patterns from family history data.
- Chi-square test: Statistical analysis to determine if observed data matches predicted ratios. Determines if parent genotypes match the observed phenotypes. Chi-square analysis is used to determine if observed data fits the predicted ratios, considering the role of crossing over or independent assortment (using observed and expected frequencies). A smaller Chi-square value indicates better fit.
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