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Questions and Answers
What condition is characterized by the presence of an extra X chromosome in males?
What condition is characterized by the presence of an extra X chromosome in males?
What phenomenon causes the zygote to have three copies of a particular chromosome?
What phenomenon causes the zygote to have three copies of a particular chromosome?
Which of the following describes the condition known as trisomy 21?
Which of the following describes the condition known as trisomy 21?
Which genetic condition is associated with an XXY male genotype?
Which genetic condition is associated with an XXY male genotype?
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Which term is used for individuals with an extra chromosome leading to developmental differences?
Which term is used for individuals with an extra chromosome leading to developmental differences?
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What type of genes are associated with mitochondria and chloroplasts?
What type of genes are associated with mitochondria and chloroplasts?
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How is the inheritance of cytoplasmic genes primarily transmitted?
How is the inheritance of cytoplasmic genes primarily transmitted?
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Who conducted the study that observed the maternal influence on offspring coloration in plants?
Who conducted the study that observed the maternal influence on offspring coloration in plants?
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What is a potential consequence of defects in mitochondrial genes?
What is a potential consequence of defects in mitochondrial genes?
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What type of DNA is typically carried by organelles in the cytoplasm?
What type of DNA is typically carried by organelles in the cytoplasm?
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Which condition is linked to defects in mitochondrial genes?
Which condition is linked to defects in mitochondrial genes?
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What does the term 'extranuclear genes' refer to?
What does the term 'extranuclear genes' refer to?
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Which phenomenon is used to illustrate maternal inheritance in plants?
Which phenomenon is used to illustrate maternal inheritance in plants?
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What is the chromosomal condition involving three copies of chromosome 21 called?
What is the chromosomal condition involving three copies of chromosome 21 called?
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Which chromosome is larger, X or Y?
Which chromosome is larger, X or Y?
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What is the term for a condition where an organism has more than two complete sets of chromosomes?
What is the term for a condition where an organism has more than two complete sets of chromosomes?
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What are the sex chromosomes for a typical female in humans?
What are the sex chromosomes for a typical female in humans?
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What is the chromosomal configuration known as tetraploidy?
What is the chromosomal configuration known as tetraploidy?
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Which condition involves three sets of chromosomes?
Which condition involves three sets of chromosomes?
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Which of the following statements is true regarding the Y chromosome?
Which of the following statements is true regarding the Y chromosome?
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Which of these types of chromosome sets is more common in plants than in animals?
Which of these types of chromosome sets is more common in plants than in animals?
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Which chromosome does an ovum provide in terms of sex determination?
Which chromosome does an ovum provide in terms of sex determination?
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What is triploidy indicative of?
What is triploidy indicative of?
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What genetic mechanism primarily influences the phenotype in leber's hereditary optic neuropathy?
What genetic mechanism primarily influences the phenotype in leber's hereditary optic neuropathy?
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What modification to cytosine nucleotides is involved in genomic imprinting?
What modification to cytosine nucleotides is involved in genomic imprinting?
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Which disorder is associated with a deletion in chromosome 5?
Which disorder is associated with a deletion in chromosome 5?
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What does the chromosome theory of inheritance primarily explain?
What does the chromosome theory of inheritance primarily explain?
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The phenomenon where the sex of the parent contributing an allele affects inheritance is characteristic of which genetic concept?
The phenomenon where the sex of the parent contributing an allele affects inheritance is characteristic of which genetic concept?
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Which of the following is NOT a mechanism of Mendelian genetics?
Which of the following is NOT a mechanism of Mendelian genetics?
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What role does independent assortment play in genetics?
What role does independent assortment play in genetics?
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What is the consequence of significant chromosomal abnormalities in mammals?
What is the consequence of significant chromosomal abnormalities in mammals?
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Which statement about Mendelian genetics is true?
Which statement about Mendelian genetics is true?
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How does genomic imprinting differ from traditional Mendelian inheritance?
How does genomic imprinting differ from traditional Mendelian inheritance?
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What effect does methylation have on gene expression?
What effect does methylation have on gene expression?
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Which aspect of embryonic development is influenced by genomic imprinting?
Which aspect of embryonic development is influenced by genomic imprinting?
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Which of the following best characterizes leber's hereditary optic neuropathy?
Which of the following best characterizes leber's hereditary optic neuropathy?
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What is the primary implication of genes being genetically unlinked but physically linked?
What is the primary implication of genes being genetically unlinked but physically linked?
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In terms of sex-linked traits, which statement is accurate?
In terms of sex-linked traits, which statement is accurate?
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Which process is responsible for creating new combinations of traits in offspring?
Which process is responsible for creating new combinations of traits in offspring?
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What is indicated by the presence of recombinant chromosomes?
What is indicated by the presence of recombinant chromosomes?
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Which trait is characterized by a recessive X-linked pattern?
Which trait is characterized by a recessive X-linked pattern?
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What does the inactive X condense into during female embryonic development?
What does the inactive X condense into during female embryonic development?
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What is a result of random fertilization in terms of genetic variation?
What is a result of random fertilization in terms of genetic variation?
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What was the significance of Morgan's discovery regarding gene linkage?
What was the significance of Morgan's discovery regarding gene linkage?
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Which of the following best explains the term 'hemizygous'?
Which of the following best explains the term 'hemizygous'?
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What role do cytogenetic maps play in genetics?
What role do cytogenetic maps play in genetics?
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What happens to genes that behave as if they are found on different chromosomes?
What happens to genes that behave as if they are found on different chromosomes?
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In terms of inheritance, what is significant about traits that are closely linked on a chromosome?
In terms of inheritance, what is significant about traits that are closely linked on a chromosome?
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What principle can be derived from Mendel's and Morgan's genetic findings?
What principle can be derived from Mendel's and Morgan's genetic findings?
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Why are recessive disorders more prevalent in males than females?
Why are recessive disorders more prevalent in males than females?
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Study Notes
Organelle Gene Inheritance
- Also known as cytoplasmic genes
- Organelles in the cytoplasm carry small circular DNA molecules
- These are known as extranuclear genes
- Organelles such as mitochondria, chloroplasts, and plant plastids carry these extranuclear genes.
- Inheritance is maternally due to the egg's cytoplasm.
Example of Organelle Gene Inheritance
- Karl Correns, in his studies, observed that the offspring coloration was determined by the maternal parent, not the paternal parent, when it comes to plastid genes.
- He conducted studies on the inheritance of yellow and white spots of leaves on an otherwise green plant.
Defects in Mitochondrial Genes
- Defects in mitochondrial genes can result in diseases that affect muscular and nervous systems.
- These diseases might prevent cells from making enough ATP.
- Examples include Leber's hereditary optic neuropathy and mitochondrial myopathy.
Genomic Imprinting
- Involves silencing of certain genes that are "stamped" with an imprint during gamete production.
- This is a result of methylation (addition of -CH3) of cytosine nucleotides.
- Only affects a small fraction of mammalian genes.
- It is critical for embryonic development.
- Is an exception to the Mendelian theory, stating that each parent contributes one allele.
Mendelian Genetics
- Involves genes located in the nucleus.
- Explains Mendel's laws of segregation and independent assortment.
Chromosome Theory of Inheritance
- States that chromosomes undergo segregation and independent assortment.
- Exceptions involve genes located outside the nucleus.
- In both cases, the sex of the parent contributing the allele is a factor in the pattern of inheritance.
Chromosome Structure and Aberrations
- The number and structure of chromosomes are associated with some serious disorders.
Chromosome Abnormalities
- In humans and other mammals, they can result in spontaneous abortions (miscarriages) or various developmental disorders.
Example of Chromosome Abnormalities: Cri du Chat Syndrome
- A deletion in chromosome 5 is a type of chromosome abnormality.
- It is known as cri du chat syndrome.
- This is named for the infants’ characteristic high-pitched cry similar to a cat's meow.
Aneuploidy
- A zygote has three copies of a particular chromosome.
- The term "trisomic" is used to describe this.
Examples of Aneuploidy: Down Syndrome and Klinefelter Syndrome
- Trisomy 21, commonly known as Down syndrome, happens in the absence of a copy of chromosome 21.
- Klinefelter syndrome is a type of sex chromosome aneuploidy.
- The male has an extra X chromosome (XXY).
Polyploidy
- A condition in which an organism has more than two complete sets of chromosomes.
- Common in plants, but not animals.
- They are more normal in appearance than aneuploids.
Triploidy and Tetraploidy
- Triploidy (3n) is three sets of chromosomes.
- Tetraploidy (4n) is four sets of chromosomes.
Chromosomal Basis of Sex Determination
- The Y chromosome ends only contain regions homologous to corresponding regions of the X chromosome.
- In humans and some animals, there is a chromosomal basis of sex determination.
- Females are XX.
- Usually, the larger X chromosome comes from the mother, and the smaller Y chromosome comes from the father.
Summary
- Organelle genes are inherited maternally because they are located in the cytoplasm of the egg.
- Genomic imprinting is an exception to Mendelian genetics and can affect embryonic development.
- Chromosome abnormalities can lead to serious disorders, such as Down syndrome and Klinefelter syndrome.
- These abnormalities are often caused by aneuploidy, which is the presence of an abnormal number of chromosomes.
- Polyploidy, which is the presence of more than two sets of chromosomes, is common in plants but not animals.
Gene Linkage and Recombination
- Genes located on the same chromosome are considered linked genes.
- Linked genes do not assort independently during meiosis.
- Recombination frequency is the percentage of offspring that exhibit recombinant phenotypes.
- Genes far apart on the same chromosome have a recombination frequency near 50%, behaving as if they are on different chromosomes.
- Cytogenetic maps, using methods like chromosomal banding, show gene positions relative to chromosomal features.
X-Linked Genes
- Sex-linked genes are located on the X chromosome.
- Males are hemizygous for X-linked genes, meaning they have only one copy.
- Females are homozygous for X-linked genes, meaning they have two copies.
- Recessive X-linked disorders are more common in males because they only need one copy of the recessive allele.
- Examples of X-linked disorders in humans include color blindness, Duchenne muscular dystrophy, and hemophilia.
Crossing Over and Recombination
- Crossing over is the exchange of genetic material between homologous chromosomes during meiosis.
- It is the mechanism that breaks the physical connection between linked genes on the same chromosome.
- Crossing over results in genetic recombination, producing offspring with combinations of traits differing from either parent.
- Recombination contributes to variation for natural selection, with new combinations of alleles and traits.
Random Fertilization and Genetic Variation
- Random fertilization combines gametes with different alleles.
- Random fertilization, along with recombination, increases the number of possible genetic combinations.
- Genetic variation is essential for natural selection.
X-Chromosome Inactivation in Females
- One of the two X chromosomes in each cell in females is inactivated during embryonic development.
- The inactive X chromosome condenses into a Barr body.
- This process ensures that females have the same effective dose of X-linked genes as males.
- Heterozygous females become mosaics for specific X chromosome genes, expressing different alleles in different cells.
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Description
Explore the fascinating world of organelle gene inheritance known as cytoplasmic genes. This quiz covers topics like maternal inheritance, the role of organelles like mitochondria and chloroplasts, and diseases caused by defects in mitochondrial genes. Test your knowledge on genomic imprinting and its implications in heredity.
