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Questions and Answers
What is the study of inherited variation?
What is a sequence of DNA that instructs a cell to produce a particular protein?
What is an alternate form of a gene that occurs at a given locus in a chromosome?
What is the term for having two identical alleles of a gene?
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What is the term for the expression of a gene in traits or symptoms?
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Who is called the Father of Genetics?
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What is the term for a cell containing two sets of chromosomes?
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What is the term for a sex cell, such as a sperm or ovum?
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What is the number of X chromosomes present in females?
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Which of the following conditions is an example of X-Linked recessive inheritance?
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When a mother is a carrier of an X-Linked recessive mutation, what is the chance that a son will be affected?
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What is the pattern of inheritance of a condition caused by a mutation on the X chromosome?
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What is the chance that a daughter will be a carrier when the mother is a carrier of an X-Linked recessive mutation?
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When a father is affected by a condition due to an X-Linked recessive mutation, what happens to his sons?
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Which of the following chromosomes is responsible for X-Linked diseases?
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Why are daughters of a carrier mother only carriers of an X-Linked recessive mutation?
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What is the purpose of crossing over during prophase 1 of meiosis?
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Which enzyme is responsible for breaking homologous chromosomes during crossing over?
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During which stage of meiosis does crossing over occur?
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What is the term for a chromosome that determines sex?
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What is the result of fertilization with a sperm containing a Y chromosome?
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How many chromosomes does a human cell have?
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What is the term for a trait determined by a gene located on the X chromosome?
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What is the main difference between the X and Y chromosomes?
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What was the ratio of Tall to dwarf offspring observed by Mendel in the F2 generation?
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What is the term for the distribution of alleles of a gene into separate gametes during meiosis?
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What is the genotype of an organism that is homozygous recessive?
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What is the term for the random arrangement of homologous chromosome pairs during metaphase 1 of meiosis?
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What type of cross involves organisms that differ in two traits?
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What is the ratio of the four possible combinations of seed characteristics in the F2 generation of a Dihybrid Cross?
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What is the term for the offspring from homozygous parents differing in three pairs of genes?
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What is the genotype of an organism that is heterozygous?
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Why are X-linked recessive diseases more common in males than in females?
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What happens when an affected male passes on the X chromosome to his sons?
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What is the probability of a daughter being affected by an X-linked dominant gene if the mother is affected?
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What is the characteristic of X-linked dominant inheritance in males?
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What is the condition that follows a pattern of X-linked dominant inheritance?
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What is the cause of colour blindness?
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What is the test used to diagnose red-green colour deficiencies?
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What is the ratio of colour blindness in men and women?
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Study Notes
Molecular Genetics
- Definition of Genetics: The study of inherited variation.
- Definition of Gene: A sequence of DNA that instructs a cell to produce a particular protein.
- Definition of Allele: An alternate form of a gene that occurs at a given locus on a chromosome.
- Definition of Homozygous: Having two identical alleles of a gene (e.g. TT or tt).
- Definition of Heterozygous: Having two different alleles of a gene (e.g. Tt).
- Definition of Genotype: The alleles combination in an individual that cause particular traits or disorders.
- Definition of Phenotype: The expression of a gene in traits or symptoms.
- Definition of Dominant: A gene variant expressed when present in even one copy (e.g. TT, Tt).
- Definition of Recessive: An allele whose expression is masked by another allele (e.g. tt).
- Definition of Diploid: A cell containing two sets of chromosomes.
- Definition of Haploid: A cell containing one set of chromosomes.
- Definition of Gamete: A sex cell (sperm or ovum).
Mendelian Genetics
- Gregor Mendel is considered the Father of Genetics (1822-1884).
- Mendel's Experiments:
- First Experiment: Crossed tall and dwarf plants, resulting in F1 offspring that were all tall (Tt).
- Second Experiment: Crossed plants with different traits, resulting in an F2 generation with a 9:3:3:1 ratio.
- Laws of Inheritance:
- Law of Segregation: The distribution of alleles of a gene into separate gametes during meiosis.
- Law of Independent Assortment: The random arrangement of homologous chromosome pairs during metaphase 1 of meiosis.
Crossing Over
- Definition: An event during prophase 1 of meiosis when homologous chromosomes exchange parts, mixing up maternal and paternal gene combinations.
- Features of Crossing Over:
- Probability of crossing over increases with increasing distance between two loci on the chromosome.
- Involves breakage of each of two homologous chromosomes by endonuclease enzymes, followed by exchange of parts and reunion by ligase enzymes.
- Occurs during prophase 1 of meiosis in the post-replication tetrad stage.
Sex Determination and X-Linked Inheritance
- Definition of Sex Chromosome: A chromosome containing genes that specify sex (X and Y chromosomes).
- Definition of Autosome: A chromosome that does not have a gene that determines sex.
- XX-XY Mechanism of Sex Determination:
- XX zygote develops into a female, and XY zygote develops into a male.
- X-Linked Inheritance:
- Refers to a trait determined by a gene located on the X chromosome.
- X-Linked diseases are inherited through one of the sex chromosomes (X or Y chromosomes).
- Examples of X-Linked recessive diseases include Hemophilia and Colorblindness.
X-Linked Inheritance Patterns
- When the mother is a carrier of an X-Linked recessive mutation:
- Sons have a 50% chance of being affected, and daughters have a 50% chance of being carriers.
- When the father is affected by an X-Linked recessive mutation:
- None of his sons will be affected, and all of his daughters will be carriers.
- X-Linked dominant inheritance:
- Examples include incontinentia pigmenti.
- Much more severe effects in males.
Sex-Linked Recessive Traits in Humans
- Colorblindness:
- Inherited and more common in men (1 in 20), affecting fewer women (1 in 200).
- The gene for red-green colorblindness lies on the X-chromosome.
- Follows a pattern of X-Linked recessive inheritance.
- Diagnosis: Uses a test with colored spots to diagnose red-green color deficiencies.
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Description
This quiz covers the basics of Mendelian genetics, including transmission genetics, crossing over in meiosis, and X-linked inheritance. Test your knowledge of how traits are passed down from generation to generation.
