Questions and Answers
What determines the colour of eyes in humans?
What is the function of DNA molecules?
How many chromosomes are present in a human body cell?
What is the relationship between genes and DNA molecules?
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What is the shape of chromosomes?
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Why do chromosomes have protective proteins?
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What determines the shape of wings in flies?
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What is the correct sequence of the components of inheritance?
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What is the number of chromosomes in a human body cell?
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What is the composition of the 23rd pair of chromosomes in a male?
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What is the composition of the 23rd pair of chromosomes in a female?
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What is the number of chromosomes in an egg cell produced by a female?
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What is the chance of a sperm cell carrying a Y chromosome?
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What determines the sex of the baby?
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What is the result of fertilization by a sperm cell carrying an X chromosome?
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What is the function of the Y chromosome?
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Study Notes
Genes and Characteristics
- A gene is a unit of inheritance that determines specific characteristics, such as eye color, hair texture, and height.
- In some cases, one gene can control one characteristic, but often, multiple genes and other factors contribute to a single trait.
Genes and DNA
- DNA is a chemical molecule that contains a precise, helix-shaped arrangement of atoms.
- The sequence of nucleotides along the DNA molecule forms a chemical code that instructs the cell on how to build proteins and structures.
- Each gene is specified by a unique code in a different DNA molecule.
- A slight difference in the DNA code sequence can result in distinct characteristics, such as straight or curly hair.
Chromosomes
- DNA molecules (genes) are wrapped up with protective proteins to form a thread-like structure called a chromosome.
- Chromosomes are typically "X-shaped" and only visible during cell division.
- Human body cells have 46 chromosomes, arranged in 23 pairs, while sperm or egg cells have only half that number.
- Chromosomes come in matching pairs, with the first 22 pairs being the same size and shape in every human.
- The 23rd pair of chromosomes, the "sex chromosomes," determine an individual's sex.
Sex Chromosomes
- The 23rd pair of chromosomes in females are a matching pair of large, X-shaped chromosomes (XX).
- Each egg produced by a female carries a single "X" chromosome.
- The 23rd pair of chromosomes in males are mismatched, with one large "X" chromosome and a small "Y" chromosome (Xy).
- Half of the sperm cells produced by a male carry an X chromosome, while the other half carry a Y chromosome.
- The sex of a baby is determined by the chromosome carried by the fertilizing sperm cell.
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Description
Understand the basics of genes, characteristics, and DNA. Learn how genes determine specific traits and how DNA molecules contain a chemical code that instructs the cell.
