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Questions and Answers
If a child inherits a recessive gene for a trait from each parent, what will be the outcome?
If a child inherits a recessive gene for a trait from each parent, what will be the outcome?
What happens when two brown-haired parents have a blond-haired child?
What happens when two brown-haired parents have a blond-haired child?
In the dominant-recessive genes principle, what is the main characteristic of a recessive gene?
In the dominant-recessive genes principle, what is the main characteristic of a recessive gene?
Why might someone carry a recessive gene but never show the associated trait?
Why might someone carry a recessive gene but never show the associated trait?
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How do dominant genes affect the expression of traits in the dominant-recessive genes principle?
How do dominant genes affect the expression of traits in the dominant-recessive genes principle?
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What determines whether a recessive gene will be expressed in an individual?
What determines whether a recessive gene will be expressed in an individual?
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During which period of prenatal development does organogenesis occur?
During which period of prenatal development does organogenesis occur?
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What is the function of the amniotic fluid during prenatal development?
What is the function of the amniotic fluid during prenatal development?
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At what stage in prenatal development do arm and leg buds start to emerge?
At what stage in prenatal development do arm and leg buds start to emerge?
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What is the approximate weight of the developing organism at eight weeks of prenatal development?
What is the approximate weight of the developing organism at eight weeks of prenatal development?
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By the end of the fourth month of pregnancy, what structures have formed on the fetus?
By the end of the fourth month of pregnancy, what structures have formed on the fetus?
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During which prenatal period do the rate of cell differentiation intensify and organs start to appear?
During which prenatal period do the rate of cell differentiation intensify and organs start to appear?
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Which layer of cells provides nutrition and support for the embryo during the germinal period?
Which layer of cells provides nutrition and support for the embryo during the germinal period?
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Which layer of cells will primarily become the circulatory system, bones, muscles, excretory system, and reproductive system?
Which layer of cells will primarily become the circulatory system, bones, muscles, excretory system, and reproductive system?
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Which life-support systems for the embryo develop rapidly as the embryo's three layers form?
Which life-support systems for the embryo develop rapidly as the embryo's three layers form?
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What is the inner layer of cells that later develops into the embryo during the germinal period called?
What is the inner layer of cells that later develops into the embryo during the germinal period called?
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Study Notes
Genetics and Inheritance
- A child inherits a recessive gene from both parents, leading to expression of the recessive trait.
- Brown-haired parents can have a blond-haired child if both carry a recessive gene for blonde hair.
- A recessive gene is characterized by its inability to express the associated trait when a dominant gene is present.
- Individuals may carry a recessive gene without expressing the trait if they have one dominant gene that overshadows the recessive allele.
- Dominant genes mask the expression of recessive genes, dictating trait expression in offspring.
Prenatal Development
- Organogenesis, the formation of organs, occurs during the embryonic period.
- Amniotic fluid cushions the fetus, allows for movement, and protects against physical trauma.
- Arm and leg buds emerge during the embryonic stage, approximately in the 4th to 5th week of development.
- At eight weeks, the developing organism weighs around 1 gram.
- By the end of the fourth month, structures like fingers, toes, and facial features have formed.
- The embryonic period sees intensified cell differentiation with the appearance of organs.
- The trophoblast, or outer layer of cells, nourishes and supports the embryo in the germinal period.
- The mesoderm layer becomes the circulatory system, bones, muscles, excretory system, and reproductive system.
- The placenta and umbilical cord develop rapidly alongside the three embryonic layers for the embryo's life support.
- The inner cell mass of the blastocyst becomes the embryo during the germinal period.
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Description
Learn about the dominant-recessive genes principle where one gene of a pair always exerts its effects over the other gene. Understand how recessive genes show their influence only when both genes in a pair are recessive.
