Dominant-Recessive Genes Principle

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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?

The child will show a different trait.

The child will be a carrier of the trait.

The child will not show the trait.

The child will show the trait. (correct)

What happens when two brown-haired parents have a blond-haired child?

The child will definitely have blond hair. (correct)

The child will definitely have brown hair.

The child can have any hair color.

The child will have a mix of brown and blond hair.

In the dominant-recessive genes principle, what is the main characteristic of a recessive gene?

It is masked by the presence of a dominant gene. (correct)

It always shows its effects.

It determines the physical appearance of an individual.

It can only exert influence if the other gene is dominant.

Why might someone carry a recessive gene but never show the associated trait?

They have a dominant gene that masks the recessive one. Signup and view all the answers

How do dominant genes affect the expression of traits in the dominant-recessive genes principle?

They mask the effects of recessive genes. Signup and view all the answers

What determines whether a recessive gene will be expressed in an individual?

Whether the individual inherits two recessive genes for that trait. Signup and view all the answers

During which period of prenatal development does organogenesis occur?

Second month Signup and view all the answers

What is the function of the amniotic fluid during prenatal development?

Acts as a shock absorber Signup and view all the answers

At what stage in prenatal development do arm and leg buds start to emerge?

Fourth week Signup and view all the answers

What is the approximate weight of the developing organism at eight weeks of prenatal development?

1/30 ounce Signup and view all the answers

By the end of the fourth month of pregnancy, what structures have formed on the fetus?

Toenails and fingernails Signup and view all the answers

During which prenatal period do the rate of cell differentiation intensify and organs start to appear?

Embryonic period Signup and view all the answers

Which layer of cells provides nutrition and support for the embryo during the germinal period?

Outer layer Signup and view all the answers

Which layer of cells will primarily become the circulatory system, bones, muscles, excretory system, and reproductive system?

Mesoderm Signup and view all the answers

Which life-support systems for the embryo develop rapidly as the embryo's three layers form?

Amnion and umbilical cord Signup and view all the answers

What is the inner layer of cells that later develops into the embryo during the germinal period called?

Blastocyst Signup and view all the answers

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.