Unit 2: Module 4

In human female reproduction, at what stage of meiosis is the egg released during ovulation?

Metaphase II

An allele is _____.

One version of genetic variation at a particular locus

Which of the following is a true statement?

Oxygen diffuses from the maternal blood in the intervillous space, through trophoblasts in the chorionic villi, and into the fetal bloodstream.

How is sex-linked inheritance defined?

Sex-linked inheritance is when a gene that controls a trait is found on one of the sex chromosomes.

Why are X-linked recessive traits expressed more often in males than females?

Since males only have one X chromosome, they only need to receive one allele for an X-linked trait to be expressed.

Which of the following forces is LEAST likely to cause a new species to arise in a population?

Stabilizing selection

Which of the following contains mostly maternal cells?

The intervillous space

Why might a doctor perform amniocentesis?

To see if the baby is okay.

Mary is pregnant and she wonders what is holding her baby in place in her uterus. Which of the following would be the best explanation?

Trophoblasts form columns of cells that anchor the placenta to the uterine wall.

When an organism is diploid, that means it has _____.

Two versions of each chromosome

All of the following statements are true about single gene-pair inheritance, EXCEPT:

When a trait is inherited though a single gene-pair, there are five possible allele combinations.

When does the germinal period end?

When the blastocyst is fully implanted into uterine tissue.

In human female reproduction, when the egg leaves the ovary, what guides it to the opening of the uterine tube?

cilia on the fimbraie

Researchers plan a study to find the proportion of identical twins that both suffer from depression. This is an example of the researchers determining the _____.

concordance rate

A statistic for measuring the extent a trait in one twin compares or contrasts with the same trait in the other twin is the _____.

correlation coefficient

In family studies, the proband refers to the _____.

first person being studied

The process by which genes are passed down from parents to their offspring is called _____.

genetic inheritance

The Minnesota Twin Study found that _____.

identical twins raised apart are about as similar as those raised together

Polygenic traits are controlled by _____.

more than one gene

If one parent has a gene-pair of 'AA' and the other parent has a gene-pair of 'aa', what will the gene-pairs of their children look like?

100% of the children will have 'Aa' for their gene-pairs.

In human female reproduction, if fertilization occurs it's usually _____.

24 hours after ovulation

In human female reproduction, how long does it usually take for the zygote to reach the uterus?

5-6 days

What is the most notable event during the fetal period?

A dramatic change in the size of the fetus.

The locus is _____.

A specific location on a chromosome

What is a teratogen?

A substance known to potentially cause a birth defect or cause a pregnancy to end.

Jane just discovered that she is pregnant. She will visit her physician to learn how she needs to take care of her unborn child. Which of the following questions about proper prenatal care should Jane ask?

All of the answers are correct.

Which of the following is true about the placenta?

All the answers are correct.

You have the gene-pair Aa. This gene controls your eye color. You have brown eyes because brown is the dominant trait. Which of the following is true?

Any of your children who receive the dominant trait for brown eyes will have brown eyes.

A situation in which two alleles of a gene are maintained in a population because heterozygotes are more fit than their homozygous counterparts is called:

Balanced polymorphism

Why is the embryonic period the most crucial part of prenatal development?

Because during this period the cells begin to differentiate and prepare the foundation for the baby.

Why are Y-linked traits only inherited by males?

Because females do not have Y chromosomes.

Why isn't the developing child protected from all unwanted environmental hazards?

Because potentially harmful substances can cross the placenta, and be transferred to the developing child from the mother.

The embryonic-derived portion of the placenta is called:

Chorion

Which of the following is NOT an example of a phenotype?

DNA sequence of the alcohol dehydrogenase gene

A scientist has observed animals in a particular habitat for some time. She notices that the slowest gazelles tend to fall victim to predators more frequently than faster ones. Over time, she notes that the gazelle herd on average runs faster. She is observing:

Directional selection

A scientist has observed animals in a particular habitat for some time. She notices that in a population of birds those with either short or long beaks can find more food than those with average sized beaks. Over time, she notices a higher proportion of birds in the population have either short or long beaks. She is observing:

Disruptive selection

Which of the following is the correct order of the germ layers from the outside to the inside?

Ectoderm, mesoderm, endoderm.

An implanted embryo which has all three germ layers and some, but not all, of the internal organs formed, is in which period of development?

In the middle of the embryonic period.

Which of the following is FALSE of the amnion?

It feeds the baby.

Which of the following is NOT a true statement about the placenta?

It is an organ that is found in all species.

Which of the following is true of a recessive trait?

It is only expressed if a person has the trait in both alleles of their gene-pair.

Why is the placenta so important?

It provides nutrients to the baby from the mother.

Which of the following is true of a dominant trait?

It will always be expressed in a person who has the trait.

In human female reproduction, what happens to the egg if it is not fertilized?

It will die.

Which of the following statements is true? I. The one-thousandth base pair on chromosome one of an organism is an example of a locus. II. Changing the DNA in a gene by one base pair could create a new allele. III. Cells in a diploid organism possess two copies of each chromosome (except gametes).

I, II and III

Some studies have shown that a single copy of the cystic fibrosis disease allele can confer resistance to tuberculosis to a person. This is an example of:

Heterozygote advantage

What is the space surrounding an embryo inside the mother's body called?

Prenatal environment

What is the main function of the prenatal environment?

Protecting the fetus.

How have twin studies proven to be beneficial?

Researchers can determine the difference between environmental and genetic factors.

The tube that brings nutrients and oxygen from the placenta to the fetus is called the_____.

umbilical cord