Question

1. multiple choice.

in the space at the left, write the letter of the choice that best answers each question.

1. when are hereditary traits determined?

a. at birth c. during adolescence
b. as the fetus develops d. at conception

1. which option would not help an infertile couple when the womans fallopian tubes

are damaged?
a. ovum transfer c. artificial insemination
b. adoption d. in vitro fertilization

1. when a couple conceives using ovum transfer, how many chromosomes does the

woman give the zygote?
a. 0 c. 46
b. 23 d. 87

1. which of the following is true of fraternal twins?

a. they look alike. c. the same egg divided.
b. they may be the same sex. d. the same zygote divided.

1. when are couples who are trying to conceive considered infertile?

a. after six months c. after one year
b. after nine months d. after two years
ii. completion.
in the space at the left, write the word or words that will best complete each statement.

1. when an individual receives two different genes for a

characteristic, the _?__ gene is weaker.

1. the child will be male when the zygote has a(n) _?__

chromosome combination.

1. each parent contributes _?__ chromosomes to the zygote.
2. a woman who carries and delivers a baby for someone else is

called a(n) _?__ mother.

1. fraternal twins occur four times more often than _?__ twins

Explanation:

1. Hereditary traits are determined by genes, and genes are fixed at conception when sperm and egg combine.
2. Artificial insemination is mainly for male infertility issues. If a woman's Fallopian tubes are damaged, it won't help. Ovum transfer, adoption, and in vitro fertilization (which bypasses Fallopian tubes) can help.
3. In any normal conception (including ovum transfer), a woman's egg (ovum) has 23 chromosomes.
4. Fraternal twins come from two different eggs fertilized by two different sperms. They can be same - sex or different - sex. Identical twins (from one egg and one sperm that splits) look alike and come from the same zygote/egg division.
5. Generally, couples are considered infertile after one year of unprotected regular intercourse without conception.
6. When an individual has two different genes (heterozygous) for a characteristic, the recessive gene is weaker (not expressed in the phenotype if a dominant gene is present).
7. A male has an XY chromosome combination.
8. Each parent (mother and father) contributes 23 chromosomes to form a zygote with 46 chromosomes.
9. A surrogate mother carries and delivers a baby for someone else.
10. Fraternal twins occur more often than identical twins.

Answer:

1. D. at conception
2. C. artificial insemination
3. B. 23
4. B. They may be the same sex.
5. C. after one year
6. recessive
7. XY
8. 23
9. surrogate
10. identical