1.
A eukaryotic cell, such as a human cell, is larger than a prokaryotic cell, such as a bacterium.
Correct Answer
A. True
Explanation
Eukaryotes are larger than prokaryotes. Eukaryotes are larger because they have organelles and a nucleus inside of them, whereas prokaryotes are much more simple and do not keep their DNA in a nucleus and do not have organelles. This is visible on the "cell size and scale" activity.
2.
Check ALL of the statements which are true about a human sperm cell.
Correct Answer(s)
B. Sperm cells contain just one copy of each of the 23 human chromosomes.
C. The head of a sperm cell is almost all nucleus to make it a more efficient swimmer.
Explanation
Sperm cells are gamete (sex) cells and are haploid - meaning they only have one copy of each of the 23 human chromosomes. This is important because in reproduction a sperm cell will join with an egg cell, which is also haploid, thus joining each set of 23 chromosomes to make 46 total (diploid) needed to make a baby. The head of a sperm cell is almost all nucleus because much of the cytoplasm has been squeezed out - this makes the sperm cell a much more efficient swimmer to deliver the DNA to the egg cell. These answers can be found in the "Cell Size and Scale" activity.
3.
Check ALL of the statements which are true about DNA.
Correct Answer(s)
A. DNA encodes a detailed set of plans, like a blueprint, for building different parts of the cell.
B. DNA stands for DeoxyRibonucleic Acid.
D. The DNA molecule comes in the form of a twisted ladder shape called a "double helix".
Explanation
All are true of DNA except that DNA is actually NOT allowed to leave the nucleus. The information encoded in DNA is so important that it is "held captive" inside the nucleus to keep it safe from destruction or mutation.
4.
The 23rd set of chromosomes are the sex chromosomes, because they determine gender. A typical human female will have two X chromosomes, or XX. On the other hand, a typical human male will only have one X chromosome and one ______ chromosome.
Correct Answer(s)
Y
Explanation
Human males are XY. The Y chromosome has the information to build the male reproductive system. The X chromosome is found in all humans because it has information to build many different parts of the body, including the female reproductive system. When Y is present, the information in X to build the female reproductive system is "canceled out."
5.
All living things have 46 chromosomes.
Correct Answer
B. False
Explanation
False - humans have 46 but other organisms may have more or less DNA. For example, a giant sequoia tree has 22 chromosomes, a fly has only 8, and a carp (type of fish) has 104! Notice that all of these numbers are even: that is because all of these organisms are diploid, meaning that they have 2 sets of chromosomes. (One set from each parent)
6.
Which of the following correctly displays complementary base-pairing of DNA nucleotides?
Correct Answer
C. A always bonds with T, and C always bonds with G.
Explanation
Please review "tour of the basics" and "build a DNA molecule" if you got this question incorrect.
7.
Which of the following do scientists use to "read" a set of chromosomes? (Check all that apply)
Correct Answer(s)
A. Size
B. Banding Pattern
C. Centromere Position
Explanation
All three are very important in "reading" a chromosome. Please review "How do scientists read chromosomes"
8.
In DNA replication, what is the name of the enzyme that adds in complementary nucleotides?
Correct Answer
C. DNA polymerase
Explanation
DNA polymerase is the enzyme that adds in new complementary bases, using base-pairing rules. You can remember this because in Replication we are building a DNA polymer - the word polymer means "large molecule." A polymerase is basically a "polymer-maker"
9.
Check all of the following that are true about DNA replication:
Correct Answer(s)
A. DNA replicates in both directions.
B. DNA Polymerase uses complementary base-pairing rules to add in new nucleotides.
Explanation
DNA replication happens in the NUCLEUS, not cytoplasm. DNA is not allowed to leave the nucleus, so all processes involving DNA will occur in the nucleus. Also, DNA replication happens BEFORE cell division, so the cell temporarily doubles its DNA before dividing so that each new cell gets the correct amount. From the "DNA Replication" activity from phschool.