Genetics › Genetics
During cell division, at what phase does the cell separate into two?
ctyokinesis
Anaphase
Metaphase
prophase
Cytokinesis is the last processes of cell replication and division and consists of the cell membrane dividing into two.
You are a dog breeder and want to figure out the genotype of the female brown dog you have. Brown is the dominant phenotype, while white is the recessive. You decide to breed her with a male who is also brown and has strictly dominant brown alleles. If the female is heterozygous, what percentage of her litter should be white?
0%
25%
50%
75%
Since the father has only dominant alleles for the brown phenotype, all of the litter will be brown. However, half the litter should carry the recessive allele. The punnet square below shows the dad's genotype on top and the mom's genotype on the left. The outcome is that half the progeny will have the genotype BB and half will have the genotype Bb. Therefore, all offspring will have the brown phenotype.
B B
B BB BB
b Bb Bb
Why do RNA viruses have mutation rates higher than those of DNA viruses?
RNA viruses lack a proofreading function in the replicatory enzymes.
RNA viruses are smaller
RNA viruses have a more redundant genetic code
RNA viruses are larger
Viral RNA polymerases do not have the same proof-reading ability as DNA polymerases. This is a contributing factor to the difficulty of making vaccines from RNA viruses.
You are a dog breeder and want to figure out the genotype of the female brown dog you have. Brown is the dominant phenotype, while white is the recessive. You decide to breed her with a male who is also brown and has strictly dominant brown alleles. If the female is heterozygous, what percentage of her litter should be white?
0%
25%
50%
75%
Since the father has only dominant alleles for the brown phenotype, all of the litter will be brown. However, half the litter should carry the recessive allele. The punnet square below shows the dad's genotype on top and the mom's genotype on the left. The outcome is that half the progeny will have the genotype BB and half will have the genotype Bb. Therefore, all offspring will have the brown phenotype.
B B
B BB BB
b Bb Bb
Females have two X chromosomes, while males have only one. Most of the genes on the X chromosome, however, are expressed at the same level in both females and males. Which of the following statements regarding X chromosomes is correct?
XIST RNA coats one copy of the X chromosome in females
The nuclei of cells in males contain Barr bodies.
Female homozygotes are mosaics.
Calico cats are almost always males.
XIST stands for X-inactivation specific transcript, which acts in the inactivation process in females since only one X will be active. The nuclei of cells in females contain the barr body. Female heterozygotes are mosaics. Calico cats are almost always female.
In which phase of mitosis do spindle fibers align chromosomes in the middle of the cell nucleus?
Metaphase
Prophase
Anaphase
Telophase
G1
In metaphase, spindle fibers align chromosomes along the middle of the cell nucleus. A good way to remember this is "M" in metaphase stands for middle. In this portion of mitosis, the cell ensures that each daughter cell will receive the appropriate genetic material. Metaphase occurs right before Anaphase.
Choose the correct answer:
Nucleic acid (at the time referred to as "nuclein") was first discovered by whom in 1869?
Friedrich Miescher
Charles Darwin
Rosalind Franklin
James Watson
Miescher, a Swiss chemist, first identified "nuclein" in the nuclei of white blood cells. He noted that the substance contained higher levels of phosphorus than other proteins and was resistant to proteolysis. This discovery was not widely appreciated for over 50 years.
Mitosis is the process by which a parent cell divides to produce two daughter cells with identical genetic material. The chromosomes must condense, align, and be pulled apart to complete this process. What is the name of the mitotic phase in which the duplicated sister chromatids are physically pulled apart?
Anaphase
Metaphase
Prophase
Telophase
Cytokinesis
Prophase and metaphase happen before anaphase, and the duplicated chromosomes (sister chromatids) condense and align. During anaphase they are pulled apart and start migrating to opposite cell poles. Telophase and cytokinesis follow anaphase to complete the division of the cell into two new cells.
If a species has a diploid number of 10 chromosomes, how many chromatids would there be in prophase of mitosis?
20
10
5
40
15
Diploid means 2_n_, where n is the number of chromosomes in a particular species. If there are 10 chromosomes, there will be 20 chromatids. For each chromosome there are two chromatids. Since this is before the cells have fully divided, there will be 2 times the number of chromosomes during prophase. Therefore, the answer is 20.
Why do RNA viruses have mutation rates higher than those of DNA viruses?
RNA viruses lack a proofreading function in the replicatory enzymes.
RNA viruses are smaller
RNA viruses have a more redundant genetic code
RNA viruses are larger
Viral RNA polymerases do not have the same proof-reading ability as DNA polymerases. This is a contributing factor to the difficulty of making vaccines from RNA viruses.