Mitosis
How many chromosomes are in the following cell?
6
What and when does crossing over happen within a cell? What and when does independent assortment happen within a cell?
Crossing over happens during Prophase 1 and it describes the process where genetic material is exchanged between homologous chromosomes. Independent assortment happens during Metaphase 1 when homologous pairs align randomly.
In a cell, where does DNA transcription happen? Translation?
Transcription happens in the nucleus and translation happens in the cytoplasm.
Regarding genes, how do cells acquire specific characteristics?
Cells acquire specific characteristics through the use of gene expression.
What are homologous chromosomes?
Homologous chromosomes are chromosomes that are the same size, have the same genes, and possibly different alleles.
During mitosis, chromosomes condense and begin to be visible during
Prophase
After ------ a cell enters mitosis. What are the 4 stages of mitosis and briefly describe what they do. Also, fill in the blank.
Interphase;
Prophase: nuclear envelope degrades and chromosomes condense
Metaphase: Chromosomes line up along the metaphase plate
Anaphase: Chromatids are pulled apart towards opposite sides of the cell
Telophase: Chromosome decondense and cell split s
What direction is the DNA template strand read. What direction is mRNA created?
The DNA template is read in the 3' to 5' direction and mRNA is created in the 5' to 3' direction
What is the central dogma? What are the two major processes involved and what do they do?
The central dogma describes the flow of genetic information of how DNA->mRNA->Protein. The two main processes are transcription (DNA is copied into mRNA) and translation (mRNA is decoded to assemble amino acids into proteins)
After what point in the cell cycle are sister chromatids introduced? How are they connected?
S phase of interphase. They are joined by the centromere.
Fill in the blank: From prophase through metaphase of mitosis, each chromosome has ___________ DNA molecule(s), while from anaphase through telophase of mitosis, each chromosome has ____________ DNA molecule(s).
two; one
Amur leopards have 38 chromosomes in their somatic cells. How many different chromosome combinations are created by independent assortment in these animals?
219
What are transcription factors and what are promoters?
Transcription factors are proteins that bind DNA at the promoters. Promoters is a sequence of DNA bases that signals the beginning of RNA synthesis.
What are the 5 enzymes involved in DNA replication and what do they do? Put them in order.
1. Helices: Unwinds the double helix by breaking hydrogen bonds
2. Single-strand binding protein (SSBs): Keep the strands separated during replication
3. Primase: Adds short RNA primers so DNA polymerase can start building
4. DNA Polymerase: Adds new DNA nucleotides to the 3′ end of a growing strand
5. DNA Ligase: Seals gaps between Okazaki fragments on the lagging strand
Why would it be dangerous for all humans to have the same DNA (in other words, be genetically identical)?
We would all be susceptible to the same infectious diseases and a single infectious agent could, in theory, wipe us out.
The image on the left is in the G1 phase of the cell cycle and image on the right is in G2. What could be said about the DNA content in each cell in relation one another.
The G1 cell has half the amount of DNA as the G2 cell/ G2 cell has twice the amount of DNA as the G1 cell
Which of the following cells are haploid?
C and D
A template DNA strand reads 3′-TAC GGA TTC-5′. Give the mRNA sequence and the tRNA anticodon for the first codon.
mRNA: 5′-AUG CCU AAG-3′. The anticodon for the first codon is UAC.
A sample of double-stranded DNA is found to be 30% adenine. What percentage of the sample is thymine, cytosine, and guanine, and how do the base-pairing rules explain this?
Thymine is 30%, cytosine is 20%, and guanine is 20%. A always pairs with T, so their amounts are equal. That leaves 40% for C and G, which also pair with each other, so each is 20%.
A mutation changes one amino acid in a protein’s sequence, and the protein no longer folds correctly. Which level of protein structure was changed first, causing the other levels to be affected?
Primary structure, the sequence of amino acids
A chemotherapy drug prevents spindle fibers from forming. At which stage will the dividing cells arrest, and which checkpoint is responsible?
Metaphase; M checkpoint
When observing the karyotype of an individual, scientists find that there is trisomy (3 chromosomes) at the 21st chromosome. What would this person's chromosome number be? What stage of meiosis is responsible for this?
47 chromosomes; Anaphase because chromosomes did not separate
A researcher compares the normal and mutated versions of a hemoglobin gene. A single base substitution changes an mRNA codon from GAG to GUG. The mutant protein is the same length as the normal one, but a hydrophilic amino acid has been replaced by a hydrophobic one, causing hemoglobin to clump into rods. What is this kind of mutation?
Missense mutation
A drug blocks DNA ligase but leaves all other replication enzymes working. Describe what would happen to the leading strand and the lagging strand, and explain why.
The leading strand would be unaffected, because it is built continuously and has no gaps to seal. The lagging strand would be left as a series of separate Okazaki fragments.
HIV carries its genetic information as RNA, yet infected human cells end up producing viral proteins that are encoded by the virus. Explain how this can be true? Does it follow the central dogma?
It does not follow the central dogma. HIV is a retrovirus, so its information flows RNA → DNA. The path is viral RNA → DNA → mRNA → protein (viral).