DNA/RNA Structure & Function
Provide the complementary strand of DNA:
3' GGA TAT CTG 5'
5' CCT ATA GAC 3'
What is the name of the process in which DNA makes an identical copy of itself?
DNA Replication
Where does transcription occur? Where does translation occur?
Transcription - nucleus, translation - ribosome
What is a mutation?
A change in the DNA sequence
What is the purpose of meiosis?
To create gametes with half the chromosome number
Compare the shapes of DNA and RNA.
DNA is a double helix, RNA is single-stranded
Bonus (200 pts): what are two other differences between DNA and RNA?
What does "semi-conservative" mean in DNA replication?
Each new DNA molecule contains one old strand and one new strand
How do ribosomes know where to start translating mRNA?
The start codon, AUG, which codes for methionine (met)
Provide two causes of mutations.
Errors in DNA replication, protein synthesis, mitosis, or meiosis
Exposure to mutagens (UV light, radiation, smoking)
Viruses
If the brain cell of a giraffe has 30 chromosomes, how many chromosomes would be found in the egg cell of a giraffe?
15 chromosomes
bonus (100 pts): how many homologous pairs of chromosomes would the giraffe have?
List the three parts of a nucleotide.
Sugar (DNA has deoxyribose, RNA has ribose), phosphate, nitrogen base
Bonus (100 pts): draw it!
Why does DNA replication only occur in the 5’ to 3’ direction?
DNA polymerase can only add nucleotides to a growing strand's free 3’ end.
Bonus (200 pts): This means the two strands are build differently from one another. What are the nicknames for these two different strands?
What are three post-transcription modifications that occur?
5' cap, poly-A tail, splicing
Bonus (300 pts): why are these important?
What is the difference between point mutations and frameshift mutations? Give an example using this strand: CGA TCC
A point mutation changes one base; a frameshift mutation inserts or deletes a base, shifting the reading frame
Point: CGA TCC --> CCA TCC
Frameshift: CGA TCC --> CAT CC
What is crossing over and when does it occur?
Exchange of DNA between homologous chromosomes when they get tangled up during Prophase I
Two bonds hold a DNA molecule together. Name these two bonds and describe where they are found.
The strong covalent bonds are found between the sugars and phosphates in the backbone of the molecules, whereas weaker hydrogen bonds are found between the nitrogen bases.
Name the four enzymes involved in DNA replication and their functions.
Helicase - "unzips" the double helix
Primase - builds an RNA primer to start replication
DNA polymerase - builds the new strand from the RNA primer, remove the RNA primer and replace with DNA, proofread the strand
Ligase - seals gaps in the backbone
Transcribe and translate the following strand of DNA:
5' ATG CAT AGA 3'
mRNA: AUG CAU UCU
amino acids: met - val - ser
Bonus (200 pts): what would need to happen for this polypeptide to be considered a protein? Draw a diagram.
What is nondisjunction, and how does it affect offspring?
When chromosomes don’t separate properly during anaphase II of meiosis, leading offspring having too few or too many chromosomes
Which phase of meiosis is described in this statement: "homologous chromosomes line up across the middle of the cell." Then, draw a picture of this phase.
Metaphase I
What are the three types of RNA, and what does each do?
mRNA brings instructions from DNA (in the nucleus) to the ribosome
tRNA brings amino acids that correspond to mRNA codons
rRNA makes up ribosomes
Why would an error in DNA replication be more problematic in a gamete than in a somatic cell?
Mutations in gametes can be passed on to offspring. Too many mutations in a somatic cell can lead to cancer, but one mutation (which could be silent) might go unnoticed
Explain why the central dogma of biology is DNA → RNA → Protein
DNA is contained in the nucleus, which it cannot leave. Proteins are made at the ribosomes. So mRNA is used as a "middle-man" to get the message to the ribosomes.
bonus (200 pts): what terms would we write on the arrows? DNA → RNA → Protein
Describe a silent, missense, and nonsense mutation.
Silent - point mutation that causes no change in the amino acid (and therefore protein)
Missense - point mutation that changes one amino acid, resulting in a misshapen protein
Nonsense - point mutation that causes an early stop to appear, causing a shortened protein that is usually nonfunctional
Describe 2 differences between mitosis and meiosis.
Mitosis - produces 2 identical diploid somatic cells, has 1 round of cell division, occurs throughout an organism's lifetime, and occurs throughout the whole body
Meiosis - produces 4 different hapoid gametes, has 2 rounds of cell division, occurs before birth for females/throughout a male's life, and only occurs in ovaries/testes