DNA/RNA Structure & Function
Provide the complementary strand of DNA:
3' GGA TAT CTG 5'
5' CCT ATA GAC 3'
When does DNA Replication occur?
S-phase of interphase
What molecule is produced during transcription?
BONUS (100 pts): What are the three ways pre-mRNA is modified to make mRNA?
What is the role of the ribosome during protein synthesis?
Site of translation! The rRNA in the ribosome also helps catalyze peptide bonds.
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
Which enzyme is responsible for transcription, and what molecule does it read as a template?
RNA polymerase, and it reads DNA as a template
What is a codon?
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!
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 the following strand of DNA.
5' A T G G A C C G G T A G A A G 3'
mRNA can only be built from 5' to 3'. To transcribe this, we need to determine the other strand of DNA first: 3' T A C C T G G C C A T C T T C 5'
Then, we can find the mRNA: 5' A U G G A C C G G U A G A A G 3'
How does tRNA know it's dropping off the correct amino acid during translation?
tRNA has an anticodon that is complementary to the mRNA codon. They bind, which ensures the correct amino acid is dropped off.
BONUS (200 pts): Provide the anticodon and amino acid that correspond with the codon "CCU"
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.
After replication is completed, there is an error changing the sequence of the new DNA (mutation). Which enzyme failed at its job, resulting in this mutation?
DNA polymerase did not proofread!
Two different proteins are produced from the same gene. Which post-transcriptional could allow this to happen?
Alternative splicing.
What could happen to the protein if one codon (and amino acid) were changed?
It could fold incorrectly, rendering it either nonfunctional or with a function it shouldn't have.
BONUS (100 pts): draw and label a diagram of protein folding!
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
BONUS (100 pts): draw them!
If DNA polymerase could add nucleotides in both directions, how would replication change? Describe at least one impact of this change.
Replication would occur continuously on both strands (no more leading and lagging; both strands would be constructed like the leading), eliminating the Okazaki fragments and multiple primers seen on the lagging strand, making replication faster and simpler.
A mutation occurs in the promoter region of a gene.
Predict how this mutation could affect transcription.
A mutation in the promoter region could prevent RNA polymerase from binding properly to the DNA. This could slow down transcription or stop it altogether.
Explain why a two-step process for protein synthesis is required.
DNA is in the nucleus, which it cannot leave, but proteins are made at ribosomes. So, we need to transcribe a messenger (mRNA) in the nucleus that can carry the DNA's instructions out to the ribosome to be translated into protein.
A species begins reproducing using mitosis instead of meiosis. Predict a long-term consequence of this.
Mitosis produces identical cells, so eventually every individual would be exactly the same.