4-1: Structure of DNA
What is DNA?
Contains instructions for cell’s growth and function.
What are 5 types of bases?
A (adenine), T (thymine), C (cytosine), G (guanine) and U (uracil).
Adenine in RNA pairs with….
Uracil
What is the purpose of DNA replication? (Tell me two reasons)
For growth / For replacement
What is the definition of codon? Explain the base-pairing rule for RNA also.
Codon: 3 pairs of nitrogenous bases /
Base-pairing rule for RNA: Cytosine - Guanine/ Adenine - Uracil
What is chromatin and what is it composed of?
It is the hereditary material of the cell and it is composed of DNA.
Answer to base pair rule (DNA): ATTTCGCATGCATGACGATATGCGCGGAAT.
TAAACGGTACGTACTGCTATACGCGCCTTA.
Fill in the black: DNA instructions are passed on to RNA molecules and eventually to _____ on which all life forms are based.
Proteins
Explain what antiparallel is
Antiparallel is the direction of two strands in DNA. One strand goes from 5’ to 3’ but the other strand goes from 3’ to 5’.
Explain the one-start codon and three-stop codons for the translation.
start: AUG / stop: UAA,UGA,UAG
What does DNA stand for?
Deoxyribonucleic acid.
What is histone?
a type of protein than helps to condense the DNA into chromatin.
Fill in the blank: DNA carries a code. Genetic instructions are coded in the _______.
Sequence of bases.
Name the four enzymes that help DNA replication
Helicase, Primase, DNA Polymerase, Ligase
Name three types of RNA and explain their roles
1. mRNA
- Helps to carry the information of making a protein from the original DNA from the nucleus to ribosomes
2. tRNA
- Helps to bring appropriate amino acids by reading the mRNA located in the ribosome.
3. rRNA
- Helps to create a ribosome
Where are nucleotides made from?
Each nucleotide is made from a 5-C (carbon) sugar, a phosphate group, and a nitrogen (N) containing base.
How many histone(s) is DNA coiled in?
DNA is coiled around 8 histone proteins in regular intervals.
Why is thymine replaced with uracil?
Thymine is protected from oxygen in the nucleus. Outside of the nucleus, thymine is quickly destroyed. Uracil is resistant to oxidation and is used in the RNA that must exist outside of the nucleus.
Explain why DNA replication is also called semi-conservative replication.
We called this a semi-conservative replication since it is copying the DNA from parent strands to daughter strands.
What is the reason why one amino acid can have more than one type of codon?
To protect the mutation.
Draw the structure of chromosomes to DNA. Include DNA, chromosomes, histones, chromatin and nucleosomes.
(Compare to the picture in the slides)
What is karyotype and what 4 things can it tell us?
It is a picture of someone’s chromosomes and it tells us 1. The shape of the chromosomes 2. The size of the chromosomes 3. The number of the chromosomes 4. The gender: female or male.
What are DNA’s three major functions?
1. DNA controls cellular activities.
2. DNA makes exact copies of itself to pass onto other cells -> Replication.
3. DNA undergoes mutations.
Explain what DNA replication is by using these words: Helicase, 5’ to 3’, DNA polymerase, leading strand, lagging strand, antiparallel.
DNA replication is the process of duplicating DNA. The first step of replication is dividing the DNA strands into two by using Helicase, the name of the enzyme. Then, DNA polymerase helps to connect the base based on the base-pairing rule to make a new daughter strand. However, the direction of making new strands is different between the upper one and the down one due to the antiparallel. Because one strand of DNA goes from 5’ to 3’, the direction of creating a new strand must be 5’ to 3’ also. In this case, we say making a ‘leading strand’. However, if the direction of the original DNA strand is 3’ to 5’, DNA polymerase will make a new strand in the opposite way which has been done to make the leading strand. In this situation, we call it creating a ‘lagging strand’. After these processes, a new copy of the original strand called the daughter strand, is created.
Explain what transcription is by using these words: (mRNA, RNA polymerase, RNA splicing, Exon, Intron,)
Transcription is the process of making mRNA based on the original DNA strand. There are two steps in this process. One is dividing the DNA strand into two strands by using RNA polymerase. The next step is splicing the RNA called RNA splicing. For the information that is copied from DNA, we can divide it into two sections: intron and exon. Intron is basically useless information for making protein; therefore, RNA gets rid of this before it goes out of the nucleus. However, exon contains quite important information, so RNA keeps them.