DNA Structure and Function
DNA is the genetic material of the cell.
Erwin Chargaff: found out that the amount of G & C, A& T were always
the same in a DNA fragment.
Rosalind Franklin and Maurice Wilkins took thousands of X-ray
photographs of DNA and discovered that it had a constant diameter.
James Watson and Francis Crick used all the information to determine the
structure of DNA as a double helix in the 1950's using X-ray
crystallography.
Watson, Crick, and Wilkins won the noble prize for their discovery in
1962. Franklin died of cancer before that.
DNA and RNA:
1. They are made up of
2. DNA has ---------------- and RNA has ------------------3. DNA has ----------------------, RNA has ----------------------------4. The backbone is a
5. Adenine and guanine are called -------------- and thymine and cytosine are
----------------. By a purine binding to a pyrimidine, the diameter of the
molecule remains the same.
6. DNA is a ---------------------, RNA is -----------------------------DNA Replication:
1. For cells to reproduce and multiply, their genetic information----------2. The two strands of DNA separate, exposing the bases.
3. Each strand
4. Enzymes link the new nucleotides to ---------------------------------------5. DNA replication begins at specific sites ---------------------------Eukaryotic DNA can have many origins of replication.
6. DNA strand is in a 5' to 3' direction, ---------------------------------------------------------------------------------------------------------------------------------------.
7. ---------------------------------------------- is the enzyme that elongates DNA.
It can only add new nucleotides to the 3' end of a strand and never a 5' end.
8. One of the strands, the ------------------------------------------------------------9. The other strand, -------------------------------, is copied in small stretches of
DNA in a non- continuous manner. These small pieces --------------------------------------------------------------------------------------------------------------------10. DNA replication ensures that all somatic cells in an organism carry the
same genetic information.
11. DNA replication is -----------------------, with the new DNA strand having
one strand from the parent and one new daughter strand.
Genotype:
Phenotype:
How can DNA encode or make proteins?
DNA molecules have the information that is needed to make proteins. The
gene sends instructions in the form of RNA, which becomes or is made into
proteins.
Transcription:
Translation:
The language in the DNA nucleotides is transferred to ----------------------------------------------------------------------DNA language is a linear sequence of nucleotides that can encode a gene.
Thousands of nucleotides make up a gene, thousands of genes are found on
DNA strands.
Triplets of nucleotides ----------------------------------------------. So every 3
nucleotides can code for an amino acid. These are called -----------------------Genetic Code:
1. Codons found ------------------------------------2. Example: UUU = Phenylalanine, AUG = Methionine.
3. There are -------------------- in RNA.
4. 61 are called -------------------- and 3 are called --------------------------------5. The stop codons are -------------------------------. These indicate the end of
protein synthesis.
6. The other 61 codons are ----------------------------------------------------------Each codon can code for more than one amino acid.
TRANSCRIPTION:
1. Occurs in the ---------------------------------2. DNA strands separate, and only one strand serves as the template.
3. The enzyme that -----------------------------------------------4. The enzyme binds at a region on the DNA called
5. RNA is made in a -------------------------------------------------------------------------------------------.
6. TTC ----> AAG, so place a U instead of a T.
7. Reach a terminator sequence and that indicates the end of transcription.
Eukaryotic RNA is processed before leaving the nucleus.
Messenger RNA ( m-RNA) is needed to make proteins. Eukaryotic m- RNA
is capped, tailed and spliced in the nucleus before it goes to the cytoplasm to
get translated. There are ------------------------------------------------- and --------------------------------------------------------, in eukaryotic RNA. Introns are
spliced out and exons are joined together before an RNA is ready to get
translated.
TRANSLATION: change of information from m-RNA to protein-------------------------------------1. Need
2. t -RNA function -------------------------------------------------------------- that
corresponds to the correct codon, and picking it up to bring it to the
ribosome to be added onto the polypeptide.
3. Ribosomes are the actual factories of polypeptides. They bring together
the t-RNA, m-RNA, and amino acids to make the polypeptide.
4. Translation occurs in three phases: initiation, elongation, and termination.
5. A m-RNA binds at a start codon on the ribosomes where translation
begins. ---------------------------- a start codon that codes for the amino acid
methionine. This occurs at the P site of ribosomes.
6. t-RNA
7. The two amino acids form -------------------------------------------------.
8. The ribosome ----------------------------------------------------------------------------------------------------9. More peptide bonds are formed between all the encoded amino acids until
the polypeptide is complete.
10.Termination or end of translation occurs when the ribosome reaches one
of the 3 stop codons on the message. UAA, UAG, UGA.
11. The polypeptide is released and now it can form its secondary and
tertiary structures.
MUTATIONS:
Point mutations: or base substitutions-------------------------------------------This can lead either in a major change in the protein that can cause a
significant disorder, or no effect on the protein. Ex: sickle cell anemia results
from a ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------this is caused by the redundancy of the genetic code. More than one codon
can code for the same amino acid.
THE MAN HAD A HAT
THE NAN HAD A HAT
Frame - shift mutations: -----------------------------------------------------------------------------------------------------------------------------------------------------.
This causes the whole reading frame of the message to change leading to
major changes in proteins. All the nucleotides that are down stream are regrouped in a different manner.
THE MAN HAD A HAT
THE ANH ADA HAT
deletion of M
THE AMA NHA DAH AT
addition of A
Mutations can occur spontaneously or can be caused by mutagens. ex: UV
light, X-rays, chemicals, nicotine, asbestos, base analogs.
VIRUSES:
1.They are -----------------------2. Have either -------------------------------------------------3. Nucleic acid in the center surrounded ---------------------.
4. Can only reproduce inside living cells.
5. Viruses can have a lytic replication cycle or a lysogenic replication cycle.
6. In a lytic cycle, the virus replicates in the cell, makes new viruses, and
lyses the cell to be released.
7. In a lysogenic cycle, the virus enters the cell, integrates itself in the
chromosome and becomes -------------------------------------------Viruses cause diseases in animals and humans. Examples: cold, flu, chicken
pox, hepatitis, polio, herpes infections, Ebola, and AIDS.
Viruses can infect ------------------------------------------------------------------Viruses originally originated from fragments of nucleic acids. Mutations to
the nucleic acids, cause the formation of new strains of viruses that continue
to produce more viruses which are a source of new or emerging infections.
AIDS: caused --------------------------------------------------------------------------------------------------------------------------. These viruses are unique in that
they can change their ------------------------------------------------------------------------------------------------------------------------------------------------------.
They then insert themselves into the genome of the host cell creating a
provirus. This virus destroys ----------------------------------------------, which
are the most important cells in the immune system. The person develops
acquired immune deficiency, which causes major infections and cancers in
that individual.