Chapter 9: DNA and Its Role in Heredity
Vocab:
Bacteriophage – Any of a group of viruses that infect bacteria. Also called phage.
Transformation experiments – A mechanism for transfer of genetic information in
bacteria in which pure DNA from a bacterium of one genotype is taken in through the
cell surface of a bacterium of a different genotype and incorporated into the chromosome
of the recipient cell. (2) Insertion of recombinant DNA into a host cell.
Helix – Shaped like a screw or spring (helix); this shape occurs in DNA and proteins.
Antiparallel – Pertaining to molecular orientation in which a molecule or parts of a
molecule have opposing directions.
Complementary base pairing – The AT (or AU), TA (or UA), CG, and GC pairing of
bases in double-stranded DNA, in transcription, and between tRNA and mRNA.
Template – A molecule or surface on which another molecule is synthesized in
complementary fashion, as in the replication of DNA.
Semiconservative replication – The way in which DNA is synthesized. Each of the two
partner strands in a double helix acts as a template for a new partner strand. Hence, after
replication, each double helix consists of one old and one new strand
DNA polymerase – Any of a group of enzymes that catalyze the formation of DNA
strands from a DNA template.
Replication fork – A point at which a DNA molecule is replicating. The fork forms by the
unwinding of the parent molecule.
RNA primer – a strand of short nucleic acid sequences (generally about 10 base pairs)
that serves as a starting point for DNA synthesis. It is required for DNA replication
because the enzymes that catalyze this process, DNA polymerases, can only add new
nucleotides to an existing strand of DNA.
Primase – An enzyme that catalyzes the synthesis of a primer for DNA replication.
Telomere – Repeated DNA sequences at the ends of eukaryotic chromosomes.
Telomerase – An enzyme that catalyzes the addition of telomeric sequences lost from
chromosomes during DNA replication.
Leading strand – In DNA replication, the daughter strand that is synthesized
continuously.
Lagging strand – In DNA replication, the daughter strand that is synthesized in
discontinuous stretches
Okazaki fragments – Newly formed DNA making up the lagging strand in DNA
replication. DNA ligase links Okazaki fragments together to give a continuous strand.
DNA ligase – Enzyme that unites broken DNA strands during replication and
recombination.
Mutagen – Any agent (e.g., a chemical, radiation) that increases the mutation rate.
Carcinogen – cancer causing agent
Point mutation – A mutation that results from the gain, loss, or substitution of a single
nucleotide.
Silent mutation – A change in a gene's sequence that has no effect on the amino acid
sequence of a protein because it occurs in noncoding DNA or because it does not change
the amino acid specified by the corresponding codon.
Loss of function mutation – A mutation that results in the loss of a functional protein
Gain of function mutation – A mutation that results in a protein with a new function.
Chromosomal mutation – Loss of or changes in position/direction of a DNA segment on
a chromosome.
Deletion – A mutation resulting from the loss of a continuous segment of a gene or
chromosome. Such mutations almost never revert to wild type
Duplication – A mutation in which a segment of a chromosome is duplicated, often by
the attachment of a segment lost from its homolog.
Inversion – A rare 180¡ reversal of the order of genes within a segment of a chromosome.
Translocation – In genetics, a rare mutational event that moves a portion of a
chromosome to a new location, generally on a nonhomologous chromosome
Spontaneous mutation – A genetic change caused by internal cellular mechanisms, such
as an error in DNA replication.
Induced mutation – A mutation resulting from exposure to a mutagen from outside the
cell.
Questions
1. Hershey - proved that DNA carried genetic information / Chargaff - Noticed that
there was a pattern that occurred in the four bases which are: adenine, guanine,
cytosine, and thymine / Franklin - Discovered the DNA double helix / Watson and
Crick - Discovered the Structure of DNA.
2. Bacterial transformation is the genetic change caused by the uptake of naked
DNA to increase the quantity of DNA and taking exogenous DNA from the
environment. Biologist used transformation experiments to check that DNA is
genetic material. They found that adding a DNA sequence from another bacteria
to a certain strand caused that bacterium to transform into the strand of the
bacteria of the DNA that was added.
3. Thymine = 15%, Guanine and cytosine = 35%
4. The ratio of A+G : C+T is always equal in a species because there are equal
amounts od adenine and thymine / guanine and cytosine in DNA.
5. A) the nucleotide base sequence of DNA encodes and stores a lot of information
B) the complementary base pairings allow for replication
C) changes to the linear strand of the sequences of base pairs results in mutation
D) the DNA is copied into RNA by transcription and is translated as proteins
which determine phenotype
6. Semiconservative replication means that a strand of parental DNA acts like a
template for a new one.
Primase is an enzyme that catalyzes the synthesis of a primer for DNA replication
DNA polymerase catalyzes the addition of nucleotides to DNA as its chain grows
Ligase is an enzyme that unites broken DNA strands during replication and
recombination
7. Since DNA strands are anti parallel and DNA replicates in a 5’ to 3’ direction
there are two types of replication: continuous and discontinuous. Continuous
replication happens on the part of the original DNA that is open at the 3’ end.
This way the strand that is being synthesis, the leading strand, is being
continuously made from its 5’ end to 3’. On the other hand, the side of the
original DNA strand going from 5’ to 3’ must have synthesis that happens
discontinuously. There for the daughter strand is call the lagging strand.
8. The point of origin in DNA replication of prokaryotes is at bp ori sequence in the
circular strand. Once a complex bind to this, the DNA unwinds and replicates in
both directions. This makes the DNA divide quickly. Eukaryote DNA synthesis is
much longer. In eukaryotes a DNA primer must attach to the DNA before
replication with DNA polymerase occurs.
9. Adjacent okazaki fragments are linked together by DNA ligase
10. Chromosomes are shortened as we aged because there this a relationship with
shortening telomeres and aging.
11. Telomerase is an enzyme that catalyzes the addition of telomeric sequences lost
from chromosomes during DNA replication. Continuously dividing cells like
bone marrow stem cells and gamete producing cells are particularly dependent on
telomerase.
12. The PCR uses DNA amplification to make various copies of short sequences of
DNA. PCR can be used to identify individuals and detect disease.
13. It uses a sample template of DNA and two synthesizes primers to restrict what is
being copied. Also PCR uses four dNTP.
14.
15. When a person develops cancer as an adult this is a somatic mutation because
germline mutations occur in cells that make gametes and the gametes pass it on.
Since the person did not have cancer until adult hood it could not have been
germline.
16. Silent mutations don’t effect gene expression and function. Most mutations are
silent. Loss-of-function mutations result in a loss of gene expression or make nonfunctional material.
17. Chromosomal mutations are changes in the structure of a chromosome; whereas
point mutations cause gain, loss, or substitution of a single nucleotide.
18. X-rays – avoid the doctor and dentist. UV radiation – don’t go out in the sun
19. Germline mutations provide more material for natural selection because they are
passed on to each generation.
20. Scientist use PCR to amplify the DNA of Neanderthals bones to study their entire
DNA sequence.
21. Neanderthal are now though to have looked very similar to humans becase we
share many of the same genes.
22. (6x10^9)*(1.1x10^-9) = 6.6 mutations per child
Most mutations are silent.