unit exam 1 Flashcards
(132 cards)
1
Q
What is biological diversity?
A
reflects an interaction between the forms that preceded them and an ongoing process of change
2
Q
All species are temporary what is as much a part of nature as is the formation of new species ?
A
extinction
3
Q
What are the requirements for evolution (by natural selection)?
A
- Variation in a population
these can be phenotypes, traits, ext.
- in between variation and increased survival or reproduction is SELECTIVE PRESSURE this is needed for evolution, this can be seen in terms of availability or avoid being the food
- increased survival or reproduction
- Inheritance of traits
this can be inheritance to next generation/offspring
- from inheritance of traits to variation in a population is MUTATIONS
- mutations increase evolution/population
- repeats back to variation
- variation shrinks overtime due to selective traits
4
Q
what is the definition of genetics?
A
study of heredity and variation in cells, individuals and populations
5
Q
what is the definition of a gene?
A
functional unit of heredity and variation (hence genetics is simply the study of genes)
- also the DNA sequence that is involved in making RNA and protein
6
Q
what is molecular genetics?
A
is the “study of structure and function of genes at the molecular level”
7
Q
what is the definition of alleles?
A
variant forms of a gene caused by differences in DNA sequence (e.g variation in eye colour, height)
8
Q
what is the definition of a genotype ?
A
gene(s) inherited by an organism
9
Q
what is the definition of a phenotype?
A
visible traits (e.g body plan, behaviour, illnesses/diseases)
10
Q
what is the definition of a genome?
A
entire DNA sequence (ACGT) of an organism
11
Q
what is gene expression?
A
Genes: found on chromosomes and are parts of the genome that encode RNA and protein
gene expression= “turning on” a gene to produce RNA and protein (coding gene)
12
Q
what is protein expression? and what do protein determine?
A
the type and abundance of protein in the cell.
- Although DNA is the information molecule that directs protein expression, proteins ultimately determine the phenotype of the cell because they control every reaction in the cell
13
Q
what are enzymes?
A
catalyzing the synthesis and transformation of all biomolecules
14
Q
what are structural proteins?
A
they are the proteins used for maintenance of cell shape
15
Q
what are signalling proteins?
A
these are proteins used for hormones and receptors
16
Q
what factors make individuals different from one another?
A
This is known as phenotypic variation
- different alleles ( the slight difference in gene sequence can result in changes in the amino acid sequence of proteins) - the genotype
- different regulation of gene and protein expression
17
Q
when will similar protein expressions and phenotypes occur?
A
when individuals possess common alleles and gene regulation
- this can be immediate family, relatives
18
Q
what are some ways studying molecular genetics important?
A
human health, forensics, agriculture, environment, and evolutionary biology
19
Q
differentiate the differences between proteins and nucleic acids (DNA) when the candidates is chromosomes?
A
PROTEINS:
-20 subunit variants (amino acids)
- majority component of chromosomes (~50-60%)
- many chemical properties and secondary structure
- enzyme activity
NUCLEIC ACIDS (DNA)
- 4 subunit variants (nucleotides)
- minority component of chromosomes (~40-50%)
- few chemical properties and low 2 degree structure
- functionally inert
20
Q
What were the three classical experiments ranked in order to establish DNA as the hereditary molecule?
A
- Griffith: found a substance that could genetically transform streptococcus pneumonia ( one strain to another strain)
- Avery, Macleod and McCarty: identified DNA as the molecule that transforms rough S. pneumonia to the infective form
- Hershey and Chase : found the final evidence establishing DNA as the hereditary molecule
21
Q
what is strepococcus pneumoniae?
A
bacterial pathogen that causes pneumonia in mammals
22
Q
what is smooth strain (S)?
A
bacterium is surrounded by a polysaccharide capsule ( this interacts in respiratory trait in animals)
- the capsule protects the S strain from the immune system, thereby allowing infection
23
Q
what is rough strain (R) ?
A
lacks polysaccharide capsule, cannot evade the immune system, thereby is known as non-virulent
- this is a mutation in the gene so it cant get in/invade the immune system
24
Q
Explain the Griffith experiment? What was his conclusion?
A
he basically had to bacteria one that was virulent, and one that was nonvirulent.
- the mouse with virulent (SMOOTH) bacteria died of pneumonia and the mouse with the nonvirulent bacteria (ROUGH) remained healthy.
- he then heat killed the virulent bacteria. the mouse remained healthy
- he then mixed dead virulent bacteria (SMOOTH) with nonvirulent bacteria (ROUGH) this transformed the rough cells to virulent cells, it caught something in the environment changing the phenotype of these cells
CONCLUSION:
some molecules (TRANSFORMING PRINCIPLE) released when S cells were killed could transform living R cells genetically to the virulent S form
- transformation was permanent and heritable ( all progeny cells in the colony were the same type)
25
Explain the Avery, Macleod, and McCarty experiment?
Hypothesis, experimental approach, and conclusion
there main concept was the question what is the chemical nature of the transforming principle?
HYPOTHESIS: transforming principle could be protein, DNA or RNA- which one?
EXPERIMENTAL APPROACH: eliminate each type of molecule in S cells and see whether transformation of R cells into the S virulent form still occurs
CONCLUSION: if type of molecule is absent, and transformation is gone, then this molecule is the transforming principle
26
what is the life cycle of a virus (bacteriophage)?
1. infection : massive reproduction of a virus resulting in host cell lysis (virulent)
2. Viral DNA replicates separately from bacterial chromosome
3. Lysogenic cycle replication of viral genome (latent)
4. Viral DNA is integrated into the bacterial chromosome.
5. Lysogeny can switch to lytic cycle if viral DNA is excised from bacterial chromosome
27
explain the lytic pathway in detail?
after the circularization of viral DNA, the viral DNA hijackes cellular bacteria and produce more protein
- there is a replication of viral DNA, RNA and protein; bacterial chromosome degradation
- then there is an assembly into progeny viral particles
- cell lysis and mature phage are released they rupture
28
explain the lysogeny pathway in detail?
- Viral DNA inserts into bacterial chromosome by recombination (Prophage)
- Prophage hitches a ride and replicates; viral genes are inactive
- prophage is inherited in bacterial daughter cells
29
explain the Hershey and Chase experiment?
there main concept was: Does the bacteriophage inject DNA or protein into E.coli?
1. label bacteriophage DNA and proteins with radioactive isotopes 32P and 35S respectively
2. allow infection of E.coli with radioactive bacteriophage
3. separate attached bacteriophage and E.coli with blender (NO CELL IS RUPTURED)
4. look for presence of 32P (DNA) and 35S (PROTEIN) in detached bacteriophage, E.coli cells and progeny bacteriophage (not shown)
RESULTS:
- There was no 35S in E.coli cells, 35S found in detached bacteriophages; no 35S in progeny bacteriophage (NOT HERITABLE)
- 32P in E.coli ; no 32P found in detached bacteriophages; 32P in progeny bacteriophage (HERITABLE)
30
Explain how gene expression produce a phenotype?
Gene expression involves the transcription of DNA into mRNA followed by translation of mRNA into proteins, determining which proteins are produced and in what quantities. Protein expression, a critical outcome of gene expression, directly influences cellular functions and processes, ultimately shaping an organism's phenotype through the proteins' roles in metabolism, structure, signaling, and regulation within cells and tissues. Thus, the intricate regulation and coordination of gene and protein expression are fundamental to the manifestation of observable traits and characteristics in living organisms.
31
explain how alleles, as well as differential regulation of gene and protein expression can cause a variation in phenotype?
Alleles are different versions of the same gene that can lead to variations in protein structure or expression levels. Differential regulation of gene and protein expression means that genes can be turned on or off, or their expression levels can be adjusted, influencing which proteins are produced and in what amounts. These variations in alleles and regulatory mechanisms can lead to differences in phenotype, such as differences in appearance, behavior, or susceptibility to diseases among individuals
32
What is the function of the gene involved in transforming R cells to S cells?
The gene responsible for transforming R cells to S cells is typically a gene encoding a capsule in bacteria like Streptococcus pneumoniae. The capsule gene allows bacteria to produce a protective polysaccharide capsule around themselves. This capsule enhances the bacteria's ability to evade the host immune system by preventing phagocytosis, ultimately increasing the bacteria's virulence and ability to cause disease
33
design an experiment that would test if lipids were the tranformation molecule?
To test if lipids could be the transformation molecule, you could design an experiment where R cells (non-virulent strain) are exposed to purified lipids extracted from S cells (virulent strain). Control groups could be exposed to lipids from non-virulent strains or no lipids at all. After exposure, assess the transformation by observing any phenotypic changes indicative of virulence, such as capsule formation or increased pathogenicity in animal models. Analyzing gene expression related to capsule production could also provide insights into the mechanism of transformation.
34
what are the components of DNA?
1. PENTOSE SUGAR:
- ribose (RNA) or deoxyribose (DNA)
2. Nitrogenous Base
- Purine (Guanine; Adenine) or
- pyrimidine (cytosine;uracil; thymine)
3. Phosphate
35
How do pentose sugars differ from DNA to RNA?
The two sugars for RNA and DNA only differ in the type of chemical group bound to the 2' carbon
36
What do the Nitrogenous bases of DNA and RNA consist of?
whats the pairing rule?
DNA: A,C,G,T
RNA: A,C,G,U
A-T
G-C
with rna its the same except
A-U
37
what are adenine and guanine known as, and what is thymine and cytosine known as?
adenine and guanine is known as purines
and
thymine and cytosine is known as pyrimidines
38
what did Watson and Crick discover ?
1. two strands of the phosphate-pentose backbone spiral as a double helix about a common axis
2. the two strands run antiparallel (one strand is 5'-3' direction while the other strand is 3'-5')
3. A purine on one strand is always base-paired with a pyrimidine ( fits chargaffs rule and the 2 nm diameter of the double helix)
4. studying their model, they saw that the backbone (exterior) is hyrophilic; the bases (interior) are hydrophobic
39
what are some factors we need to consider that makes the structure of the DNA DOUBLE HELIX?
- base pairing is COMPLEMENTARY and therefore base pair sequence on one strand can be used to specify the sequence of the other strand
- base pairs are STACKED flat lying perpendicular to the axis and contribute to stability of double helix (hyrdophobic wanderwalls)
- hydrogen bonding between bases keeps two strands intact
40
How many hydrogen bonds does guanine and cytosine have?
and how many adenine and thymine hydrogen bonds have?
G-C= 3 BONDS
A-T= 2 BONDS
41
How can we create nucleic acid hybridization?
annealing (which means heating or cooling) of single strands of DNA or RNA by forming H-bonds
- highly specific (two strands must be complementary in sequence), temperature-driven and concentration-dependent
- Hybrids can be formed through denaturing conditions such as heat, alkali
- or cooling down which is known as reannealing
- it can also denature and add RNA
- RNA hybridizes to complementary DNA strand
42
What was the watson and crick's model of DNA replication?
- complementary base pairing allows parental strands to act as templates for DNA replication of new strands
- parental strands can unwind by breaking the hydrogen bonds between bases
43
what is semiconservative replication?
where the double helix will contain a parental strand and a newly synthesized strand
44
How is DNA organized in prokaryotes and eukaryotes?
-In prokaryotes, DNA is organized into a single, circular chromosome located in a region called the nucleoid. In eukaryotes, DNA is organized into multiple, linear chromosomes contained within a membrane-bound nucleus, with DNA wrapped around histone proteins to form chromatin.
45
what is a chromatin?
a given region of DNA with its associated proteins on a chromosome
46
chromonsomes can either be what?
linear or circular
47
prokaryotes typically have what when DNA is organized?
one chromosome (predominantly circular) and other small independent circular DNA called plasmids in the cytoplasm
48
eukaryotes chromosomes look like what, and where can they be found?
linear and enclosed in a nucleus
49
what is an essential component of eukaryotic chromosomes?
- the chromosomes need to be fully duplicated (DNA REPLICATION) and properly transmitted to each daughter cell during mitosis/meiosis
50
what are the three components of a eukaryotic chromosome structure ?
1. origins of replication
2. centromeres
2. telomeres
51
what is the role of the origin of replication in eukaryotic chromosomes?
DNA sequences along chromosome which initiate DNA replication
52
what is the role of the centromere in eukaryotic chromosomes?
DNA sequences required for correct segregation of chromosomes by directing formation of the kinetochore in which the mitotic spindle attaches
53
what is the role of the telomeres in the eukaryotic chromosomes?
DNA sequences located at the ends of the chromosome that prevent degradation and allow proper replication of the chromosomal ends
54
55
what is the majority of eukaryotic cells ?
they are diploid ( two copies of each chromosome= homologous chromosomes)
- mostly identical, centromere same place, size, position of genes are also the same)
56
what does it mean when a chromosome is said to be diploid?
an organism or cell with two copies of each type of chromosome in its nucleus
57
what does it mean when a chromosome is haploid?
an organism or cell with only one copy of each type of chromosome in its nuclei
58
what is a ploidy?
the number of chromosome sets of a cell or species
59
which cells only have a haploid genome?
sexually reproductive cells
60
Can a eukaryote be a polyploid if so why? and what are some examples
yes, but only few. it can have a > 2 chromosomes sets such as large protists
protists are single celled and contain many sets of chromosomes
- it results from incorrect meiosis, fertilization or cell division
61
what are the reasons for DNA being organized as chromosomes ?
1. chromosomes compact DNA so that it can fit into the cell/nucleus
2. chromosomal structure protects DNA from damage (naked DNA is very unstable)
3. chromosomes can be easily separated and transmitted to each daughter cell during cell division. makes sure each daughter cell gets the right amount of DNA
62
in humans what is the total length of DNA in a diploid cell?
is about 2 meters
- the nucleus is only 10-15 micrometers in diameter, so DNA needs to be compacted around 10,000 times to fit inside
63
what are histones? how does it interact with DNA?
they are basic, positively charged proteins that DNA wraps around
- DNA is negatively charged due to tis sugar-phosphate backbone, so it easily interacts with the positively charged histones
64
what is a nucelosome?
a nucleosome is a complex of eight histone proteins (two each of H2A, HSB, H3, AND H4) dont need to memorize
- about 147 base pairs of DNA wrap around this histone octamer, forming the basic unit of DNA packing
65
what is histone H1?
this histone binds the DNA between nucleosomes and helps pack them into a more compact structure called the 30 nm chromatin fiber
66
What is the difference between prokaryotes vs. eukaryotes when it comes to histones?
prokaryotes (like bacteria) do not have histones. Instead, they have other positively charged protein associated with their DNA.
- bacterial chromosomes do not need to be as tightly packed as eukaryotic chromosomes because bacteria have smaller genomes.
67
label each part
68
is it true that DNA packing/ compaction along the chromosome is not uniform?
yes its not even across the entire chromosome
69
What is a euchromatin region?
on a chromosome these are regions with lower DNA compaction and genes are actively expressed
70
what is a heterochromatin ?
are chromosomal regions of high DNA compaction where gene expression is silenced.
71
why are some regions of gene expression silenced?
they have tightly compact and there is less exposure to genes trying to come in
72
what is a constitutive heterochromatin ?
these are regions where DNA is always highly compacted. (CENTROMERES AND SUB-TELOMERIC REGIONS), THESE ARE AREAS WITH NO ACTIVE GENES PRESENT
73
what is a facultative heterochromatin?
can switch to euchromatin depending on cell type and during development
74
how can you identify the 5' and 3' ends of a double stranded piece of DNA?
The 5' end has a phosphate group (P) not attached to another nucleotide.
The 3' end has a hydroxyl group (OH) on the sugar.
75
explain how Watson and Crick combined their molecular modelling approach with other sources of data, to solve the structure of DNA?
Watson and Crick combined their molecular modeling approach with critical data from other scientists to solve the structure of DNA. They used Erwin Chargaff's rules, which indicated base pairing, and Rosalind Franklin's X-ray diffraction images, which revealed the helical structure. Integrating these insights, they built a three-dimensional model showing the double helix with complementary base pairs, explaining DNA's ability to replicate accurately.
76
describe the main differences between chromosomes in prokaryotes and eukaryotes
Structure:
Prokaryotes: Typically have a single, circular chromosome that is not enclosed in a nucleus. It is found in a region called the nucleoid.
Eukaryotes: Have multiple, linear chromosomes contained within a membrane-bound nucleus.
Packaging:
Prokaryotes: DNA is relatively less packaged and is associated with fewer proteins, primarily nucleoid-associated proteins.
Eukaryotes: DNA is highly packaged around histone proteins to form chromatin, which further condenses into chromosomes during cell division.
Replication Origin:
Prokaryotes: Generally have a single origin of replication where DNA replication begins.
Eukaryotes: Have multiple origins of replication along each chromosome to facilitate the rapid copying of their larger genomes.
77
label the DNA structure
78
79
describe how chromatin is organized in eukaryotes and their effects on gene expression
In eukaryotes, chromatin is organized into nucleosomes, where DNA is wrapped around histone proteins, forming a beads-on-a-string structure. These nucleosomes further coil into a 30-nanometer fiber and higher-order structures, compacting the DNA within the nucleus. Chromatin organization affects gene expression by regulating accessibility; tightly packed heterochromatin is generally transcriptionally inactive, while loosely packed euchromatin is more accessible for transcription and active gene expression.
80
what are the different models of DNA replication?
semiconservative
conservative
dispersion
81
what is a semiconservative model of DNA replication?
each daughter strand remains paired with its complementary parental strand
82
what is the conservative model of DNA replication consist of?
after replication, both daughter strands pair up
83
what is the dispersion model of DNA replication?
daughter strands will have a mixture of parental and newly-synthesized DNA
84
what is a semiconservative model?
know that DNA replication produces molecules with one old and one new strand
85
what is the Meselson and Stahl experiment?
to determine how DNA replicates.
the method was to use nitrogen isotopes 15N and 14N to label DNA and track parental and newly synthesized strands over several generations
1. initial labelling: bacteria are grown in a medium with 15N (heavy nitrogen) which gets incorporated into the DNA
2. switch to 14 N medium :
bacteria are then transferred to a medium with 14N (light nitrogen) and allowed to replicate
3. DNA analysis after each replication
- after one round of replication: DNA is a hybrid with one strand of 15N and one strand of 14N
- after two rounds of replication: half of the DNA is hybrid (15N/14N)
and half is fully 14N (light)
key findings: after one replication cycle, DNA is hybrid. After two cycles, you get both hybrid and light DNA
86
what direction does DNA synthesis occur?
in the 5'-3' direction
- nucelotides can only be added to the new strand at the 3'-OH end
87
what are the properties of DNA polymerases?
- synthesizes the new strand only in the 5'-3' direction ( it can only add new bases to the 3-OH' end of the existing strands)
- cannot synthesize a new strand
- requires a RNA primer with a 3'-OH for synthesis
- DNA polymerase has a single active site that can catalyze the incorporation of all four nucelotides
88
what is a primer?
a short RNA segment that initiates DNA synthesis
89
what is a single active site in a a DNA polymerase ?
the part of the enzyme that can process different nucleotide substrates
90
what direction is a DNA read?
from 3'-5' but is synthesized in the 5' to 3'
91
what is a replisome?
molecular machine of enzymes that replicate DNA
92
what is the job of the helicase enzyme?
An enzyme that untwists the double helix of DNA at the replication forks helix by breaking
the hydrogen bonds
- unwinds double helix, RNA primase lays down RNA primer
92
what is the role of the single-strand binding protein?
it stabilizes the single strands before replication by preventing reannealing so that the strands can serve as template
92
what is the job of the primase DNA replication enzyme?
makes a starting point (primer) for synthesis
-synthesized RNA primers for DNA polymerase
92
what is the role of DNA ligase?
- joins the ends of DNA segments by forming phosphodiester bonds
- seals the DNA fragments together
- seals the nicks by reforming the phosphodiester bond
92
What is the DNA polymerase III as a DNA replication enzyme?
synthesizes DNA by adding nucleotides to the new DNA strand it builds new DNA
- extends RNA primer
92
What is the role of DNA polymerase I? as an enzyme
replaces RNA primer with DNA
- removes RNA primer and fills the gaps with DNA
- removes RNA primer of Okazaki fragments and fills in gap with dNTPs
93
What are the key things we need to know about the replication forks, and the sites of DNA synthesis?
- synthesizes if the two strands from the template strands occurs concurrently at the forks
- however, because DNA polymerase can only synthesize in the 5'-3' direction
- one new strand is synthesized continuously (leading strand)
- while the other new strand is synthesized discontinuously (lagging strand) in small DNA fragments (Okazaki fragments)
93
what is DNA topoisomerase/gyrase as a DNA replication enzyme?
removes super coils that form ahead of the replication fork, relieves torque of mainly circular
DNA
- prevents twisting ahead of replication fork during unwinding
93
what is the role of the sliding clamp for DNA replication?
attaches DNA pol III to DNA template, replication is more efficient
- holds DNA Polymerase III in place
94
95
96
97
98
what are the three steps to DNA replication of bacterial chromosomes?
1. inititation
2. elongation
3. termination
99
what is initiation for DNA replication of bacterial chromosomes?
unwinding and separation of the two template DNA strand at the origin of replication
100
what is the role of Elongation of DNA relication of bacterial chromosomes?
simultaneous synthesis of the two new DNA strands from the template strands by DNA polymerase
101
what is the role of termination during DNA replication of bacterial chromosomes?
DNA replication stops when reaches a termination site or at the end of the chromosome (for circular and linear DNA, respectively)
102
lable the parts of DNA of bacterial chromosomes
103
Explain the key points of DNA replication of eukaryotic chromosomes?
- have to deal with much larger genomes and linear chromosomes
- there are multiple origins along the chromosome so that DNA replication can be completed on time during S phase
- DNA replication proceeds in opposite directions away from the origin
- complications replicating the ends of linear chromosomes
104
Draw out how DNA replication is happening at a fork for eukaryotic?
- leading is always from 3' to 5; but synthesises 5' to 3'
- lagging is the opposite way going from 5' to 3' but in lagging strands or okazaki fragments
105
what is a polymerase chain reaction or PCR?
Polymerase Chain Reaction (PCR) is a technique used to amplify a specific segment of DNA, making millions of copies from a small initial sample. It involves repeated cycles of heating to separate the DNA strands, cooling to allow primers to attach, and using DNA polymerase to replicate the DNA. This process enables researchers to analyze the amplified DNA in various applications, such as genetic testing and research.
106
what are some places where pcr takes place?
genetic fingerprinting
- genetic engineering (cloning)
- sequencing genomes
- phylogenetic analysis
- Diagnosis of hereditary diseases
107
what is the dilemma to replicate ends of linear chromosomes ?
- RNA primer : DNA synthesis needs an RNA primer to start, which creates a problem at the 3' ends of linear chromosomes
Gap at chromosome ends: no DNA polymerase can fill in the gaps where the RNA primers were removed at the ends of chromosomes
- Additive loss: each round of DNA replication leads to a loss of a small portion of DNA from the ends of chromosomes (telomeres)
108
what is the solution to end the replication problem (telomeres)?
- noncoding single stranded DNA added to the 3' end of chromosomes by Telomeres
- usually repeats of 5-8 G's and T's
- telomeres will be worn away after each DNA/ cell division
- when the telomere region is gone, the cell stops dividing
109
what is telomerase
is an enzyme that restores shortened telomeres
110
Is telomerase present in most eukaryotic cells
no
111
what happens to telomeres when you get older vs younger?
telomeres shorten in older indiviudals potentially leading to natural death
- newborns have longer telomeres
112
are telomeres present in gametes?
yes and stem cells
113
how can some cancers be treated with tolomerase?
many cancers aquire mutations to activate telomerase to negate the limitations of rapid cell division
- some time there are anticancer therapeutics: telomerase inhibitors or telomerase vaccine
114
what is fedelity?
refers to the accuracy with which DNA is copied during replication
high fedelity means that the DNA is replciated with very few errors, ensuring genetic stability and proper functions
115
what are some consequences of low fidelity?
erros in DNA replication can lead to defective genomes
- this can result in diseases such as cancer and can be fatal to the organism
116
what is the role of telomeres?
helps ensure that the ends of linear chromosomes are fully replicated, preventing the loss of genetic information
117
what is the error rate and repair mechanisms for high fidelity of DNA replication?
DNA repair mechanisms work with enzyme complexes to keep the error rate extremely low
118
what are the proofreading activities of DNA polymerases?
1. synthesis direction - DNA polymerase III synthesizes new DNA in the 5' to 3' direction
2. optimal conformation: the active site of DNA polymerase III is shaped to add the correct nucleotide
3. Error detection and removal: DNA polymerase III can detect mistakes (mismatched nucleotides)
- it uses its proofreading activity to remove the incorrect nucleotide
4. Correction and continuation
- after removing the wrong nucleotide, DNA polymerase III adds the correct one and continuous DNA synthesis
5. High fidelity: polymerases with proofreading abilities significantly reduce the error rate
119
what is the purpose of DNA mismatch repair?
purpose: corrects replication errors that escape the proofreading activity of DNA polymerase
120
what are the steps of DNA mismatch repair?
1. recognition: MutS and MutL proteins recognize and bind to the mismatched DNA
2. Nick creation: MutH endonuclease makes a cut (nick) on the newly synthesized daughter strand near the mismatch
3. Excision: Exo1 exonuclease removes a section of the daughter strand that includes the mismatched nucleotide
4. synthesis: DNA polymerase III fills in the gap by adding the correct nucleotides using the template strand
5. sealing: DNA ligase seals the nick, completing the repair
MutS and MutL: Find the mismatch
MutH: cuts the DNA near the mismatch
Exo1: removes the incorrect section
DNA polymerase III: replaces the correct nucelotides
DNA ligase: seals the repaired DNA
121
what are nucelosides?
molecules of a sugar and a base
122
what is a ribonucleoside?
A ribonucleoside is a molecule consisting of a nitrogenous base (adenine, cytosine, guanine, or uracil) attached to a ribose sugar. It is a fundamental component of RNA (ribonucleic acid).
123
what is a deoxyribonucleotide vs deoxyribosnucleoside?
A deoxyribonucleotide is a molecule composed of a nitrogenous base, a deoxyribose sugar, and one or more phosphate groups. A deoxyribonucleoside, on the other hand, consists of only a nitrogenous base and a deoxyribose sugar, without any phosphate groups.
124
what is a nucelotide?
nucleoside molecule and a phosphate
- the phosphate group is attached to a carbon- 5 of the ribose and deoxyribose sugars
125
what is the chargaff rule?
analyzed overall quantities of the four nitrogenous bases in various organisms
charguffs rule: %A=% T. %C=%G
1. %purines (A+G) = % PYRIMIDINES (C+T)
2. C+G CANNOT EQUAL A+T
3. A, C, G AND T are not present in equal amounts
