lecture one Flashcards
1
Q
What makes up a chromosome
A
dna and protein
2
Q
What is interphase composed of
A
G1 phase
S phase - synthesis
and G2 phase
3
Q
What happens in each step of interphase
A
In G1 the cell grows
In synthesis, chromosomes are copied
In G2 both copies continue to grow
4
Q
What happens in M-Phase
A
The cell divides, and since in synthesis the chromosomes are doubled, each cell has their own set of chromosomes
5
Q
Describe what happens in g2 of interphase carefully
A
The nuclear envelope surrounds nucleus
The centrosome is composed of two centrioles
The chromatid is not condensed yet and therefore not yet visible
6
Q
What happens in prophase
A
the centrosomes begin to move to opposite poles
The chromosomes begin to condense begin to be seen
the early mitotic spindle forms
7
Q
What happens in prometaphase
A
The centrosomes are now at opposite poles of the cell
the nuclear envelope is in pieces
the microtubules attach to the chromosomes that have broken out of the nuclear envelope
8
Q
What are the different types of microtubules
A
The kinetochore microtubules are the microtubules that are attached to the chromosomes
The microtubules not attached to chromosomes are called non-kinetochore microtubules
astral rays stick out from the centrosomes
9
Q
What happens in metaphase
A
The chromosomes all line up on the mitotic plate
centrosomes are at opposite poles
10
Q
What happens in Anaphase
A
The sister chromatids that make up a chromosome are pulled apart to opposite poles of the cell by kinetochore microtubules
lkinetchore microtubules shorten
the cell elongates because as the kinetochore microtubules shorten, the non-kinetochore microbules grow
11
Q
What happens in telophase
A
Two nuclei begin to form, nuclear envelopes begin to piece back together from their fragments
chromosomes begin to fade from the eye, becoming less condense
the spindle microtubules are depolymerized
Then cytokinesis happens and the cells are pinched from one another, resulting in a two copies of the first cell
12
Q
What is a gene’s locus?
A
A locus is a location. A gene’s locus is the location or place of the genes on a chromosome
13
Q
How many human chromosomes in a single cell?
A
46! and 2 are the sexual chromosomes
There are 22 pairs of homologous chromosomes and one pair of sex chromosomes
14
Q
Where do a person’s chromosomes come from
A
Humans inherit one chromosome from each pair of chromosomes from each parent
15
Q
what is a gamete
A
A human gamete is a sex chromosome that is a haploid cell (23 chromosomes)
16
Q
What makes a zygote
A
Two gametes: an egg and a sperm cell
17
Q
What is the human life cycle
A
cells from ovaries and testicles go through meiosis so they get rid of half of their chromosomes, then they become eggs and sperm, then they fertilize making a zygote. This zygote then goes through mitosis and then development before the cycle repeats
18
Q
What does one regular cell become when it goes through meiosis?
A
4 daughter cells (n)
19
Q
Meiosis I - prophase I
A
spindle formation
envelope breakdown
chromosomes are slightly crossed over at chiasmata (site of crossover)
20
Q
Metaphase I
A
Pars of homologous chromosomes are at the metaphase plate, (opposite pair together)
21
Q
Anaphase I
A
Breakdown of proteins holding chromosomes
the chromosomes begin moving to opposite poles
22
Q
Telophase I and cytokinesis
A
each half of cell has 23 chromosomes
cytokinesis forms two haploid daughter cells
23
Q
Meiosis II - Prophase II
A
spindle apparatus forms
chromosomes start moving towards metaphase II plate
24
Q
Metaphase II
A
Chromosomes at Metaphase II plate
because of the crossing over, the sister chromatids in each chromosome are not identical
The kinetochore microtubules are attached to sister chromatids
25
Anaphase II
Breakdown of protein at centromeres allows the sister chromatids to separate and move towards opposite poles
26
Telophase II and cytokinesis
Nuclei form
chromosomes begin to decondense
cytokineses pinches the cell into two cells
27
The end of meiosis: result
4 daughter cells (n) came from one parent cell (2n)
28
character
A heritable feature that varies among individuals
| ex: hair colour
29
trait
Each varient for a character is a trait
| ex: brown, blonde, red hair colour
30
Medel's Laws?
Law of segregation and the law of independant assosrtment
31
Explain the law of segregation
The alleles for a heritable character segregate during gamete formation and end up in different gametes
32
Explain law of independant assortment
Each pair of allels segregate independantly from other par of alleles during gamete formation
33
Deviations from mendels laws? (7)
1) some traits not on nuclear chromosomes
- -> sometimes traits determined from mitochondrial or chloroplast chromosomes
2) traits on the same chromosome
- -> what happens if crossing over doesn't happen
- -> linked genes do not separate during formation of gametes
3) Traits carried on sex-chromosomes
- -> X, Y, Male or female
4) incomplete dominance
- -> heterozygous is combo of both
- -> dominant isn't completely expressed
- -> red and white alleles make pink
5) co-dominance
- -> two alleles affect phenotype in separate distinguishable ways
- -> speckled chickens
6) Multiple alleles
There can be multiple genotypes for the same phenotype
--> Type A blood is IAIA or IAiA
7) lethal alleles
- -> immediate death
34
Autosomal and sex chromosomes?
22 pairs autosomal chromosomes
1 pair sex chromosomes
makes 23 pairs of human chromosomes total
35
what are abnormal numbers of chromosomes caused by?
Nondisjunction
36
What is nondisjunctino
Where chromosomes that are in a pair do not move apart during some stage in meiosis I or sster chromatids fail to seperate during meiosis II
37
What is the result of nondisjunction?
One chromosome receives both chromosomes of one pair/type while the other receives no copy
38
What does Aneuploidy mean? What are its subtypes?
zygote with abnormal number of a particular chromosome
- subtypes
- monosomic (2n-1) - trisomic (2n+1)
39
What does polyplidy mean? subtypes?
Means the organism has more than two complete chromosomes sets
subsets
- triploidy (3n) - tetraploidy (4n)
40
What is Klinefelter syndrome
XXY sterile male with female body characteristics
41
What is Turner syndrome?
XO sterile female, short stature and immature sex organs
42
XXX syndrome
associated with learning difficulties; fertile
43
XYY syndrome
associated with behavioral difficulties; fertile
44
Explai single gene diseases
Casued by a mutant gene
mutant gene may be on one chromosome of a homologous pair or on both chromosomes
ex cystic fibrosis
huntingtons disease sinckle cell amenia
45
Questions clinical genesist must ask themselves?
Autosomal or sex-linked?
--> if it's sex-linked it will be predominatley in males
Dominant or recessive trait?
---> if dominant, every affected will have an affected parent
Caused by single or multiple gene?
--> if single, heterogenous parents will have 25% of their kids affected
46
Discovery of DNA material
1) Miescher isolates nuclein
2) Fred Griffin demonstrates transformation of bacteria
3) Oswald avery purifies the transforming principle of bacteria
4) Hershey-Chase experment shows that DNA = genes
5) Watson and crick report the structure of DNA
6) Meselson and stahl determine DNA replication is semiconservative
7) Arthur Koberg and others deduce the molecular components of DNA replication
47
Fred Griffins experiment demonstarting transformation of bacteria
living S cells and R cells and heat killed S cells
- the s train alive, was virulent
He mixed the heat-killed S cells and the harmless living R cells
- -> R- cells did not mutate
- -> The R-cells had been TRANSFORMED: a permanent change in their hereditary system in the R-Strain of the bacterium
48
Oswald Avery purifies the transforming principle DNA
Blender
-Sulfur in Protein
-Phospherous in DNA
Sulfur labeled protein and phospherous labeled DNA infected cells, he blended them, he centrifuged them
Phosphorous was found in cells but sulfur was not
--> DNA is genetic material
49
Watson and Crick report the structure of DNA
DNA is Double Helix
DNA strands are complementary with nitrogeous bases fitting long it
DNA strands run in opposite directs, antiparallel
Basic replication idea, the complementary stands seperte, became templates, complamentary nucleotides line up, new DNA strand attached to old DNA strands --> product: two DNA strands
50
Meselon and Stahl determine DNA replication is semiconservative
3 models proposed :
- semiconservative (two strands seperated, new DNA matches)
- conservative (DNA strays together, whole other DNA replicates)
- dispersive (Parts of the old strands fuse together with parts of new strand creating fused old and new DNA strands that match together)
51
What as the theoretical basis for Meselon and Stahl's experiment?
DNA incorporated with heavy nitrogen isotope (15N) would be separated from SNA incorporated with the light isotope of nitrogen (14N) during density gradient centrifugation
52
Watson and Crick report structure of DNA:
DNA is a polymer of nucleotides
53
Nucleotide
5-carbon ribose (sugar) group
Phosphate group on 5' carbon of ribose
A base on 1' carbon of ribose
A base could be...
- adenine "A"
- thymine "T"
- guanine "G"
- cytosine "C"
54
There are two types of Nucleic Acids
DeoxyribNucleic Acid - DNA
- double stranded molecule
RiboNucleic Acid - RNA
- single stranded molecule
55
The chemical difference between DNA and RNA
DNA has deoxyriboses
RNA has riboses
RNA has the base Uracil while DNA has thymine
56
Bonds between base pairings
Thymine and adenine - double bond
| Guanine and cytosine - triple bond
57
Direction of DNA structure
Strands curl up to the right
| Stands are antiparellel
58
DNA replication
- begins at "origin of replication" (short stretches of DNA with a specific sequence of nucleotides)
- proteins that initiate DMA replication, recognize the origins of replication and attach
- the proteins that have attached create a bubble between the complementary DNA strands
- Replication process in BOTH DIRECTIONS until the entire molecule is occupied
- At the end of a replication bubble between the DNA strands is a replication fork
59
What happens if the DNA molecule is incredibly long?
DNA replication bubbles happen at different site on molecule and eventually join up creating one large bubble until the entire molecule is occupied
60
What is a replication fork?
a y- shaped region where the parental strands of DNA are being unwound- several different proteins participate in this unwinding: Helicases and Topisomerase
61
What are helicases?
Proteins.
| Enzymes that unwind the double helix/ parental strands
62
What happens to the parental strands as they untwist?
They become templates from a new complementary strand to form onto
63
Detailed description of the unwinding?
While unwinding, the parent strands will what to repair again, to keep this from happening, single strand binding proteins bind to the newly unpaired DNA strands to stabilize them
64
What is the protein topoismerase's role in the unwinding of DNA?
While the parental DNA strands unwind, the wound part ahead of the replication fork gets tighter and tighter creating tension.
Toposiomerase helps relieve this tension by breaking, swiveling and then rejoining the DNA strands to themselves
65
OKay, so now the Parental DNA strands are unwound and are no templates..... so.....
We need DNA polymerases as it catalyzes the synthesis of DNA by adding nucleotides to a preexisting chain
66
What does DNA polymerase need?
a primer
| a DNA template strand
67
What is a primer?
a short RNA chain that can be synthesized by the enzyme primase
- 5-10 nucleotides long
- goes in 5' to 3' direction
68
Why does DNA polymerase need a primer?
The enzyme DNA polymerase cannot make DNA out of thin air. However, it can build off of something by adding nucleotides to an existing chain that is already base-paired with the template DNA strand
69
What is Primase's role?
Primase synthesizes the primer (short strand of RNA) starting off with a single RNA nucleotide. Primase then adds nucleotides one by one using the DNA strand as a template
70
What happens after Primase makes the Primer?
DNA polymerase can now build a new DNA strand from the primer
71
Where do the nucleotides that are being added to the growing chain come from?
Each nucleotide comes from a nucleotide triphosphate (nucleotide (a sugar and base) and three phophates
72
What nucleotide triphosphates ?
A nucleotide (composed of a sugar and a base) and three phosphates
- nucleotide phosphates are chemically reactive because of the three phosphates on the end that have a negative charge
73
What happens to the nucleotide triphosphates as nucleotides are stolen from them
Nucleotides are made from a sugar, a base, and a phosphate, so two phosphates are left over if a nuclotide is taken away
These two phosphates leave as a pyrophosphate molecule and then proceed thorugh the exothermic reation of hydrolysis. This exothemeric reaction actually helps drive polymerization
74
What direction does DNA form in
DNA forms in the 5' --> 3' end as DNA polymerase III can only add nucloetides to the 3' end
75
What is the leading strand ?
The DNA strrand made by the CONTINUOUS addition of nucleoides in the 5' to 3' direction
the front end of the new DNA strand with the arrow
76
What is the lagging strand ?
- The DNA strand made by the DISCONTINUOUS addition of nucleotides in OKAZAKI FRAGMENTS
- The lagging strand is made in the diraction AWAY from the replication fork
- -> the back end of the new DNA strand wihtout the arrow
77
Okazaki fragments
RNA synthesizes a short RNA primer which DNA polymerase III lengthens to form an Okazaki fragment
78
How does the lagging strand become one unit rather than a bunch of Okazaki fragments?
First--> DNA polymerase I replaces the RNA nucleotides in the primer with DNA nucleotides
Then--> DNA ligase comes in to join the fron of an Okazaki fragment with the end of the next one (the primer, now DNA nucleoties)
79
What is the "central dogma" of microbiology?
DNA--(transcription)--> RNA --(translation)--> Protein
80
How many genes code for a polypeptide?
ONE gene codes for ONE polypeptide
81
What is transcription?
DNA and RNA are written in a different language (bases) so to get to RNA, DNA has to be transcribed
This can happen because DNA can act as a template strand for a complimentry sequence of RNA nucleotides
82
What is mRNA? Why is it called this?
- messanger RNA
- RNA that came from a protein coding gene is called mRNA because the RNA is carrying a genetic message to the protein from the DNA. THe RNA is the "messanger"
83
Where does transcription happen?
In the nucleus
84
What is translation?
- another change in 'language'?
| - change from nucleotide sequence of RNA into an amino acid sequence of a polypeptide
85
What is the site of translation?
Ribsomes!
| ribosomes are the site of translation as they facilitate the orderly linking of amino acids into the polypeptide chains
86
What are codons?
sequences of nucleotide triplets from mRNA during translation
Each codon specifies an amino acid to be added to the growing polypeptide chain
mRNA is read 5' to 3'
87
What is the promotor and terminator?
specific sequences of nucleotides mark where transcription of a gene begins and ends
The promoter is the DNA sequence that the RNA polymerase attaches to and intiates transcription
The terminator is the DNA sequence that signals the end of transcription
88
What are the three steps of transcription?
1) initiation
2) Elongation
3) Termination
89
Explain the initiation step of transcription?
RNA polymerase binds to the promoter
DNA strands unwind
RNA polymerase initiates RNA synthesis at the start point on the template strand
NOTE*** RNA can start a chain from scratch, doesn't need a primer
90
Explain the elongation step of transcription
The RNA polymerase moves down the DNA strand, unwinding it like a zipper and elongates the RNA transcript in the 5' to 3' direction
After the RNA polymerase passes, the DNA reform their double helix
91
Explain the termination stage of transcription
Eventually the RNA transcript is released and the RNA polymerase detaches from the DNA strand
92
How many RNA types are transcribed by RNA polymerase from DNA
3
93
WHat are the three types of RNA transcribed by RNA polymerase
```
messanger RNA (mRNA)
- these contain info to be converted to a polypeptide (protein) through translation
```
```
transfer RNA (tRNA)
- transports specific amino acids to ribosomes which contain growing polypeptides
```
```
ribosomal RNA (rRNA)
- complexed with proteins to form a ribosome
```
94
Translation steps
Initiation
Elongation
Termination
95
Where is GTP require
In certain parts of chain initiation and elongation
96
What are the parts ribosomes
```
small subunit
large subunit
exit site "E"
Peptidyl- tRNA binding site "P"
Aminoacyl-tRNA binding site "A"
```
97
Initiation phase of translation
- The mRNA binds and the small subunit of the ribosome bind together
- An initiator tRNA base pairs with its complementary start codon
- The large subunit arrival completes the inition
- proteins called initiation factors are required to bring all translation components together
GTP hydrolysis provides the energy needed for this
98
Elongation cycle of translation
-1) codon recognition (the anticodon of an incoming aminoacyl tRNA base pairs with the complementary mRNA codon in the A site)
Hydrolysis of GTP increases the accuracy and efficiency of this
2) Peptide bond formation (An rRNA molecule of the large subunit of the ribosome catalyzes the formation of a peptide bond between the amino of the new amino acid in the A site and the carboxyl end of the growing polypeptide in the P site)
This means that the polypeptide from the tRNA in the P site is removed and attched to the amino acid on the tRNA in the A site
3) Translocation (The ribosome relocates the tRNA in the A site to the P site (they switch spots). At the same time the empty tRNA in the P site is moved to the exit and released. The mRNA moves along wit its bound tRNAs, bringing the next codon to be translated into the A site
Now the ribosome is ready for its next aminoacyl tRNA
99
The termination phase of translation
1) When a ribosome reaches a stop codon on the mRNA, the A site of the ribosome accepts a "release factor", (a protein shapes like a tRNA) instead of an aminoacyl tRNA
2) The release factor promotes hydrolysis of the bond between the tRNA in the P site and the last amino acid of the polypeptide that the tRA is attached to, freeing the polypeptide from the ribosome
3) The two ribosomal subunits and other components of the assembly dissociate
100
Whats within a gene?
- promoter
- controlling/ operator
- induction site
- coding sequence
- terminator
101
What is the Operator?
- CONTROLS WHETHER GENE IS TRANSCRIBED AT ALL
- most often located within the promoter
- on the induction site
102
What is the operon?
Contains the promoter, operator within the promoter, and the genes that the promoter controls
103
Why are enzymes trying to breakdown lactose sugar?
the breakdown of lactose makes glucose and galactose which bacteria can use for energy
104
lac operon example
| what gene codes for producing the repressor?
lac I
105
why do we need a repressor?
when lactose isn't present, it is a waste of energy to make the enzyme that breaks down the lactose
106
lac operon example
| what happens if lactose isn't present?
the repressor binds so RNA polymerase path is blocked and mRNA is not produced/ blocks transcription of the operon
107
lac operon example
| what does lactose function as, when it is around the gene that codes for producing the enzyme to break up lactose?
lactose functions as a coreprocessor
108
lac operon example
| what does lactose doe, acting as a core processor?
lactose, the core processor, binds to the repressor, making the repressor go through a conformational change, meaning it can no longer bind to the operator
109
lac operon example
| No that the repressors has undergone a conformatinoal change what happens?
the repressor can no longer do its job of blocking RNA polymerase's path, so RNA polymerase no has a clear path and protein/ enzymes can be made to break down lactose
110
what are allosteric proteins?
proteins that have undergone a conformational change
111
lac operon example
| what is the allosteric protein?
the repressor
- because lactose binded to it, making the repressor undergone a conformational change and it can no longer bind to the operator
112
what do regulatory genes code for?
regulatory proteins
| ** can be repressor
113
what do regulatory genes do?
control the expression of other genes
114
what are regulatory proteins?
| - ** can be repressor
proteins that help control the synthesis of proteins in cells
115
How does the conformational change of a regulatory protein affect the rate of transcription?
the conformational change effects whether the regulatory protein binds to the operator
116
what is a positive transcription factor?
means the increased rate of transcription
117
what is a negative transcription factor?
the decreased rate of transcription
| - can decrease to the point of no production
118
what happens with transcription, with repressible operons?
TRANSCRIPTION USUALLY TAKES PLACE unless something else happens to it
119
what happens with transcription, with inducible operons?
TRANSCRIPTION DOESN"T USUALLY TAKE PLACE
| unless something else happens to it
120
What is the effector molecule?
the molecule that binds to the repressor, triggering a conformational change in the repressor, so the repressor can no longer bind to the operator, which means it can no longer block RNA polymerase's path
121
what is the effector molecule of an inducible operon
the substrate
122
lac operon example
| what is the effector molecule?
lactose
| - binds to repressor, triggers conformational change
123
what is the effector molecule of a repressible operon?
the end product of the metabolic pathway
124
ex: tryptophan operon
| what is the effector molecule?
trp
125
what is a mutation?
a pernament change in hereditary material/ in DNA
126
what are the threee main types of mutations?
1) chromosomal translocation
2) transposition of a gene
3) point mutation
127
what is chromosomal translocation?
when chuncks of chromosomes can be moved to another place
128
what is transposition of a gene?
genes that are flipped to each others place
129
What are point mutations?
single mutations within a DNA code
130
what are mutagens?
physical and chemical gents that promote muations
131
examples of mutagens?
- ionzing radiation
- UV radiation
- chemicals
132
example of mutagens with:
| Thymindine dimers formed due to UV radiation
UV LIGHT ADDED TO THYMINE BESIDE EACH OTHER ON SAME STRAND makes thymine dimer--> attached thymine sitting next to each other, their base that they come out of i also bent ---> resulted in: KINK IN DNA
133
what do DNA repair enzymes do?
recognize and correct damaged DNA
134
what type of bond is inbetween thymine and adenine?
double bond
135
what tpe of bond is in bewteen Guanin and cytosine?
triple bond
136
What are the two ways chemical mutagens do?
1) mimic DNA nucleotides and sneak into the DNA sequence --> promote incorrect base pairing
2) add or remove groups of nucleotides causing incorrect base pairing
137
what do chemical mutagens result in?
base-pair substitution or point mutation
| introduced during DNA replication
138
what are spontaneous mutations?
when nucleotide baes undergo conformational changes to forma nother kind of nucleotide base
--> results in miss-paired bases during DNA replication
139
what are the two types of small-scale mutations?
1) single- nucleotide- pair substitution (always point mutation)
2) nucleotide pair insertion or deletions (sometimes point (one pair) mutation however they can involve more pairs)
140
effects of point-mutations?
- silent mutation
- missense
- nonsense
141
effect of nucleotide insertions or deletions?
- frameshift causing immediate nonsense
- frameshift causing extensive missense
- no frameshift but extra or missing amino acid
142
what does a silent mutation mean?
substitution that has no effect on amino acids
143
what does missense mutation mean ?
single substitution that changes codon and results in different amino acid
144
what does nonsense mutation mean?
single substitution that changes previous amino acid to terminating amino acid
145
technology and applications
1) gene cloning
2) production of pharmeceuticals
3) vaccines
4) DNA fingerprinting
5) transgenic organisms(organisms that recieve genes from another organism)
6) Diagnostic of gene diseases and gene therapy
146
Implications
1) Privacy of genetic info (at what point is it too much)
2) prenatal diagnosis of genetic diseases and gene therapy (some contraversy, but saves lots of lives)
3) safety of genetically engineered products and organisms; their impact on the environment and consumers
147
what does Watson and Crick's report on the structure of DNA lead to?
Nathan and Smith's discovery of the first site-specific restriction enzyme
148
what are restriction enzymes?
enzymes that cut at specific sites on a dNA molecule
149
where are restriction enzymes used by organisms already?
BACTERIA
- bacteria use as defense mechanism
- cut up viral DNA to defend against viruses whent hey're infected
- cut specific sites on unmethylamated DNA, as their DNA is methylmated
150
what are "sticky ends"
sticky ens are unpaired bases that need to be paired, part of one strand of DNA has no pairs, and stick out from ht rest of the attached strands
151
How are sticky ends repaired?
DNA molecules cut by the same restriction enzyme have complementry ends and can trick toegther temporarily
152
What sticks complementary sticky ends toegther pernamently?
DNA ligase
153
how are genes isolated?
using restriction enzymes
154
how do genetic engineers clone DNA?
using DNA ligase and restriction enzymes
155
What are plasmids used as?
cloning vectors
156
what so special about plasmids?
they can:
- carry DNA that codes for protein
- carry genes that are resistant to antibiotics so they can live in an enironment hat contains that antibiotic
- they can grow in vito and then be intorduced into bacterial cells
157
How do Genetic Engineers use plasmids when cloning?
- take plasmid vector (shape of circle) , cut with restriction enzyme
- fit with another piece of DNA gene of interest they cut with same restriction enzyme
- fuse together with ligase to form plasmid as circle again
- plasmid is inserted into host cell, with its piece of foreign DNA within it
- cell multiplies with gene of interest
158
what are antibiotics?
drugs that specifically inhibit a metabolic process to impede growth or kill bacterial cells
159
what are antibiotics?
drugs that specifically inhibit a metabolic process to impede growth or kill bacterial cells
160
Genetically modified organisms (GMOs)
| produced by different technologies
- selective breeding
- artificial and in-vitro insemination; embryo tranfer
- cloning organisms
- specific site-directed mutation of an organisms DNA
- transgenic organisms (introduction of forgein gene)
