Molecular Genetics Flashcards
1
Q
What are the three things genes must be capable of?
A
Carrying info from one generation to the next, putting the info to work to produce traits, have a mechanism of easily copying the gene
2
Q
Who determined the structure of DNA?
A
James Watson and Francis Crick
3
Q
What is Chargaff’s Law?
A
amount of cytosine and guanine are equal, as are amounts of adenine and thymine are equal
4
Q
What are the monomers of DNA and what are they composed of?
A
nucleotides, composed of a phosphate group, a nitrogen base, and a deoxyribose sugar
5
Q
How is eukaryotic DNA organized?
A
DNA strands are wrapped around proteins called histones, forming nucleosomes
6
Q
What is conservative replication?
A
the DNA molecule would be copied completely leaving the two parents strands together
7
Q
What is semi-conservative replication?
A
separates the strands and copies each individual parent strand
8
Q
What kind of replication does DNA use?
A
semi-conservative
9
Q
What is the first step of DNA replication?
A
Separation of strands
10
Q
What is the second step of DNA replication?
A
Building complimentary strands
11
Q
What is step three of DNA replication?
A
Fixing errors
12
Q
What does topoisomerase do?
A
unwinds the DNA strands ahead of the replication bubble to relieve tension
13
Q
What does helicase do?
A
Breaks the hydrogen bonds between nucleotides to separate the strands?
14
Q
What are SSBs and what do they do?
A
Single-stranded binding proteins prevent DNA from reannealing
15
Q
What direction must DNA be built in?
A
3’ to 5’
16
Q
What direction must DNA be read in?
A
5’ to 3’
17
Q
What does RNA primase do?
A
brings in RNA primers to begin building new nucleotides
18
Q
What does DNA polymerase I do?
A
removes RNA nucleotides and replaces them with DNA
19
Q
What does DNA polymerase II do?
A
reads for errors in DNA
20
Q
What does DNA polymerase III do?
A
brings in new nucleotides to the template strand
21
Q
What is the leading strand?
A
strand that is continuously built towards the replication fork
22
Q
What is the lagging strand?
A
strand that is discontinuously built away from the replication fork in fragments
23
Q
What are the fragments of the lagging strand called?
A
Okazaki fragments
24
Q
What does DNA ligase do?
A
catalyzes a phosphodiesterase bond to repair gaps between Okazaki fragments
25
How does DNA perform mismatch repair?
DNA polymerase III will back up and replace incorrect bases with the correct base
26
What happens if mismatches are missed?
DNA polymerase I & II will read for errors and another enzyme will remove the mismatched portion, and DNA polymerase III and ligase will repair the gap
27
How is prokaryotic DNA organized?
DNA is circular and made of almost entirely one chromosome
28
What are telomeres?
repetitive non-coding regions of DNA found at the ends of eukaryotic DNA
29
Why are telomeres necessary?
when DNA replicates, sections of the lagging strand are lost, with telomeres, the telomeres will be lost instead of coding regions
30
What is the Hayflick Limit?
after about 60 replications telomeres will be completely gone
31
What is cell scenescence?
when a cell "dies": it still exists in your body but it does not divide or replicate
32
Why do cells enter a scenescent state?
if they may cause damage
33
What is the difference between a mitotic and post-mitotic cell?
a mitotic cell performs mitosis, post-mitotic cells regenerate from stem cells
34
What is a codon?
set of three bases that code for an amino acid
35
What is the central dogma of molecular genetics?
DNA is transcribed into RNA and then translated into proteins
36
What is transcription?
a gene on the DNA molecule is copied to mRNA, where it then is brought to the ribosome
37
What is messenger RNA?
RNA that carries instructions from the nucleus to the cytoplasm
38
What is transcription RNA?
has an anticodon at one end and an amino acid binding site at the other, and gathers amino acids
39
What is ribosomal RNA?
used to bind mRNA and tRNA to the ribosome
40
What are promoter and terminator sequences?
sequences that signal the beginning and end of RNA transcription
41
What occurs during RNA transcription?
RNA polymerase binds to the promoter, separates the strands, only one strand of DNA is copied, continues until terminator sequence, hydrogen bonds reform
42
What are introns and exons?
introns are sequences that are not involved in making proteins, exons are sequences that are involved in making proteins
43
How is RNA edited before entering the cytoplasm?
introns are removed, exons are spliced together to form mRNA, 5' methylguanosine cap and poly-A tail are added to identify the start and end points
44
What edits RNA?
spliceosome
45
How do introns and exons allow for alternative splicing?
a single gene can code for more than one protein depending on which segments are treated as introns and exons
46
What is a codon?
group of 3 nitrogen bases that code for a specific protein
47
What are stop and start codons?
specific codons that signal the beginning and end of every set of mRNA instructions
48
What is the start codon?
AUG, codes for methionine
49
What is translation?
synthesis of proteins, base sequence of mRNA is translated into amino acid sequence of a protein
50
What occurs during translation?
mRNA attaches to a ribosome, as each codon passes through the ribosome, the proper amino acid is brought in by tRNA, ribosome hitches the amino acids together with peptide bonds to form a polypeptide
51
Where are polypeptides shaped into functioning proteins?
endoplasmic reticulum and golgi apparatus
52
What are the subunits of a ribosome?
made up of a large and small subunit, made up of proteins and rRNA, subunits only come together when they attach to an mRNA molecule
53
What are ribosomal binding sites?
each ribosome has 3 binding sites: A, P, and E, A holds the tRNA with the next amino acid, P holds the tRNA with the growing polypeptide chain, E is where empty tRNAs leave the ribosome
54
What are point mutations?
changes in one base pairs of a gene
55
What are base pairs substitutions?
type of point mutation, one nitrogen base is changed for another, affects just one codon
56
What are silent mutations?
a base pair substitution that only affects the 3rd codon position and might not impact the organism
57
What are base pairs insertions and deletions?
nitrogen base is removed, or an extra is added
58
What is a nonsense mutation?
when a premature stop codon is created as a result of a base pair substitution
59
What is a missense mutation?
when the wrong amino acid is created as a result of a base pair substitution
60
What is a frame shift mutation?
as a result of an insertion or deletion, code is still read in groups of 3 bases, would shift the reading frame over
61
When are mutations going to be passed on to offspring?
if a mutation occurs in a somatic cell, it will not be passed on. if a mutation occurs in a gamete can be passed to offspring
62
What does it mean if a gene is turned on or off?
The cell is actively transcribing and translating a gene (expressing it) if the gene is on, if the gene is off, it is not being expressed
63
What is a regulatory gene?
a gene that regulates another gene, it will code for a regulatory protein, which will attach to a regulatory sequence, allowing RNA polymerase to join
64
What is a regulatory sequence?
allows RNA polymerase to join and begin transcription
65
What is the lac operon?
in prokaryotes, regulates whether or not enzymes to break down lactose need to be produced, based on whether or not there is lactose
66
What is an operon?
a group of prokaryotic genes that are transcribed together
67
What is an operator?
location on prokaryotic DNA where operon is turned on or off
68
How does the lac operon regulate when lactose needs to be broken down?
If lactose is present, it will bind to a repressor, removing it from the operator so RNA polymerase can bind and transcribe an enzyme to break down lactose. If there is no lactose, the repressor remains bound to the operator
69
What is a promoter/binding site in eukaryotic DNA?
location on eukaryotic DNA where transcription factor protein binds
70
What are transcription factor proteins?
proteins used during gene expression to turn genes on, bind to the promoter sequence which attracts RNA poymerase
71
What is the transcription factor proteins complex made of?
Activator, mediator, and TATA binding proteins
72
What are activator proteins?
turn genes on by signalling to the mediator proteins to assemble the transcription complex
73
What are mediator proteins?
bind to activator and TATA binding proteins, acts like a bridge
74
What are TATA binding proteins?
binds to TATA box and DNA sequence and RNA polymerase so it can begin transcription
75
What is the TATA box?
DNA sequence found in the promoter region of genes found in archaea and eukaryotes, where the TATA binding proteins bind
76
What are repressor proteins?
turn genes off by binding to the repressor site and to RNA polymerase, keeps transcription factors from binding
77
How do histones act as repressors?
keep DNA wound up so it cannot be transcribed, unexpressed DNA stays wound up
78
What is DNA methylation?
when histones are tightly packed together, genes cannot be expressed, called heterochromatin
79
What is histone acetylation?
nucleosomes are loosely packed together, genes can be expressed, called euchromatin
80
What is CRISPR?
repeating sections of DNA found in bacteria, bacteria keep genetic code remnants of past invaders so the cell can detect and destroy the invader, uses endonucleases (cas proteins) and guide RNA
81
How does CRISPR work?
Cas proteins act like scissors and cut out part of the infecting agent's DNA and inserts it into the CRISPR region of its own DNA, DNA is copied into RNA which attaches to a different Cas protein which moves around the cell
82
How is CRISPR used for gene editing?
scientists create custom RNA that can cut out any gene in the organism and modify it to meet their needs
83
What is the PCR (polymerase chain reaction)
lab technique for making millions of copies of a specific DNA region, artificial DNA replication
84
What are the basic steps for the PCR?
1. Denaturation: heat the reaction to 95C, DNA strands separate
2. Annealing: cool the reaction to 50C-55C, primers bind to complementary sequence
3. Extension: raise the temperature to 72C, DNA polymerase extends the primer
85
What polymerase must be used in the PCR and why?
Taq polymerase, taken from thermophile bacteria that lives in hot springs, used since it can withstand high temperatures
86
What is gel electrophoreis?
used to visualize genes by using an electric field to separate fragments by size
87
Describe the process of gel electrophoresis.
1. agarose gel arrives in a dry, powdered form, heated in a buffer of salt and water, then cooled to form a gel with wells at one end for the DNA
2. gel is placed in a gel box with buffer, box has a positive anode and a negative cathode at either ends and since DNA is negatively charged, it moves towards the anode and salts in buffer carry electricity
3. stain is added to the gel, buffer or DNA, loading dye is also added to weigh down DNA, stain allows DNA to be seen under UV light
