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BIO130—sec 1 MR > week 3 > Flashcards

week 3 Flashcards

1
Q

How can organelles do such complicated things with such a small genome?

A

Some DNA in mitochondrial genome and chloroplast genome was taken up by nucleus over evolutionary time so those organelles can “get away” with having a smaller genome

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2
Q

what do organellar genomes look like?

A

they are circular

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3
Q

How many base pairs are there in the human genome?

A

~3 billion bp/genome, you have ~6 billion bp b/c we have diploid cells (one genome from each parent)

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4
Q

how many protein-coding genes are there across the 23 human chromosomes?

A

~19 000

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5
Q

an example of genome size not comparing to organism complexity

A

an amoeba has a much larger genome than a human but are much less complex

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6
Q

approximately half of the human genome is ___________

A

repetitive DNA

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7
Q

a large part of the repeated sequence of DNA is __________

A

mobile genetic elements

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8
Q

what are the names of some mobile genetic elements?

A

SINEs and LINEs

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9
Q

what are mobile genetic elements?

A

regions that over evolutionary time have duplicated many times, can move around genome, can have an affect on human health if they insert in certain places

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10
Q

half of the human genome is _____________

A

unique sequences

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11
Q

what percentage of the human genome actually encodes protein?

A

~1.5%

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12
Q

protein coding exons are________________ while introns are ____________

A

transcribed and translated, transcribed but not translated

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13
Q

nonrepetitive DNA tend to be______________

A

regulatory sequences (e.g. promoter sequences)

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14
Q

what is the prokaryotic nucleoid?

A

DNA condensed through folding and twisting and complexed with proteins (in pros obvi)

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15
Q

how long is our DNA if it were outstretched

A

2 metres

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16
Q

how is DNA packaged into cells

A

chromosomes

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17
Q

what does FISH stand for?

A

Fluorescence In Situ Hybridization

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18
Q

what is FISH?

A

a diagnostic test where you can look for a particular sequence in a chromosome

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19
Q

how does FISH work?

A

creation of a probe that is the same as target sequence (complimentary and antiparallel), when you denature the probe and label with fluorescent dye and heat up DNA of chromosome as well and mix together and slowly cool it, base pairing will occur and renaturing can happen b/w DNA and probe

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20
Q

what is chromatin

A

a single, long, linear DNA molecule and associated proteins

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21
Q

why is chromatin dynamic?

A

chromatin is tightly packed but the DNA must remain accessible for transcription, replication, and repair

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22
Q

what is a karyotype?

A

an artificial array of chromosomes

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23
Q

what is a centromere?

A

where sister chromatids are held together

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24
Q

where are telomeres?

A

on the ends of chromosomes

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25
why are centromeres hard to sequence?
they are very tightly packed
26
why are telomeres hard to sequence?
they are repetitive
27
when can you not distinguish chromosomes?
during interphase
28
what is the basic structural unit of chromatin?
nucleosomes
29
what are histones a part of?
nucleosome
30
what are histones?
small proteins rich in lysine and arginine
31
What charge do histones have? what charge does DNA have?
histones are positively charged and DNA is negatively charged. They charges neutralize each other (electrostatic interaction).
32
what modifications can be done to the N-terminal tail of histone proteins
they can be modified covalently and reversibly by adding groups on to them (acetyl, methyl, and phosphate groups)
33
what are the four core histone proteins?
H2A, H2B, H3, H4
34
how many histones are there at the core of a nucleosome?
eight (octamer core). pair of each: 2 H2A & 2 H2B (associated w each other), 2 H3 & 2 H4 (associated w each other)
35
what does H1 do?
linker histone. Acts as a paperclip holding together. Helps to package chromatin tightly
36
what are the components of the "beads on a string" form of chromatin
linker DNA and core histones
37
what do non-histone clap proteins do
they are involved in the packaging of nucleosomes: forming chromatin loops (proteins interact w each other)
38
how much shorter is a chromosome than it's extended length
10 000x shorter
39
what do chromatin remodelling complexes and histone modifying enzymes do?
can make changes in chromatin structure and alter access to DNA for replication or transcription
40
histone modifying enzymes can _________ add or remove _____________ from the __________ of histones
reversibly, acetyl methyl or phosphate groups, N-terminal
41
chromatin remodelling complexes are ______ dependent
ATP
42
what do chromatin remodelling complexes do
slide histone core along DNA strand
43
what is heterochromatin?
highly condensed chromatin
44
where is heterochromatin found?
meiotic and mitotic chromosomes, centromeres and telomeres, one X chromosome in human females (inactive one)
45
heterochromatic regions of interphase chromosomes are areas where gene expression is __________
suppressed
46
what is euchromatin?
relatively non-condenses chromatin
47
"euchromatic" regions of interphase chromosomes are regions where genes tend to be ___________-
expressed
48
Is DNA synthesis conservative or semiconservative? what does this mean?
semiconservative—each cell has one original and one newly synthesized strand
49
DNA is synthesized from _____________
deoxyribonucleoside triphosphates (dNTPs)
50
RNA is synthesized from _______________
ribonucleoside triphosphates (NTPs)
51
nucleotides are linked by
phosphodiester bonds
52
where to nucleoside triphophates add onto during DNA synthesis
3' OH
53
what are the three possible models of DNA replication and give an example of each
1. unidirectional growth of single strands from two starting points (e.g. linear virus) 2. unidirectional growth of two strands from one starting point (e.g. some plasmids: small circles of DNA found in bacteria) 3. bidirectional growth from one starting point (e.g. eukaryotes and bacteria)
54
where does DNA replication start?
TATA box—recognized by and binding of initiator proteins occurs, not G&C b/c A&T only have 2 H-bonds
55
How many origins of replication do bacteria v. eukaryotes have?
single (bacteria), multiple (eukaryotes: need more b/c have larger genome)
56
is the replication fork symmetrical?
no (leading and lagging strand)
57
why is no genome unique?
all genomes are modifications of previous genomes
58
list the basic types of genetic change that are crucial in evolution
mutation within a gene, mutation within regulatory DNA sequences, gene duplication and divergence, exon shuffling, transposition of mobile genetic elements, horizontal gene transfer
59
what do similarities in the genome of humans and fishes indicate?
The overlap in most genes and many regulatory DNA sequences indicates that the intron structure of most vertebrae genes was already in place in the common ancestor of fish and mammals
60
why are there size differences among modern vertebrate genomes?
small blocks of sequence are lost and added to genomes
61
What is the "cleansing" process in the Fugu genome?
the genome is so tiny that it lost sequences faster than it gained them. Helpful to biologists as it left a slimmed-down version of a vertebrate genome in which only the DNA sequences that are very likely to have important functions remain
62
what gene has been used by biologists to construct a phylogenetic tree and why this gene?
the gene that codes for rRNA. rRNA is essential to the process of translation which is essential to all living things. Thus, this gene has been conserved throughout evolutionary time.
63
what is the evidence that humans have evolved from a time when mobile genetic elements were a large part of our genome?
almost half of our DNA is made up of mobile genetic elements that can no longer move due to accumulated mutations
64
Why is it important for DNA to be packaged into loops and coils by specialized proteins?
Allows for increasingly higher levels of organization which prevent the DNA from becoming tangles.
65
Why is the way DNA is folded important?
Allows enzymes and proteins that replicate and repair it and cause gene expression to access it

BIO130—sec 1 MR (5 decks)

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