1
Q
what is independent assortment
A
meaning that genes are inherited independently of each other within sex/haploid cells
-from mendel
2
Q
what happens during first round of meiosis
A
-chromosomes pair up
-crossing over of genes
-number of chromosomes cut in half
-chromosomes become different to make combinations different
3
Q
what are alleles
A
different forms of the same genes
-physical differences come from codons-SNPs
-causes transcription/translation to be different
4
Q
where does variation come from
A
any chromosome and any allele can end up in any sex cell
random orientation of chromosomes in metaphase
random segregation in anaphase
5
Q
what is a dihybrid cross
A
4x4 punnet square that shows how 2 traits are inherited
6
Q
what is a genotype
A
probability of trait
ex: Aa, Bb
7
Q
ratio for both parents heterozygous
A
9:3:3:1
8
Q
ratio for 1 parent heterozygous, 1 parent homozygous recessive
A
1:1:1:1
9
Q
what is a locus
A
location of gene on chromosome
10
Q
what are linked genes
A
genes close together on chromosome
usually inherited together, messes up ratios
11
Q
how are unlinked genes inherited
A
independently
-metaphase and anaphase for separate chromosomes
-crossing over if on same chromosome
12
Q
what are recombinants
A
a combination of alleles in offspring that neither parent had
13
Q
how are recombinants found in unlinked genes
A
looking whichever genetype is in offspring and not in parent
14
Q
how are recombinants found in linked genes
A
line diagram
-crossing over had to happen
15
Q
what does a way lower amount of recombinants mean
A
genes are linked
16
Q
what is the null/expected hypothesis for genetics
A
genes are unlinked
17
Q
chi squared testing for genetics
A
if observed results are far from expected, null is rejected meaning genes are linked
sum>7.81
18
Q
what are DNA’s 2 jobs
A
pass along traits and make traits through transcription and translation
19
Q
what was our knowledge of DNA structure in the 1940s
A
chromosomes duplicated and inherited
chromosomes made of DNA and proteins
used to think proteins carried traits because DNA is simple
20
Q
what was the Hershey-chase experiment
A
-used bacteriophage viruses because viruses are made of DNA and proteins
-used radioactive tags-phosphorus showed Dna, sulfur showed proteins
-virus injects genetic information into bacteria and duplicates
-virus blended and removed by centrofusion- separation of mass-heavy part outside
-pellet, the bacteria/genes found in heavier part
-inside liquid called supernaten at top of test tube
-phosphorus radioactive tag found more in the duplicated virus-DNA inherited-carries genes
21
Q
what was chargaff’s data
A
tested theory that the 4 bases just repeat-tetranucleotide theory
tested on many different organisms and disproved theory
found out that the A and T, and C and G percentages were very similar
22
Q
what did watson and crick do
A
found that the bases pair between the 2 strands of DNA in the center
23
Q
what does the helix shape of DNA do
A
the shapes of nitrogen bases would make pairing difficult and the strand would break otherwise
24
Q
what are purines and pyrimidines
A
purines:2 rings of nitrogen and carbon-adenine and guanine
pyrimidines:1 ring-thymine and cytosine
makes DNA 3 rings wide-makes very stable
25
what does anti-parallel mean
1 side is upside down is relation to the other
26
why does DNA/RNA directionality matter
they fit in specific active site of enzymes
27
what is the directionality of replication, transcription, and translation
replication enzymes read original DNA in 3'-5' and new DNA added 5-3
transcription enzymes read original DNA in 3'-5' and RNA added 5'-3'
translation enzymes read single strand RNA read by ribosomes in 5'-3' direction and anticodons read codons opposite
28
why do chromosomes package DNA in nucleosomes
so it can fit in cells and be easily moved
29
why aren't prokaryotic DNA packaged
they have a small amount of DNA so it's unneeded
30
what is a histone
protein that DNA condenses around
-always in groups of 8(octamers)
31
what is a nucleosome
8 histones with DNA wrapped around held together by H1 protein
32
what is linker DNA
the loose stretch of DNA that links nucleosomes
-eventually wraps
33
what is supercoiling
condensing on condensing on condensing of DNA
34
What is helicase's role in prokaryotic DNA replication
enzyme that opens DNA by breaking hydrogen bonds
-moves down DNA, opening as it moves
35
what is the replication fork
area where helicase is working
36
what is RNA primers
short stretches of RNA that start replication
37
what is the leading strand in replication
strand that moves toward replication fork 3'-5'
-needs 1 RNA primer
38
what is the lagging strand
strand that moves in opposite direction, has to start over and over
-needs multiple RNA primers
39
what are okazaki fragments
fragments of new DNA on lagging strand
40
What is DNA primase
Enzyme adding RNA nucleotides by reading DNA
41
what is DNA polymerase III
forms covalent bonds along new backbone
reads old DNA 3-5, new DNA 5-3
continuously on leading strand as it opens
discontinuously on lagging strand
proofreading to make sure bases match
42
what is DNA polymerase I
took out RNA primers to replace with DNA nucleotides
43
what is DNA ligase
connects leftover DNA nucleotides(okazaki fragments) with covalent bonds because polymerase III didnt
44
Gene definition
places on DNA that is transcribed-other DNA is "junk"
45
How much of a persons DNA is transcribed
1-2%
46
what is the purpose of the 98% of DNA not transcribed
1. coding for tRNA and rRNA
-different than transcription
2. enhancers and silencers: turn on and off genes
3. speed or slow transcription
4. promoters: tell where genes are to start transcription
5. telomeres: made of satellite DNA-junk repetitive DNA
-protects chromosome because it doesn't matter that its not transcribed-why mutations are rarely harmful
47
where is the Promotor
comes before the gene-not transcribed
between 100-1000 base pairs
48
steps of transcription
1. initiation
-RNA polymerase binds to promoter
-RNA polymerase unwinds and unzips DNA
2.elongation
-floating RNA nucleotides pair up added 5'-3'
-RNA polymerase adds new covalent bonds along backbone of new RNA
-RNA polymerase prevents DNA nucleotides and proofreads bases
3. termination
RNA reaches stretch of DNA not being transcribed-called terminator sequence
-end RNA is mRNA
49
Sense vs anti-sense strand
Anti-sense: used for transcription
sense strand: not used -same as RNA strand except DNA bases
50
what is gene regulation
gene expression, speeding and slowing
-happens after transcription in nucleus-doesnt happen in prokaryotes
51
what is pre mRNA
made from transcription in eukaryotes
52
what are introns
sections in genes that don't code for amino acids
-gets copies on mRNA unlike other non coding sequences
-get cut/left out
53
what are exons
important part of gene that gets coded
-left in
54
what is splicing
combining pieces of exons after introns get cut
allows cells to leave out exons as well
makes multiple combinations of mRNA which makes eukaryotes complex
each gene makes many different polypeptides
55
what is tropomyosin
protein found in muscle cells
gene has 11 exons
-different cells need different exons-different left out-different protein
56
modifications that happen to pre mRNA
1. splicing
2. 5' cap: adding nucleotides that aren't easily degraded to protect mRNA-usually guanine
3. poly-A tail: adding adenine to 3' end to protect mRNA from degrading
has to happen before mRNA can leave nucleus
57
ribosomes role in translation
hold parts together
58
what are the 3 sites on ribosome for tRNA
1. aminoacyl site/A site: amino acids brought in
2. peptidyl site: amino acid moves to when another is brought-peptide bond forms
3. exit site: tRNA leaves, amino acid stays
59
where is the amino acid and anticodons located on tRNA
anticodon is on bottom
amino acid on top
60
Steps of translation
1. initiation: initiator tRNA scans 5'-3' to find AUG(methionine) for its anticodon UAC to bind to
-mRNA binds to small subunit which allows large subunit to bind. 1st tRNA binds to P site which allows for 2nd to bind to A site
2. elongation: polypeptide elongated
-tRNA enters A site, polypeptide bond formed
-initiator tRNA moved to E site, 2nd to P site, initiator leaves, next enters A site
3. termination: reaches stop codon-no tRNA for codon
-last tRNA reaches E site
-parts disassemble, process can repeat
61
modifications of polypeptides
1. initial methionine removed
2.secondary and tertiary structure
3. many amino acids removed
4. conjugated proteins: extra molecule added
62
example of modified protein
-gene makes pre-proinsulin in rough ER bound ribosomes
-25% of amino acids cut out to make pro-insulin
-vesicle forms and takes into golgi by endocytosis
-1 cisterna removes 1/2 of remaining and last amino acids cut in half
-makes 2 chains: A chain and B chain
-more amino acids removed
-chains combine to make quarternary structure-insulin
-released into blood to lower blood sugar
63
why are amino acids broken down/recycled
-getting rid of unused proteins and old proteins that don't work
-breaking down amino acids to build something else
-not enough lysosomes to break these down
64
what is a proteome
all of a person's proteins-more unique than genomes because each gene makes many different proteins
-proteins constantly changing and being broken down
65
what is a proteosome
no membrane, made of amino acids
breaks down proteins faster than lysosomes
66
gene expression definition
the genotype(DNA) becoming phenotype(physical appearance)
-depends on proteins
67
differences between cells
different proteins combinations and different genes turned on and off
68
what are activators and repressors
transcription factors-proteins that bind to activator and repressors sequences within promoter
-usually turn on and off genes
-can be removed
69
what are activators and repressors sequences
nucleotides within the promoter that get binded to by transcription factors
70
what are enhancers and silencers
sequences far from gene
-usually in charge of speed
-can require transcription factors to bind to them
71
why does mRNA need broken down
nucleotides need to be reused eventually
72
what are nucleases
enzymes that break down mostly mRNA to separate nucleotides
73
how does cell regulated mRNA degradation
by regulating the time mRNA survives- stabilize it
-length of poly A tail: the longer, the more stable
-more nucleases: increase rate of shortening
74
what is a zygote
1st cell made-all genes turned on, not regulated yet
-totipotent
75
what does totipotent mean
stem cell that can become any type by cell differentiation
76
what does epigenesis mean
"permanent" turning off and on genes-finalizing differentiation
-doesnt change genome, changes transcriptome and proteome
77
what are epigenetic tags
molecules that affect nucleotides to turn off or on gene
-not transcription factors but can influence them
78
epigenetic tag example
methyl group- CH3 instead of CH4 so it can bind somewhere
Acetyl group
Phosphate group
79
what is methylation
adding methyl somewhere- most common tag
-usually cytosine within promoter to turn off genes
80
how does methylation turn off genes
if DNA wraps around nucleosome, it isn't available for trancription
methylation of histone keeps gene wrapped up to keep it turned off
-can unwrap genes too
81
how does environment affect gene expression
it can cause epigenetic tags to be added or removed and affect the speeds this happens
82
what are the top 3 environmental effects on epigenesis
Diet, physical activity, stress
-air pollution also has high effect
83
at what age are we most sensitive to environment
fetus
84
how do nitrous oxides(cigarette smoke, fossil fuels) affect gene expression
they can decrease methylation which turns on genes that affect the immune system by making too many proteins, causing it to be less effective
-increases chance for diseases
85
when does epigenetic inheritance happen
during mitosis-same cells have same functions
86
what does meiosis do to epigenetic tags
removes most of them- all are removed at fertilization to make them undifferentiated
87
are epigenetic tags passed to offspring
because they are acquired from the environment, not usually
-are exceptions
88
What are non-mendelian genetics
traits that cant be predicted, like epigenetic tags being inherited
ex: multiple alles, linked genes
89
what is genomic imprinting
inheriting epigenetic tags
parent imprinting on offsprings genome
90
how do epigenetic tags mess up dominant vs recessive genes
dominant genes can be inherited but not expressed if turned off in parent
91
what are hybrids
offspring from cross between different species or things
92
how do ligers and tigons show epigenetic tags
liger(father lion, mother tiger) is way bigger than both parents because of inherited epigenetic tags from mother
can compare to tigon with is way smaller
93
how are twin studies important for studying epigenetic tags
sees if its genetics or epigenetic tags
-environment or DNA, nature vs nurture
twins have exact same DNA so if they share traits its likely DNA, if they have different traits, its probably environment influenced
94
how does DNA affect how we turn out
it gives us range of what we can be- what we are is based off our decisions
95
how can the environments influence be useful
some organisms rely on the environment to turn off and on genes and have genes that only turn on and off because of environment
96
why do single cell organisms not make many proteins
don't want to waste energy or amino acids
-need based and time base
97
example of single cell organisms making proteins for its needs
e coli bacteria-eat lactose sugar(disaccharide)
-needs to split it using lactase enzymes-not made all the time
-if there's no lactose, lactase gene is off because of repressor
-if there's lactose, repressor is removed by lactose to make lactase
-lactose broken down again, repressor starts working again, gene turned back off
98
examples of multicellular organisms making proteins based off time or needs
1. Arctic fox makes pigment when warm, but when cold the gene that makes the pigment turns off. blends in with any environment
2. menstrual cycle responds to different hormones at different times which turns off and on different genes
99
what is gene sequencing
finding someones entire DNA sequence
looking for start and start and stop codons to find gene
can predict what amino acid will be added
100
why is it difficult to predict someones phenotype from sequencing
exons and introns
polypeptides split and changed
other modifications
101
how do researchers find what a gene does
turning it off to see what happens to phenotype
-information uploaded to libraries of genes
102
how do scientists turn off genes
-chemicals
-gene knockout: complete removal of gene- nucleases cut up DNA only in specific spots
103
what does CRISPR-CAS9
clustered, regularly interspaced, short palindromic repeats
104
how does CRISPR work in bacteria
virus DNA sequences are pasted onto bacteria
bacteria keeps DNA as a record so that offspring know about virus
CRISPR-CAS9 system searches bacteria for other virus DNA and destroys it
105
what is the CRISPR-CAS9 system
CRISPR is transcribed onto guide RNA(gRNA) that bind to enzyme/nuclease CAS9
can destroy virus DNA
we have modified it to be able to cut any DNA by surrounding it with CRISPR
can edit and change DNA-creates controversy
106
what are conserved sequences
sequence of DNA identical in different organisms-more concerved if in more organisms
came from common ancestor and wasn't changed
107
example of conserved sequences
ones that make enzymes for cell respiration
108
hypotheses about why conserved sequences exist
1. important for survival so it is passed down
2. non coding sequences being conserved suggests that maybe different sequences mutate at different times and hadn't mutated at time of inheritance
Ib bio
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