BIO202 EXAM 3 Flashcards
(170 cards)
1
Q
What is interphase?
A
When cells are not dividing
2
Q
What is mitosis?
A
The separation of duplicated chromosomes
3
Q
What are the 4 phases of the cell cycle?
A
G1, S, G2, and M phase
4
Q
Which of the stages of the cell cycle make up “interphase”?
A
G1, S, and G2
5
Q
Does Mitosis take place in prokaryotes?
A
No, they only contain 1 chromosome and are only 1 cell.
6
Q
In G1 phase….
A
each chromosome contains 1 DNA molecule
7
Q
In S phase…
A
DNA molecules replicate, 2 identical copies are formed, and stay attached to one another.
8
Q
Kinetichore MT
A
attach to chromatids
9
Q
non-kinetochore MTs
A
go from centrosome to metaphase plate and overlap
10
Q
What’s the metaphase plate?
A
The center of the cell
11
Q
What are the 5 phases of mitosis?
A
Prophase, Prometaphase, metaphase, anaphase, and telophase.
12
Q
What is prophase?
A
The first stage of mitosis. This is where the chromosomes condense into visible chromosomes and then microtubule form in the cytoplasm between centriole pairs. It lengthens as the microtubules grow.
13
Q
What is prometaphase?
A
The second stage of mitosis. This is where the nuclear envelope fragments, the mitotic spindle invades the nucleus, and microtubules bind chromatids at kinetochores.
14
Q
What is metaphase?
A
The third stage of mitosis. This is where centrosomes are at the opposite ends of the cell. The chromosomes that are attached to microtubules line up at the metaphase plate.
15
Q
What is anaphase?
A
The 4th stage of mitosis. This is where sister chromatids separate and are pulled toward opposite poles. Kinetichore MTs shorten as tubulin dimers are removed.
16
Q
What is telophase?
A
The fifth and final phase of mitosis. This is where the nuclear envelope reforms and chromosomes partly unfold.
17
Q
What stage do non-dividing cells remain in?
A
G0 phase
18
Q
What are checkpoints?
A
Places in the cell cycle where it stops unless it is given the “go ahead” signal
19
Q
Where are the major checkpoints?
A
The G1, G2, and M phases
20
Q
What happens if a cell does not get the “go ahead” signal at a checkpoint?
A
It enters G0 phase
21
Q
G1 checkpoint
A
The most important checkpoint. It is called the restriction point. If a cell gets passed the restriction point, it typically completes the cell cycle.
22
Q
What’s beneficial about leaving the cell cycle at the restriction point?
A
It ensures that the cell has the correct amount of DNA
23
Q
cdk’s
A
(Cyclin-dependent kinases.) Provide cell cycle signals by phosphorylating other proteins. Each cdk regulates a different step. They’re inactive alone but active when bound to a cyclin protein
24
Q
Which cyclin acts at the G2 checkpoint?
A
MPF
25
PDGF
Platelet-derived growth factor
26
asexual reproduction
offspring have the same DNA as parents (they're identical)
27
sexual reproduction
2 parents both contribute DNA to offspring
28
What process makes sure in sexual reproduction, the offspring don't have double the amount of DNA they should have?
meiosis
29
somatic cells
all cells except sperm and egg cells
30
chromosomes of human somatic cells
22 pairs of homologous chromosomes + 2 sex chromosomes
31
haploid number
n = number of chromosomes/cell in gametes
32
diploid number
2n = the number of chromosomes in somatic cells
33
meiosis
The formation of haploid cells from diploid cells. (The formation of eggs and sperm with only 1 chromosome of each pair.
34
basic steps of meiosis
1 round of DNA replication and 2 rounds of cell division (meiosis I and meiosis II)
35
What happens in interphase I of meiosis?
DNA is duplicated in the S phase and sister chromatids stay attached. Centrosome, centrioles duplicate
36
What happens in prophase I on meiosis?
The meiotic spindle forms. The structure of the spindle is the same in mitosis, meiosis 1 and meiosis II.
37
prophase I of meiosis
Chromosomes attach to the spindle. Homologous chromosomes attach to each other in a process called synapsis. Then, homologous chromosomes break and rejoin at equivalent positions. This is called crossing over.
38
2x2 sister chromosomes is called a
tetrad or bivalent
39
chiasma
sites of crossing over
40
chromosomes that have crossed over are called
recombinant chromosomes
41
Metaphase I of meiosis
Chromosomes line up at the metaphase plate. The homologous chromosomes stay attached. The two chromosomes of the pair are linked to opposite spindle poles.
42
Anaphase I of meiosis
Homologous chromosomes separate and sister chromatids stay attached
43
Telophase I of meiosis
Same events as in telophase of mitosis. Nuclei reform.
44
Cytokinesis of meiosis
The same as mitosis
45
Meiosis I
Reductional division because each daughter cell has only one chromosome of each pair
46
Interkinesis
The time between meiosis I and meiosis II
47
What happens between Meiosis II
Centrioles and centrosomes are replicated but DNA is not.
48
Meiosis II
Almost the same as mitosis
49
Prophase II
Spindle forms and chromosomes attach to it
50
Metaphase II
Sister chromatids attach to opposite poles of the spindle
51
Anaphase II
sister chromatids are separated
52
Telophase II
Same as mitosis; nuclei form
53
DNA
Stores and transmits hereditary information. It codes for protein.
54
Gene
DNA that specifies (codes for) amino acids in 1 protein
55
Homologous chromosomes
They're almost identical. They have the same genes that may have slight changes
56
Allele
Different versions of the same gene
57
What causes variation between individuals?
Different forms of the same proteins coded for by different alleles of the same genes. They cause variation between individuals
58
Homozygous (for a gene)
having the same allele on both chromosomes of a pair
59
Heterozygous (for a gene)
having different alleles on the two chromosomes
60
Heredity
Transmission of different alleles between generations by meiosis and sexual reproduction
61
Genetics
The study of heredity and how heredity variation is passed down through generations
62
Mendel
discovered laws of inheritance using peas before genes and chromosomes were known
63
character
a heritable feature (e.g. flower color)
64
trait
one variant of a character (e.g. purple or white flowers)
65
Genetic cross
controlled mating of 2 organisms
66
What are "heritable factors" that Mendel postulated?
genes
67
genotype
what alleles an individual has
68
Phenotype
appearance
69
Law of independent assortment
different characters are inherited independently
Alleles of genes on nonhomologous chromosomes assort independently during gamete formation
70
An easier way of predicting outcomes of a genetic cross other than using Punnett squares
Calculate results for each character independently and then multiply
71
Predict the possible results for a het. x. het. cross (Aa x Aa)
1/4 AA
1/2 Aa
1/4 aa
72
Predict the possible results for a hom. x. het. cross (AA x Aa)
1/2 AA
| 1/2 Aa
73
AaBbCc x AABbCC: Chance of AaBBCC
1/16
74
How do you determine the chance of a desired phenotype?
Figure the chance of each genotype that fits the bill and then add the probabilities
75
Co-dominance
two alleles both have effects
76
Multiple alleles
more than 2 versions of a gene and its protein
77
epistasis
1 gene affects the expression of another
78
Polygenic inheritance
many genes contribute to phenotype
79
Pleiotropy
1 gene has several effects on phenotype
80
monohybrid cross
crossing two individuals each heterozygous for one character
81
Law of segregation
The two alleles for each gene separate during gamete formation. Organisms have 2 copies of each heritable factor but each gamete has only one copy.
82
locus
The position of a gene on a chromosome
83
Linked genes
are on the same pair of homologous chromosomes
84
wild type
normal appearance
85
mutant
abnormal phenotype
86
Unequal numbers in a dihybrid x double recessive test cross shows that
two genes are linked
87
Smaller numbers of offspring are always
recombinants
88
recombination frequency definition
how often recombination occurs between 2 genes
89
Recombination frequency is ____ when genes are close together.
Low
90
Recombination frequency is ___ when genes are far apart.
High
91
recombination frequency equation
(# of recombinants / total number of offspring) * 100
92
Genetic map
describes relative distances of genes along a chromosome
93
1% recombination frequency =
1 map unit
94
Autosomes
chromosomes in homologous pairs
95
Barr body
compact structure on the inside of the nuclear envelope
96
X-inactivation in female mammals
1 of the X chromosomes in each cell condenses into a Barr body early in dev
97
Which X chromosomes in inactivated?
Decision is random and independent in each cell in the embryo
98
Non-disjunction
failure of chromosomes to separate correctly in meiosis
99
Result of non-disjunction
daughter cells have abnormal number of chromosomes
100
Aneuploidy
having the wrong number of chromosomes
101
Trisomy
1 extra chromosome
102
Monosomy
missing 1 chromosome
103
Karyotype
Ordered display of chromosomes from a cell in mitosis. Reveals aneuploidy
104
Polyploidy
having extra sets of chromosomes
105
Why is aneuploidy often worse than polyploidy?
Chromosome balance is important.
106
Genomic imprinting
A type of inheritance pattern that doesn't follow Mendel's laws. During gamete formation, DNA in a few genes is modified.
107
Imprints
remain through life but imprints are erased and new imprints are made during gametogenesis
108
Genes in mitochondria and chloroplasts
These don't exhibit Mendel's laws. All mitochondria and chloroplast genes come from the mother.
109
hemizygous
Having only one copy of sex-linked genes
110
S cells
smooth cells that have a capsule to avoid the immune system and are pathogenic
111
R cells
rough cells that have no capsule. Host kills them and they are not pathogenic
112
Bacteriophage
virus that infects bacteria; turns bacteria into factories for making virus
113
What is implied when it is said that DNA replication is semi-conservative?
Each molecule has 1 old strand and 1 new strand
114
Leading strand
is made as a continuous strand
115
Lagging strand
synthesized in short fragments made in the 5' to 3' direction then joined later.
116
Okazaki fragments
Made 5' to 3'. Start at the fork. DNA polymerase moves away from the fork
117
Primer
Short segment of RNA made by primase
118
DNA polymerase
adds dNTPs to the 3' end of the primer
119
How are primers on Okazaki fragments replaced?
Another DNA polymerase replaces RNA with DNA
120
DNA ligase
joins the Okazaki fragments by forming a phosphodiester bond to link adjacent fragments into a continuous strand
121
Telomeres
(TTAGGG) A repeated short sequence in eukaryotic chromosomes they solve the issues faced when replicating DNA. In replication it can't get all the way to the end of the strand so it shortens it a bit. Telomeres get shortened rather than losing genetic information.
122
Mismatch repair
DNA polymerase proofreads each dNTP after adding it and removes it if it's incorrect
123
Excision repair
Repair of damaged DNA. A nuclease cuts out damaged region. Then, DNA polymerase and ligase fill in the gap
124
RNA polymerase II
The RNA pol. used to make mRNA
125
The direction of transcription is called
downstream
126
A promotor is _____ of its gene
upstream
127
First step of transcription
Binding of RNA pol. to a promoter
128
Transcription factors
Help RNA pols to bind to the promoter in eukaryotic cells
129
TATA box
one of the many transcription factors that first bind to DNA. It is located upstream f the start of transcription
130
Transcription initiation complex
RNA polymerase and other transcription factors
131
Initiation of transcription
DNA strands are separated only where RNA pol is bound. RNA pol starts an RNA strand at the transcription start point
132
Elongation phase of transcription
RNA pol. moves downstream (away from the promoter) RNA lengthens and DNA strands snap back together displacing RNA
133
Termination of transcription
RNA pol. falls off DNA at the end of the gene. RNA is released
134
Transcription terminator
A DNA sequence that signals the end of transcription in bacteria.
135
mRNA specific event
In eukaryotes, mRNA transcription continues through a polyadenyation signal, but RNA pol. II is released from the DNA shortly afterward
136
rRNA specific event
rRNA is made and assembled into ribosomes in the nucleolus
137
mRNA codes for
protein
138
mRNA processing occurs in the
nucleus. The initial transcription product is pre-mRNA, is converted to mRNA that leaves the nucleus
139
How is pre-mRNA modified in processing?
1. Addition of 5' cap
2. Poly-A tail
3. RNA splicing
140
Addition of 5' cap and Poly-A tail
Stabilizes mRNA and facilitates ribosome attachment. Poly-A tail also enhances transport from the nucleus
141
RNA splicing
cut and paste removal of some sequences from pre-mRNA in the nucleus (only in eukaryotes)
142
Intron
A sequence that is removed
143
Exon
A sequence that remains and codes for protein
144
What are snRNPs?
(small nuclear ribonucleoproteins) made of RNA and proteins act in splicing
145
How do snRNPs act?
They bind to the pre-mRNA at the intron ends
146
spliceosomes
A complex formed when snRNPs bind other proteins. They bind both ends of an intron bringing them together then rejoins the ends of adjacent exons
147
Alternative RNA splicing
Some exons may be cut out as well as introns to give a different mRNA
148
tRNA
Folded by internal base pairing. Would look like a cloverleaf if flattened out. Interpret the genetic code
149
Anticodon in tRNA
binds codon
150
aminoacyl-tRNA synthetase
binds to a specific aa and a specific tRNA and covalently links them using energy from ATP hydrolysis
151
Ribosomes
sites of protein synthesis. Both contain RNA and protein. rRNA is the most abundant RNA in a cell
152
A site
aminoacyl-tRNA binding site
153
P site
peptidyl tRNA binding site
154
E site
Exit site
155
tRNA binding sites
Ribosomes binds mRNA near 5' end. Ribosomes have 3 tRNA binding sites
156
Translation overview
aminoacyl-tRNAs bind to sequential codons and insert aa's into protein
157
3 stages of translation
Initiation, elongation, and termination
158
Initiation of translation
Small ribosomal subunit binds mRNA at or near the 5' end and also binds the initiator tRNA. Initiator tRNA binds to AUG in mRNA, (start codon) via its anticodon.
159
AUG
start codon
160
Initiation complex
Large ribosomal subunit bints to the initiator tRNA that is in the P site
161
Steps in elongation (translation)
1. Codon regonition
2. Peptide bond formation
3. Translocation
162
Codon recognition
Incoming aminoacyl-tRNA binds to codon in A site
163
Peptide bond formation
Peptide bonds form between new aa and carboxyl end of growing chain. The chain is now linked to tRNA in the A site
164
Translocation
ribosomes moves along mRNA by the distance of 1 codon.
165
Result of translocation
tRNA that was in A site is now in P site, leaving A site free to restart cycle. tRNA that was in P site is now in E site and is released from ribosome
166
Termination
Occurs when a stop codon is present in mRNA
167
release factor
A protein that binds to a stop codon if it's present in the A site. It releases a finished protein from the tRNA in the P site
168
Polyribosomes/polysome
many ribosomes on 1 mRNA
169
cytosolic proteins are made on
free ribosomes
170
Non-cytosolic proteins are made on
bound ribosome
