Unit 4 Flashcards
(119 cards)
1
Q
Where does DNA replication start in prokaryotic cells?
A
origin of replication initiation sequence
2
Q
What do prokaryotic cells divide through?
A
binary fisssion
3
Q
What does binary fission occur in?
A
prokaryotes and amoeba
4
Q
What kind of reproduction is binary fission?
A
asexual reprotuduction
5
Q
What is binary fission?
A
Begins with DNA replication, cell membrane expands, septum forms between 2 halves of the cell, cell pinches into 2 to form 2 genetically identical daughter cells
6
Q
Where does DNA replication occur in eukaryotic cells?
A
s-phase of the cell cycle
7
Q
What happens after s-phase?
A
each chromosome consists of 2 DNA molecules linked together at the centromere
called sister chromatids
8
Q
What are sister chromatids?
A
- Carry identical genetic information for the same hereditary characteristics
- Result from DNA replication
- Are an exact copy of the chromosome directly after replication
-Same genes and alleles held together at centromere
9
Q
What are the 3 kinds of chromosomes?
A
homologous, non-homologous, and sister chromatids
10
Q
What are homologous chromosomes?
A
same genes, different alleles
Diploid cells have 2 copies of every chromosome
11
Q
What are non-homologous chromosomes?
A
encode genetic information for different traits and do not have similar structure and size
different genes
12
Q
What are the 4 stages of the cell cycle?
A
G1, s-phase, G2, M-phase
13
Q
What is G1?
A
making everything it needs to go through S-phase
Gene expression, rearrangement
1 centrosome, 2 centrioles
14
Q
What is s-phase?
A
Cell is synthesizing a complete copy of the whole genome (all chromosomes in the nucleus)
Cell is making a copy of the centrosome (microtubule organizing center)
Each cell needs a copy of the centrosome
Occurs simultaneously with DNA replication
Each centrosome consists of 2 centrioles
15
Q
What is G2?
A
Building machinery needed for cell division
Chromosomes consist of 2 sister chromatids joined at the centromere
Centrosome consists of 4 centrioles
16
Q
What are checkpoints?
A
places before the cell is allowed to go into the next phase, there are mechanisms in place to make sure the cell has the proper number of chromosomes and to make sure there aren’t major mistakes
Can prevent division from occurring if the cell is defective
17
Q
What are somatic cells?
A
all of the cells in an organism’s body except the gametes
Have diploid number of chromosomes
Produces through mitosis
Muscle cells, nerve cells, skin cells
18
Q
What does diploid mean?
A
2 copies of each chromosome (homologous chromosomes)
19
Q
What are gametes?
A
eggs and sperm
Haploid number of chromosomes
Produces through meiosis
One copy of each chromosome
20
Q
What does haploid mean?
A
half of the diploid number
21
Q
What are the stages of mitosis?
A
prophase
metaphase
anaphase
telophase
22
Q
What is prophase?
A
Diploid cell, 2 copies of each chromosome, centrosomes on both poles of the cell
-chromosomes condense down
23
Q
What is metaphase?
A
Microtubules are going to attach to chromosomes
Chromosomes have a protein complex located at the centromere called the conneticore
Microtubules connect to the conneticore formed on the centromere
Chromosomes move to the metaphase plate in a single filed line along the plate
(4 homologous chromosomes: 2 big ones and 2 small ones)
24
Q
What is anaphase?
A
Microtubules pull sister chromatids apart from each other
Each is its own chromosome with 1 DNA molecule
25
What is telophase?
Forms nuclear envelope around the genome
Cytokinesis: division of the cytoplasm
Genome needs to be duplicated and divided in between 2 daughter cells
If daughter cells don’t get exactly 1 copy of every chromosome, and have a diploid content, that cell will not survive
Cytoplasm is often times unequally distributed between the daughter cells
Cytoplasm contains organelles, RNA, ribosomes, proteins
2 genetically identical daughter cells
26
What are the outcomes of mitosis?
Occurs in all cell types
Metaphase: homologous chromosomes independently line up
Anaphase: sister chromatids separate
Produces 2 genetically identical, diploid nuclei
Each newly formed cell contains approximately half of cytoplasm and organelle content as parent cell
-Want daughter cells to have a complete genome and to make more of the same cells
27
What is asymmetric cytoplasmic division?
where a cell divides unequally, resulting in daughter cells with different fates or properties
28
What is plasmid and does it get replicated in binary fission?
extragenomic DNA in prokaryotes, yes
29
Why does the genome have to be distributed equally, but the cytoplasm does not?
genome must be distributed equally so the cell can function, survive, and not have any defects in its traits, while the cytoplasm does not have to be distributed equally because that allows for cell differentiation and daughter cells can develop into different cell types
30
When is the diploid chromosome number restored?
when a haploid sperm joins a haploid egg
31
What are autosomes?
all of the chromosomes in an organism shared between the sexes
Chromosomes 1-22
32
What are sex chromosomes?
contain genes used to control differences into the male and female phenotypes
X and Y chromosomes
33
What are the 2 kinds of meiosis?
meiosis I and meiosis II
34
What is prophase I?
2 DNA molecules (sister chromatids)
Cell has already proceeded through s-phase prior to meiosis
first miotic division
First reductional division
35
What is metaphase I?
Chromosomes line up in pairs along the metaphase plate
They find their homologous pairs
36
What is anaphase I?
separating homologous pairs of chromosomes
37
What is telophase I?
2 daughter cells that have half of the diploid chromosome content, making them haploid
38
What is prophase II?
Starting with haploid cells already consisting of 2 sister chromatids (no DNA replication occurring between meiosis 1 and meiosis 2)
39
What is metaphase II?
chromosomes line up in a single file line on the metaphase plate
40
What is anaphase II?
sister chromatids are pulled to the opposite sides of the cell
41
What is telophase II?
production of haploid gametes
42
What are the outcomes of meiosis?
Only occurs in gametes and consists of 2 divisions
Metaphase 1: homologous chromosomes pair
Anaphase 1: homologous chromosomes separate
Metaphase 2: chromosomes individually line up
Anaphase 2: sister chromatids separate
Produces four genetically unique, haploid nuclei
43
Describe Mitosis vs Meiosis
Mitosis: one round of division
Product: 2 diploid cells
Chromosome number maintained
Chromosomes line up individually at the metaphase plate
Daughter cells are genetically identical to one another and to the parental cell
Meiosis: crossing over that occurs in prophase 1
When the homologous pairs of chromosomes exchange pieces
2 rounds of division
Product: 4 haploid cells
Chromosome number is halved during meiosis 1
Chromosomes pair during metaphase 1
Dauget cells are genetically different from each other and from the parental cell
44
Do sister chromatids separate in mitosis, M1, M2?
mitosis, M2
45
Do chromosomes move because of their attachments to microtubules in mitosis, M1, M2?
all 3
46
Does DNA replication occur prior to this division in mitosis, M1, M2?
mitosis, M1
47
Do homologous chromosomes separate in mitosis, M1, M2?
M1 (anaphase 1)
48
Does one cell (or nucleus) divides into 2 cells (or nuclei) that are genetically identical to the first (assume there is not crossing over during M1) in mitosis, M1, M2?
mitosis
49
Is the chromosome number halved in mitosis, M1, M2?
M1
50
Is the DNA amount per nucleus halved in mitosis, M1, M2?
all 3
51
What is an allele?
variations in a specific gene
52
What is homozygous AA?
big A on both chromosomes
2 of the same allele
53
What is heterozygous Aa?
big A on one chromosome, little a on the other
Different alleles of gene A
54
What is random alignment?
pairs of homologous chromosomes align randomly along the metaphase plate before being separated
55
What stage of Meiosis does crossing over occur in?
prophase 1
56
What are individual monomers of DNA polynucleotides?
deoxyribonucleoside triphosphates (dNTP)
57
What is the structure of dNTPs?
5 carbon sugar, nitrogenous base, and 3 phosphate groups
58
What are dNTPs linked together by?
phosphodiester bonds
59
How are phosphodiester bonds formed between dNTPs?
2 phosphates are cleaved off, third phosphate and 3’ hydroxyl group form a bond together
60
What are characteristics of DNA?
double-stranded and antiparallel
61
What are complementary base pairs held together by?
hydrogen bond
62
What does A pair with and how many hydrogen bonds?
T, 2
63
What does C pair with and how many hydrogen bonds?
G, 3
64
What group does the 3' end have?
hydroxyl group
65
What group does the 5' end have?
phosphate group
66
What are genomes?
all of the chromosomes that make up the cell
67
What are chromosomes?
consists of DNA wound around histone proteins
68
What is chromatin?
DNA complexed with histone proteins
Each individual structure is a nucleosome
69
How many ORIs do prokaryotes have?
1
70
How many ORIs do eukaryotes have?
multiple
71
What are the molecular mechanisms for DNA replication?
initiation, elongation, termination
72
What phase is DNA replication taking place in?
s-phase (one chromatid → 2 identical sister chromatids)
73
What does DNA polymerase do in both prokaryotes and eukaryotes?
copies DNA
74
How does DNA polymerase work?
to synthesize DNA from a DNA template
75
What direction does DNA synthesis always occur?
5' to 3' direction
76
What is RNA polymerase?
synthesize RNA from a DNA template
77
1) What is initiation?
2) What is the ORI within the DNA sequence?
3) What is the ORI rich in and why?
1) DNA replication machinery assembles on chromosomes
2) origin of replication initiation
3) A: T base pairs because they have two hydrogen bonds that make them easier to separate
78
1) What is the first step of initiation?
2) What is helicase?
3) What direction is DNA unwinding?
4) What do single-stranded binding proteins do?
5) what is topoisomerase?
1) initiator proteins bind to ORI sequence and lead to an initial strand separation
2) separates template strands by cleaving Hydrogen bonds
3) both directions
4) bind onto single stranded DNA to prevent template strands from coming together
5) works ahead of the helicase by preventing knots or tangles from forming in the double-stranded DNA
79
1) What direction is elongation?
2) What is a primer and what synthesizes primers?
3) What does Primase synthesize, what kind of enzyme is it, and what is it's purpose?
4) What does DNA polymerase add onto primer?
5) What kinds of synthesis are on either side of the strand?
1) 5' to 3'
2) short sequence of RNA nucleotides, Primase
3) Synthesizing RNA from a DNA template,
Primase is an RNA polymerase,
Purpose of primase is to provide a 3’ hydroxyl group for DNA polymerase to add onto
4) adds nucleotides to 3' hydroxyl on the primer
5) one part has a continuous synthesis and other has a discontinuous synthesis
80
Can DNA polymerases start synthesis on their own?
no, but RNA synthesis can
81
What strand is continuous synthesis?
leading
82
What strand is discontinuous synthesis?
lagging strand, Okazaki fragments
83
How can you tell which strand is leading or lagging?
by the orientation of our strands relative to the direction of unwinding
84
What is the right side of the top ORI?
unwinding goes in the same direction as unwinding, so it is leading
85
What is the left side of the bottom ORI?
unwinding goes in the same direction as unwinding, so it is leading
86
What is the right side of the bottom ORI?
unwinding is going in the opposite direction of synthesis, so it is lagging
87
1) What is termination?
2) What is the job of the enzyme that comes in?
1) primers leave a gap in the phosphodiester backbone
Another enzyme comes in called DNA ligase
2) DNA ligase: job is to form a phosphodiester bond between DNA molecules
88
Where are phosphodiester bonds found in DNA?
between the phosphate of one nucleotide and the hydroxyl group attached to the 3' carbon on the 5' sugar
89
Where are hydrogen bonds found in DNA?
between base pairs
90
How is dNTP added to a growing nucleotide chain through the formation of a phosphodiester bond?
forms a phosphodiester bond between the 3' hydroxyl group of the last nucleotide and the 5' phosphate group of the incoming dNTP
91
Why do eukaryotic chromosomes need multiple ORIs than prokaryotic chromosomes?
eukaryotic chromosomes are much longer and there are many of them
92
What is the difference between leading and lagging strands?
leading strand is synthesized in the same direction as DNA is unwinding whereas lagging is synthesized in the opposite direction
93
What is the proofreading capability of DNA polymerases?
polymerase can detect wrong nucleotides so it can remove or replace the nucleotide the right way
94
Explain what Chargaff’s rules mean about base pairing between purines and pyrimidines. Which bases pair with each other?
Different species had equal amounts of purines (A and G) and pyrimidines (T and C), but different ratios of the bases. A and T pair together, and G and C pair together.
95
What are the structures of purines and pyrimidines?
Purines have a double ring structure with a six-membered ring fused to a five-membered ring. Pyrimidines are smaller and have a single six-membered ring structure.
96
What is the phosphate backbone?
connected to the 5’ carbon on the sugar by formation of an ester linkage between phosphoric acid and the 5’ OH group
97
What is a sugar group?
deoxyribose in DNA and ribose in RNA, numbered 1’-5’
98
How do nucleotides vary between DNA and RNA?
Sugar in DNA is deoxyribose, and RNA is ribose. Nucleotides in DNA have a 3’ carbon of deoxyribose attached to an OH group, and nucleotides in RNA have a 2’ carbon of ribose attached to an OH group.
99
What does it mean that DNA is a double helix with antiparallel strands?
Two strands are twisted around each other, and they run in opposite directions. 3’ end of one strand faces the 5’ end of the other strand.
100
What are loci?
location of each gene on the chromosome
101
What are SNPs?
single-nucleotide polymorphism
There is a difference of just one base pair in the DNA sequence
102
What is the central dogma?
DNA sequences are converted to phenotypes
Says that DNA makes RNA sometimes makes protein
103
How is DNA converted to RNA?
transcription
104
How is RNA converted to proteins?
translation
105
What makes proteins?
mRNA
106
What is a dominant allele?
Dominant allele only needs to be present in 1 copy to see that particular phenotype
107
Are dominant alleles always more common than recessive phenotypes?
no
108
Are dominant alleles always better tan recessive alleles?
no
109
What are recessive alleles?
need 2 copies of the same allele to see that phenotype
110
What is sickle-cell disease?
Due to a single nucleotide change in the amino acid sequence in a subunit of hemoglobin
111
What is hemoglobin?
protein that carries oxygen in red blood cells
112
What is the multiplication rule?
the probability of 2 or more independent events occurring simultaneously is the product of their individual probabilities
113
What is the addition rule?
the probability of 1 or more mutually exclusive events occurring is the sum of their individual probabilities
114
What is the law of segregation?
separation of the homologous pairs of chromosomes
Diploid organism that has 2 copies of a gene has 2 alleles that separate in anaphase 1 and get distributed to the daughter cells
115
What is the law of independent assortment?
shows that there are 2 possible ways homologous pairs can line up on the metaphase plate
Random
All maternal chromosomes on the same side or all paternal chromosomes on the same side or flipped with 1 maternal on the left and 1 paternal on the left and 1 maternal and the right and 1 paternal on the right
Contributes to genetic variation
Allows shuffling of parental alleles
116
Do X chromosomes have more genes than Y chromosomes?
yes
117
Is X or Y required for survival?
X, can't survive without an X but can survive without a Y
118
When do X chromosomes and Y chromosomes align?
in meiosis
119
What does hemizygous mean?
only have one allele of a given gene (males for X-linked genes)
