Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MCAT Biochemistry > DNA Replication, Mitosis, and Mutations > Flashcards

DNA Replication, Mitosis, and Mutations Flashcards

1
Q

Cell Division in human cells

A

Not all cell types undergo cell division including fully differentiated cells (e.g. neurons)

Cells with short lifespans have progenitor cells to routinely replace them (skin cells and intestinal cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

DNA replication

A

Synthesis of an exact copy of the genome to be included in the newly created cell after division

Takes place during S phase of interphase portion of cell cycle

Semiconservative, as resulting DNA double helix has one new and one old strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Replisome

A

Group of proteins that governs mechanism of DNA replication
Attaches to the chromosome at origin of replication, marked by epigenetic factors
Creates a replication fork that moves along chromosome over course of replication
DNA helicase, DNA polymerase, primase, DNA ligase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

DNA Helicase

A

Enzyme in replisome which unwinds the double helix, separating the two DNA strands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

DNA polymerase

A

Enzyme in replisome which synthesizes new DNA strands by pairing complementary free-floating deoxynucleotides which sequence of nucleotides on exposed DNA strand

Reads parental strand in 3’ to 5’ direction, can only add nucleotides to existing strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Primase

A

RNA polymerase that creates an RNA primer of around 10 ribonucleotides to initiate replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Single Strand Binding Tetramer Proteins

A

AKA helix destabilizer proteins or SSB

stabilizes the looped around lagging strand to prevent it from folding back on itself

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Leading Strand

A

Continuously synthesized strand in DNA replication from which the direction of DNA polymerase movement (3’ to 5’) on the template strand is the same as the direction of the replication fork across the DNA helix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Lagging Strand

A

Strand synthesized by series of disconnected strands (Okazaki fragments) during DNA replication.
This is due to the direction of movement of the replication fork being 5’ to 3’ on the template strand. DNA polymerase is always moving 3’ to 5’ on template strand, so has to create discrete fragements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Okazaki Fragments

A

Series of disconnected fragments in DNA replication produced on lagging strand
Around 200 nucleotides long in Eukaryotes and 1000-2000 long in Prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

DNA Ligase

A

Joins together adjacent Okazaki fragments on lagging strand in DNA replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

RNAase H

A

Removes RNA primers in DNA replication after DNA strands are synthesized

Gaps are then filled in by DNA polymerase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Telomeres

A

Repeated six nucleotide units from 100 to 1000 units long that protect the ends of chromosomes

Can become shortened through by repeated rounds of replication- linked to aging and disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Telomerase

A

Catalyzes lengthening of telomeres in Eukaryotic organisms by adding many 5’ TTAGGG 3’ nucleotide sequences to ends of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Five main steps of DNA Replications

A
  1. Helicase unzips double helix
  2. RNA polymerase (primase) binds a primer
  3. DNA polymerase assembles leading and lagging strands
  4. RNAase H removes primers
  5. DNA ligase joins Okazaki fragments together
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does DNA polymerase function to correct errors in DNA replication?

A

One of the subunits in DNA polymerase is an exonuclease that removes nucleotides from the strand

Automatically proofreads each new strand during synthesis and repairs mismatched nucleotides
1 out of every 10^9-10^11 base pairs is incorrect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Mitosis

A

Process by which two cells are created that are identical to both each other and to original cell

Occurs in succession with DNA replication

Nuclear division without genetic change
Four main stages: prophase, metaphase, anaphase, telophase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Prophase

A

Condensation of chromatin into chromosomes
Tightly coiled chromosomes down-regulates gene expression during mitosis
Centrioles move to opposite poles of cell
Nucleolus and then nucleus disappear
Spindle apparatus begins to form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Sister Chromatids

A

Two identical copies of duplicated chromosomes

Joined near centers, called centromeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Centrosomes

A

Structure in which the centrioles are located in the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Spindle Apparatus

A

Consists of asters (microtubules radiating from centrioles), kinetochore microtubules growing from centromeres, and spindle microtubules connecting the two centrioles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Kinetochore

A

Structure of protein and DNA located at centromere of joined chromatids of each chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Metaphase

A

Chromosomes align along the equator of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Anaphase

A

Sister chromatids split at attaching centromeres and segregate to opposite sides of cell
Kinetochore microtubules shorten to pull sister chromatids apart (disjunction)

25
Cytokinesis
Actual separation of cellular cytoplasm due to constriction of microfilaments around center of cell Can happen at end of anaphase or in telphase
26
Telophase
Nuclear membrane reforms, followed by reformation of nucleolus Chromosomes de-condense (difficult to see under light microscope) Cytokinesis finishes
27
Mutation
Any alteration in the genome that is not due to genetic recombination Source of genetic variation within populations - Evolution Spontaneous or Induced
28
Spontaneous Mutation
Mutations that occur due to random errors in the natural process of replication and genetic recombination
29
Induced Mutations
Mutations that occur due to physical or chemical agents called mutagens - cause damage to DNA and increase frequency of mutations above baseline error rates
30
Effect of Mutation
Advantageous, deleterious, or no effect at all Can occur at the level of the nucleotide or the level of the chromosome
31
Gene mutation
Alteration in the sequence of DNA nucleotides in a single gene
32
Chromosomal Mutation
Structure of chromosome is changed
33
Somatic Mutation
Mutation in somatic cell | Somatic mutation of a single cell may have very little effect on an organism with millions of cells
34
Point Mutation
Mutation that changes a single nucleotide in a double strand of DNA Includes a base substitution mutation, addition mutation, and deletion mutation
35
Base substitution mutation
One nucleotide is swapped for another during DNA replication Transition mutation: swaps a purine for other purine or pyrimidine for other pyrimidine Transversion mutation: exchanges a purine for a pyrimidine or vice versa
36
Addition mutations
Inserting a new nucleotide into the sequence Can have profound effect on function of gene
37
Neutral Mutation
Has no effect on organism’s fitness Could change amino acid without a change to protein’s function, or could change codon without changing resultant amino acid (silent mutation)
38
Silent mutation
A base pair change without a change to the resultant amino acid Possible through wobble in genetic code
39
Missense Mutation
Base substitution changes a codon which results in the translation of a different amino acid Can be neutral, or can significantly change polypeptide’s function
40
Nonsense Mutation
Change to the nucleotide sequence creates a stop codon where none previously existed Usually create a truncated, non-functional protein Serious consequences
41
Frameshift Mutation
Deletions or additions occur in multiples other than three This changes the reading frame of the code, which means that the entire sequence after the mutation will be shifted Most often results in a completely non-functional protein
42
Structural Mutations
Point mutation - base substitution mutation - addition mutation - deletion mutation
43
Functional Mutation
- Silent mutations - Missense mutations - Nonsense mutations - Frameshift mutations
44
Chromosomal Mutations
Structural changes may occur to a chromosome in the form of: - deletions - duplications - translocations - inversions
45
Chromosomal Deletions
Portion of chromosome breaks off or is lost during homologous recombination or crossing over Serious consequences for organism
46
Chromosomal duplications
DNA fragment breaks free of one chromosome and incorporates into a homologous chromosome Gene duplication/amplification: can increase amount of a gene’s product Aneuploidy: entire chromosome duplicated Polyploidy: set of chromosomes duplicated
47
Chromosomal Translocation
Segment of DNA from one chromosome is exchanged for a segment of DNA on another chromosome (reciprocal translocation)
48
Chromosomal Inversions
Orientation of a section of DNA on a chromosome is inverted
49
Transposition
A process in Eukaryotic and Prokaryotic cells in which DNA segments called transposable elements or transposons can excise themselves from a chromosome and reinsert themselves at another location Mechanism by which a somatic cell of multicellular organism can alter its genetic makeup without meiosis
50
What are some causes of DNA damage?
1. Oxidation by free radicals 2. Errors in DNA replication 3. Exposure to environmental carcinogens
51
Effect of Ultraviolet light on DNA
Covalently links two neighboring thymine bases together - causes kink in DNA strand DNA repair enzymes can cleave cross-links
52
How are oxidized nucleotide bases repaired?
Can be corrected through excision repair in which damaged nucleotides are removed and replaced
53
Cancer
Unrestrained and uncontrolled growth of cells that results when the regulation of the cell cycle has gone awry
54
Proto-oncogenes
Genes that stimulate normal growth in human cells Can be converted to oncogenes by mutagens such as UV radiation or chemicals, or random mutations Oncogenes: genes that cause cancer
55
Carcinogens
Mutagens that can cause cancer
56
Tumor suppressor genes
Genes that help regulate normal cell growth Can be checkpoints during the cell cycle - retinblastoma (Rb) - p53 proteins
57
Deletion mutation
Deleting a nucleotide from the sequence Can have profound effects on function of gene
58
Replication Units
AKA replicons Discrete segments of DNA replication in Eukaryotic cells Eukaryotic chromosomes contain multiple origins of replication due to long length of chromosomes
59
What direction does DNA replication proceed from replication fork?
DNA replication is a bidirectional process, because replisomes proceed in opposite directions from origin of replication

MCAT Biochemistry (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions