Exam 2 Study Flashcards
(117 cards)
1
Q
What are the four phases of mitosis?
A
Prophase, Metaphase, Anaphase, Telophase
2
Q
During which phase does DNA replication occur?
A
S phase of interphase
3
Q
What is the function of spindle fibers in mitosis?
A
They attach to chromosomes and separate sister chromatids during anaphase
4
Q
What checkpoint ensures that all chromosomes are properly attached to the spindle?
A
The M (spindle) checkpoint
5
Q
What happens during cytokinesis?
A
The cytoplasm divides, forming two daughter cells
6
Q
What is the G0 phase?
A
A resting phase where the cell exits the cycle and stops dividing
7
Q
Which phase of mitosis do chromosomes align at the center of the cell?
A
Metaphase
8
Q
What are sister chromatids?
A
Two identical copies of a chromosome joined at the centromere
9
Q
What enzyme is responsible for DNA replication?
A
DNA polymerase
10
Q
What is the function of nucleosomes?
A
To package and compact DNA into chromatin
11
Q
What are the three parts of a nucleotide?
A
A sugar, a phosphate group, and a nitrogenous base
12
Q
What base pairs with adenine in DNA?
A
Thymine (A-T)
13
Q
What is the sugar found in DNA?
A
Deoxyribose
14
Q
What are the four nitrogenous bases in DNA?
A
Adenine, Thymine, Cytosine, Guanine
15
Q
What type of bonds hold base pairs together?
A
Hydrogen bonds
16
Q
What does ‘anti-parallel’ mean in the context of DNA structure?
A
The two DNA strands run in opposite directions (5’ to 3’ and 3’ to 5’)
17
Q
What is the role of DNA ligase?
A
It joins Okazaki fragments on the lagging strand
18
Q
What is the function of helicase?
A
It unwinds the DNA helix for replication
19
Q
What is a replication fork?
A
The area where DNA is unwound and replication occurs
20
Q
What is a primer, and what enzyme creates it?
A
A short RNA sequence made by primase to start DNA replication
21
Q
How many chromosomes are in a human somatic cell?
A
46 (23 pairs)
22
Q
What is the difference between chromatin and chromosomes?
A
Chromatin is uncondensed DNA, while chromosomes are tightly packed DNA
23
Q
What are autosomes?
A
The 22 pairs of non-sex chromosomes in humans
24
Q
What are homologous chromosomes?
A
Chromosomes of the same size and shape that contain genes for the same traits
25
What does 'haploid' mean?
A cell with one set of chromosomes (n)
26
What does 'diploid' mean?
A cell with two sets of chromosomes (2n)
27
What is a karyotype?
A visual representation of an organism’s chromosomes
28
What are the sex chromosomes for a biological male?
XY
29
What are the sex chromosomes for a biological female?
XX
30
What is the purpose of telomeres?
To protect chromosome ends from degradation
31
What is passive transport?
Movement of molecules down their concentration gradient without energy input
32
What is osmosis?
The diffusion of water across a selectively permeable membrane
33
What is active transport?
Movement of molecules against their concentration gradient using ATP
34
What is facilitated diffusion?
Passive transport using a membrane protein
35
What does the sodium-potassium pump do?
Moves 3 Na⺠out and 2 K⺠into the cell using ATP
36
Which molecules pass freely through the plasma membrane?
Small, nonpolar molecules like Oâ‚‚ and COâ‚‚
37
What is endocytosis?
The process of a cell engulfing substances into a vesicle
38
What is exocytosis?
The process of a cell expelling substances in vesicles
39
What type of transport moves glucose into cells?
Facilitated diffusion
40
What is the function of aquaporins?
Water channel proteins that facilitate osmosis
41
What is the function of ribosomes?
They synthesize proteins
42
What is transcription?
The process of copying DNA into RNA
43
What is translation?
The process of converting mRNA into a protein
44
What is the role of mRNA?
It carries genetic instructions from DNA to the ribosome
45
What does tRNA do?
It brings amino acids to the ribosome during translation
46
What is the role of rRNA?
It helps form ribosomes and catalyzes peptide bond formation
47
What is the start codon for translation?
AUG (Methionine)
48
Where does transcription occur?
In the nucleus
49
Where does translation occur?
In the cytoplasm at ribosomes
50
What is a codon?
A three-nucleotide sequence on mRNA that codes for an amino acid
51
What is p53?
A tumor suppressor protein that regulates the cell cycle and induces apoptosis
52
What is a tumor suppressor gene?
A gene that inhibits cell division to prevent uncontrolled growth
53
What is an oncogene?
A mutated proto-oncogene that promotes excessive cell division
54
What is apoptosis?
Programmed cell death
55
How does cancer develop?
From uncontrolled cell division due to mutations in regulatory genes
56
What is metastasis?
The spread of cancer cells to other parts of the body
57
What role do proto-oncogenes play?
They normally promote cell growth in a regulated way
58
Why are p53 mutations dangerous?
They prevent the cell from stopping division or undergoing apoptosis
59
What is the role of telomerase in cancer?
It extends telomeres, allowing cancer cells to divide indefinitely
60
Which enzyme relieves supercoiling tension ahead of the replication fork?
Topoisomerase
61
Why is the lagging strand synthesized discontinuously?
Because DNA polymerase can only synthesize in the 5' to 3' direction
62
What is the function of the M checkpoint in mitosis?
Ensures all chromosomes are attached to spindle fibers before anaphase
63
What phase of mitosis follows metaphase?
Anaphase
64
Which type of molecule moves most easily across the plasma membrane without assistance?
Small nonpolar molecules like O2 and CO2
65
What is the role of cyclins in the cell cycle?
Regulate progression through the cell cycle by activating CDKs
66
Which nucleotide is unique to RNA and not found in DNA?
Uracil (U)
67
How do histones help regulate gene expression?
By controlling the accessibility of DNA for transcription
68
What is the primary function of lysosomes?
Break down macromolecules and cellular waste
69
How many chromatids are present in a human cell during metaphase?
92 chromatids (since each chromosome is duplicated)
70
What is the significance of the fluid mosaic model of the plasma membrane?
Describes membrane flexibility and dynamic movement of proteins and lipids
71
What is the purpose of telomerase?
Extends telomeres to prevent chromosome shortening
72
Which DNA repair mechanism corrects mismatched bases after replication?
Mismatch repair
73
What is the difference between exocytosis and endocytosis?
Exocytosis expels substances from the cell; endocytosis brings them in
74
Why do cancer cells often have unregulated cell division?
Mutations in tumor suppressor genes (e.g., p53) and activation of oncogenes
75
What is the role of RNA polymerase in transcription?
Synthesizes RNA from a DNA template
76
Which type of mutation is least likely to alter a protein’s function?
Silent mutation (does not change the amino acid sequence)
77
How does DNA polymerase prevent errors during replication?
By proofreading and correcting mismatched bases
78
Why do cells undergo apoptosis?
To eliminate damaged or unnecessary cells
79
How does ATP provide energy for active transport?
By phosphorylating transport proteins to change their shape
80
What is the primary function of the rough endoplasmic reticulum?
Synthesis of membrane-bound and secreted proteins
81
What property of the plasma membrane allows selective permeability?
Its phospholipid bilayer with embedded transport proteins
82
How does facilitated diffusion differ from active transport?
Facilitated diffusion moves substances down their gradient without ATP, while active transport moves against the gradient with ATP
83
What is the importance of the sodium-potassium pump?
Maintains the electrochemical gradient essential for nerve signaling
84
What are Okazaki fragments?
Short DNA fragments synthesized on the lagging strand during replication
85
What part of the cytoskeleton helps move chromosomes during mitosis?
Microtubules (spindle fibers)
86
Which stage of the cell cycle involves DNA replication?
S phase
87
Why do prokaryotes lack a nucleus?
Their DNA is not enclosed in a membrane-bound compartment
88
What is the function of chaperone proteins?
Help proteins fold into their correct shape
89
How do cells regulate membrane fluidity?
By incorporating cholesterol into the phospholipid bilayer
90
What type of cellular transport requires a receptor protein?
Receptor-mediated endocytosis
91
Which checkpoint prevents the cell from entering mitosis if DNA is damaged?
G2 checkpoint
92
How does temperature affect membrane fluidity?
Higher temperatures increase fluidity; lower temperatures decrease fluidity
93
What organelle is responsible for sorting and packaging proteins?
Golgi apparatus
94
What molecule acts as the final electron acceptor in cellular respiration?
Oxygen (O2)
95
What process allows bacterial cells to share genetic material?
Conjugation
96
Which type of bond holds adjacent nucleotides together in a DNA strand?
Phosphodiester bonds
97
Which organelle is responsible for photosynthesis?
Chloroplast
98
What is the role of the kinetochore during mitosis?
It is a protein structure on the centromere where spindle fibers attach to pull chromatids apart.
99
What happens during prometaphase that distinguishes it from prophase?
The nuclear envelope breaks down, and spindle fibers attach to kinetochores.
100
Why do cancer cells often bypass cell cycle checkpoints?
Mutations in tumor suppressor genes (e.g., p53) and unchecked activation of proto-oncogenes allow uncontrolled division.
101
Which phase of the cell cycle involves organelle duplication and cell growth in preparation for mitosis?
G2 phase.
102
How do microtubules facilitate chromosome movement during anaphase?
They shorten by depolymerizing at the kinetochore, pulling chromatids toward opposite poles.
103
What is the difference between anaphase of mitosis and anaphase I of meiosis?
In mitosis, sister chromatids separate; in meiosis I, homologous chromosomes separate while sister chromatids stay together.
104
How does the mitotic spindle ensure accurate chromosome separation?
It exerts tension on kinetochores and aligns chromosomes properly before division.
105
What happens if the M checkpoint fails?
Aneuploidy (abnormal chromosome number) can result, leading to conditions like Down syndrome or cancer.
106
Why does cytokinesis occur differently in plant and animal cells?
Plants form a cell plate via vesicles, while animal cells use a cleavage furrow created by actin filaments.
107
Which type of microtubule interacts with those from the opposite pole to stabilize the mitotic spindle?
Polar microtubules.
108
What is the function of DNA polymerase I in replication?
It removes RNA primers and replaces them with DNA nucleotides on the lagging strand.
109
Why is the leading strand synthesized continuously, but the lagging strand is not?
DNA polymerase III can only add nucleotides in the 5' to 3' direction, requiring discontinuous synthesis on the lagging strand.
110
What prevents single-stranded DNA from reannealing after helicase unwinds it?
Single-strand binding proteins (SSBs) stabilize the separated strands.
111
Which enzyme creates a short RNA primer for DNA polymerase to begin replication?
Primase.
112
Why does DNA polymerase require a primer to begin synthesis?
It can only add nucleotides to an existing 3'-OH group, not start a new chain from scratch.
113
How does topoisomerase prevent supercoiling during DNA replication?
It cuts and rejoins DNA strands to relieve torsional strain ahead of the replication fork.
114
What is the function of the sliding clamp in DNA replication?
It increases DNA polymerase processivity, keeping it attached to the template strand.
115
How do eukaryotic and prokaryotic DNA replication differ in terms of origins?
Prokaryotes have a single origin of replication, while eukaryotes have multiple origins per chromosome.
116
What is the function of ligase in DNA replication?
It seals nicks between Okazaki fragments by forming phosphodiester bonds.
117
How does the cell ensure accuracy in DNA replication?
DNA polymerase has a proofreading function that detects and removes mismatched nucleotides.
