Exam 2
Ch. 7 DNA Structure and Replication — Flashcard Format
1. Chromosome
Large DNA molecule with genes, found in nucleus. Humans have 46 (23 pairs).
2. Number of Chromosomes
46 total (23 pairs): 23 from mom, 23 from dad.
3. Autosomes
22 pairs of non-sex chromosomes. Carry most trait info.
4. Sex Chromosomes
1 pair (XX = female, XY = male). Determine biological sex.
5. Male vs. Female Chromosomes
Female = XX, Male = XY. Y has SRY gene for testes.
6. DNA Structure
Double helix. Made of nucleotides: sugar, phosphate, base.
7. DNA Bases
Adenine (A), Thymine (T), Cytosine (C), Guanine (G). A-T, C-G.
8. Base Pairing Example
A pairs with T, C with G.
Example: AATCG → TTAGC
9. DNA Replication
DNA copied before cell division. Each strand is a template.
10. Replication Process
Helicase unzips DNA. DNA polymerase builds new strands. Makes 2 identical DNAs.
11. PCR (Polymerase Chain Reaction)
Lab technique to make many DNA copies.
12. PCR Steps
Heat to separate strands → cool to add primers → DNA polymerase builds new DNA. Repeats to amplify.
13. Genome
All DNA in an organism. Includes genes + non-coding DNA.
14. STR (Short Tandem Repeat)
Short, repeated DNA sections. Vary per person—used in forensics.
15. Gel Electrophoresis
Separates DNA by size. STRs show as bands = DNA profile.
16. CODIS
DNA database used by law enforcement. Stores STR profiles.
17. Protein Structure
Proteins have 4 levels:
Primary: amino acid chain
Secondary: coils (alpha helices) and folds (beta sheets)
Tertiary: 3D shape
Quaternary: multiple chains together
18. Gene Expression
The process of making a protein from DNA:
Transcription: DNA → mRNA
Translation: mRNA → protein
19. Regulatory vs. Coding Sequences
Regulatory: controls when, where, how much protein is made
Coding: tells the cell what amino acids to use
20. Transcription Process
RNA polymerase reads DNA and builds mRNA using the DNA as a template
21. DNA to mRNA Base Pairing
A → U
T → A
C → G
G → C
Example: TACG → AUGC
22. Location of Transcription
Happens in the nucleus of eukaryotic cells
23. Translation Process
Ribosomes read mRNA and use tRNA to build a chain of amino acids (a protein)
24. Codons vs. Anticodons
Codons: 3-letter mRNA codes for amino acids
Anticodons: tRNA parts that match codons during translation
25. Location of Translation
Happens in the cytoplasm at a ribosome
26. Genetic Code is Universal
Almost all life uses the same codons to make the same amino acids, so genes can work across species
27. Amino Acids and Codons
20 amino acids
64 codons (3-letter codes)
Each codon = 1 amino acid or a stop signal
28. Start Codon
AUG = start codon
Codes for methionine
Tells the ribosome where to begin
29. Transgenic
An organism with a gene from another species (genetically modified)
30. Recombinant Gene
A custom gene made by mixing coding and regulatory parts from different sources
31. Creating a Transgenic Organism (Yeast/Spider Silk)
Scientists put the spider silk gene into yeast using a vector so the yeast makes silk protein
32. GMO
An organism with DNA changed by genetic engineering
33. Insulin Production
Scientists put the human insulin gene into bacteria, which then make human insulin for medicine
34. Gene Therapy
Adding healthy genes to fix faulty ones to treat or cure genetic diseases
35. Ethics of Genetic Engineering
Concerns include health risks (like eating GMOs), environmental effects, and human gene editing issues
36. Mutation
A change in DNA sequence that can affect proteins, cause disease, or create new traits
37. Mutation’s Role in Evolution
Mutations create differences in DNA that drive evolution by natural selection
38. Point Mutation
Changes one DNA base — might or might not affect the protein
39. Missense, Silent, Nonsense Mutations
Missense: changes amino acid
Silent: no change to amino acid
Nonsense: causes early stop, shortens protein
40. Frameshift Mutation
Caused by adding or removing DNA bases — shifts how the gene is read and changes the whole protein
41. Insertion vs. Deletion Mutation
Insertion: adds bases
Deletion: removes bases
Both can mess up how the gene is read
42. Rearrangement Mutation
Changes large DNA sections — can change gene structure and how it works
43. Inversion vs. Translocation Mutations
Inversion: flips a DNA piece
Translocation: moves DNA to a new chromosome
Both affect protein function
44. Protein Shape and Function
A protein’s job depends on its shape, which comes from its amino acid order and folding
45. Mutagen
Something that causes mutations — like UV light, radiation, or smoking
46. Gene Therapy for Sickle Cell
Replaces faulty gene in blood cells using a virus so cells can make healthy hemoglobin
47. Turning Genes On/Off with Gene Therapy
Can activate helpful genes (like fetal hemoglobin) or silence harmful ones to treat disease
48. CRISPR
A tool that edits DNA using a guide RNA and enzyme to cut at a specific spot
49. How CRISPR Edits DNA
CRISPR cuts DNA at a target spot, and the cell repairs it — can fix or replace genes
50. Somatic vs. Germ-line Cells
Somatic: body cells, changes affect only that person
Germ-line: sperm/egg cells, changes can be passed to kids
51. How CRISPR Changes Can Be Passed to Children
If CRISPR edits germ-line cells, the change can be inherited. Somatic cell changes stay with the person.
52. Sickle Cell Trait
Person has one normal and one sickle gene — usually no symptoms but can pass it to children
53. Why Sickle Cell Trait Can Be Good
It helps protect against malaria, so it’s beneficial in places where malaria is common
54. Why Cells Reproduce
To grow, fix damage, and replace old cells
55. Tissues That Don’t Do Mitosis
Nerve and heart muscle cells don’t divide in adults
56. Interphase
Cell grows, works, and gets ready to divide (G1, S, G2)
57. G1 Phase
Cell grows and makes more parts (cytoplasm and organelles)
58. S Phase
DNA is copied so each chromosome has two chromatids
59. G2 Phase
Cell checks for DNA errors and prepares for mitosis
60. Mitosis
Nucleus divides so each new cell gets the same chromosomes
61. Prophase (Mitosis)
Chromosomes condense, nucleus breaks down, spindle forms
62. Metaphase (Mitosis)
Chromosomes line up in the middle, spindle attaches
63. Anaphase (Mitosis)
Sister chromatids are pulled to opposite sides
64. Telophase (Mitosis)
Nucleus reforms, chromosomes relax, division almost done
65. Cytokinesis
Cytoplasm divides → two new daughter cells
66. G0 Phase
Resting phase — cells not dividing (like neurons)
67. Cell Cycle Checkpoints
Points where the cell checks if it’s safe to keep dividing
68. G1 Checkpoint
Checks cell size, nutrients, and growth signals
69. S Checkpoint
Checks DNA for errors during copying — bad errors → apoptosis
70. G2 Checkpoint
Makes sure DNA was copied correctly before mitosis
71. Mitosis Checkpoint
Checks if chromosomes are lined up and ready to split
72. Carcinogen
Anything that causes cancer (e.g., smoking, UV, radiation)
73. Proto-oncogene
Normal gene that tells cells to divide when needed
74. Normal Proto-oncogenes
Help cells divide only when they’re supposed to
75. Mutated Proto-oncogenes
Become oncogenes that make cells divide too much
76. Tumor Suppressor Gene
Slows cell division, fixes DNA, or causes cell death if needed
77. Normal Tumor Suppressor Genes
Stop cell division when there’s a problem
78. Mutated Tumor Suppressor Genes
Can’t stop damaged cells from dividing → more mutations
79. Sporadic vs. Genetic Cancer
Sporadic: happens from life events
Genetic: inherited mutations (e.g. BRCA1/2)
80. Steps of Cancer Progression
Starts with one cell → benign tumor → more mutations → malignant → spreads
81. Contact Inhibition
Normal cells stop dividing when crowded; cancer cells ignore this
82. Anchorage Dependence
Normal cells need to stick to something to divide; cancer cells don’t
83. Angiogenesis
Cancer makes new blood vessels to feed the tumor
84. Benign vs. Malignant Tumors
Benign: slow, don’t spread
Malignant: fast, invade other areas
85. Metastasis
Cancer spreads to new body parts and forms new tumors
86. Conventional Cancer Treatments
Surgery: removes tumor
Chemo: kills fast-growing cells
Radiation: damages DNA in cancer cells
87. Targeted Cancer Therapy
Treats specific mutations in cancer cells, spares healthy ones
88. Immunotherapy
Boosts the immune system to attack cancer cells
89. 6 Ways to Lower Cancer Risk
Don’t smoke
Stay at a healthy weight
Get vaccinated (e.g. HPV)
Avoid too much sun
Eat healthy
Get regular cancer screenings
90. Genetics
The study of how traits are passed from parents to children
91. Haploid vs. Diploid
Diploid: 46 chromosomes (body cells)
Haploid: 23 chromosomes (sex cells)
92. Homologous Chromosomes
Chromosome pairs (one from each parent) with the same genes, possibly different versions (alleles)
93. Replicated vs. Unreplicated Chromosome
Replicated: two identical chromatids
Unreplicated: one DNA strand
94. Gamete
Sex cells (sperm and egg), made by meiosis, and combine to form a baby
95. Meiosis
Cell division that makes 4 non-identical haploid sex cells from 1 diploid cell
96. Phase Before Meiosis
Interphase – DNA is copied and cell prepares to divide
97. Prophase I (Meiosis)
Chromosomes pair up, cross over, and nucleus breaks down
98. Metaphase I (Meiosis)
Chromosome pairs line up in the center and spindle attaches
99. Anaphase I (Meiosis)
Pairs split apart, moving to opposite sides; chromatids stay together
100. Telophase I (Meiosis)
Cell splits into 2 haploid cells, each still with chromatids
101. Products of Meiosis I
Two haploid cells with chromosomes made of sister chromatids
102. Prophase II (Meiosis)
Chromosomes condense again in each haploid cell
103. Metaphase II (Meiosis)
Chromosomes line up in the middle; spindle attaches to chromatids
104. Anaphase II (Meiosis)
Sister chromatids pull apart to opposite ends
105. Telophase II (Meiosis)
Nuclei reform, and cells divide into 4 unique haploid cells
106. Products of Meiosis II
Four different sex cells, each with 23 chromosomes
107. Recombination (Crossing Over)
In Prophase I, chromosomes swap genes → more variety
108. Independent Assortment
Chromosome pairs line up randomly in Metaphase I → genetic diversity
109. Allele
Different versions of a gene
110. Dominant vs. Recessive Alleles
Dominant: shows up if present
Recessive: only shows if both alleles are recessive
111. Homozygous vs. Heterozygous
Homozygous: two same alleles
Heterozygous: two different alleles
112. Genotype vs. Phenotype
Genotype: the genes (letters)
Phenotype: physical traits you see
113. Punnett Square Probability
Tool to predict trait outcomes in offspring based on parent genes
114. Inheriting Dominant Traits
Need just one dominant allele from a parent
115. Inheriting Recessive Traits
Need two recessive alleles — one from each parent
116. What It Means to Be a Carrier
Has one normal and one disease allele — no symptoms but can pass it on
117. Recessive Genetic Conditions
Need two copies to have the disease
Examples: Albinism, Cystic Fibrosis, Sickle Cell, Tay-Sachs
118. Dominant Genetic Conditions
Need only one copy to have the trait/disease
Examples: Huntington’s, Freckles, Dimples, Extra fingers/toes
119. Dihybrid Cross Probability
Shows inheritance of 2 traits using a 4x4 Punnett square
120. Autosomes vs. Sex Chromosomes
Autosomes: chromosomes 1–22 (traits)
Sex chromosomes: X and Y (biological sex)
121. Sex Chromosomes in Males vs. Females
Female: XX
Male: XY (Y determines male development)
122. Sex Hormones & Genitals
Males: testosterone
Females: estrogen
Hormones guide genitals and other sex traits
123. Intersex
People born with chromosomes/genitals that don’t fit typical male/female
124. Sex-Linked Inheritance
Genes on X or Y chromosomes; mostly X-linked and affect males more
125. Why Males Are More Affected by X-Linked Traits
Males have 1 X — so one bad copy causes the condition
126. X-Linked Traits
Traits on the X chromosome; different effects in males vs. females
127. 3 X-Linked Traits
Red-green colorblindness
Hemophilia
Duchenne muscular dystrophy
128. Pedigree
A family tree chart showing how traits are passed through generations
129. Y-Chromosome Analysis
Tests Y chromosome to trace male ancestors or identify males
130. Incomplete Dominance
Both alleles blend in heterozygote (red + white = pink)
131. Familial Hypercholesterolemia
Incomplete dominance:
One copy = medium cholesterol
Two = very high cholesterol
132. Codominance
Both alleles show up (like AB blood = A + B antigens)
133. Blood Types – Antigens & Antibodies
A: A antigens, anti-B
B: B antigens, anti-A
AB: A + B antigens, no antibodies
O: no antigens, both antibodies
134. Blood Type Compatibility
Type O = universal donor
Type AB = universal receiver
Match antigens & antibodies to prevent reaction
135. Universal Donor vs. Recipient
Donor: O negative
Recipient: AB positive
136. ABO Genotypes
A: AA or AO
B: BB or BO
AB: AB
O: OO
137. Rhesus (Rh) Factor
Rh protein on red blood cells:
Rh+ = has it
Rh– = doesn’t
Important for pregnancy/blood donation
138. Transfusion Reaction
Happens when mismatched blood causes immune attack — can be deadly
139. Polygenic Inheritance
Trait controlled by many genes (e.g., height, skin color)
140. Continuous Variation
Small differences across a range (like height) due to polygenic traits
141. Multifactorial Inheritance
Traits shaped by genes + environment (e.g., heart disease, diabetes)
142. Environment Affects Height
Nutrition & health during growth can change how tall you become
143. Epigenetics
How the environment changes gene expression without changing DNA
144. Nurturing Rat Pups & Anxiety
Nurtured pups = calm
Uncared pups = anxious
Example of epigenetics in action
145. Aneuploidy
Wrong number of chromosomes (like 45 or 47) from meiosis errors
146. Trisomy 21 (Down Syndrome)
3 copies of chromosome 21 — from nondisjunction in meiosis
147. Amniocentesis
Prenatal test using fluid from womb to find chromosome problems
148. Karyotype
Picture of all chromosomes used to find abnormalities