1
Q
What is the Law of Segregation?
A
Alleles segregate during gamete formation, with each gamete receiving one allele for each character
2
Q
What is the phenotypic ratio in the F2 generation according to Mendel’s Law of Segregation?
A
3:1
3
Q
What is the Law of Independent Assortment?
A
Different gene pairs assort independently during gamete formation
4
Q
What is the phenotypic ratio produced from dihybrid crosses?
A
9:3:3:1
5
Q
What does the multiplication rule in probability state?
A
Probability of independent events occurring together = product of individual probabilities
(independent) x probabilities.
(mutually exclusive) + probabilities.
If two events don’t affect each other (independent), the chance of both happening is multiplying their individual chances.
6
Q
What does the addition rule in probability state?
A
Probability of mutually exclusive events = sum of individual probabilities
sum of each separate chance.
events that cannot happen at the same time
7
Q
Define complete dominance.
A
Heterozygote looks like dominant homozygote
So Aa looks just like AA.
Complete dominance happens when a heterozygote (Aa) looks the same as a dominant homozygote (AA). One copy of the dominant allele is enough to fully show the dominant trait, so the recessive allele only shows if both copies are recessive (aa).
8
Q
Define incomplete dominance.
A
Heterozygote shows intermediate phenotype
9
Q
Define codominance.
A
Both alleles expressed simultaneously
10
Q
What is pleiotropy?
A
Single gene affects multiple phenotypic characters
Pleiotropy = “Plenty of traits” from one gene.
Pleiotropy happens when a single gene influences more than one physical trait (phenotypic character).
Example
In sickle-cell disease:
11
Q
What is epistasis?
A
One gene affects expression of another gene
when it overpowers the other gene
12
Q
What is polygenic inheritance?
A
Multiple genes affect a single trait
13
Q
What is a pedigree?
A
Family tree tracing inheritance patterns
14
Q
What are recessive disorders?
A
Disorders requiring two copies of the allele to manifest
15
Q
What are dominant disorders?
A
Disorders requiring only one copy of the allele to manifest
16
Q
What is genetic counseling?
A
Helping families make informed decisions regarding genetic disorders
17
Q
What is the definition of an allele?
A
Alternative versions of a gene
18
Q
What does true-breeding mean?
A
Plants that produce offspring identical to parents when self-pollinated
19
Q
What is the F1 generation?
A
First filial generation (hybrid offspring)
20
Q
What is a monohybrid cross?
A
Cross between heterozygotes for one character
21
Q
What is a dihybrid cross?
A
Cross between individuals heterozygous for two characters
22
Q
What is the significance of Mendel’s experiments?
A
Laid the foundation for understanding heredity and genetics
23
Q
What is the role of environment in genetics?
A
It can influence phenotypic expression
affects physical traits
24
Q
What are multifactorial traits?
A
Characters influenced by multiple genes and the environment
25
What is the significance of crossing over?
Homologous chromosomes exchange segments, **creating new allele combinations**
26
What is the result of independent assortment during meiosis?
Many possible gamete combinations
27
What are some examples of recessive disorders?
* Cystic fibrosis
* Sickle-cell disease
* Albinism
28
What are examples of dominant disorders?
* Achondroplasia
* Huntington's disease
29
What is the importance of genetic testing?
Identifies carriers and detects genetic disorders early
30
What is hybridization?
Crossing two true-breeding varieties
31
What does a testcross involve?
Breeding an organism of unknown genotype with a recessive homozygote
32
What is the definition of genotype?
Genetic makeup of an organism
33
What is the definition of phenotype?
Observable traits of an organism
34
What is the significance of Mendel's Law of Segregation?
It explains how alleles separate during gamete formation
35
What is the impact of inbreeding on genetic disorders?
Increases the chance of recessive disorders due to shared alleles
36
What are some traits studied by Gregor Mendel in pea plants?
* Seed shape
* Plant height
* Pod type
* Flower color
* Seed color
* Pod color
* Flower position
37
What is the role of the bHLH transcription factor in flower color?
Mutations control the color of flowers
38
What is the genetic basis of sickle-cell disease?
single DNA letter change in the hemoglobin gene, leading to anemia
39
What is the significance of the IGF gene in dogs?
It links size variation to a single nucleotide change
## Footnote
A single nucleotide change (one “letter” in DNA) **can cause variation in size traits, such as height or body part length.**
40
What does CRISPR gene editing offer for future genetic research?
Functional validation of traits
41
What is linkage disequilibrium?
when alleles at different locations on DNA are inherited together more often than expected by chance.
42
What is the role of structural variations in genetics?
They often control traits, not just coding mutations
43
What is the effect of environmental factors on polygenic traits?
They can shape the expression of traits
44
What does the Law of Independent Assortment state?
Alleles on different chromosomes are passed to offspring independently, so the inheritance of one doesn’t affect the other.
45
What is independent assortment and how does it contribute to genetic variation?
Random orientation of chromosomes in meiosis I leads to many possible gamete combinations (humans: 2²³ ≈ 8 million).
46
What is crossing over in genetics?
Homologous chromosomes exchange segments, resulting in new allele combinations.
47
How does random fertilization contribute to genetic variation?
Any sperm can fertilize any egg, leading to trillions of possible zygotes.
48
Who discovered sex-linked traits and in which organism?
Thomas Hunt Morgan discovered sex-linked traits in fruit flies.
49
What is the significance of the white-eye allele in fruit flies?
It is located on the X chromosome.
50
What is the sex determination system in humans?
Males are XY (Y has SRY gene → testes) and females are XX.
51
Name some alternative sex determination systems.
* X-0 (insects) * Z-W (birds, fish) * Haplodiploidy (bees/ants) * Temperature-dependent in some reptiles.
52
What are X-linked disorders and who do they mostly affect?
X-linked disorders mostly affect males, as they have only one X chromosome.
53
Give examples of X-linked disorders.
* Color blindness * Hemophilia.
54
What happens to one X chromosome in females?
One X chromosome is randomly inactivated, forming a Barr body.
55
What is nondisjunction and what can it lead to?
Nondisjunction is the failure of chromosomes to separate in meiosis, leading to abnormal chromosome numbers (aneuploidy).
56
What is an example of a condition caused by nondisjunction?
Down syndrome (Trisomy 21).
57
What is a karyotype?
An ordered display of chromosomes used to detect abnormalities.
58
What defines linked genes?
Genes that are close together on the same chromosome and are inherited together.
59
What is the role of crossing over in relation to linked genes?
Crossing over can separate linked genes, resulting in recombinant gametes.
60
What is genomic imprinting?
Only one parental allele is expressed, depending on the parent of origin.
61
Give an example of genomic imprinting.
Igf2 gene in mice (only father's allele expressed).
62
What is mitochondrial donation therapy?
An experimental treatment for diseases caused by defective mitochondrial DNA.
63
What is the Central Dogma of Molecular Biology?
DNA → RNA → Protein.
64
What were the early beliefs about genetic material before the 1940s?
Proteins were thought to be the genetic material due to their complexity (20 amino acids vs 4 nucleotides).
65
What was Griffith's experiment in 1928 about?
It demonstrated transformation; heat-killed pathogenic (S) + living nonpathogenic (R) → mice died.
66
What did Hershey & Chase's experiment prove?
Only DNA entered bacteria, confirming DNA as genetic material.
67
What is the structure of DNA?
DNA is a polymer of nucleotides consisting of a base, deoxyribose sugar, and phosphate.
68
What are Chargaff’s Rules?
DNA composition varies between species; A = T and G = C.
69
Who contributed to the discovery of the helical structure of DNA?
Rosalind Franklin through X-ray diffraction.
70
What did Watson & Crick propose in 1953?
The double helix model of DNA with a sugar-phosphate backbone and paired bases (A–T, G–C).
71
What is the semiconservative model of DNA replication?
Each daughter DNA molecule contains one old strand and one new strand.
72
What is the process of DNA replication?
Begins at origins of replication, is bidirectional, and involves DNA polymerase.
73
What are Okazaki fragments?
Short DNA segments on the lagging strand that are joined by ligase.
74
What is the significance of the Human Genome Project (HGP)?
Goals included sequencing all human DNA and identifying gene locations and sequences.
75
What were the results of the Human Genome Project?
* Draft genome (2001) * Completed genome (2003) * Identified ~22,000 human genes.
76
What is personalized medicine?
Genome sequencing used for tailored treatment and medical decisions.
77
What is gene expression?
The process where DNA directs protein synthesis, involving transcription and translation.
78
What is the one gene – one enzyme hypothesis?
Each gene encodes a specific enzyme, later updated to one gene – one polypeptide.
79
What is the genetic code?
A triplet code where each codon (3-base) corresponds to one amino acid.
| 3 letters = 1 word.
80
What are the types of RNA?
* mRNA – carries code * tRNA – brings amino acids * rRNA – structural part of ribosomes.
81
What occurs during transcription?
RNA polymerase binds to the promoter, elongates RNA, and terminates at the terminator.
82
What is RNA processing?
Modifications of pre-mRNA to mature mRNA, including 5' cap, 3' poly-A tail, and splicing.
83
What is the function of tRNA?
Transfers the correct amino acids to the ribosome during protein synthesis.
84
What are the components of ribosomes?
Made of rRNA and proteins, consisting of small and large subunits with three binding sites.
85
What is an example of a modern application of the central dogma?
mRNA vaccines, such as those developed for COVID-19.
86
What did Darwin observe during his voyage on the HMS Beagle?
Geographic proximity predicted relationships better than environment.
87
What is Darwin’s theory of descent with modification?
All species descended from common ancestors, explaining diversity and extinction.
88
What is the fossil record's significance in evolution?
It shows gradual change and transitional forms, revealing ancestry.
89
What is natural selection?
The mechanism where favorable traits increase survival and reproduction rates.
90
What is the Hardy-Weinberg Principle?
Describes expected genetic makeup in a non-evolving population with conditions for equilibrium.
91
What are the mechanisms of evolutionary change?
* Natural Selection * Genetic Drift * Gene Flow.
92
What is the significance of genetic variation in evolution?
It provides the raw material for natural selection.
93
What is the difference between individuals and populations in evolution?
Individuals do not evolve; populations evolve through changes in allele frequencies.
94
What are the types of mutations?
* Point mutations * Insertions/Deletions (indels) * Chromosomal changes * Polyploidization.
95
What are the effects of genetic drift?
Random changes in allele frequencies, stronger in small populations, leading to founder and bottleneck effects.
96
What is balancing selection?
Maintains genetic diversity through mechanisms like heterozygote advantage.
97
What limits natural selection?
Natural selection is limited by Variation, Constraints, Compromises, and Chance.
| Very Cool Cats Chase.
98
What is the overall summary of evolution?
Evolution occurs at the population level, driven by natural selection, genetic drift, and gene flow.
## Footnote
Pop Stars Never Dance Gracefully.”
Pop = Population (where evolution happens)
N = Natural selection
D = Drift (genetic drift)
G = Gene flow
99
What is a population?
Group of same species in one area, interbreeding.
100
Define gene pool.
All alleles at all loci.
101
What is a fixed locus?
Only one allele exists in population.
102
What is evolution?
Change in allele frequencies over generations (microevolution).
103
What does the Hardy-Weinberg Principle describe?
Non-evolving population (allele & genotype frequencies remain constant).
104
What is the Hardy-Weinberg equation?
p² + 2pq + q² = 1.
105
List the conditions of the Hardy-Weinberg Principle.
* Large population
* No gene flow
* No mutations
* Random mating
* No natural selection
106
What does deviation from the Hardy-Weinberg equilibrium suggest?
Evolution is occurring.
107
What is natural selection?
Consistent adaptive change.
108
Define genetic drift.
Random allele fluctuations, stronger in small populations.
109
What is the founder effect?
Type of genetic drift that occurs when a new population is established by a small number of individuals.
110
What is the bottleneck effect?
A sharp reduction in population size due to environmental events (e.g., elephant seals, cheetahs, sea otters).
111
What is gene flow?
Movement of alleles between populations (e.g., pollen, migration).
112
What is the only mechanism that consistently increases fitness?
Natural selection.
113
How does natural selection alter variation?
* Directional selection (shifts mean trait)
* Stabilizing selection (favors intermediate traits)
* Disruptive selection (favors extremes)
114
What is sexual selection?
Leads to sexual dimorphism.
115
What is intrasexual selection?
Competition within a sex (e.g., males fighting).
116
What is intersexual selection?
Mate choice (e.g., females preferring 'good genes').
117
How does diploidy preserve genetic variation?
Hides recessive alleles in heterozygotes.
118
What is balancing selection?
Maintains multiple alleles.
119
What is heterozygote advantage?
E.g., sickle cell & malaria resistance, warfarin resistance.
120
What is frequency-dependent selection?
Fitness depends on how common trait is (e.g., left/right-mouthed fish).
121
List the limitations of natural selection.
* Works only on existing variation
* Constrained by evolutionary history
* Adaptations involve compromises
* Chance + environment interact unpredictably
122
What is speciation?
Process where one species splits into two or more.
123
What does microevolution refer to?
Small-scale changes in gene pools.
124
What does speciation explain?
Both unity (shared traits) and diversity (new forms) of life.
125
Define the Biological Species Concept.
Species = group of populations that interbreed and produce fertile offspring.
126
What maintains species boundaries?
Reproductive isolation.
127
What are prezygotic barriers?
Prevent fertilization.
128
List the types of prezygotic barriers.
* Habitat isolation
* Temporal isolation
* Behavioral isolation
* Mechanical isolation
* Gametic isolation
129
What are postzygotic barriers?
Occur after fertilization.
130
List the types of postzygotic barriers.
* Reduced hybrid viability
* Reduced hybrid fertility (e.g., mule)
* Hybrid breakdown
| very fragile babies
131
What is allopatric speciation?
Geographic isolation leading to divergence.
132
What is sympatric speciation?
Occurs without geographic separation.
133
What are the mechanisms of sympatric speciation?
* Polyploidy
* Habitat differentiation
* Sexual selection
| Plants places and partners
134
What is a hybrid zone?
Areas where species meet and interbreed.
135
List the possible outcomes of hybrid zones.
* Reinforcement
* Fusion
* Stability
136
What is punctuated equilibrium?
Long periods of stability with sudden bursts of change.
| long naps with sudden sprints.
137
What is gradualism?
Slow, steady accumulation of changes.
138
What does the fossil record provide evidence for?
Major evolutionary changes.
139
What is relative dating?
Strata/biostratigraphy.
140
What is absolute dating?
Radiometric dating.
141
List the major events in life's history.
* Prokaryotes (3.5–2.0 bya)
* Oxygen Revolution (~2.7–2.4 bya)
* First Eukaryotes (~1.8 bya)
* Multicellularity (~1.2 bya)
* Cambrian Explosion (~535–525 mya)
* Colonization of land
| purple octopuses eating many crunchy cookies
142
What is continental drift?
Plate tectonics leading to shifting landmasses.
143
What are mass extinctions?
Five major extinctions in the last 500 mya.
144
What was the Permian extinction?
96% marine species lost due to volcanism and anoxia.
145
What was the Cretaceous extinction?
Asteroid impact leading to the extinction of dinosaurs.
146
What is adaptive radiation?
Diversification after extinctions or into new environments.
147
What is the Oparin-Haldane hypothesis?
Early reducing atmosphere favored organic synthesis.
148
What did the Miller-Urey experiment confirm?
Abiotic synthesis of amino acids.
149
What is the RNA world hypothesis?
RNA acted as both genetic material and enzyme.
150
What is the geologic record divided into?
Eons → Eras → Periods → Epochs.
| Evil Elephants Play Easily
151
What characterizes the Phanerozoic eon?
Includes Paleozoic, Mesozoic, Cenozoic.
152
Hardy-Weinberg equation
p² + 2pq + q² = 1
BISC 120
flashcards
Decks in class (2)
# Cards
