Genetics Flashcards
Mutation
Change of the structure of a gene
Random Mutation
Just happens
Translational Error
RNA —> Amino acid (protein) sequence
Transcriptional Error
DNA —> mRNA
Point Mutation (Base Substitution)
Change a Nucleotide (A, T, C, G)
Silent Mutation
Cannot tell there is a mutation
Ex: Mutation on the intron is silent b/c this does not create a protein
Ex: Mutation in the wobble position (3rd base in codon) that still codes for the same amino acid
Exon
Exits the nucleus
Intron
Cut out and gets digested; remains in the nucleus (junk)
Missense Mutation
- Codon is change to code for a different amino acid
- “miss one part” = wrong nucleotide put in
Nonsense Mutation
Premature stop codon
- UGA
- UAG
- UAA
Start Codon
Methionine (AUG)
Inversion Mutation
Flip nucleotide sequence (reversed)
Addition Mutation
- Add in nucleotides
- The # inserted impacts what you see and the overall type of mutation
Deletion Mutation
- Delete nucleotides
- The # inserted impacts what you see and the overall type of mutation
Translocation Mutation
- Nucleotides (gene) is cut out and moved to a different location
- This is what Viruses do to incorporate their DNA into host DNA
Central Dogma of Biology
DNA ———————> RNA ——————> Protein
Transcription Translation
DNA = Nucleotides (T, A, C, G) RNA = Nucleotides (U, A, C, G) Protein = Amino Acids
Mispairing Mutation
Wrong base pair; meaning wrong base was copied and they do not match
Ex: A-C, T-G, G-A, etc…
Advantageous Mutation
Mutation that benefits the species; increasing likelihood of survival (passed to the next generation)
Deleterious Mutation
Harmful mutation to the organism; can be fatal or lethal
Inborn Errors of Metabolism
Genet disorder that prevents or changes a person’s ability to metabolize (breakdown food and function)
Carcinogen
Cancer causing mutation
Mutagen
Anything that causes a mutation
Evolution
Organism / species slowly evolve and change genetically over time; often due to external factors that select for one trait over another
Natural Selection
Nature selects the most “ideal” genetic organism to survive
Fitness
- Ability to reproduce and those offspring are able to survive, mature and reproduce as well
- Ability to pass on genes to the next generation
Group Fitness
Entire group works together to survive
Speciation
Organisms of the same species evolve into separate species (can no longer reproduce to create viable offspring who can also reproduce)
Polymorphism
Different variations / versions of traits
Adaptation
Mutation to survive in a new environment
Specialization
Specific adaptation to one part of an environment (niche) to suit a particular way of life or skill
Inbreeding
Mating with relatives or family
Outbreeding
Mating outside of the family (more diverse selection of genes)
Bottleneck
A large population that was mostly wiped out
Genetic Regression
Species that start over (ex: bottleneck) to become more diverse
Evolutionary Time (Molecular Clock)
Measured by gradual, random changes in the genome
Genotype
Genes (not always shown) that you carry
Phenotype
What you see; the physical traits that are a result of your genotype
Gene
Codes for a gene produce, generally a protein that determines a characteristic or trait
Chromosome
A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes
- 24 types found in humans (22 pairs are autosomal and 2 sex chromosomes (x and y))
- 46 in somatic cells
- 23 in germ cells
Homologous (homologs)
Same type of chromosomes but from different parents that can code for different alleles
Alleles
Different versions of the same gene
Locus
Specific location on a gene
Homozygous
Same alleles / genes from both parents
Heterozygous
Two different alleles / genes for the same trait
Wild Type
Common dominant gene; typical trait found in nature
Dominant
Gene that is expressed (allele is seen)
Recessive
Gene that is hidden or masked (allele not seen)
Codominance
Both alleles are equally dominant
Ex: Blood type
Leakage
Interbreeding between species results in a viable offspring; Genes therefore “leak out” into a new species
Penetrance
Percent of a gene that is expressed in the population or how much “penetrates” the population
Expressivity
Degree to which an allele is expressed
Hybridization
Mixing species (interbreeding) to increase fitness with new traits
Gene Pool
All alleles in a population (master list for a species)
Independent Assortment
- (Mendel)
Alleles do not depend on each other to separate; alleles are independent from one another
Monohybrid Cross
Phenotype = 3 dominant : 1 Recessive
Dihybrid Cross
Phenotype:
- 9 Homozygous Dominant
- 3 Heterozygous Dominant in trait A
- 3 Heterozygous Dominant in trait B
- 1 Homozygous Recessive
Trihybrid Cross
Phenotype ratio = 27: 9: 9: 9: 3: 3: 3: 1
Linkage
Connected genes (on the same chromosome) - unless crossing over occurs which would separate them, they are passed on together
*The closer the genes the higher the probability that they will be passed on together (less likely to separate)
Synaptonemal Complex
A protein that holds onto the tetrad and assists in the crossing over (protects it)
Tetrad
Set of 4 chromosomes (2 homologous pairs) come together
Nondisjunction
Chromosome do not separate correctly
Ex: Trisomy 21 leads to down syndrome
Sex Linked Trait
Trait on the X or Y chromosome; linked to gender
XX = female XY = male
Spermatozoa
Creates 4 gamete cells that can be passed on; only contain genetic information
Ova
Ova + 3 polar bodies
- Ova passes on nucleus and the entire cell (cytoplasm, mitochondria, organelles, etc…)
Genetic Drift
Changes in the gene pool, slowly over time due to random chance (external factors, environment, mutations, etc…)
Hardy - Weinberg Theory
Allele and genotype frequency remain constant in a population generation to generation in the absence of outside factors
Hardy - Weinberg Theory Conditions
- Cells must be diploid (2n) - 2 parents
- Population reproduces sexually
- Random Mating
- Infinitely large population (no inbreeding)
- No migration
- No mutation / Natural Selection
**Equilibrium is to be maintained
Hardy - Weinberg Equations
Dominant Alleles = p
Recessive Alleles =q
p + q = 1
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Homozygous Dominant Alleles = p
Homozygous Recessive Alleles =q
Heterozygotes = pq
p^2 + 2pq + q^2 = 1
Test Cross
Cross a parent with a homozygous recessive to determine the genotype
- if parent is homozygous dominant then the phenotype is 100% dominant and genotype is 100% heterozygotes
- if parent is heterozygote then the phenotype will be 50% dominant and 50% recessive and the genotype with be 50% heterozygote and 50% homozygous recessive
Gene Mapping
Methods used to identify the locus (specific location) of a gene and the distances between the genes
- Looks at % of genes that separate vs % of genes that do not separate
Linked Genes
Genes connected on the same chromosome
