Genetics and Inheritance (MISS ESTRUCH VIDEO)

Inheritance

• Genotype: The genetic constitution of an organism
• Phenotype: The expression of the genes, influenced by the environment
• Homozygous: Having two identical alleles (forms) of a gene
• Heterozygous: Having two different alleles of a gene
• Recessive allele: Only expressed if there is no dominant allele present
• Dominant allele: Always expressed if present
• Codominant: Both alleles are equally expressed in the phenotype
• Multiple alleles: More than two alleles for a single gene
• Sex linkage: A gene located on the X chromosome
• Autosomal linkage: Genes linked on the same chromosome (not sex chromosomes)
• Epistasis: One gene modifies or masks the expression of another gene

Representing Genotypes

• Monohybrid: Representing one gene (e.g., cystic fibrosis)
  • Capital letter for dominant allele, lowercase for recessive
• Codominant: Both alleles equally dominant (e.g., blood group)
  • Base letter represents the gene, superscript letter represents the allele
• Multiple alleles: More than two alleles for a single gene (e.g., blood group)
• Sex linkage: Representing genes on the X chromosome
• Autosomal linkage: Representing genes on the same chromosome (not sex chromosomes)

Genetic Crosses

• Punnett square: A table to predict the outcome of a genetic cross
• Monohybrid cross: Analyzing the inheritance of one gene
• Dihybrid cross: Analyzing the inheritance of two genes
• Epistasis: One gene affects the expression of another gene
• Autosomal linkage: Genes linked on the same chromosome affect the outcome

Probability and Chi-Squared

• Probability: The chance of an event occurring
• Chi-squared: A statistical test to determine if there is a significant difference between expected and observed frequencies
• Null hypothesis: There is no difference between the expected and observed frequencies
• Degrees of freedom: The number of categories minus one

Hardy-Weinberg Principle

• Gene pool: All alleles of all genes in a population
• Population: All individuals of one species in one area
• Allele frequency: The proportion of an allele in a gene pool
• Hardy-Weinberg equation: Used to predict allele frequencies in a population
• p and q: Representing the dominant and recessive alleles, respectively### Topic 7: Genetics, Variation, and Evolution

Genetics and Probability

• To calculate the probability of a genotype or phenotype, divide the frequency by 100 to convert it to a decimal.
• Rearrange the equation to make p (probability of dominant allele) or q (probability of recessive allele) the subject.
• Calculate 2pq to find the proportion of carriers (heterozygous individuals).

Variation and Evolution

• Genetic variation occurs due to mutations, random fertilization of gametes, and crossing over during meiosis.
• Natural selection acts on this variation, favoring individuals with phenotypes that provide a selective advantage.
• As a result, the allele frequency changes, leading to evolution.
• Disruptive selection occurs when individuals with extreme traits are more likely to survive and pass on their alleles, leading to a loss of the middling trait and eventually, speciation.

Speciation

• Speciation occurs when a population becomes reproductively isolated, resulting in the accumulation of differences in their gene pools.
• Allopatric speciation occurs when a geographical barrier separates the population, while sympatric speciation occurs when reproductive mechanisms prevent interbreeding.

Population Genetics

• Genetic drift is the change in allele frequency within a population between generations.
• The smaller the population, the greater the impact of genetic drift on evolution.
• Population genetics is the study of the allele frequency changes within a population over time.

Ecology

• A population is a group of organisms of the same species living in the same habitat.
• A community is all the populations of different species in the same area at the same time.
• An ecosystem is a community and the non-living components of the environment (abiotic and biotic factors).
• A niche is an organism's role within an ecosystem, including its position in the food web and habitats.

Abiotic and Biotic Factors

• Abiotic factors are the non-living components of the ecosystem, such as temperature, oxygen, and carbon dioxide concentration.
• Biotic factors are the living components of the ecosystem, including interactions between organisms.
• Adaptations develop through natural selection in response to abiotic and biotic factors.

Sampling

• Sampling is used to estimate population size, and there are three types of sampling:
  • Random sampling: used for uniform distributions, involves using a random number generator to select coordinates.
  • Line transect: used for non-uniform distributions, involves placing a tape measure at a right angle to the shoreline or other feature.
  • Mark-release-recapture: used for moving animals, involves marking and releasing individuals, then recapturing and estimating the population size.

Succession

• Succession is the change in an ecological community over time.
• Primary succession starts with a pioneer species colonizing bare rock or sand, while secondary succession occurs when the succession is disrupted and the plants are destroyed.
• As succession occurs, species richness and biodiversity increase over time, and larger plant species and animals colonize the area.

Conservation

• Conservation of habitats involves controlling succession to maintain a greater variety of habitats and species.
• Management involves balancing human needs with conservation goals to maintain sustainability.

Inheritance

• Genotype refers to the genetic constitution of an organism.
• Phenotype is the expression of the genes, influenced by the environment.
• Homozygous individuals have two identical alleles of a gene, while heterozygous individuals have two different alleles.
• Recessive alleles are only expressed if there is no dominant allele present, and dominant alleles are always expressed if present.
• Codominant alleles are equally expressed in the phenotype, and multiple alleles refer to more than two alleles for a single gene.
• Sex linkage occurs when a gene is located on the X chromosome, while autosomal linkage occurs when genes are linked on the same chromosome (not sex chromosomes).
• Epistasis occurs when one gene modifies or masks the expression of another gene.

Representing Genotypes

• A monohybrid represents one gene, with a capital letter for the dominant allele and a lowercase letter for the recessive allele.
• Codominant alleles are represented by a base letter for the gene and a superscript letter for the allele.
• Multiple alleles refer to more than two alleles for a single gene.
• Sex linkage represents genes on the X chromosome, and autosomal linkage represents genes on the same chromosome (not sex chromosomes).

Genetic Crosses

• A Punnett square is a table used to predict the outcome of a genetic cross.
• A monohybrid cross analyzes the inheritance of one gene, while a dihybrid cross analyzes the inheritance of two genes.
• Epistasis occurs when one gene affects the expression of another gene.
• Autosomal linkage occurs when genes are linked on the same chromosome, affecting the outcome.

Probability and Chi-Squared

• Probability is the chance of an event occurring.
• The chi-squared test is a statistical test to determine if there is a significant difference between expected and observed frequencies.
• The null hypothesis states that there is no difference between the expected and observed frequencies.
• Degrees of freedom refer to the number of categories minus one.

Hardy-Weinberg Principle

• A gene pool consists of all alleles of all genes in a population.
• A population is all individuals of one species in one area.
• Allele frequency is the proportion of an allele in a gene pool.
• The Hardy-Weinberg equation is used to predict allele frequencies in a population.
• p and q represent the dominant and recessive alleles, respectively.

Genetics and Probability

• To calculate the probability of a genotype or phenotype, divide the frequency by 100 to convert it to a decimal.
• Rearrange the equation to make p (probability of dominant allele) or q (probability of recessive allele) the subject.
• Calculate 2pq to find the proportion of carriers (heterozygous individuals).

Variation and Evolution

• Genetic variation occurs due to mutations, random fertilization of gametes, and crossing over during meiosis.
• Natural selection acts on this variation, favoring individuals with phenotypes that provide a selective advantage.
• As a result, the allele frequency changes, leading to evolution.
• Disruptive selection occurs when individuals with extreme traits are more likely to survive and pass on their alleles, leading to a loss of the middling trait and eventually, speciation.

Speciation

• Speciation occurs when a population becomes reproductively isolated, resulting in the accumulation of differences in their gene pools.
• Allopatric speciation occurs when a geographical barrier separates the population, while sympatric speciation occurs when reproductive mechanisms prevent interbreeding.

Population Genetics

• Genetic drift is the change in allele frequency within a population between generations.
• The smaller the population, the greater the impact of genetic drift on evolution.
• Population genetics is the study of the allele frequency changes within a population over time.

Ecology

• A population is a group of organisms of the same species living in the same area.
• Ecology studies the interactions between organisms and their environment.