BIO 1A – Unit 4 Notes Genetics

Genetics 11.1 Genetics - the scientific study of heredity Gregor Mendel is considered the father of genetics. He conducted research on pea plants in a monastery garden.

Mendel’s Principles of Genetics Inheritance - Genes are passed from parents to offspring. Dominance - One form of a gene, an allele, may be dominant over another. Segregation - Genes segregate during gamete formation in sexually reproducing organisms. Independent assortment - Alleles for different genes segregate independently of one another.

Fertilization Fertilization – a process where sperm and egg cells join during sexual reproduction. Fertilization produces a new cell. Mendel studied pea plants. Pea plants are self-pollinating.

Fertilization true-breeding – organisms that will produce identical offspring through self-pollination (ex. TT, tt) hybrids - the offspring of crosses between parents with different traits through cross-pollination (ex. Tt)

Fertilization

Generations P generation: Each original pair of parents F1 Generation: The offspring of the P generation or “first filial,” generation F2 Generation: The offspring of the F1 generation or “second filial” generation

Genes trait - a specific characteristic that varies from one individual to another: (physical representation) genes - factors of biological inheritance that determine traits, passed through generations: (genetic sequence) allele - different forms of a gene: (variation of genetic sequence)

Traits / Genes / Alleles

Mendel’s Crosses

Principle of Dominance principle of dominance - states that some alleles are dominant and others are recessive. An organism with a dominant allele for a trait will always exhibit that form of the trait. An organism with the recessive allele for a trait will exhibit that form only when the dominant allele for that trait is not present.

Principle of Dominance

Principle of Segregation segregation – alleles for genes separate from each other during the formation of gametes (sex cells) Two alleles segregate from each other so that each gamete carries only a single copy of each gene.

Principle of Segregation

Dominance / Segregation

Probability 11.2 probability - the likelihood that a particular event will occur The principles of probability can be used to predict the outcomes of genetic crosses.

Probability Probabilities predict the average outcome of a large number of events. Probability cannot predict the precise outcome of an individual event. In genetics, the larger the number of offspring, the closer the resulting numbers will get to expected values.

Punnett Squares Punnett square – a diagram used to predict the gene combinations that might result from a genetic cross Punnett squares can be used to predict and compare the genetic variations that will result from a cross.

Punnett Squares

Genotypes / Phenotypes Genotype – genetic makeup of an organism for a particular trait Ex. TT, Tt, tt Phenotype – physical characteristic expressed from the organism’s genetics Ex. tall, tall, short

Genotypes homozygous - organisms that have two identical alleles for a particular trait (Ex. TT, tt) Homozygous organisms are true-breeding for a particular trait. heterozygous - organisms that have two different alleles for the same trait (Ex. Tt) Heterozygous organisms are hybrid for a particular trait.

Genotypes / Phenotypes

Probability / Segregation Because the allele for tallness (T) is dominant over the allele for shortness (t), 3/4 of the F2 plants should be tall. The ratio of tall plants (TT or Tt) to short (tt) plants is 3:1. The predicted ratio showed up in Mendel’s experiments indicating that segregation did occur.

Independent Assortment 11.3 independent assortment – genes for different traits can segregate independently during the formation of gametes. Genes that segregate independently do not influence each other's inheritance. Alleles for seed color and seed shape segregate independently of each other.

Independent Assortment To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a two-factor cross. Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy). All of the F1 offspring produced round yellow peas (RrYy). Mendel crossed the heterozygous F1 plants (RrYy) with each other to determine if the alleles would segregate from each other in the F2 generation.

Two-Factor Cross: F1 Generation

Mendel’s Results The F1 generation produced seeds that were… round and yellow

Two-Factor Cross: F2 Generation

Mendel’s Results The F2 generation produced seeds that were… round and yellow wrinkled and green round and green wrinkled and yellow

Mendel’s Results The alleles for seed shape segregated independently of those for seed color. This principle is known as independent assortment. Genes that segregate independently do not influence each other's inheritance.

Mendel’s Principles Inheritance - Genes are passed from parents to their offspring. Dominance - If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive. Segregation - In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed. Independent Assortment - The alleles for different genes usually segregate independently of one another.

Incomplete Dominance incomplete dominance - when one allele is not completely dominant over another In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes.

Incomplete Dominance

Codominance codominance - both alleles contribute to the phenotype. In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately.

Codominance

Codominance

Codominance

Multiple Alleles multiple alleles - genes that are controlled by more than two alleles More than two possible alleles can exist in a population. A rabbit's coat color is determined by a single gene that has at least four different alleles.

Multiple Alleles

Polygenic Traits polygenic traits - traits controlled by two or more genes Skin color in humans is a polygenic trait controlled by more than four different genes.

Polygenic Traits

Applying Mendel’s Principles Mendel’s principles can be used to study inheritance of other organisms’ traits and to calculate the probability of certain traits appearing in the next generation. Thomas Hunt Morgan – Fruit Flies Small, easy to study in lab, reproduce quickly, simple genetics

Genetics and Environment Characteristics of any organism are determined by the interaction between genes and the environment.

Genetics and Environment: Arctic Fox

Disease disease - a condition of the living animal or plant body or of one of its parts that impairs normal functioning and is typically manifested by distinguishing signs and symptoms Ex. infectious disease, genetic disease, heart disease, diabetes, cancer, AIDS

Disease infectious disease (communicable disease) - an infectious disease transmissible (as from person to person) by direct contact with an affected individual or the individual's discharges or by indirect means (as by a vector) Ex. AIDS, tuberculosis, malaria, common cold non-infectious disease (non-communicable disease) – a disease that is not transmissible by direct contact. Ex. cancer, diabetes, asthma, heart disease

Genetics and Disease Genetic Disease - Some disease can be caused by mutations in chromosomes (non-disjunction) or single genes (recessive traits). Down Syndrome – caused by duplication of 21st human chromosome (non-disjunction) Hemophilia – caused by inheritance of 2 recessive alleles

Genetics and Disease Medelian Inheritance - the manner by which genes and traits are passed from parents to their children Ex. dominant traits Non-mendelian Inheritance - a general term that refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws. Ex. polygenic traits

Genes and Disease The Guardian Video https://www.theguardian.com/science/video/2012/oct/13/genes- disease-video

Genetic Engineering vs. Disease Time Video: http://time.com/4882855/crispr-gene-editing-human-embryo/

Activity Genetics of Disease Visual Project BIO 1A 40 pts Topic 5 Description: 10 Disease Role of Genetics Keywords: Unit 4 Vocabulary (5 minimum) 5 Images / Visuals (2 minimum) 10 Creativity 5 Organization 5

Introduction Name the disorder Definition and Description What happens to the body What part(s) of the body does this generally affect? How many and what type of people are likely to have the disorder? How prevalent is it (common or not?)? Is one race, gender, or even geographic location more likely to have the disorder? Cause of the Disorder What causes this disorder to occur in the body? Is it a mutation? How is the disorder inherited? Is it sex-linked? Is there a particular chromosome it is located on? Is it dominant or recessive? How is the disorder treated or regulated? Medications? Therapy? Other? How is the disorder diagnosed? What tests are done? Is genetic counseling an option?

References WHO: Enrichment Reading http://www.who.int/genomics/public/geneticdiseases/en/ NIH: https://www.cancer.gov/about-cancer/causes-prevention/genetics The Guardian: https://www.theguardian.com/science/video/2012/oct/13/genes-disease-video Time: http://time.com/4882855/crispr-gene-editing-human-embryo/