Semester I Final Review The SEMESTER IS OVA

Semester I Final Review The SEMESTER IS OVA!!!!!!!

Part I. Meiosis and Punnett Squares

Standards: Meiosis v BI 2. Mutation and sexual reproduction lead to genetic variation in a population. As a basis for understanding this concept: v BI 2. a. Students know meiosis is an early step in sexual reproduction in which the pairs of chromosomes separate and segregate randomly during cell division to produce gametes containing one chromosome of each type. v BI 2. b. Students know only certain cells in a multicellular organism undergo meiosis. v BI 2. c. Students know how random chromosome segregation explains the probability that a particular allele will be in a gamete.

Standard Explanations • BI 2. a. Meiosis produces sex cells, • • chromosomes pairs are separated randomly during this process, producing gametes containing one chromosome of each type (haploid). BI 2. b. Only sex cells (gametes) are produced meiosis. BI 2. c. -Chromosomes segregate randomly during meiosis.

Standards: Meiosis and Punnett Squares v v v v BI 3. A multicellular organism develops from a single zygote, and its phenotype depends on its genotype, which is established at fertilization. As a basis for understanding this concept: BI 2. d. Students know new combinations of alleles may be generated in a zygote through the fusion of male and female gametes (fertilization). BI 2. e. Students know why approximately half of an individual’s DNA sequence comes from each parent. BI 2. f. Students know the role of chromosomes in determining an individual’s sex. BI 2. g. Students know how to predict possible combinations of alleles in a zygote from the genetic makeup of the parents. BI 3. a. Students know how to predict the probable outcome of phenotypes in a genetic cross from the genotypes of the parents and mode of inheritance (autosomal or X-linked, dominant or recessive). BI 3. b. Students know the genetic basis for Mendel’s laws of segregation and independent assortment.

Standards Explanation-Meiosis and Punnett Squares • BI 2. d. -New combination of genes (alleles) are • • produced from fertilization. BI 2. e. -Half of an organisms chromosomes come from each parent because of Meiosis. BI 2. f. -XX-female, XY-male BI 2. g. , 3. a. -Punnett Squares BI 3. b. -Mendel’s Laws-chromosome pairs separate, and genes for different traits are inherited independently of each other.

What we’ve learned so far… • Chromosomes contain genetic info • We get ½ our genetic info from our mom and ½ from our dad • We don’t look exactly like our parents or siblings. Why? • Meiosis-formation of sex cells (sperm and egg) • Human body cells=46 chromosomes

Chromosomes

Meiosis Vocabulary • Homologous chromosomes- chromosomes that each have a corresponding chromosome from the opposite-sex parent • Crossing Over – exchange of portions of chromatids, genetic recombination

What are sex cells? • Scientific name–gametes (sperm and egg) • In humans, gametes have 23 chromosomes (haploid=1 set) • Half of 46 • Fertilized egg contains 23 chromosomes from each parent (diploid= 2 sets)

What happens during meiosis? • Two stages (Meiosis I & II) • Meiosis 1 -divides homologous chromosomes, crossing over • Meiosis 2 -divides sister chromatids • 1 diploid cell produces 4 genetically different haploid cells

Meiosis

Mendel’s Principle of Dominance • Some alleles (diff. forms of gene) are dominant and some are recessive • Organisms with dominant alleles will always show that form of the trait (YY, Yy) • Organisms with recessive alleles will only show that form of the trait when there are no dominant alleles present (yy)

Mendel’s Laws • Law of Segregation: alleles that make up a gene separate from each other, or segregate, during the formation of gametes. • Law of Independent Assortment: the way in which alleles from different genes separate and then recombine is unconnected to other genes.

Allele Combinations • Homozygotes- two identical alleles for a certain trait (YY, yy) • Heterozygotes- two different alleles for the same trait (Yy)

What are Punnett Squares? • Punnett Squares are… • a grid system for predicting all possible genotypes resulting from a cross. • The sides of the square represent the possible gamete genotypes of each parent. • Shows all possible genotypes of offspring

What’s actually happening?

Part II. Evolution

Big Idea: Evolution • is theory that life has changed on Earth over long periods of time through a process called natural selection, where individuals with beneficial inherited traits produce more offspring than other individuals. This changes the frequency of the alleles in the gene pool. There is a broad range of evidence that supports evolutionary theory such as fossils, anatomical evidence, and genetic evidence.

Standards: Evolution • BI 7. • • • The frequency of an allele in a gene pool of a population depends on many factors and may be stable or unstable over time. As a basis for understanding this concept: BI 7. a. Students know why natural selection acts on the phenotype rather than the genotype of an organism. BI 7. b. Students know why alleles that are lethal in a homozygous individual may be carried in a heterozygote and thus maintained in a gene pool. BI 7. d. Students know variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.

Standards Breakdown: Evolution • • BI 7. The frequency of an allele in a gene pool of a population depends on many factors and may be stable or unstable over time. As a basis for understanding this concept: BI 7. a. Students know why natural selection acts on the phenotype rather than the genotype of an organism. Means: NS acts on the physical or physiological traits of an individual. • BI 7. b. Students know why alleles that are lethal in a homozygous individual may be carried in a heterozygote and thus maintained in a gene pool. Means: Lethal copies of genes (for homozygotes-have two copies of the gene) can be carried in the gene pool by heterozygotes. • BI 7. d. Students know variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions. Means: The more genetic variation a species has the better chance they will have of surviving a changing environment because atleast some individuals will have the characteristics needed to survive.

Standards: Evolution • BI 8. Evolution is the result of genetic changes • • • that occur in constantly changing environments. As a basis for understanding this concept: BI 8. a. Students know how natural selection determines the differential survival of groups of organisms. BI 8. b. Students know a great diversity of species increases the chance that at least some organisms survive major changes in the environment. BI 8. e. Students know how to analyze fossil evidence with regard to biological diversity, episodic speciation, and mass extinction.

Standard Summaries: Evolution • BI 8. Evolution is the result of genetic changes that occur in constantly changing environments. As a basis for understanding this concept: • BI 8. a. Students know how natural selection determines the differential survival of groups of organisms. Means: Survival of the fittest and the struggle for existence. • BI 8. b. Students know a great diversity of species increases the chance that at least some organisms survive major changes in the environment. Means: The more variety of organisms there are in an environment the better the chances are that some organisms will survive any major environmental changes. • BI 8. e. Students know how to analyze fossil evidence with regard to biological diversity, episodic speciation, and mass extinction. Means: Trend in fossil evidence show evolutionary patterns.

What is natural selection’s role in evolution? • Natural selection-mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. • These adaptations occur over many generations in a population (descent with modification)

How does natural selection drive evolution? • Struggle for Existence-individuals within a species compete for common resources • Survival of the Fittest- Individuals better suited for their environment reproduce more and have more offspring

What are adaptations? • The inherited characteristics that increase an organism chances of survival are called adaptations • Natural selection results in changes of the inherited characteristics of a population