Chapter 11 Introduction to Genetics. 11-1 The work of Gregor Mendel I. Gregor Mendel A. Studied pea plants 1. Reproduce sexually (have two sex cells =

Chapter 11 Introduction to Genetics

11-1 The work of Gregor Mendel I. Gregor Mendel A. Studied pea plants 1. Reproduce sexually (have two sex cells = gametes) 2. Uniting of male and female gametes =Fertilization 3. Pollination = Transfer of pollen from male part of plant to female part of plant a. Two Types: i. Self-pollinate: Male and female gametes come from same plant, offspring are identical to parents 1. Allows for true breeding:Produce identical offspring to self

ii. Cross-pollinate: Male and female gametes are from two different plants Self-pollination

II. Laws of Heredity A. Heredity: Passing on of characteristics from parents to offspring B. Genetics:Study of heredity C. Traits:Characteristics that are inherited E. Genes: Determines traits-ex: gene for flower color F. Alleles:Different forms of a gene-ex: allele for purple flower vs. allele for white flower D. Hybrid:Offspring of crosses between parents with different traits III. Mendel’s Experiment A. Crossed plants with contrasting traits 1. Studied seven traits

D. all plants of intermediate height. Mendel’s F 1 Crosses on Pea Plants Page 264

2. First crossed monohybrid (one trait) plants a. P = parents b. F 1 = first filial generation c. F 2 = second filial generation Example: P = tall x short F 1 = all tall Self-pollinate: F 1 x F 1 F 2 = ¾ tall, ¼ short  3:1 ratio

B. Three Conclusions: Mendel’s Laws/ Principles/ Rules 1. Biological inheritance is determined by factors (genes) passed from one generation to the next. 2. Rule of Dominance: Some alleles are dominant and others are recessive. 3. Law of Segregation: Gametes randomly pair producing four combinations of alleles (page 266).

11-2 Probability and Punnett Squares IV. Probability A. Likelihood a particular event will occur B. Can be used to predict the outcomes of genetic crosses V. Punnett Squares A. Visual diagram to find all possible genetic variations of offspring of a cross B. Phenotype 1. Physical characteristic (looks/behavior/you can see it)

C. Genotype 1. Genetic make-up 2. Made up of alleles 3. Three combinations a. Homozygous DominantTT b. Homozygous recessivett c. HeterozygousTt D. Example: Cross: Homozygous Dominant X Homozygous Recessive Cross: HeterozygousXHeterozygous

VI. Dihybrid Cross (2 traits) A. Round YellowRRYY x wrinkled greenrryy B. F 1 = RrYy C. F 1 x F 1 (self-pollinate) Page 270 11-3

D. 9 Round Yellow, 3 Round Green, 3 wrinkled Yellow, 1 wrinkled green E. Get a 9:3:3:1 Ratio Page 271 F. Law of Independent Assortment: Genes for different traits are inherited independently from each other during gamete formation

VII. Complex Modes (Different Ways to Inherit) of Inheritance A. Incomplete Dominance (Page 272 Figure 11-11) 1. Phenotype somewhere between the two alleles Example: Red (RR)x White (R’R’)= PINK (RR’) B. Codominance 1. Both alleles contribute to phenotype Example: Black Rooster (BB) x White Hen (WW) = Checkered Chickens (BW)

C. Multiple Alleles (Page 273 Figure 11-12) 1. More than 2 alleles are available Examples: eye color, rabbit fur color p273, blood type, pigeon feather color (red, blue or chocolate)

D. Polygenic Traits 1. Traits controlled by more than 2 genes Examples: human skin color, weight, height,

11-4 Meiosis VIII. Chromosome Number B. Haploid 1. Chromosome appear in pairs (1 from mom and 1 from dad) 2. n C. Diploid 1. Gamete cell has one of each kind of chromosome 2. 2n A. Homologous Chromosomes 1. Paired chromosomes with genes of same traits in same order 2. Not always identical

IX. Meiosis-Aka: Gametogenesis- Spermatogenesis (males) and Oogenesis (females) A. Occurs in specialized cells that produce gametes 1. Gamete = sperm/ovum B. Organisms inherit a single copy of every gene from each parent C. Produces gametes with only 1 set of genes D. Two divisions 1. Meiosis I and Meiosis II 2. Diploid (2n) cell at beginning of Meiosis I and 4 haploid (n) cells at he end of Meiosis II

1. Interphase I a. DNA replicates 2. Meiosis I a. Prophase I 1. Chromatin coils, spindle fibers form, homologous chromosomes pair up (matched gene by gene = TETRAD) 2.Nonsister chromatids overlap and exchange material = Crossing Over (Page 277) Interphase I Prophase I E. Stages

b. Metaphase I 1. Chromosomes attach to spindle fibers and homologous chromosomes line up side by side Metaphase I c. Anaphase I 1. Homologous chromosomes separate by fibers and move to opposite ends of the cell Anaphase I

d. Telophase I and Cytokinesis 1. Nuclear membranes form and cell separates Telophase I 2. The two cells produced by meiosis I have chromosomes and alleles that are different from each other and from the diploid cell that entered meiosis I. e. The two cells produced by meiosis I now enter a second meiotic division. f. Unlike meiosis I, neither cell goes through chromosome replication.

Meiosis I PAGE 276 Interphase I Prophase I Meiosis I Metaphase I Anaphase I Telophase I and Cytokinesis

3. Meiosis II a. Prophase II 1. Spindle fibers forms Prophase II b. Metaphase II 1. Chromosomes line up in the middle of the cell Metaphase II

c. Anaphase II 1. Centromere splits sister chromatids and go to opposite ends of the cell Anaphase II d. Telophase II and Cytokinesis 1. Nuclei reform, spindle fibers break down, cytoplasm divides Telophase II e. END RESULT: 4 haploid cells (different)

Meiosis II PAGE 277 Telophase I and Cytokinesis I Meiosis II Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis

X. Gamete Formation-Spermatogenesis A. In male animals, meiosis results in four equal-sized gametes called sperm. Page 278

B. In many female animals, only one egg results from meiosis (oogenesis). The other three cells, called polar bodies, are usually not involved in reproduction. Page 278

XI. Comparing Mitosis and Meiosis Mitosisvs Meiosis 1 division2 divisions 2 identical diploid cells4 different haploid cells Body cells (somatic cells) Sex cells-reproductive cells ½ the # of chromosomes as parent cell Same # of chromosomes as parent cell

11-5 Linkage and Gene maps XII. Gene Linkage- if genes are very close together they are more likely to be inherited together A. Chromosomes are groups of linked genes B. Chromosomes assort independently not the genes XIII. Gene Maps C. Crossing over sometimes separates genes on chromosomes if the genes are far enough apart= Genetic Diversity A. Show distance between genes on chromosomes by considering the “recombinants”-offspring that is not like either parent.

11-1 Gametes are also known as A. genes. B. sex cells. C. alleles. D. hybrids.

11-1 The offspring of crosses between parents with different traits are called A. alleles. B. hybrids. C. gametes. D. dominant.

11-1 In Mendel’s pea experiments, the male gametes are found in the A. eggs. B. seeds. C. pollen. D. sperm.

11-1 In a cross of a true-breeding tall pea plant with a true-breeding short pea plant, the F 1 generation consists of A. all short plants. B. all tall plants. C. half tall plants and half short plants.

11-1 If a particular form of a trait is always present when the allele controlling it is present, then the allele must be A. mixed. B. recessive. C. hybrid. D. dominant.

11-2 Probability can be used to predict A. average outcome of many events. B. precise outcome of any event. C. how many offspring a cross will produce. D. which organisms will mate with each other.

11-2 Compared to 4 flips of a coin, 400 flips of the coin is A. more likely to produce about 50% heads and 50% tails. B. less likely to produce about 50% heads and 50% tails. C. guaranteed to produce exactly 50% heads and 50% tails. D. equally likely to produce about 50% heads and 50% tails.

11-2 Organisms that have two different alleles for a particular trait are said to be A. hybrid. B. heterozygous. C. homozygous. D. recessive.

11-2 Two F 1 plants that are homozygous for shortness are crossed. What percentage of the offspring will be tall? A. 100% B. 50% C. 0% D. 25%

11-2 The Punnett square allows you to predict A. only the phenotypes of the offspring from a cross. B. only the genotypes of the offspring from a cross. C. both the genotypes and the phenotypes from a cross. D. neither the genotypes nor the phenotypes from a cross.

11–3 In a cross involving two pea plant traits, observation of a 9 : 3 : 3 : 1 ratio in the F 2 generation is evidence for A. the two traits being inherited together. B. an outcome that depends on the sex of the parent plants. C. the two traits being inherited independently of each other. D. multiple genes being responsible for each trait.

11–3 Traits controlled by two or more genes are called A. multiple-allele traits. B. polygenic traits. C. codominant traits. D. hybrid traits.

11–3 In four o'clock flowers, the alleles for red flowers and white flowers show incomplete dominance. Heterozygous four o'clock plants have A. pink flowers. B. white flowers. C. half white flowers and half red flowers. D. red flowers.

11–3 A white male horse and a tan female horse produce an offspring that has large areas of white coat and large areas of tan coat. This is an example of A. incomplete dominance. B. multiple alleles. C. codominance. D. a polygenic trait.

11–3 Mendel's principles apply to A. pea plants only. B. fruit flies only. C. all organisms. D. only plants and animals.

11-4 If the body cells of humans contain 46 chromosomes, a single sperm cell should have A. 46 chromosomes. B. 23 chromosomes. C. 92 chromosomes. D. between 23 and 46 chromosomes.

11-4 During meiosis, the number of chromosomes per cell is cut in half through the separation of A. daughter cells. B. homologous chromosomes. C. gametes. D. chromatids.

11-4 The formation of a tetrad occurs during A. anaphase I. B. metaphase II. C. prophase I. D. prophase II.

11-4 In many female animals, meiosis results in the production of A. only 1 egg. B. 1 egg and 3 polar bodies. C. 4 eggs. D. 1 egg and 2 polar bodies.

11-4 Compared to egg cells formed during meiosis, daughter cells formed during mitosis are A. genetically different, while eggs are genetically identical. B. genetically different, just as egg cells are. C. genetically identical, just as egg cells are. D. genetically identical, while egg cells are genetically different.

11-5 According to Mendel's principle of independent assortment, the factors that assort independently are the A. genes. B. chromosomes. C. chromatids. D. gametes.

11-5 A chromosome is actually a group of A. independent genes. B. linkage groups. C. crossed-over genes. D. linked genes.

11-5 Thomas H. Morgan is credited with the discovery of the principle of A. segregation. B. independent assortment. C. gene linkage. D. dominance.

11-5 Linkage maps can be produced because the farther apart two genes are on a chromosome, A. the less likely they are to assort independently. B. the more likely they are to be linked. C. the more likely they are to be separated by a crossover. D. the less likely they are to be separated by a crossover.

11-5 If two genes are close together on the same chromosome, they are more likely to A. behave as though they are linked. B. behave independently. C. move to different chromosomes. D. belong to different linkage groups.

Dihybrid Cross Parents are heterozygous for both traits. Trait- Flower color –Purple dominant over white Height- Tall dominant over short List parents, gamete combos, Punnett Square and Phenotypes with ratios or fractions.

11-1 Gametes are also known as A. genes. B. sex cells. C. alleles. D. hybrids.

11-1 The offspring of crosses between parents with different (contrasting) traits are called A. alleles. B. hybrids. C. gametes. D. dominant.