Biology Chapters 5 6 7 8 Mitosis Genetics

Biology Chapters 5, 6, 7, 8 Mitosis & Genetics

In order for a cell to reproduce: § 1. DNA must be copied (replication) § 2. Nucleus must divide § 3. Cytoplasm must divide

Cell Cycle § Interphase § period between cell divisions § Not part of mitosis § DNA replication occurs here § Chromosomes not visible Cell cycle pg. 245 -247

Phases of Mitosis (division of somatic cells) 1. Prophase § § § Chromosomes appear Spindle fibers appear Nuclear membrane disappears § Centrioles migrate to poles

2. Metaphase § Chromosomes align at the center of the cell

3. Anaphase § Chromatids divide & form chromosomes (migrate toward poles) § Chromosomes pulled apart by spindle fibers

4. Telophase § Chromosomes disappear § Spindle fibers disappear § Nuclear membrane forms

§ Meiosis (reduction division) - division of sex cells § Compare mitosis to meiosis: Mitosis Meiosis cells somatic #divisions 1 sex cells (gametes) 2 #produced 2 (diploid) 4 (haploid)

§ Diploid - cells containing double sets (pairs) of chromosomes (2 n) § For humans, n = 23 § (2 n = 46 chromosomes)

§ Haploid - cells containing single set of chromosomes (1 n) § For humans, n = 23

§ Gamete - sex cell (egg or sperm) § Haploid § Fertilization - two gametes unite § CHROMOSOME THEORY OF INHERITANCE: genes governing inheritance are located on chromosomes

Biology Chapter 7: Genetics § Gregor Mendel father of genetics § Austrian monk (1860 s) § Studied pea plants

True-breeding (pure line) - offspring always the same ex: tall x tall ===> tall short x short ===> short (parents are both pure)

§ Hybrid - results as a cross between parents with § § different traits (pure tall x pure short) Dominant - expressed characteristic Recessive - masked (hidden) characteristic

§ Gene - unit of heredity (section of DNA) § 2 alleles (factors) per gene (characteristic) § Allele - one form of a gene § Ex: height of a pea plant is either tall (TT, Tt) or short (tt). Alleles are “T” and “t”.

Abbreviations: P - parent generation F 1 - (filial) first generation offspring F 2 - second generation offspring

§ Monohybrid cross - study inheritance of one characteristic § Punnett square - shows all possible combinations of a cross § Show cross between pure tall (TT) and pure short (tt) pea plants §TT x tt

In pea plants, tall (T) is dominant over short (t). Using the Punnett square, show the results of crossing a pure tall pea plant with a pure short pea plant. pure tall x pure short TT x tt T T – tall t - short t t T t 100 % tall T T t

In a pea plants, tall (T) is dominant over short (t). Using the Punnett square, show the results of crossing a hybrid tall pea plant with a hybrid tall pea plant. hybrid tall x hybrid tall Tt x Tt T T TT T – tall t - short t T t 3 tall: 1 short t T t t t

1. In a certain species of rabbit, brown fur (B) is dominant over gray fur (b). Using the Punnett square, show the results of crossing a pure brown rabbit with a hybrid brown rabbit. pure brown x hybrid brown BB x Bb B B BB B – brown b - gray b Bb 100 % brown B BB Bb

2. In humans, free earlobes (F) is dominant over attached earlobes (f). Show the results of crossing a hybrid free with a hybrid free x hybrid free Ff x Ff F F FF F – free f - attached f Ff 3 free: 1 attached f Ff ff

3. In pea plants, smooth seeds (S) is dominant over wrinkled seeds (s). Show the results of crossing a pure smooth with a pure wrinkled. pure smooth x pure wrinkled SS x ss S s Ss S – free s - attached 4 smooth: 0 wrinkled S Ss Ss

4. In water buffalo, a wide snout (W) is dominant over a thin snout (w). Show the results of crossing a hybrid wide buffalo with a pure thin buffalo. hybrid wide x pure thin Ww x ww W w w Ww Ww W – wide w - thin 2 wide: 2 thin w ww ww

• Symbols - capital is dominant (T) -Lower case is recessive • Phenotype - appearance (ex: tall) -Expression of a gene • Genotype - set of alleles for a trait • Ex: Tt, TT

• Homozygous - pure (same alleles: TT, tt) • Heterozygous - hybrid (different alleles: Tt)

Dihybrid cross - involves two traits (characteristics) Show possible results crossing hybrid tall, hybrid green (Tt. Gg) pea plant with hybrid tall, hybrid green pea plant (Tt. Gg)

In pea plants, tall (T) is dominant over short (t), and green seeds (G) are dominant over yellow seeds (g). Show the results of crossing a hybrid tall, hybrid green plant with a hybrid tall, hybrid green plant. hybrid tall x hybrid green Tt. Gg x hybrid tall hybrid green Tt. Gg TG Tg t. G tg TG TTGg Tt. GG Tt. Gg Tg TTGg TTgg Tt. Gg Ttgg t. G Tt. Gg tt. GG tt. Gg tg Tt. Gg Ttgg tt. Gg ttgg T – tall t – short G – green g - yellow 9 tall, green 3 tall, yellow 3 short, green 1 short, yellow

In werewolves, gray hair (G) is dominant over black hair (g), and pointy ears (P) is dominant over blunt ears (p). Show the results of crossing a pure black, pure blunteared werewolf with a hybrid gray, hybrid pointy-eared werewolf. pure black pure blunt x ggpp x GP hybrid gray hybrid pointy Gg. Pp Gp g. P gp gp Gg. Pp Ggpp gg. Pp ggpp G – gray g – black P – pointy p - blunt 1 gray, pointy 1 gray, blunt 1 black, pointy 1 black, blunt

Extra Credit (25 points): Trihybrid Cross Create a punnett square showing a cross between a hybrid tall, hybrid green, hybrid smooth (Tt. Gg. Ss) with a hybrid tall, hybrid green, hybrid smooth (Tt. Gg. Ss). Symbols: T - tall t - short G - green g - yellow S - smooth s - wrinkled

• Principle of Independent Assortment: • Inheritance of alleles for one characteristic does not affect the inheritance of alleles for another characteristic. • COIN TOSS: 100 times each group

1 st Period 3 rd Period 2 nd. Period 5 th Heads 424 1 st 640 Period 640 2 nd 706 656 Period 656 5 th 532 555 Period Tails 376 660 644694 Ratio Tails Ratio 1: 1. 03 1. 02: 1 644 545578 1. 02: 1 475491 545 1: 1. 18 1. 02: 1 7 th 548 713 7 thth Period 6 & 7 th Period 1138 787552 1: 1. 11 1262 1: 1. 12 20122719 2989 2014 totals 2012 Results 2989 3111 2691 1: 1. 04 3111 1: 1. 04 6 th 5 th Period Past results + 2014 results Past results Cumulative results 6 th 509 555 425 Period 27053 27174 22047 22170 1. 02: 1 1 : 1. 00557899

Mendel’s Law of Segregation 1. Each characteristic is governed by two alleles (factors). 2. Each parent contributes one of each allele (factor). 3. Recessive trait is only expressed when offspring has two recessive alleles.