Unit 8 Meiosis and Mendel Genetics and Inheritance

Unit 8 Meiosis and Mendel Genetics and Inheritance Quiz Date: Jan. 11 /12 Test Date: Jan. 18/19

UNIT 8 - INTRODUCTION TO GENETICS • Although the resemblance between generations of organisms had been noted for thousands of years, it wasn’t until the 1800 s that scientific studies were carried out to develop an explanation for this. Today we heredity know that we resemble our parents because our parents of ________, which is the set of genetics characteristics we receive from ___________. The study of heredity is known as _________.

I. SEXUAL REPRODUCTION & MEIOSIS (pp. 275 -278) • In sexual reproduction, an egg and sperm cell fuse together to create a fertilized zygote egg or ________.

A. Chromosome Number Body 1. Somatic Cells - _______ cells 46 Human somatic cells contain ____ Diploid 2 n chromosomes double 23 _______ or ____ meaning they Mom Dad contain a ______ set of chromosomes, half ( _____ ) from _____ and half from Homologous pairs ____. “Matching” chromosomes known as not identical genes __________. mitosis made up of a copy of a chromosome from each parent, with the same ______, but they are __________. Somatic cells use ______ for growth,

Homologous Chromosomes

GAMETES Egg Sperm 2. Gametes - ______ and ________ cells 23 Human gametes contain ______ Haploid n chromosomes. gene one _______ or ______ meaning there is _____ set of instructions for each zygote fertilization ______. diploid 46 When gametes fuse together in ___________, the ________ produced is meiosis _______ and has _______

Haploid vs. Diploid Karyotypes

B. Meiosis Special type of cell division that only ovaries occurs in specialized germ cells (sex cells) testes in ______ of females and _______ of males. S interphase Before meiosis, DNA is replicated once (during ______ phase of 2 X, two times 4 ________)… 1/2 …But during meiosis cell divides ________, resulting in ______ non-identical cells with _______ the original

Identical somatic cells Unique gametes

Meiosis occurs in two stages:

1. Meiosis I Prophase I Unlike in prophase of mitosis, In prophase Homologous pairs I ______________ come tetrad together and stick to each other to form a _______.

Meiosis I Crossing Over Exchange of genetic information between a Sister chromatid ________________ with its Non-sister homologue __________________. Occurs very frequently Allows for _____________. Genetic variation

Meiosis I Metaphase I Tetrads _______________ align in equator of cell Each homologue consists of __________________ Two sister chromatids ___. Homologous pairs Anaphase I __________________ Centromeres Sister chromatids ______ are pulled apart _________, _____________ still intact

Meiosis I Telophase I 23 Two cells are formed, each with _______ chromosomes Sister chromatids Each chromosome still composed of two __________ There are no homologous pairs present Two cells produced at the end of meiosis I are haploid ________ because___________

MEIOSIS II

2. Meiosis II Prophase II Continues with the two cells formed moving directly into prophase II without replication any further ___________ of DNA. Chromosomes Metaphase II Sister chromatids ________ (not tetrads) composed of _________ are randomly aligned at the equator of the cell.

2. Meiosis II Anaphase II Spindle fibers shorten Sister chromatids ___________ are pulled apart, just like in anaphase of mitosis. Telophase II Four nuclei form around chromosomes, spindles break down

2. Meiosis II Cytokinesis II Two new cells are formed from each of the two cells formed in meiosis I, resulting in a 4 total of ______ new cells, each with 1/2 ______the original number of chromosomes. Gametes Cells produced are called __________.

MEIOSIS In females, process is known as oogenesis ____________. In males, process is known as spermatogenesis _____________.

3. Oogenesis vs. spermatogenesis • Spermatogenesis: Males produce 4 viable sperm cells • Begins: puberty ______ • Ends: death ______

3. Oogenesis vs. spermatogenesis • Oogenesis: Females produce only one egg and 3 polar bodies • Begins: ______ Before birth • Ends: ______ menopause

Spermatogenesis vs Oogenesis

II. HISTORY OF GENETICS (pp. 263270) • A. Gregor Mendel Known as the “Father of Genetics pea ________” Famous for his experiments with ____ plants.

Mendel Used true-breeding pea plants, which means ____________; pureline, purebred P characteristics always show. Known as the ______ generation. characters Studied seven _______, including plant height, seed color, flower color, etc. o A character is an Inherited characteristic _______________. o A trait is a variant of a character o Example: Eye color is a character, brown eyes or blue eyes are traits

Mendel Pea plants cross-pollinate, meaning pollen from one plant fertilizes an egg from another, but they can also self-pollinate, same meaning pollen can fertilize egg from _______ plant. Mendel controlled the fertilization process of the pea plants Self-pollination by preventing _________________ Cross-pollination and controlling _________________

Pea Traits Studied •

B. Mendel’s Results True-breeding P generation – Crossed _________ plants with one trait with ________ True-breeding plants with the other. TT (tall) x tt (short) For example, ____________________ PXP disappeared _____ F 1 generation – Offspring produced from All tall plants _________. In F 1, one trait ______. For example, tall plants X short F 1 X F 1 plants = _____________. F 2 generation – Offspring produced from 1/4 Dominant trait 2, trait that disappeared _________. In F in F 1 reappeared in _____ of the offspring; the other ¾ showed _______________.

Mendel’s Principles • C. Mendel’s Principles – After analyzing his results carefully, Mendel formed conclusions that increased understanding of inheritance and opened the door for the genes study of genetics. Individual units called ______ DNA inheritable characteristics. A determine trait gene is a portion of ______ that codes for a specific ______.

Alleles and Genes

Mendel’s Principles For each gene, an organism inherits two parent alleles, one from each _________. gene Alleles are different forms or versions __________ of a ______. For any given trait, homozygous o If an organism is __________ (for a gene), its alleles are the same and the trait will be expressed. heterozygous o If the alleles differ, the organism is said to be dominant __________ for that character and only upper one allele will be expressed. The recessive expressed allele is the _______ allele, lower designated by an _____-case letter. The allele homozygous that is not expressed in a heterozygous trait is _________, designated by a _______-case letter. A recessive allele is only expressed when an organism is ________ for that gene.

Mendel’s Principles Principle of Segregation - In meiosis, the separate two alleles for a trait segregate (________). Each egg or sperm cell receives a copy of one of the two 50% alleles present in the somatic cells of the organism. There is a _____ chance that a copy of that allele will end up in the gamete produced. Principle of Independent Assortment – The way one pair of alleles segregates has no influence on any other pair of alleles.

Independent Assortment

D. Genetics Terminology Physical • 1. Phenotype - ________ description of trait; for example, Tall, short _______ • 2. Genotype – Genetic make-up of an TT, Tt, heterozygous, etc. . organism or set of alleles; for example, __________.

Genetics Terminology • 3. Application of Terminology - If round pea seeds are dominant to wrinkled pea seeds, round is designated _____ and R r wrinkled is designated ______. • a. Homozygous dominant RR round • Genotype = ____; Phenotype = ____ round Rr • b. Heterozygous • Genotype = ____; Phenotype = rr wrinkled ____ • c. Homozygous recessive • Genotype = ____; Phenotype =

III. ANALYZING INHERITANCE (pp. 135137) • A. Probability segregation Due to the law of________, if you know the genotype of the parents, you can predict the likelihood of a trait occurring in the offspring. Probability can be written 3 ways. The probability of a coin coming up 1/2 50% heads after being flipped is (fraction) _____, 1: 1 (ratio) ____, or (percent) _______.

B. Punnett Squares • A Punnett square is a tool used to predict meiosis the possible outcomes of ________ and __________; in other fertilization words, a Punnett square is used to determine the probability of certain traits appearing in offspring.

Punnett Practice Monohybrid crosses A-D • • Must have a key And Cross with Each problem For full credit

A: Construct a Punnett square to determine the probability of white flowers is a heterozygous purple flower (Pp) is crossed with a homozygous white flower (pp) P=purple, p=white 1. Key: ____________ 2. Cross: ________ Pp X pp P p p p Pp pp Pp pp 50% Probability of White flowers: ______

B: Construct a Punnett square to determine the probability of short pea plants if a homozygous tall plant (TT) is crossed with a heterozygous tall plant (Tt) T=tall, t=short 1. Key: _________ 2. Cross: ________ TT X Tt T T 0% Probability of short pea plants: ______ T TT t Tt 100% Probability of tall pea plants: ______

C: If round peas are dominant over wrinkled peas, make a Punnett square to determined the genotype and phenotype ratios of the offspring if a heterozygous plant is crossed with a homozygous recessive plant R=round, r=wrinkled 1. Key: _________ 2. Cross: ________ Rr X rr R r r Rr rr r Rr rr RR: Rr: rr 0: 2: 2 Genotypic ratio: _________ 2: 2 Phenotypic ratio: _________

D: Use a Punnett square to determine the genotype and phenotype ratios of the offspring from a cross between a homozygous dominant yellow pea plant and a homozygous recessive green pea plant Y=yellow, y=green 1. Key: _________ 2. Cross: ________ YY X yy Y Y y Yy YY: Yy: yy 0: 4: 0 Genotypic ratio: ________ 4: 0 Phenotypic ratio: _________

Dihybrid crosses The punnett squares we have been doing are known as __________ crosses, monohybrid meaning that only one traits has been considered 2 at a time. In a dihybrid cross, _____ genes different _______ on 2 different _______ chromosomes are analyzed.

Punnett Practice dihybrid crosses A -B 1. Key 2. Cross 3. Punnet square

A. Peas homozygous for round shape and heterozygous for color are crossed with heterozygous yellow peas, heterozygous for shape Key: R=round, r=wrinkled Y=yellow, y=green Cross: ___________ Genotypic ratio: ___________________________ Phenotypic ratio: ______________

B. Key: G= gray body, g= black body; R=red eyes, r =black eyes Cross: GGRr X Ggrr What are the phenotypes of the parent fruit flies: ______________ Genotypic ratio: ______________ Phenotypic ratio: ______________

Incomplete Dominance • Neither allele has “complete” dominance over the other; heterozygous phenotype is a blend of the 2 homozygous phenotypes • Ex: snapdragons R = red W = white RW = pink

Incomplete Dominance: cross a pink snapdragon with a white snapdragon 1. Key: _____________ 2. Cross: ____________ Phenotypic ratio: __________ Genotypic ratio: __________

Incomplete Dominance: cross a red snapdragon with a white snapdragon 1. Key: _____________ 2. Cross: ____________ Phenotypic ratio: __________ Genotypic ratio: __________

Codominance • Codominance – Both alleles share dominance and are always expressed if present. • Ex: In chicken X B = black feathers W = white feathers BW = black AND white feathers

Codominance: cross a black chicken with a black and white chicken 1. Key: _____________ 2. Cross: ____________ Phenotypic ratio: __________ Genotypic ratio: __________

Codominance: cross a white chicken with a black and white chicken 1. Key: _____________ 2. Cross: ____________ Phenotypic ratio: __________ Genotypic ratio: __________

Polygenic Traits • “Many genes” ; Many traits are controlled by more than one gene; have a variety of choices for expression. • Ex: _hair color, eye color, skin tone

Multiple Alleles • Many genes that have more than 2 alleles, although an individual only has 2 alleles for the gene. • Ex: blood group. • There are 3 possible • alleles for this gene.

Suggested study questions • p. 283 (1 -5, 11, 12, 17 -20)