Unit 7 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 1800s that scientific studies were carried out to develop an explanation for this. Today we know that we resemble our parents because of _______________, which is the set of characteristics we receive from ______________________. The study of heredity is known as _________________. heredity our parents genetics

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

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

Homologous Chromosomes

GAMETES n Egg Sperm 2. Gametes - ___________ and _______________ cells Human gametes contain ______ chromosomes. ______________ or ______ meaning there is _____ set of instructions for each ______. When gametes fuse together in _____________________, the ________________ produced is _____________ and has _______ chromosomes. Gametes are produced by a process called __________, rather than mitosis Sperm 23 Haploid n one gene fertilization zygote diploid 46 meiosis

Haploid vs. Diploid Karyotypes

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

Identical somatic cells Unique gametes

Meiosis occurs in two stages:

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

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

Meiosis I Metaphase I Anaphase I Tetrads Two sister chromatids _____________________________ align in equator of cell Each homologue consists of _______________________________________. Anaphase I __________________________________________ are pulled apart _________________, _________________________ still intact Tetrads Two sister chromatids Homologous pairs Centromeres Sister chromatids

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

MEIOSIS II

2. Meiosis II Gametes replication Sister chromatids 4 1/2 Continues with the two cells formed moving directly into prophase II without any further _____________________ of DNA. In anaphase II, ______________________ are pulled apart. Two new cells are formed from each of the two cells formed in meiosis I, resulting in a total of ___________ new cells, each with ____________the original number of chromosomes. Cells produced are called ____________________. replication Sister chromatids 4 1/2 Gametes

MEIOSIS In females, process is known as ________________________. In males, process is known as _________________________. oogenesis spermatogenesis

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

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

II. HISTORY OF GENETICS (pp. 263-270) A. Gregor Mendel Known as the “Father of _______________” Famous for his experiments with ________ plants. Genetics pea

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

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

Pea Traits Studied

True-breeding B. Mendel’s Results True-breeding TT (tall) x tt (short) P generation – Crossed __________________ plants with one trait with ________________ plants with the other. For example, _____________________________________________ F1 generation – Offspring produced from _________________. In F1, one trait ____________. For example, tall plants X short plants = __________________________. F2 generation – Offspring produced from _________________. In F2, trait that disappeared in F1 reappeared in __________ of the offspring; the other ¾ showed _____________________________. True-breeding TT (tall) x tt (short) P X P disappeared All tall plants F1 X F1 1/4 Dominant trait

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

Alleles and Genes

Mendel’s Principles parent gene versions homozygous heterozygous For each gene, an organism inherits two alleles, one from each __________________. Alleles are different forms or ____________________ of a ___________. For any given trait, If an organism is ___________________, its alleles are the same and the trait will be expressed. If the alleles differ, the organism is said to be ___________________ for that character and only one allele will be expressed. The expressed allele is the ______________ allele, designated by an __________-case letter. The allele that is not expressed in a heterozygous trait is _________________, designated by a _____________-case letter. A recessive allele is only expressed when an organism is ________________. parent gene versions homozygous heterozygous dominant upper recessive lower homozygous

Mendel’s Principles Principle of Segregation - In meiosis, the two alleles for a trait segregate (_______________). Each egg or sperm cell receives a copy of one of the two 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. separate 50%

Independent Assortment

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

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

III. ANALYZING INHERITANCE (pp.135-137) A. Probability 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 heads after being flipped is (fraction) _____, (ratio) ________, or (percent) _______. segregation 1/2 50% 1:1

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

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 50% Probability of White flowers:___________ p Pp pp Pp pp

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% T t Probability of short pea plants:___________ Probability of tall pea plants:___________ TT TT Tt Tt 100%

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 RR:Rr:rr 0:2:2 r Genotypic ratio:__________________ Phenotypic ratio:_________________ Rr rr Rr rr 2:2

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 YY:Yy:yy 0:4:0 y Genotypic ratio:________________ Phenotypic ratio:_________________ Yy Yy 4:0

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

Punnett Practice dihybrid crosses A-B Key Cross 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 B = black feathers W = white feathers BW = black AND white feathers X

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)