Biology Ch 10 Notes.pdf

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Biology

Chapter 10 Section 1 Meiosis Section 2 Mendelian Genetics Section 3 Gene Linkage and Polyploidy

10.1 Meiosis

Chromosomes and Chromosome Number *Human body cells have 46 chromosomes *Each parent contributes 23 chromosomes *Homologous chromosomes—one of two paired chromosomes, one from each parent

10.1 Meiosis

Chromosomes and Chromosome Number

Homologous

Chromosomes Are:

1. Same length

2. Same centromere

position

3. Carry genes for the

same traits

10.1 Meiosis

Haploid and Diploid Cells

*An organism produces gametes to maintain the same number of chromosomes from generation to generation.

*Human gametes contain 23 chromosomes. *A cell with n chromosomes is called a haploid cell. *A cell that contains 2n chromosomes is called a

diploid cell.

10.1 Meiosis Meiosis

*The sexual life cycle in animals involves meiosis. *Meiosis produces gametes. *When gametes combine in fertilization, the number of chromosomes is restored. *Involves two

consecutive cell

divisions called meiosis I and meiosis II

10.1 Meiosis

Stages ofMeiosisI

*The job of meiosis I is to _{reduce the}

chromosome number by half through the separation of homologous chromosomes

Interphase

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10.1 Meiosis Prophase I

*Pairing of homologous chromosomes occurs. *Each chromosome consists of two chromatids.

*The nuclear envelope breaks down.

*Spindles form.

10.1 Meiosis

Prophase I

*Crossing over produces exchange of genetic information. *Crossing over—chromosomal segments are exchanged

between a pair of homologous chromosomes.

10.1 Meiosis Metaphase I

*Chromosome centromeres attach to spindle fibers.

*Homologous chromosomes line up at the equator.

10.1 Meiosis

*Homologous chromosomes separate and move to opposite poles of the cell.

Anaphase I

10.1 Meiosis

Telophase I

*The spindles break down.

*Chromosomes uncoil and form two nuclei. *The cell divides.

10.1 Meiosis

Meiosis II

Prophase II

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10.1 Meiosis Meiosis II Metaphase II

*A haploid number of chromosomes line up at the equator.

10.1 Meiosis

Meiosis II Anaphase II

*The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.

10.1 Meiosis Meiosis II Telophase II

*The chromosomes reach the poles, and the nuclear membrane and nuclei reform.

10.1 Meiosis Meiosis II

*Cytokinesis results in four haploid cells, each with n number of chromosomes.

Video!

10.1 Meiosis

The Importance of Meiosis

*Meiosis consists of two sets of divisions

*Produces four haploid daughter cells that are not identical

*Results in genetic variation

10.1 Meiosis

Meiosis Provides Variation

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10.1 Meiosis

Sexual Reproduction v. Asexual Reproduction

Asexual reproduction

*The organism inherits all of its chromosomes from a single parent.

*The new individual is genetically identical to its parent.

Sexual reproduction

*Beneficial genes multiply faster over time.

Classwork

*Data Analysis Lab 10.1 *Page 274

*Answer the Thinking Cri>cally *Sec>on 1 Review

*Page 276 # 1 -‐ 6

Homework

*Study Guide for 10.1

10.2 Mendelian Genetics How Genetics Began

*The passing of traits to the next generation is called inheritance, or heredity.

*Mendel performed cross-pollination in pea plants.

*Mendel followed various traits in the pea plants he bred. Including: pea color, pea texture, plant height

*He chose these traits because they were an either/or trait.

Ex: The pea color was either green or yellow. There were no other colors possible.

10.2 Mendelian Genetics

*Mendal's first cross was between a yellow pea colored plant and a green colored pea plant *P = Parental generation

*Pure-breeding = always has the same colored offspring

*Mendel decided that there were two factors (also called alleles) that determined pea color *Since the yellow peas were the only ones in the F1 generation he called this the dominant trait

*Always a capitol letter

*Since the green peas were not present in the F1 generation he called it the recessive trait

*Always a lowercase letter

*Homozygous = Two of the SAME alleles for a trait

*Heterozygous = Two DIFFERENT alleles for a trait

*Also called hybrids

*Genotype = the allele pairs of a specific trait *Represented by letters

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So what was happening to the genes so that Mendel saw the 3:1 ratio in is F2 generation?

Parental GenerationYY x YY

Pure Breeding Plants Example

How do we get the F1 Generation? YY x yy

How do we get the F2 Generation?

Yy x Yy

*Mendel's law of segregation states that the two alleles for each trait separate during meiosis

Y Yy y Y

Y

y y

10.2 Mendelian Genetics Dihybrid Cross - Two traits

YYRR x yyrr

Dihybrid Cross - Mendel then allowed the F1 Yellow Round plants to self-fertilize

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Results:

Yellow & Round:

Yellow & Wrinkled:

Green & Round:

Green & Wrinkled:

Dihybrid Cross - Mendel crossed Yellow Round plants with Green Wrinkled

Y YR R

_x

y y rr

Lets practice making gametes from a dihybrid cross. How many gametes can you make and what are they?

Tt

_PP

*This is called the law of independent assortment *There is a random distribution of alleles during gamete formation (meiosis)

Probability

*Genes can be compared to flipping a coin. Heads means you get one allele and tails means you get the other allele

*How do you figure out the probability of flipping a coin 5 times and getting heads ALL 5 times?

Classwork

*10.2 Assessment *#1-3, 5

Homework *Read 10.3 *10.2 SG

10.3 Gene Linkage and Polyploidy

*Genetic Recombination = new combinations of genes produced by crossing over and

independent assortment

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Gene Linkage

*Mendel didn't use any traits that were linked *Recall that crossing over will mix genes *The closer the genes are to each other on a chromosome, the more likely it is that they will cross over together

Chromosome Maps

*Using data that tells how often genes cross over with each other, you can make a chromosome map

*The higher the crossover frequency, the farther apart the genes are

*Prepare a chromosome map from the

following data set; D-F 15%, G-D 2%,

E-G 8%, E-D 10%, G - F 17%,

E - F 25%

*Polyploidy = the occurrence of one or more extra sets of chromosomes (not 2n!)

*Deadly in animals but very common in plants

*Wheat and oats are 6n! *Sugar cane is 8n! *Triploidy = 3n

Classwork *10.3 Assessment

*#1- 4

*6 is extra credit! The better your story is the more extra credit you will get!

Homework *Finish Ch 10 SG *Chapter 10 Review