SEXUAL REPRODUCTION AND GENETICS

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CHAPTER 10

• SEXUAL REPRODUCTION AND GENETICS

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• SECTION 10.1 MEIOSIS
• MAIN IDEA MEIOSIS PRODUCES HAPLOID GAMETES.
• All of the differences you see in the room,
  different hair color, eye color, ear shapes, is
  the result of 2 sex cells combining during sexual
  reproduction.
• QUESTION How are the following cell parts
  involved in mitosis?
• Chromosome, spindle fibers, nucleus, and nucleolus

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• CHROMOSOMES AND CHROMOSOME NUMBER
• Everyone has characteristics passed on to them
  from their parents.
• Each characteristic is called a trait.
• Ex hair color, height or eye color
• The instructions for each trait are located on
  the chromosomes, which are found in the nucleus
  of cells.
• The DNA on the chromosomes is arranged in
  segments called genes that control the production
  of proteins.
• Each chromosome has 100s of genes.

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• HOMOLOGOUS CHROMOSOMES
• Human body cells (somatic cells)
  have 46 chromosomes.
• Each parent gave you 23 chromosomes creating 23
  PAIRS of chromosomes or 46 chromosomes.
• The chromosomes that make up a pair (the one from
  mom the one from dad) are called homologous
  chromosomes
• Homologous chromosomes in body cells have the
  same length, same centromere position, and carry
  genes that control the same inherited traits.
• These genes each code for the same trait (ex
  earlobe) but maybe not the same type of trait
  (earlobe)

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• HAPLOID AND DIPLOID CELLS
• Gametes are sex cells that have half the number
  of chromosomes.
• In humans the number of chromosomes in a gamete
  is 23.
• Each species has a different of chromosomes
• The symbol n can be used to represent the number
  of chromosomes in a gamete.
• Cells with n number of chromosomes is called a
  haploid cell.
• Haploos means single.
• Fertilization is the process by which one haploid
  gamete (egg) combines with another haploid gamete
  (sperm)
• Fertilization creates cells that are 2n (one n
  chromosome from mom one n chromosome from dad)
• 2n cells are called diploid cells

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• MEIOSIS I
• Gametes are formed during a process called
  meiosis.
• Meiosis is a type of cell division that reduces
  the number of chromosomes
• Meiosis is a reduction division.
• Mitosis maintains the chromosome , meiosis
  reduces the chromosome by half through the
  separation of homologous chromosomes.
• Cells begin as 2n, but create gametes with n
  number of chromosomes
• Meiosis occurs in the reproductive structures of
  organisms that reproduce sexually.
• Meiosis involves 2 consecutive cell divisions
  called meiosis I meiosis II

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• INTERPHASE
• Just like with mitosis, cells that undergo
  meiosis also go through interphase as part of
  their cell cycle.
• While in interphase cells carry out various
  metabolic processes, including the replication of
  DNA and the synthesis of proteins

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• PROPHASE I
• Cells entering prophase I, the replicated
  (copied) chromosomes become visible.
• Creating sister chromatids
• Homologous chromosomes (moms sister chromatid
  dads sister chromatid) form during synapsis and
  are held tightly together. Can be called a
  tetrad.
• Crossing over occurs this time.
• Crossing over is a process when segments of
  chromosomes are exchanged between a pair of
  homologous chromosomes.
• Prophase I continues with the centrioles moving
  to the cells opposite poles, spindle fibers
  forming and binding to the sister chromatids at
  the centromere.

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• PROPHASE I

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• METAPHASE I
• 2nd phase of meiosis
• Homologous chromosomes line up at the equator of
  the cell.
• Spindle fibers are attached to the centromere of
  each homologous chromosome

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• ANAPHASE I
• During anaphase I homologous chromosomes
  separate.
• Sister chromatids are pulled to opposite poles of
  the cell
• Chromosome number is reduced from 2n to n when
  the homologous chromosomes separate.

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• TELOPHASE I
• Homologous chromosomes (sister chromatids) reach
  the cells opposite poles.
• Sister chromatids are still joined at the
  centromere
• Sister chromatids might not be identical from
  when it started because of crossing over.
• During telophase I, cytokinesis usually occurs
  pinching in the animal cell or forming cell plate
  in plant cells.
• May or may not go into interphase. If cell goes
  into interphase, DNA is NOT duplicated again.

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• Telophase I

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• MEIOSIS II
• Meiosis is only half done after meiosis I.
• Prophase II the sister chromatids condense and
  spindle apparatus forms
• Metaphase II the sister chromatids line up at the
  equator by the spindle fibers.
• Anaphase II the sister chromatids are pulled
  apart at the centromere by the spindle fibers and
  the chromosomes move toward the opposite poles of
  the cell.
• Telophase II the chromosomes reach the poles and
  the nuclear membrane and nuclei reform.
• At the end of meiosis II, cytokinesis occurs
  creating 4 haploid cells each with n number of
  chromosomes

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• MEIOSIS II

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• MEIOSIS PROVIDES VARIATION
• Genetic variation is produced during crossing
  over and during fertilization when gametes
  randomly combine.
• Depending on how chromosomes line up at the
  equator, 4 gametes with 4 different combinations
  of chromosomes can result.
• SEXUAL REPRODUCTION VS. ASEXUAL REPRODUCTION
• Asexual reproduction the organism inherits all of
  its chromosomes from a single parent and are
  genetically identical to the parent.
• Ex bacteria
• Sexual reproduction allows variation and
  beneficial mutations to accumulate faster in the
  population.

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• SECTION 10.2 MENDELIAN GENETICS
• MAIN IDEA Mendel explained how a dominant
  allele can mask the presence of a recessive
  allele.
• QUESTION Do all dogs look alike?
• What types of features indicate a particular
  breed?
• Are these features inherited?
• What does this tell you about the inheritance of
  these features?

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• HOW GENETICS BEGAN
• In 1866 Gregor Mendel, an Austrian monk,
  published a book on the method of inheritance in
  garden pea plants.
• Inheritance or heredity is the passing of traits
  from one generation to the next.
• Mendel chose pea plants to study because they are
  true-breeding, meaning that they consistently
  produce offspring with only one form of a trait.
• EX always purple flowers
• Pea plants self-pollinate, but Mendel began to
  cross-pollinate the pea plants.

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• THE INHERITANCE OF TRAITS
• Mendel noticed that some varieties of peas
  produced a specific form of a trait generation
  after generation.
• EX always green seeds or yellow seeds
• Mendel cross-pollinated (male gamete of one plant
  combined with female gamete of the other plant)
• Mendel referred to the male gamete female
  gametes used in the cross-pollination as the P
  generation or the parent generation.

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• F1 AND F2 GENERATION
• Mendel grew the seeds from the cross from the
  parent generation (P generation), one green seed
  and one yellow seed and the results were all the
  offspring had yellow seeds.
• The offspring from the parent generation (P
  generation) are called the F1 generation or first
  filial generation.
• Mendel questioned if the green seed was gone or
  being hidden or masked.
• Mendel planted the F1 generation and allowed them
  to self-pollinate and then examined the seeds
  from this cross.
• The offspring from the F1 generation is called
  the F2 generation or second filial generation.
• Mendels results were a 31 ratio of 6022 yellow
  seeds to 2001 green seeds

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• GENES IN PAIRS
• Mendel concluded there must be 2 forms of the
  seed trait in pea plants yellow and green
  seeds.
• Allele is an alternative form of a single gene
  passed from generation to generation.
• Gene for yellow seeds and the gene for green
  seeds are each different forms (alleles) of a
  single gene.
• In Mendels experiments the yellow seed color was
  dominant over the recessive green seed color.
• Reason why the F1 generation was yellow and
  explaining why the F2 generation had the 31
  ratio of yellow to green

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• DOMINANCE
• When the dominant allele is present it will be
  the one that is shown.
• Ex Yellow seeds are dominant over the green
  seeds, results shown in the F1 generation cross
  that Mendel made
• When modeling inheritance, the dominant allele is
  represented by a capital letter.
• The letter used is the beginning letter of the
  dominant trait.
• Ex Yellow seeds used the capital Y
• Ex Round seeds dominant use capital letter R
• When modeling inheritance, the recessive allele
  is represented by a lower case letter.
• Homozygous for a particular trait means that the
  organism has the same 2 alleles.
• Ex homozygous (dominant) yellow seeds YY
• EX homozygous (recessive) green seeds yy

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• DOMINANCE CONTINUED
• Heterozygous for a particular trait means that
  the organism has 2 different alleles.
• EX one yellow allele and one green allele Yy
  
• The dominant allele will always be expressed when
  the organism is heterozygous

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• GENOTYPE AND PHENOTYPE
• Genotype is the organisms allele pairs.
• Ex YY is the genotype for homozygous dominant
  yellow seeds
• Ex Yy is the genotype for heterozygous yellow
  seeds
• EX yy is the genotype for homozygous recessive
  green seeds
• Phenotype is the observable characteristic or
  outward expression of an allele pair.
• Ex yellow seeds or green seeds

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• MENDELS LAW OF SEGREGATION
• Mendels Law of Segregation states that the 2
  alleles for each trait separate during meiosis.
• During fertilization the 2 alleles for that trait
  unite.
• Hybrids are
  heterozygous
  organisms.

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• LAW OF INDEPENDENT ASSORTMENT
• Law of independent assortment states that a
  random distribution of alleles occurs during
  gamete formation. Genes on separate chromosomes
  sort independently during meiosis.
• Ex an organism heterozygous for seed color (Yy)
  crossed with another heterozygous organism (Yy)
  means that the Y allele and the y alleles from
  both organisms can recombine in any combination.
• Either YY, Yy or yy

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• PUNNETT SQUARES
• Punnett squares are used to predict the possible
  offspring of a cross between 2 known genotypes.
• PUNNETT SQUARE MONOHYBRID CROSS
• The number of squares is determined by the number
  of types of alleles produced by each parent.
• Male gametes are written across the horizontal
  side.
• Female gametes are written on the vertical side
  of the Punnett square.
• Possible combinations of each male and female
  gamete are written on the inside of each
  corresponding square.
• Dominant allele is written first, whether it
  comes from the male or female gamete.

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• PUNNETT SQUARE
• Cross between heterozygous male (Bb) and a
  heterozygous female (B)

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• PUNNETT SQUARE DIHYBRID CROSS
• Dihybrid crosses is when we look at the
  inheritance of 2 traits at the same time.
• Ex pea plants with yellow seeds (1trait) and
  round seeds (1 trait)
• If Mendel started with homozygous yellow round
  seeds plant and green wrinkled seeds the F1
  generation would be represented by YyRr
• Crossing the F1 generation yields a 9331 ratio

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• PUNNETT SQUARE DIHYBRID CROSS

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• PROBABILITY
• The inheritance of genes can be compared to the
  probability of flipping a coin.
• Probability of the coin landing on heads is 50
  or half the time.
• Large number of results makes it more likely that
  the results will match the predicted results of
  the Punnett square

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• SECTION 10.3 GENE LINKAGE POLYPLOIDY
• READ TAKE NOTES OVER PAGES 283, 284, 285.
• BE PREPARED TO SHARE YOUR NOTES WITH THE CLASS
• BE PREPARED TO TAKE A SHORT QUIZ OVER THESE PAGES