What is the purpose of mitosis?

To produce 2 new cells which have the diploid # of chromosomes.

These cells are used for growth, repair and replacing old cells.

What are the stages of mitosis & what event occur in each?

Interphase (before mitosis) During the S phase chromosomes make copies of themselves. They are now consist of 2 chromatids held together with a centromere.Prophase – The nuclear membrane breaks down. Centrioles migrate to the poles to begin making the spindle fiber network. Chromosomes supercoil & become visible. Spindle fibers attach to the centromeres of the chromosomes.

Metaphase – Chromosomes line up single file along the equator.

Anaphase – The centromere splits & each chromatid (now called a chromosome) is pulled toward the poles of the cell.

Telophase – The nucleus reforms; the cell splits into 2 cells. (Plant cells build a cell plate to form the separation; animal cells pinch into 2.mitosis hyperlink animation

Scroll down to the bottom for the animation.

What is the purpose of meiosis?

Production of haploid sex cells. (sperm and eggs)

http://www.stolaf.edu/people/giannini/flashanimat/celldivision/meiosis.swf

Meiosis animation

Crossing over occurs during meiosis I in Prophase. Parts of 2 homologous chromosomes break off & are exchanged. Therefore part of the original chromosome from the mother is now on the father’s chromosome & part of the father’s on the mother’s.Homologous chromosomes are the same size, shape, share the same traits (but not necessarily the same alleles). One came from the mother & one from the father.During synapsis homologous chromosomes are joined. The bundle of 4 chromatids is called a tetrad. This occurs during Prophase I.Diploid cells contain the 2n or full # of chromosomes (one from each parent). Haploid cells contain the 1n or ½ the number of chromosomes. One representative from each homologous pair.

The cell becomes haploid at the end of telophase I.

Comparing Meiosis and Mitosis

• The way chromosomes line up in metaphase.

1.Mitosis: Chromosomes line up single file. They are independent.

2.Meiosis: Homologous chromosomes pair forming tetrads.

• Chromosome number in resulting cells.

1.mitosis- identical daughter cells

2.meiosis- daughter cells haploid

• The number of cells that are produced.

1.Mitosis: Two identical daughter cells

2.Meiosis: Four daughter cells have new assortment of parental chromosomes

3. Oogenesis – 1 large egg & 3 polar bodies. Spermatogenesis – 4 equal sized cells.

Comparing mitosis & meiosis questions hyperlink

Click below to try questions.

For each of the following statements choose either Mitosis or Meiosis.

1.Chromosomes in prophase form tetrads (a homologous pair joined together). ____

Meiosis2. Whole chromosome (containing 2 chromatids) separate during

anaphase. ____Meiosis I3. Four cells are produced.Meiosis4. Diploid cells are produced.Mitosis5. Resulting cells can be used for repair, growth or replacement of

other body cells.Mitosis

FOR EACH STATEMENT CHOOSE DIPLOID OR HAPLOID

1. Daughter Cells from MitosisDiploid2. Daughter cells from MeiosisHaploid3. Gametes Haploid4. Zygote Diploid5. Somatic / body cellsDiploid

For each of the following choose either DNA or RNA or both.1. Nucleic acid.Both2. Sugar is ribose.RNA2. Double stranded.DNA3. Bases consist of Thymine, Adenine, Cytosine and Guanine.DNA4. A pairs with TDNA5.Three different types.RNA6. A pairs with U.RNA

DNA vs RNA.

Double-stranded Single-stranded

Bases A,C,G & T Bases A,C,G & U

1 Type 3 types: m-RNA, t-RNA, r-RNA

Carries the genetic code Transcribes & translates the genetic code.

Found in the nucleus Found in both nucleus & cytosol

http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf

DNA replication animation.

The helicase enzyme is used to open up (unzip) the DNA strand.

The DNA polymerase enzyme attaches the new complimentary bases using the base-pairing rules.

The base-pairing rules. = A with T and G with C

The role of DNA:

Cookbook for proteins!What is the function of protein synthesis?

Construct a protein using the code contained in the DNA bases.

3 types of RNA

t-RNA Hairpin shape with anti-codons on one end & a specific amino acid on the other end. Job: transport amino acids to the protein synthesis site.

m-RNA Transcribes the DNA code, takes the code out of the nucleus & joins with the ribosome.

r-RNA Docking station for m-RNA & t-RNA to enable amino acids to be delivered & joined (peptide bond) in order. Docking begins at the start codon & ends at the stop codon.

Messenger RNA

Transfer RNA

Ribosomal RNA

This is a picture of

Transcription.

The mRNA is copied from the DNA strand. The mRNA represents one “gene’s” worth of DNA (one protein).

mRNA

tRNA

Protein (Made up of many linked amino acids.)

Transcription hyperlink animation

Translation hyperlink annimation

http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

Transcription animation 2

GENETICS DEFINITIONS:

1.      homozygous = pure: Both genes for a certain trait are the same. EX. BB or bb where B = brown fur and b = white fur

2.      heterozygous = hybrid = carrier : Each gene (allele) carried for a certain trait are different. EX. Bb

3.      genotype: The genes carried by an individual and expresses as letters. EX. Bb , BB or bb

4.      phenotype: The appearance of an individual that is the outward expression of the genes = alleles they are carrying.

5.      dominant: The gene which can mask other genes. EX. Bb is brown even though this individual is carrying a gene for white fur (b). Capitol letters are used to indicate dominant genes. Generally the letter chosen represents the dominant trait. EX. B is used for brown.

6.      recessive: The gene which can be masked by other genes and is only expressed if both genes are recessive. A lower case letter is used to represent the recessive gene. EX. b would be used to represent white fur.

BB = brown Bb = brown bb = white

7.      punnet square: Used to predict the offspring of a genetic cross.

8.      Monohybrid cross: A cross that involves one pair of contrasting traits.

9.      Dihybrid cross: A cross that involves 2 pairs of traits.

10.Incomplete dominance: Two or more alleles influence the phenotype. EX. RR = red flowers, rr = white flowers but Rr = pink flowers (We would normally expect this combination to produce red flowers.

11.Codominance: both alleles for a gene are expressed in a heterozygous individual. EX. Human blood: An individual who inherits A & O will be type “A”, one who inherits B & O will be type “B” (so far this is what we expect!) but an individual who inherits A & B will be blood type “AB”! Of course AA = type A & BB = type B and OO = type O.

12.Sx-linked: The allele is carried on the “X” chromosome so that females inherit 2 alleles but males only inherit 1 allele since they are “XY”.

For each of the following genetics problems draw a punnet square and state the phenotypic and genotypic ratios.

1. Cross a heterozygous tall plant with a short plant.Tt x tt Results: 2 Tt: 2tt 2 Tall: 2 Short2. Cross a pink 4 O’clock flower with a red 4 O’clock flower. 4

O’clock flower color is an example of incomplete dominance.

Rr x RR Results: 2 Rr: 2 RR 2 Pink: 2 Red3. How could you tell if a tall pea plant is homozygous dominant

or heterozygous dominant?Do a test cross and cross by crossing the tall plant with a

homozygous short (tt) plant. If any of the offspring are short then you know the genotype of the parent is Tt.

4.How can 2 tall pea plants produce a short pea plant?Both parents must be carrying one short allele. Tt x Tt5. Cross a person who is heterozygous for type B blood with a

person who is type O.IBIB x ii Results in all children with type B blood.

Different types of crosses.

Contrasting traits of dominant & recessive alleles.

Test cross: To determine if the genotype is homozygous dominant or heterozygous dominant. Done by crossing with a homozygous recessive individual.

Incomplete dominance. When alleles blend in the phenotype. White & Red alleles = pink flowers.

Co-dominance: Both alleles, which are different are expressed in the phenotype. Example: Roan horse with red & white hairs or human blood type AB.

X-linked: Allele is carried on the x chromosome but not on the Y.

Answer the following questions using the pedigree shown.1. How many generations are represented? _____32. How many people are affected by this genetic trait?73. The couple in the 1st generation had ________ # of children.54. How many of their children were girls? ____ Boys? _Girls = 3 Boys = 25. Is the mother in the 1st generation homozygous dominant or

heterozygous? Heterozygous. 6. How can you tell the genotype of the mother in the 1st generation? You know because she has a child who is homozygous recessive.

Genetic engineering is done by creating gene sequences for use in medicine, medical therapy, or research. It is also done by cutting portions of a DNA molecule out (using restriction enzymes) & inserting them into other organisms to create medications, resistance etc.

Gel electrophoresis uses DNA slightly negative charge as a way to separate pieces of DNA by weight (length). The DNA is first cut into pieces using restriction enzymes & then pulled to one side of a gel where a positive charge is located. The gel is covered by a ionic solution to enhance the movement of charges.