Genetics, Protein synthesis Mitosis Meiosis

1. Genetics, Protein synthesis Mitosis Meiosis

2. State the base pairing rules. • A pairs with T; C pairs with G • 2. Which molecules holds the base? • Deoxyribose sugar. • 3. Which 2 molecules make up the sides of the ladder? • Phosphate & sugar • 4. What is the name of the monomer for nucleic acids? • Nucleotide

3. http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swhttp://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.sw • Animation of DNA replication • When does DNA replication take place during the cell cycle? • During the S phase of Interphase.

4. 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. Teleophase – 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. http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html

5. Comparing Meiosis and Mitosis • Chromosome behavior • Mitosis: Homologous chromosomes independent • Meiosis: Homologous chromosomes pair forming bivalents until anaphase I • Chromosome number- reduction in meiosis • mitosis- identical daughter cells • meiosis- daughter cells haploid • Genetic identity of progeny: • Mitosis: identical daughter cells • Meiosis: daughter cells have new assortment of parental chromosomes • Meiosis: chromatids not identical, crossing over

6. Stages of Meiosis

7. 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.

8. 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”.

9. 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

10. 3 types of RNA Messenger RNA m-RNA Transcribes the DNA code, takes the code out of the nucleus & joins with the ribosome. Transfer 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. Ribosomal RNA 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.

11. Transcription hyperlink annimation Translation hyperlink annimation

12. Gregor Mendel’s an Austrian monk who experimented with garden peas & came up with principles of genetics. LAW OF SEGREGATION: A pair of factors is segregated, or separated during the formation of gametes. (Anaphase I) LAW OF INDEPENDENT ASSORTMENT: Factors for different characteristics are distributed to gametes independently. Traits are either dominant (mask or dominate other traits) or recessive (the trait that can be covered up & appeared in the F1 generation of Mendel’s experiments.)

13. 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. Codominance: Both alleles, which are different are expressed in the phyenotype. 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.

14. Mutations come in 2 types chromosome or gene. Chromosome mutations: Non-disjunction results in either 1 too many (trisomy) or 1 too few (monosomy) chromosomes. A piece of a chromosome can break off (Cri di chat). • Mutations of genes: • Deletion of 1 or more bases. • 2. Insertion of 1 more bases. • Both of the above mutations result in frame shifts where the entire code is incorrect after the deletion or insertion. • 3. Substitution of a base with a different base.

16. This shows the inheritance of a trait which is recessive. How many people are affected? How many generations are shown? What is the genotype of individual 1 in generation I? What is the genotype of individual 2 in generation I? What is the genotype of individual 3 in generation II? How do you know? Can you be sure of the genotype of individual 3 in generation III? Why or why not?

17. 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.

18. Now it's up to you! Study Hard!