Objective 3.01 (DNA, RNA and Protein Synthesis)

Transcription

1 Objective 3.01 (DNA, RNA and Protein Synthesis) DNA Structure o Discovered by Watson and Crick o Double-stranded o Shape is a double helix (twisted ladder) o Made of chains of nucleotides: o Has four types of nitrogen bases: Guanine (G) Cytosine (C) Adenine (A) Thymine (T) o Guanine and Cytosine always pair together o Adenine and Thymine always pair together DNA Replication o DNA replication is they process of copying a strand of DNA o Occurs in the nucleus o Strands are separated, and new matching chains are created

2 Example: Original DNA: ATCGAGGCG New DNA: TAGCTCCGC Protein Synthesis o DNA RNA Protein o Transcription The process of converting DNA into mrna Occurs in the nucleus There is no thymine in RNA, so the base Adenine in DNA is paired with Uracil in RNA Example: DNA: ATCGAGGCG RNA: UAGCUCCGC o Translation The process of converting RNA into proteins Occurs at the ribosomes trna carries amino acids to the ribosomes Each group of three nitrogen bases (codon) codes for one amino acid The chain of amino acids is linked to form a protein

3 Mutations o Mutations are any change in DNA. o They cause the wrong mrna and protein to be created. Genes o Genes are segments of DNA that are found on chromosomes. o Each gene codes for a specific protein. Objective 3.02 (Cell Division) Chromosome Structure o Chromosomes are highly coiled sections of DNA. o There are 22 types of chromosomes in the human body called autosomes. o The human body also contains 2 sex chromosomes (X and Y) that determine sex. o Diploid cells (2n) contain two copies of each chromosome (44 autosomes and 2 sex chromosomes). Each pair of similar chromosomes is called a homologous pair. Most cells in the body are diploid. Males have the sex chromosomes XY Females have the sex chromosomes XX o Haploid cells (1n) contain one copy of each chromosome (22 autosomes and 1 sex chromosome). The only haploid cells are the sex cells (sperm and egg cells).

4 Mitosis o Mitosis is a form of asexual reproduction. o Once mitosis is complete, there are two identical diploid daughter cells. o These daughter cells have identical DNA (unless a mutation has occurred). Meiosis o Meiosis is a form of sexual reproduction. o During meiosis, there are two separate cell divisions, and four daughter cells are created. These daughter cells are all genetically different, and they are haploid. o Crossing over and independent assortment occurs. Crossing over: Genetic Variation o Variation is having genetic differences in the DNA. o Variation helps populations survive stressful situations like disease and predation. o Only mutations and sexual reproduction provide genetic variation.

5 Objective 3.03 (Genetics) Alleles o Different forms of a gene o Dominant alleles are expressed with a capital letter (T), recessive with a lowercase letter (t). o Every diploid cell has two alleles: TT homozygous dominant Tall Tt heterozygous Tall tt homozygous recessive short Genotype o The genes an organism has Example: TT, homozygous dominant Phenotype o The physical characteristic of an organism based on its genotype Example: Tall, short Punnett Squares o To predict the outcome of genetic crosses, use a punnett square. o Tutorial available at: s/01t.html Incomplete Dominance o Unlike complete dominance, the heterozygote does not have the dominant phenotype. It is an intermediate form of the two phenotypes. Example: Tt = medium (not tall) Codominance o The heterozygote shows both the dominant and recessive phenotypes. Example: Rr = red and white spots (not red) Objective 3.04 (Genetic Engineering) Genetic Engineering o The process of manipulating an organism s genes (may take out or add to change the function of the cell). Human Genome Project o Goals were to sequence entire human genome and locate every gene o Benefits are increased understanding of gene organization, new treatments and cures for diseases, and improved diagnoses for diseases

6 Objective 3.05 (Evolution) Evolution o Change in organisms over time o All organisms originated from a common ancestor. Lamarck s Explanation o Lamarck believed that organisms changed over time because of acquired traits. Acquired traits come from the organisms actions and are not genetic. Example: Giraffes stretched out their necks by reaching for food, and over time the neck length of giraffes increased. o His theory was disproved because acquired traits are not hereditary. Darwin s Explanation o Darwin believed that organisms changed over time because of natural selection. Organisms with more beneficial adaptations were more likely to survive and reproduce. Example: Giraffes with longer necks were able to obtain more food, and therefore they had more offspring. Eventually all the giraffes in the population had long necks. First Life-Forms o The first living organisms were prokaryotic and anaerobic. o Over time, they evolved to become photosynthetic, aerobic and multicellular. Evidence for Evolution o Organisms are similar in their DNA sequences, embryology and appearance. o Organisms with more similarities are more closely related.