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B-4 Demonstrate an understanding of the molecular basis of heredity Genetics Review
B 4.1 Compare DNA and RNA in terms of structure, nucleotides, and base pairs.
Nucleic Acids • Nucleic acids are made of nucleotides. • Nucleotides have three parts: • Sugar • Phosphate • Base
RNA vs. DNA Sugar: Ribose Bases: A, U, C, G Shape: single strand of nucleotides Sugar: Deoxyribose Bases: A, T, C, G Shape: Double helix
DNA vs. RNA I am: • double stranded • found in the nucleus • have four nitrogen bases • contain deoxyribose sugar • contain thymine instead of uracil • What important molecule am I? A. DNA B. RNA C. Enzyme D.protein
DNA, Genes, and Chromosomes • DNA • made of nucleotides • blueprint for proteins • Genes • a segment of DNA • a specific location on a chromosome • A code for a protein • Chromosome • One long thread of DNA with many genes
DNA, Genes, and Chromosomes A segment of DNA that codes for the ability to make one type of protein molecule is known as a(n)____________________. • Codon • Exon • Gene • Intron
B 4.3 Explain how DNA functions as the code of life and the blueprint for proteins.
Blueprint for Proteins • The sequence of bases in DNA determines which protein is made • Each cell has a complete set of information—two copies of each autosome and a pair of sex chromosomes (46 total chromosomes in humans) • Sex cells have one set of chromosomes (23 in humans) • Organisms that are closely related will have many genes in common.
DNA Replication Semi-Conservative Model of Replication
Blueprint for Proteins The process of converting the genetic message from DNA into __________ is called transcription. • RNA • amino acid • nucleic acid • nucleotide base
B 4.4 Summarize the basic processes involved in protein synthesis (including transcription and translation).
Protein Synthesis • Transcription: • DNA is copied into RNA • Happens in the nucleus • Messenger RNA moves to the cytoplasm • Translation: • Ribosomal RNA reads a code off of the mRNA • Each codon is 3 nucleotides • Transfer RNA has a matching anticodon and drops off amino acids at the correct location
Which type of nucleic acid is responsible for the transmission of information from the genetic code in the nucleus to the ribosome? • DNA • mRNA • rRNA • tRNA
What type of biomolecule will be produced at the end of the process shown in the illustration? • a fat • a sugar • a lipid • a protein
Form a cluster of four chromatids called a tetrad Prophase I Two haploid cells Four haploid cells
Meiosis In normal humans, sex cells contain the _________ number of chromosomes. • Diploid • Haploid • Multiploid • Tetraploid
In order for meiosis to create four, genetically different gametes, DNA replication must occur. Which of these best describes when DNA replication would occur during meiosis? • interphase of meiosis I • anaphase I in meiosis I • interphase in meiosis II • anaphase II in meiosis II
B 4.6 Predict inherited traits by using the principles of Mendelian genetics (including segregation, independent assortment, and dominance)
Inheritance of Traits - Dominance Some alleles are dominant and some are recessive. Having two identical alleles for the same trait (TT or tt) is homozygous Having two different alleles for the same trait (Tt) is heterozygous
Genotype vs. Phenotype • Genotype: the genetic makeup • Example: TT is homozygous dominant Tt is heterozygous tt is homozygous recessive • Phenotype: the physical characteristics or expression of a trait • Example: tall or short
Law of Segregation Each parent has two copies of each gene. Each gamete gets only one of the two copies. When egg and sperm fuse (fertilization), the child receives one copy from each parent.
Law of Independent Assortment • The segregation of the alleles of one trait does not affect the alleles of another trait’s alleles. • Genes on separate chromosomes can separate independently. • Exception: “linked genes” are found on the same chromosome—they are sometimes inherited together
Mendelian Genetics In a classic experiment using pea shape, Mendel conducted two separate genetic crosses. In the first cross the parent plants were “true breeding” for pea shape; one had round peas ( R )and the other had wrinkled (r). The first cross produced a filial 1 generation of all round peas. In the second cross, Mendel bred plants from the filial 1 generation. This cross produced different results. Out of approximately 1000 plants, about 75% were round and 25% were wrinkled.From these experiments, Mendel developed four hypotheses. They include all BUT • one heritable factor may be dominant and mask the other factor. • any organism that "shows" a heritable factor must be homozygous. • an organism has two "heritable factors", now called genes, one from each parent. • a sperm or egg carries only one heritable factor for each trait in the offspring.
Mendelian Genetics A dominant gene that codes for red eye color in fruit flies is represented by the symbol W, while the recessive white eye gene is represented by the symbol w. If a parent fly with the genotype WW is crossed with a parent of the genotype Ww, what percentage the offspring will have red eyes? • 100% • 75% • 50% • 25%
Incomplete Dominance: Blending of alleles in heterozygous individuals Example: pink flowers
Codominance Heterozygous individuals express both dominant traits
Polygenic Traits Two or more genes affect the phenotype of one trait
Pedigree ChartsConstructed to show the inheritance of a trait within a family
Complex Inheritance A cross between a blue blahblah bird & a white blahblah bird produces offspring that are silver. The color of blahblah birds is determined by just two alleles. • What are the genotypes of the parent blahblah birds in the original cross? (choose 1 or 2) A. BB B. Bb C. BW D. WW • What is/are the genotype(s) of the silver offspring A. BB B. Bb C. BW D. WW • What would be the phenotypic ratios of offspring produced by two silver blahblah birds? A. 1:2:1 B. 3:1 C. 4:0 D. 1:1
B 4.8 Compare the consequences of mutations in body cells with those in gametes.
Mutations • Can affect somatic cells or sex cells: • Mutations in somatic cells with affect other daughter cells, but NOT future offspring. • Mutations in gametes can be passed on to the offspring AND all future generations. • DNA changes can be: • Gene mutations: affecting only a single gene • Chromosomal mutations: affecting a group of genes or a whole chromosome
Mutations Transcription translation errors often result in physical, or ___________, changes in an organism. • Carbohydrate • Chemical • Genotypic • Phenotypic
B 4.9 Exemplify ways that introduce new genetic characteristics into an organism or a population by applying the principles of modern genetics.
Genetic Engineering • Genetic engineering: the process of replacing specific genes in an organism in order to ensure expression of a desired trait • Gene map: Shows where genes are on a chromosome • Cloning: creating a copy of a gene or organism • Gene therapy: inserting a normal gene to replace a missing or abnormal gene
Selective Breeding • Selective Breeding is only breeding those organisms with desired traits • Examples: crops and most domestic animals • Inbreeding: crossing closely related individuals • Hybridization: selective breeding in order to create a combination of desired traits • Example: a mule—stronger than a horse but more intelligent and less stubborn than a donkey
DNA Fingerprinting • DNA is copied and chopped into fragments • Fragments are sorted by length • A matching set of samples means the samples came from the same organism
Genetic Engineering ________ is a technique that involves putting a healthy copy of a gene into cells that have a defective copy of the same gene. • Gene therapy • Binary fission • Tumor necrosis • DNA fingerprinting