Domain III - Genetics

 Deoxyribonucleic acid  Made up of nucleotides  Sugar – deoxyribose  A phosphate group  One of four nitrogen bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T)  Is in the shape of a double helix

 The two strands are held together by hydrogen bonds between the nucleotides  Adenine pairs with thymine  Guanine pairs with cytosine  The order of the bases is the genetic code

 DNA makes an exact copy of itself  Takes place in the nucleus 1. An enzyme ‘unzips’ the DNA 2. Free nucleotides pair up with the exposed nucleotides 3. This continues until two identical copies of the DNA molecule are made  The two copies each contain one side from the ‘original’ DNA and one ‘new’ side

 Ribonucleic acid  3 differences (from DNA):  Sugar is ribose instead of deoxyribose  Uracil instead of thymine  Single helix instead of a double helix  3 types of RNA:  Messenger RNA (mRNA)  Transfer RNA (tRNA)  Ribosomal RNA (rRNA)

 The process of making RNA from DNA  Occurs in the nucleus  Only one side of the DNA strand is used to make the RNA

 The process of converting the information on the mRNA into a protein  The mRNA carries the message from the nucleus to the ribosomes, where the proteins are made  The tRNA molecules bring the amino acids to the ribosomes  The 3 base codon on the mRNA corresponds to a 3 base anticodon on the tRNA  Each codon carries the code for a specific amino acid

 Which of the following shows how information is transformed to make a protein? a. DNA → RNA → protein b. gene → chromosome → protein c. cell respiration → ATP → protein d. ATP → amino acid → protein

 Information on mRNA is used to make a sequence of amino acids into a protein by which of the following processes? a. replication b. translation c. transcription d. transference

 ‘Father of Genetics’  Studied inheritance in pea plants  Concluded that each organism has two genes for each trait – one from mom, one from dad  Genes come in different forms called alleles  Dominant – the trait that is expressed  Recessive – the trait that is hidden

 Law of Dominance – the dominant allele will prevent the recessive allele from being expressed  Law of Segregation – gene pairs separate when gametes are formed, so each gamete has only one allele of each pair  Law of Independent Assortment – different pairs of genes separate independently of each other when gametes are formed

 Homozygous – two identical alleles (TT or tt)  Heterozygous – two different alleles (Tt)  Monohybrid – genetic cross involving one trait  Dihybrid – genetic cross involving two traits  Genotype – the genetic makeup of the organism (Tt)  Phenotype – the physical appearance of the trait (tall)

 Pea plants have seeds that are either round or wrinkled. In this cross, what will be the phenotypic ratio of the offspring? a. 50% RR and 50% Rr b. 25% RR, 50% Rr, and 25% rr c. 50% round seeds and 50% wrinkled seeds d. 100% round seeds

 Interphase  G1 phase – cell growth  S phase – DNA replication  G2 phase – preparation for mitosis  M phase  Mitosis  Cytokinesis – division of the cytoplasm

 Division of the nucleus  Two identical daughter cells are produced  The chromosome number remains the same  Purpose:  Growth and tissue repair  Asexual reproduction

 Prophase – the duplicated chromosomes become visible and spindle fibers form across the cell; the nuclear envelope starts to break up  Metaphase – the chromosomes attach to the spindle and line up randomly in the middle of the cell  Anaphase – the chromosomes are pulled to opposite ends of the cell  Telophase – a nuclear membrane forms around the chromosomes at each end of the cell; spindle fibers disappear; chromosomes become less visible

 Why is it important for the cells of multicellular organisms to undergo mitosis? a. Mitosis allows for reproduction with male and female gametes. b. Mitosis increases variation within an organism. c. Mitosis produces cells that are different from the original dividing cell. d. Mitosis produces identical cells to the original dividing cell.

 The production of gametes (sex cells – sperm and eggs)  The chromosome number is cut in half, producing haploid gametes  Diploid (2n) – 2 of each chromosome Normal body cells  Haploid (n) – 1 of each chromosome Sex cells

 There are two divisions  Meiosis I Prophase I – crossing over can occur Metaphase I Anaphase I Telophase I  Meiosis II Prophase II Metaphase II Anaphase II Telophase II

 Changes in the nucleotide sequence of a DNA molecule  Substitution – a single nucleotide is substituted for another one (A instead of G)  Insertion – a nucleotide is added  Deletion – a nucleotide is removed  A mutation can be harmful, neutral, or beneficial depending on how it affects the protein that is produced

 What is a source of genetic variation? a. mutation b. adaptation c. replication d. transcription

 Recombinant DNA – inserting foreign genes  Human insulin is mass produced by bacteria that have had the human insulin gene inserted  Creates genetically modified organisms  Cotton plants have been modified to resist worm attacks  Bacteria have been modified to clean up oil spills, manufacture alcohol, and process minerals

 Which of the following is the correct base-pairing rule for DNA? a. A-U; C-G b. A-G; T-C c. A-T; G-C d. A-C; T-G

 A mutagenic factor that can alter DNA by the loss of a chromosome segment is known as a. translocation b. crossing over c. deletion d. nondisjunction

 In Mendel’s experiments with a single trait, the trait that disappeared in the first generation and reappeared in the next generation is called the a. homozygous trait b. dominant trait c. recessive trait d. heterozygous trait

 Which of the following correctly shows the shape of a DNA molecule?

 Changes to an organism’s DNA can cause unexpected traits to be expressed in its offspring. DNA in an individual’s gametes will most likely be altered before being passed to offspring if exposed to a. x-rays b. loud sounds c. magnetic fields d. extreme temperatures

 Agricultural companies have developed the ability to control the genetic characteristics of their crops. Genetic engineering techniques have been used to produce all of the following effects except a. grow salt-tolerant crop plants b. decrease harvesting time c. make crop plants resistant to disease d. decrease soil nitrogen levels

 In fruit flies, the gray body color (G) is dominant to the ebony body color (g). What is the genotypic ratio of the offspring of a heterozygous gray female and an ebony male? a. 25% Gg, 75% gg b. 50% Gg, 50% gg c. 75% gray, 25% ebony d. 100% gray

 The process of meiosis produces gametes. How does this process increase reproductive variability? a. Different combinations of alleles are produced. b. Each allele from the parent cell forms a separate gamete. c. Each pair of genes undergoes crossing- over with different genes. d. The two genes are passed on to a daughter cell, resulting in new traits.

 DNA and RNA are nucleic acids. A characteristic of RNA is that it a. remains in the chromosomes in the nucleus b. is involved in translating information in DNA into proteins c. undergoes crossing-over during meiosis d. is replicated during the process of mitosis

 ATG is a DNA triplet that codes for an amino acid. Which mRNA codon will pair with the ATG triplet a. ATG b. GTU c. TAC d. UAC

1. A 2. B 3. D 4. D 5. A 6. C 7. C 8. C 9. D 10. A 11. D 12. B 13. A 14. B 15. D

 g.aspx?PageReq=CI_TESTING_EOCT& SubPageReq=GUIDES g.aspx?PageReq=CI_TESTING_EOCT& SubPageReq=GUIDES  Google image search  Campbell, Neil A. and Reece Jane B (2001). "6". Biology. Benjamin Cummings.  Miller, Kenneth R. and Levine Joseph S. (2002). Biology. Prentice Hall.