Genetics Review and Questions Living Environment Mrs. Paparella Spring 2009

DNA provides the set of coded instructions required by every organism for specifying its traits. The DNA molecule also provides for a reliable way for parents to pass their genetic code from one generation to the next. Heredity refers to this passage of these instructions from one generation to another. Gene-Chromosome Model Hereditary information is contained in genes, which are composed of DNA, located in the chromosomes of each cell. Chromosomes are found in the nucleus of each cell. Each gene carries a separate piece of information. An inherited trait of an individual can be determined by one genes, but is usually determined by the interaction of many different genes. A single gene can influence more than one trait. A human cell contains many thousands of different genes coding for many different traits.

Independent assortment is the principle that states that genes located on different homologous chromosomes will be distributed independently of each other. This allows for greater variety in the offspring.

Changes in the sequence of the DNA molecule and therefore the gene are called mutations. A mutation may change the manner in which a trait is expressed by an organism. Mutations which occur in non sex cells of sexually reproducing organisms will not be passed on to the offspring, although they may result in disease or death for the organism involved. One possible consequence of a mutation in a non sex cell is uncontrolled mitotic cell division or cancer. Mutations which occur in sex cells or gametes may be passed to the offspring. Along with crossing over and genetic recombination, mutation provides for a source of variation in sexually reproducing individuals.

DNA-> mRNA in nucleus mRNA then leaves the nucleus RNA DNA codes for the formation of RNA in the nucleus of the cell. RNA is short for another kind of nucleic acid called ribonucleic acid. RNA is very similar in structure to DNA except for three small differences: a. RNA is a single stranded molecule, b.RNA lacks the base thymine (T) as it is replaced by the base uracil (U), c. its five carbon sugar is ribose ,not deoxyribose Three different types of RNA exist: mRNA or messenger RNA, tRNA or transfer RNA, and rRNA or ribosomal RNA.

One of the primary jobs of DNA is to Direct Protein Synthesis Cells store and use coded information. The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires. The chemical and structural properties of DNA are the basis for how the genetic information that underlies heredity. DNA is encoded in the sequence of nitrogenous bases which directs the formation of proteins in the cell.

Transcription-- Translation First, the DNA code is copied on to the mRNA (messenger RNA) codon. A codon is a sequence of three nitrogenous bases. This process is called transcription. This mRNA codon is then carried from the nucleus out to the ribosome. Messenger RNA attaches to another kind of RNA called tRNA (transfer RNA). Transfer RNA attaches to amino acids and carries them to the ribosome located in the cytoplasm of the cell. Ribosomes may be on the Rough ER or free in the cytoplasm. This assembly of amino acids due to the code provided to RNA by the original DNA molecule is what produces proteins for the cell. Translation is the production of proteins by decoding mRNA produced in transcription. Translation occurs in the cytoplasm where the ribosomes are located. Ribosomes are made of a small and large subunit which surrounds the mRNA. Remember a protein is a long molecule formed from amino acid subunits.

1.The gene-chromosome theory states that genes are segments of DNA located on chromosomes and are found in homologous pairs. Which figure below would represent the theory?

2.A molecule of DNA is a polymer composed of which of the following?? A. glucose B. amino acids C. fatty acids D. nucleotides 3. The presence of DNA is important for cellular metabolic activities because DNA A. directs the production of enzymes B. is a structural component of cell walls C. directly increases the solubility of nutrients D. is the major component of cytoplasm

4. Which nitrogenous bases make up DNA nucleotides. A 4. Which nitrogenous bases make up DNA nucleotides? A. adenine, thymine, guanine, and cytosine B. adenine, uracil, guanine and cytosine C. adenine, thymine, uracil, and cytosine D. adenine, thymine, guanine, and uracil

5. In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). If 50% of a large litter of squirrels are gray, the parental cross that produced this litter was most likely 1. GG x Gg 2. GG x GG 3. Gg x gg 4. gg x gg

6. Which cross could produce a child with type O blood? 1. AO x BB 2. AA x BO 3. AB x OO 4. AO x BO

7. Which diagram most correctly represents the process of mitosis?

. 8. Which represents the genotype of a homozygous condition? 1. Bb 2. BC 3. bb 4. bc

9. Geneticists have observed that fruit flies that commonly inherit vestigial wings also inherit lobed eyes. Observations such as this have helped to develop the genetic concept known as 1. segregation 2. dominance 3. gene linkage 4. crossing-over

10. Chromosomes normally occur as homologous pairs in 1. a sperm cell 2. an egg cell 3. a zygote 4. a gamete

11. Because the gene for hemophilia is located on the X-chromosome, it is normally impossible for a 1. carrier mother to pass the gene to her son 2. hemophiliac father to pass the gene on to his son 3. hemophiliac father to pass the gene to his daughter 4. carrier mother to pass the gene to her daughter

12. A man with a blood genotype AO marries a woman with a blood genotype of AO. What blood types could be expected in their children? 1. type A, only 2. type O, only 3. both type A and type O 4. neither type A nor type O

13. When many hybrid tall pea plants are cross-pollinated, the offspring produced will probably be 1. 100% homozygous tall 2. 100% heterozygous tall 3. 50% homozygous tall 4. 50% heterozygous tall

14. A hybrid black-coated guinea pig produces two million sperm cells 14. A hybrid black-coated guinea pig produces two million sperm cells. Approximately what number of its sperm cells contain the recessive gene for white coat color? 1. 1 million 2. 2 million 3. 0 4. 0.5 million

15. Some individuals with blood group A may inherit the genes for blond hair, while other individuals with blood group A may inherit the genes for brown hair. This can be explained by the principle of 1. dominance 2. multiple alleles 3. independent assortment 4. incomplete dominance

16. The outward appearance (gene expression) of a particular trait in an organism is referred to as 1. a genotype 2. a phenotype 3. an allele 4. a chromosome