Genetics Test
Terms
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- Archibald Garrod
- First to recognize a link between genes and proteins (1923)
- George Beadle and Edward Tatum
- did experiments in Neurospora, They showed a mutation on a gene caused the loss of function of an enzyme
- Watson and Crick proposed genetic information is carried in
- sequences of nucleotides
- Nuclein
- What the material in the nucleus of the cell was calle din the 1800's
- What does DNA contain?
- Genetic Information
- What year did Francis Crick and James Watson find the structure of DNA
- 1953
- When did Francis Crick, James Watson, and Maurice Wilkins win the Nobel Prize?
- 1962
- Rosiland Franklin
- Her work with xray diffraction and the structure of nucleotides were key in the discovery of the structure of DNA, yet she was overlooked for credit.
- Chemical bond
- A link between atoms in a molecule
- Covalent bond
- When two atoms share electrons, they are stable and can be broke by chemical reactions
- Hydrogen bonds
- weak interactions between two atoms; one of them must be H, they are weak bonds, but in living systems are important and hold molecules together by sheer numbers
- Two types of Nucleic Acids
- RiboNucleic Acid (RNA) and DeoxyriboNucleic Acid (DNA)
- Purines
- Guanine and Adenine
- Pyrimidines
- Thymine and Cytosine
- Components of a nucleotide held together by:
- Covalent Bonds
- How is DNA composed?
- by two polynucleotide strands running in opposite directions (meaning strands are antiparallel)
- What is the backbone to DNA?
- phosphate groups and sugars
- How does DNA copy itself during mitosis?
- Strands are separated and each one serves as a template for a new double strand
- high capacity for coding genetic information
- A molecule with n base pairs has 4n possible combinations
- Functions of RNA
- Found in the nucleus and the cytoplasm. Functions: Transfer of genetic information to the cytoplasm (mRNA) Participation in protein synthesis (tRNA) Structural component of ribosomes (rRNA)
- Differences of RNA from DNA
- Sugar is ribose, not deoxyribose The base uracil is used instead of thymine RNA is single stranded
- RNA Secondary Structure
- ⬦the single strand can fold back on itself and complementary bases pair up
- DNA is compacted with proteins to form:
- Chromatin
- Proteins called ________ play a major role in the structure of DNA
- Histones
- DNA wraps around a core of eight histones forming a __________
- Nucleosome
- Several models have been proposed to explain the organization of DNA within the chromosome, an accepted model states:
- DNA and histones form nucleosomes Nucleosomes form a rosary-like structure, where each nucleosome represents a “bead†linked to others by threads of DNA The “rosary†is coiled as a cylindrical fiber …and that fiber is supercoiled into chromosomes
- The process of DNA replication:
- The double helix is unwound DNA strands are separated and each one is the template for a new double helix
- semi conservative replication
- Is what DNA replication is called because every new double helix has an old strand and a new one
- DNA polymerase reads template strands in the:
- 3'-5' end
- new strands are synthesized in the:
- 5'-3' end
- Proteins are made of sub units called
- amino-acids
- Codon
- A triplet of nucleotides that encodes the information of one amino-acid
- The list of codons and their translation into amino acids is known as the
- genetic code
- Why is genetic code said to be redundant?
- Several codons can encode the same amino acid
- stop codons
- UAA, UAG, and UGA
- Start Codon
- AUG, encodes methionine
- The flow of genetic information from nucleus to cytoplasm occurs in two steps:
- Transcription and Translation
- Transcription
- an mRNA molecule is synthesized based on the information stored in the gene
- Translation
- the mRNA goes to the cytoplasm and its information is used to synthesize a protein
- Three Stages of Transcription
- Initiation: RNA polymerase binds to a DNA sequence called the promoter, adjacent to the gene The DNA double helix gets unwind and the strands exposed so one of them can be the template for the mRNA synthesis Elongation: The RNA polymerase links RNA nucleotides together to form the mRNA transcript Termination
- Sequences within the gene with no genetic information are called
- introns
- Sequences within the gene with genetic information are called
- exons
- The poly-A tail is formed in a process called
- polyadenylation which protects the mRNA molecule from enzymatic degradation in the cytoplasm and aids in transcription termination, export of the mRNA from the nucleus, and translation
- Amino acids
- building blocks of proteins
- each Amino acid has three distinct chemical elements:
- An amino group (NH2) A carboxyl group (COOH) An R group, where the R represents an organic chain that varies fro each amino acid
- Amino acids are linked through
- covalent peptide bond
- four levels of protein structure
- Primary structure, Secondary structure, Tertiary structure, and Quaternary structure
- Primary structure
- The amino acid sequence
- Secondary structure
- determined by interactions among amino acids. Hydrogen bonds can make the polypeptide form pleated sheets or helices (coils)
- Tertiary structure
- Sheets and helices fold back on themselves
- Quaternary structure
- The shape of several polypeptides interacting together in functional proteins that are composed by more than one polypeptide
- Chemical reactions catalyzed by enzymes follow specific
- metabolic pathways
- Humans can synthesize ____________amino acids required to put proteins together
- 11 out the 20
- essential amino acids
- The amino acids we can’t synthesize, must be ingested
- Phenylalanine
- An essential amino acid used to incorporate into proteins and to synthesize the amino acid tyrosine
- Carbohydrates include
- sugars, starches, and celluloses