DNA & Genetics Biology

Remember chromosomes? What are genes? Made up of DNA and are units of heredity; unique to everyone What are traits? Are physical and unseen characteristics. Examples: physical: color of skin or eyes unseen: blood type or intelligence level

Remember chromosomes? What are chromosomes? Carrier of genetic materials, thread-like fibers found in the nucleus They are composed of genes What is an allele? Gene form for each variation of a trait of an organism. Example: gene for height can express tall or short

DNA structure DNA = deoxyribonucleic acid A nucleic acid, genetic material Carries the code for all proteins that make up the human body Composed of paired nucleotides Nucleotides contain a phosphate group, 5-carbon sugar (deoxyribose), and a nitrogen base

DNA structure The 4 nitrogen bases of DNA: –Thymine (T) –Cytosine (C) –Adenine (A) –Guanine (G)

DNA structure Nucleotide structures: 1 phosphate group 1 5-carbon sugar 1 nitrogen base

DNA structure Structurally pyrimidines pair with purines Thymine (T) and Cytosine (C) are pyrimidines Adenine (A) and Guanine (G) are purines Nitrogen bases are held together by hydrogen bonds Guanine (G) pairs with Cytosine (C) Adenine (A) pairs with Thymine (T)

DNA structure Composed of 2 complementary strands Complete the following DNA strand: TACGTACCGCAGGTAATC ATGCATGGCGTCCATTAG

DNA

What does DNA look like? Double helix 1 st published in 1951 Credited to Watson and Crick 1 st seen by Rosalind Franklin, whose pictures were stolen from her lab

DNA Replication Process where DNA copies itself DNA replicates before mitosis DNA replicates before meiosis I The 2 strands of a DNA molecule separate when the hydrogen bonds break. Two complimentary strands form, each using one of the single DNA as a template

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Steps of DNA Replication Enzyme breaks hydrogen bonds between paired nucleotides DNA strand unzips Free nucleotides move in and bond with complementary pairs on unzipped strands of DNA Enzyme bonds the newly paired nucleotides together 2 exact copies of the original DNA strand are produced

Steps of DNA Replication Replicate the following DNA strand: TACGTACCGCAGGTAATC ATGCATGGCGTCCATTAG

DNA Replication

RNA structure RNA is produced from a DNA strand What is RNA? Ribonucleic acid Consists of 1 strand of nucleotides RNA nucleotides have 1 phosphate group, 1 5-carbon sugar (ribose), and 1 nitrogen base

RNA structure The 4 nitrogen bases of RNA: –Uracil (U) –Cytosine (C) –Adenine (A) –Guanine (G)

RNA structure Nitrogen bases are held together by hydrogen bonds Guanine (G) pairs with Cytosine (C) Adenine (A) pairs with Uracil (U)

Compare DNA and RNA DNA: 2 strands Deoxyribose sugar Phosphate group 4 nitrogen bases: adenine thymine guanine cytosine RNA: 1 strand Ribose sugar Phosphate group 4 nitrogen bases adenine uracil guanine cytosine

Types of RNA Messenger RNA – mRNA: carries sequence of nucleotides that code for protein from nucleus to ribosomes Transfer RNA – tRNA: picks up individual amino acids in the cytoplasm & carries them to the ribosomes Ribosomal RNA – rRNA: found in ribosomes, helps bind mRNA and tRNA together during translation (protein synthesis)

Transcription: DNA into RNA Enzymes break hydrogen bonds in DNA strands Unzipped strand of DNA gets paired with free RNA nucleotides RNA nucleotides bond together Enzymes break hydrogen bonds between DNA and RNA strands. RNA strand becomes mRNA and leaves the nucleus

Transcription: DNA into RNA

mRNA Composed of a codons A codon is a series of “3” letters or bases that make up the code of mRNA Codons are the “recipe” for making all amino acids in the body Every strand of mRNA starts with the codon AUG or the start codon – starts protein synthesis. There is only 1 start codon Every strand of mRNA ends with a terminator or “stop” codon – stops protein synthesis. There are 3 stop codons.

Translation of mRNA Translate the following mRNA into amino acids using the Universal codon chart AUGAGGGCUCGAUGA MET-ARG-GLY-ARG-STOP

Universal codon chart

What does mRNA do? Brings the code for protein production and assembly to the ribosome At the ribosome the code in the mRNA is translated into amino acids mRNA codons enter the ribosome transfer RNA or tRNA brings the complementary base pairs or the anti-codon - to the ribosome from the cytoplasm A protein is produced when the mRNA codon and the tRNA anti-codon bond

Translation