Section 6-4 “Traits & genes” Write everything that is BLACK

KEY CONCEPT Genes encode proteins that produce a diverse range of traits

State Standards 4. Genes are a set of instructions encoded in the DNA sequence of each organism that specify the sequence of amino acids in proteins characteristic of that organism. As a basis for understanding this concept: D. Students know specialization of cells in multi cellular organisms is usually due to different patterns of gene expression rather than to differences of the genes themselves.

The same gene can have many versions Alleles are made up of genes. A Gene is a piece of DNA that directs a cell to make a certain protein Each gene has a locus, a specific position on a pair of homologous chromosomes

Again a gene is a piece of DNA that directs a cell to make a certain protein DNA Brain POP w/ activity

An allele is an alternative form of a gene Each parent donates one allele for every gene Pea plants have 2 alleles for shape - they receive one from each parent For shape, there is a wrinkled allele and a round allele

What are proteins made of? Proteins are made up of smaller building blocks called amino acids, joined together in chains. There are 20 different amino acids. Some proteins are just a few amino acids long, while others are made up of several thousands.

Gene Expression: Transcription The majority of genes are expressed as the proteins they encode. The process occurs in two steps: Transcription = DNA → RNA Translation = RNA → protein Taken together, they make up the "central dogma" of biology: DNA → RNA → protein.

Genes influence the development of traits All of an organism’s genetic material is called the genome A genotype refers to the actual genes A phenotype is the physical expression of a trait

Genotype: The gene combination of an organism It consists of 2 alleles For example: Pure dominant, 2 dominant genes Pure recessive, 2 recessive genes Hybrid, 1 dominant and 1 recessive gene

The way an organism looks Phenotype: The way an organism looks No matter what genes are present, phenotype of a tall pea plant is tall and a short pea plant is short

Dominant alleles are represented by uppercase letters A dominant allele is expressed as a phenotype when at least one allele is dominant A recessive allele is expressed as a phenotype only when two copies are present Dominant alleles are represented by uppercase letters Recessive alleles by lowercase letters

Mendel’s observed traits Dominant traits: covers up the other traits Recessive traits: traits that “disappear” Rule of Dominance: When a dominant trait is present the recessive trait is hidden

R = Red flower r = Purple flower Label the dominant Step 1: Label the dominant and recessive traits R = Red flower r = Purple flower

Write the genotypes of each Step 2: Write the genotypes of each parent to be crossed Purple (since it is recessive it has to be homozygous) Hybrid Red (means heterozygous) Rr rr Rr x rr

Set up the punnett square. Step 3: Set up the punnett square. Each parent will give up one gene or the other so there will be one gene per box for each parent R r r Rr rr

Step 4: Analyze the genotypes Rr rr R r r 2 of the 4 (50%) offspring will be pure recessive 2 of the 4 (50%) will be hybrids

Step 5: Analyze the phenotypes Punnett Square Handout Rr rr R r r 50% of the offspring will be red 50% of the offspring will be purple

DNA Structure and Function DNA Model Lab DNA contains the genetic information that codes for the RNA and proteins necessary for cell function. All DNA in the chromosomes has to be copied (replicated) and transmitted to daughter cells via mitosis. Non-faithful replication or inability to correct errors and damage to DNA results in mutations. Structure of DNA A= Adenine T= Thymine C= Cytosine G= Guanine RNA ONLY U= Uracil Four nucleotides (A,T,C,G) are chemically joined through sugar and phosphate molecules in the backbone. During synthesis of mRNA (where U is used instead of T)

RNA carries DNA’s instructions The central dogma is the basic concept proposed by Crick (one of the scientists that discovered DNA) It states that: information flows in one direction from DNA to RNA to proteins

Replication Transcription Translation The central dogma includes three processes: Brain POP- Mutation Replication Transcription Translation replication transcription translation Transcription = DNA → RNA Translation = RNA → protein RNA is a link between DNA and proteins Mistake in Replication = Mutation

RNA differs from DNA in 4 ways: RNA has a ribose sugar RNA has uracil instead of thymine RNA is a single-stranded structure RNA can leave the nucleus and go into the cytoplasm DNA can’t

Transcription makes three types of RNA Transcription copies DNA to make a strand of RNA

The RNA strand detaches from the DNA once the gene is transcribed

Amino acids are coded by mRNA base sequences Translation converts mRNA messages into polypeptides (protein) A codon is a sequence of three nucleotides that codes for an amino acid codon for Methionine (Met) Leucine (Leu)

A change in the order in which codons are read changes the resulting protein Regardless of the organism, codons code for the same amino acid

Amino acids are linked together by a peptide bond to become a protein An anticodon is a set of three nucleotides that is complementary (opposite) to an mRNA codon An anticodon is carried by a tRNA transfer RNA (translation)

Transcription vs. Translation Review Process by which genetic information encoded in DNA is copied onto messenger RNA Occurs in the nucleus DNA mRNA (DNA unzipped) Translation Process by which information encoded in mRNA is used to assemble a protein at a ribosome Occurs on a Ribosome mRNA protein 31

Why are proteins important? Well, for starters, you are made of proteins. 50% of the dry weight of a cell is protein of one form or another. Meanwhile, proteins also do all of the heavy lifting in your body: digestion, circulation, immunity, communication between cells, motion-all are made possible by one or more of the estimated 100,000 different proteins that your body makes. Here are several examples of how RNA codes for amino acids. These codons are for tryptophan, the amino acid that contributes to the sleepy feeling you may have after eating turkey; phenylalanine, an amino acid used in the aspartame sweetener in diet soda; tyrosine, an important amino acid in intracellular signaling processes; and cystine.

Genes control the genetic traits, and genes are DNA, which is organized into chromosomes

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