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Chapter 4: Patterns of Heredity

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1 Chapter 4: Patterns of Heredity
4.1 Living things inherit traits in patterns 4.2 Patterns of heredity can be predicted 4.3 DNA is divided during meiosis 4.4 Cells use DNA and RNA to make proteins Before, you learned: Traits pass from parents to offspring in predictable patterns Traits are passed on through genes In sexual reproduction, offspring get half their genes from each parent 4.4 Now, you will learn: How the structure of DNA stores information the cell needs How DNA is copied How RNA uses the information from DNA to make proteins

2 Review (t/f) Genes are units of heredity that determine traits True
A genotype refers to the observable characteristics of an organism A phenotype refers to the observable characteristics of an organism A dominant trait is expressed only if two alleles are present on a chromosomes A dominant trait is expressed if one or two alleles are present on a chromosome

3 4.4 Cells use DNA and RNA to make proteins
Template vs a copy A: B: Write a set of rules to describe how the characters in line A related to the characters in line B Use the rules to produce a template (corresponding pattern) that goes with: C: A copy is a duplicate of what already exists. A template forms a pattern that enables one to make a copy.

4 DNA is the information molecule
DNA stores information Like an instructional book: recipes for food, model boats, card games, computer games The books don’t do these things, they hold the information, the instructions, that a cell needs to function/grow/divide Proteins do most of the work

5 Proteins and Amino Acids
Proteins: large molecules made up of chains of amino acids 20 different amino acids combine to make up thousands of different proteins found in humans Small: 129 amino acids; large: 2685 amino acids DNA: stores information for the cell to put together right sequences of amino acids needed to produce specific proteins DNA contains a “code” – set of rules and symbols – used to carry information

6 DNA and the Genetic Code
Double-stranded spiral…twisted ladder Nucleic acids (DNA and RNA) are made of nucleotides: Nucleotide subunits make up the side rails and rungs (two bases) One nucleotide base attaches to another from the opposite strand = “base pairs”

7 DNA and the Genetic Code
Four different nucleotides in DNA, identified by their bases: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) ALWAYS: A - T and C – G “All Tigers Can Growl”

8 DNA and the Genetic Code
DNA, a molecule, contains information to produce other molecules: proteins Genes are a segment of DNA A set of bases specifies the amino acids needed to form a particular protein: Triplet (3 bases) per 1 amino acid gives 64 possible combinations (4*4*4) Ex: T-C-T codes for arginine A gene is the entire sequence of the bases that codes for all the amino acids in a protein Each gene is made up of a sequence of bases at a particular location on the DNA Set of bases Amino acids proteins Gene DNA

9 Replication Recall - Cell division: daughter cells receive an identical copy of the DNA DNA is copied before the cell divides: Replication Two strands of DNA separate Nucleotides in the area around the DNA match up, base by base (C-G and A-T) Results in two identical DNA molecules, each with one strand of the each the old and new DNA


11 Replication Each strand of DNA is used as a template (pattern or shape) to produce a copy of the other strand

12 RNA is needed to make proteins
DNA is not used to make proteins directly RNA (ribonucleic acid) Connects three bases (physically) to an amino acid carries the info from DNA to a ribosome where the amino acids are brought together to form a protein DNA codes for RNA; 3 types: mRNA: messenger RNA – forms a copy of the DNA recipe rRNA: ribosomal RNA – brings together the other two types of RNA to form the amino acid chain tRNA: transfer RNA – transfers an amino acid to the growing chain of amino acids Has 3 bases on one end, can hold an amino aid on the other Set of bases Amino acids proteins Gene DNA

13 RNA is needed to make proteins
Prokaryotic cells: RNA and proteins are both made in the cytoplasm Eukaryotic cells: DNA is copied in the nucleus, then RNA moves to the cytoplasm where the proteins are made

14 Transcription Transcription: the process of transferring information from DNA to RNA RNA similar to DNA: four types of nucleotide subunits 3 bases: guanine (G), cytosine (C), and adenine (A) 4th base NOT thyminne, it is uracil (U)

15 Transcription DNA is used like a template:
Transcription: the process of transferring information from DNA to RNA DNA is used like a template: One side of DNA is used to make a complementary strand of mRNA **Only individual genes are transcribed, not the whole DNA molecule! DNA opens up just where the gene is located Base pairs separate Each base is joined by a matching base of mRNA (A-U and C-G)


17 Transcription Different from replication:
Only one strand of DNA is transcribed, so mRNA molecule is just a single strand When transcription is complete, mRNA is released and can be used again to make more copies of the gene in a short time! At the end, the DNA molecule closes

18 Translation Replication and transcription pass along information that is coded in the language of nucleotide bases To make a protein, a cell must translate this language  amino acids language Takes place in the cytoplasm Involves all three types of RNA: mRNA, tRNA, rRNA

19 Translation Proteins are made on ribosomes (which are made of RNA and proteins) mRNA is a recipe for making one protein Ribosome is where the cooking gets done tRNA gathers the ingredients (amino acids) tRNA shape can attaches to a specific amino acid Other end matches three bases that can match an mRNA tRNA does the actual translation of bases to amino acids when it matches up with mRNA Ribosomes connect the amino acids and remove them from the tRNA molecule

20 1. Translation begins when a ribosome attaches to the beginning of an mRNA molecule.
2. A tRNA molecule carrying an amino acid joins up to a matching triplet on mRNA on the ribosome. 3. The ribosome attaches one amino acid to another as the ribosome moves along the mRNA molecule. 4. Each tRNA molecule is released after the amino acid it carries is attached to the growing chain of amino acids. 5. The ribosome completes translation when it reaches the end of the code for the protein. The new protein molecule, made of a chain of amino acids, is released.

21 DNA replication, transcription, translation
Process is basically the same in all cells Flow of information goes from: DNA  RNA  protein Proteins are responsible for an organism’s traits – you are a product of proteins Proteins are made at different times for different purposes, all using different recipes in the DNA cookbook to carry out the various functions


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