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Learning Goals: Explain what forms genetic code. Describe how a cell produces proteins. Explain...
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Transcript of Learning Goals: Explain what forms genetic code. Describe how a cell produces proteins. Explain...
Learning Goals: Explain what forms genetic code. Describe how a cell produces proteins. Explain how mutations affect an organism.
Warm-up: How can mutations affect an organism?
Homework: Packet pages 29-32
Tuesday 11/24/15
The DNA ConnectionChapter 4 Section 4
The main function of genes is to control the production of proteins in an organism’s cells
Proteins help determine the size, shape, and many other traits of an organism
The Genetic Code
Chromosome are composed mostly of DNA
Review: DNA is made up of four different nitrogen bases… ◦ Adenine (A), Thymine (T), Guanine (G), Cytosine (C)
A gene is a section of a DNA molecule that contains the information to code for one specific protein
A gene is made up of a series of bases in a row
The bases on a gene are arranged in a specific order
Genes and DNA
The DNA Code
The order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced
Proteins: long-chain molecules made of individual amino acids
A group of three DNA bases codes for one specific amino acid
Order of the Bases
Protein synthesis: production of proteins
During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein
Where? Ribosomes in the cytoplasm
Where are the chromosomes found?
So how do they get into the cytoplasm…
How Cells Make Proteins
A “messenger” first carries the genetic code from the DNA inside the nucleus into the cytoplasm
The genetic “messenger” is called ribonucleic acid, or RNA
RNA and DNA differ in some important ways…◦RNA only has one strand◦Different sugar molecule◦RNA contains uracil instead of thymine
The Role of RNA
Messenger RNA (mRNA): copies the coded message from the DNA in the nucleus, and carries the message from the ribosome in the cytoplasm.
Transfer RNA (tRNA): carries amino acids to the ribosomes and adds them to the growing proteins
Types of RNA
Mutations: any change in a gene or chromosome
◦Can cause a cell to produce an incorrect protein during protein synthesis
◦The organisms trait, or phenotype may be different from what it normally would have been
Body cell – the mutation will NOT be passed to offspring
Sex cell – the mutation can be passed to an offspring and affect the offspring phenotype
Mutations
Substitution◦One base pair is substituted for another
Deletion◦One base pair is removed
Addition◦One base pair is added
Types of Mutations
Mutations can be a source of genetic variety
Some mutations can be helpful, some can be harmful
Harmful to an organism if it reduces the organism’s chance for survival and reproduction
A mutation that is harmful or helpful depends partly on the organism’s environment
Effects of Mutations