G7 Ch5.3 - DNA and Genes
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Transcript of G7 Ch5.3 - DNA and Genes
I. Structure of DNA
A.) Chromosomes are made of proteins and DNA
i. Genes are sections of chromosome
ii. Genes are parts of DNA
iii. DNA in a chromosome is tightly coiled
B.) DNA is a macromolecule.
i. Scientists Franklin and Wilkins made and studied X-rays of DNA
i. Watson and Crick built the final model.
a.) The model showed how the smaller molecules bonded to form the double helix
Failed Models
C.) DNA is made of 4 nucleotides (A, T, G, C)
i. A nucleotide has 3 partsa.) nitrogen base
b.) sugar
c.) phosphate group
ii. The sugar and phosphate group form the sides of DNA, or “backbone”
iii. The nitrogen bases stick inwards like teeth on a zipper
iv. The nitrogen bases are:a.) Adenine (A)b.) Thymine (T)c.) Cytosine (C)d.) Guanine (G)
v. The nitrogen bases pair and form bondsa.) A – Tb.) C – G
II. DNA Replicates
A. During mitosis all chromosomes must be copied.
i. A strand of DNA will separate or “unzip”
ii. New nucleotides will bond with the exposed nitrogen bases
iii. 2 identical strands of DNA are produced
B. During replication…
* What is a code?
Codes use numbers, letters, or symbols to represent other information
III. Making Proteins
A. DNA codes for proteinsi. Most DNA is not part of any geneii. 97% of genes are non-coding or “junk DNA”iii. Junk DNA has functions other than protein buildingiv. DNA contains the information for all proteins in every
cellv. However, DNA cannot leave the nucleus
B. RNA is a nucleic acid that carries the code for making proteins from the nucleus to
the cytoplasm i. DNA cannot leave the nucleus
so RNA carries the messageii. RNA has a different sugar
group the DNAiii. In RNA the nucleotide uracil
(U) replaces thymine (T)a.) A – Ub.) C – G
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C. RNA’s role in the cell
i. There are 3 types of RNA:a. mRNA – transports messages from the
nucleus to the cytoplasm
b. tRNA – transports amino acids throughout the cell
c. rRNA – make up part of the ribosome
D. Making Proteins Step 1: Transcription
i. RNA is made from DNA
a.) process is similar to DNA replication
ii. RNA leaves the nucleus
E. Making Proteins Step 2: Translation
i. Occurs at the ribosome (free or rough ER)
ii. mRNA attaches to the ribosome
iii. tRNA which has an amino acid on its tail move to the ribosome
iv. rRNA connects the amino acids and the tRNA leaves
v. Repeats
F. Codes
i. Proteins are made of amino acidsii. 3 bases on a tRNA codes for one
amino acidiii. A group of 3 nitrogen bases is
called a codoniv. 60 codons make 20 amino acidsv. Some codons do not add amino
acids but are start and stop signals.
IV. Most mutations occur during replication
i. Mutations can be triggered by x-rays, UV light, and chemicals
B. 3 Types of Mutations
i. Substitution a.) a base is replaced
ii. Insertion
b.) base pairs has been added
iii. Deletion
c.) base pairs has been removed