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Chapter 12: DNA/RNA Review

DNA History, Structure, Replication, and Protein Synthesis

Vanessa Dreessen

on 8 December 2014

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Transcript of Chapter 12: DNA/RNA Review

Deoxyribonucleic Acid
Chapter 12 Part I
History, Structure,
and Replication
Three important experiments:
Linkage = one chromosome contains many different genes that control many different traits

Linked genes DO NOT sort independently
Linked genes will always be expressed together because they are on the same chromosome

Crossing Over = genetic information is swapped between tetrads

Gene Mapping = scientists can use linked genes and crossing over to locate genes on specific chromosomes
Sex Linkage
Sex Chromosomes = determine gender
(XX or XY)
Autosomes = DO NOT determine gender
(all other chromosomes)
Human Genome
Genome = the sequences of bases of all
of the DNA within one cell of an organism

Human Genome Project = sequencing of the human genome was completed in 2000

Karyotype = photograph of the chromosome pairs within one cell of an organism

Nondisjunction = chromosomes do not separate completely in anaphase (if in mitosis = death)

Monosomy = only one copy of a chromosome is present when there should be two

Trisomy = three copies of a chromosome
are present when there should
only be two (example: Down Syndrome)

Polyploidy = MANY chromosomes
have too many copies
Tested two strains of bacteria
Injected mice with
live harmless bacteria (mice lived)
live fatal bacteria (mice died)
heat killed fatal bacteria (mice lived)
mixture of heat killed fatal/harmless (mice died)
* Whatever transformed the harmless bacteria into fatal bacteria must be the genetic material *
Supported theory that DNA is the molecule of heredity
Hershey and Chase
Used bacteriophages to track genetic molecule
Bacteriophages are made of protein and DNA
Tracked radioactive protein and radioactive DNA
Found radioactive DNA in bacteria cells
Proved DNA is the genetic molecule
First images of DNA using x rays
Showed DNA is a Double Helix
DNA is a double helix of two chains of nucleotides
One nucleotide consists of:
one deoxyribose sugar
one phosphate
one nitrogen base (A, T, G, C)
Three steps:
1. DNA molecule is unzipped by
helicase (enzyme)
2. Correct base pairs are brought in by
DNA Polymerase (enzyme) to
complement the separated strands
- A to T
- G to C
3. Deoxyribose/Phosphate backbone
is completed
Sex Limited = trait expressed only if appropriate male or female hormone is present

Sex-influenced = in presence of male hormones, trait is dominant
in presence of female hormones,
trait is recessive
Sex-Linked Traits = genes on X or Y chromosome
examples: Color Blindness, Hemophilia
Read Chapter 12, Sections 1, 2, 3, and 4
Happy Studying!
Double check your homework packet
Down Syndrome
(Trisomy - 21)
Protein Synthesis
Transcription (in nucleus)
1. RNA polymerase splits DNA
2. RNA polymerase brings in matching bases
(A-U, G-C)
3. mRNA strand is spliced
- introns stay in the nucleus
- exons are put together to form final mRNA
4. mRNA is exported out of the nucleus
5. DNA reforms the double helix
6. Transcription is complete
Translation (in cytoplasm)
1. Initiation
Ribosome (rRNA) attaches to the mRNA strand
2. Elongation
Ribosome (rRNA) reads codons
tRNA matches with anticodon
tRNA drops off specific amino acid
Ribosome moves down, reading codons
Amino Acid chain is formed (protein)
3. Termination
Ribosome reaches a STOP codon
Protein is released
Ribosome and mRNA separate
4. Translation is complete
Full transcript