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Bellringer – Part 1
• 1. Define DNA
• 2. Define RNA
• 3. Define messengerRNA
• 4. Define Nucleotide
• 5. Define histone
• 6. Define DNA polymerase
• 7. Define Double-Helix (pg 293)
Chapter 12
Genetic facts in 1900:
• Both female and male organisms have identical chromosomes except for one pair.
• Genes are located on chromosomes
• All organisms have two types of chromosomes:• Sex chromosomes
• Autosomes
Male vs Female
• MALE
• Usually the Y chromosome.
• Y is usually smaller
• Male genotype = XY
• FEMALE
• Usually the X chromosome.
• Larger than the Y
• Female genotype XX
Except BirdsMale = XX
Female = XY
COPY: Frederick Griffith
• COPY:
• British bacteriologist
• 1928 = designed and performed experiment on rats and bacteria that causes pneumonia.
• 2 strains of the bacteria
• Type S = causes severe pneumonia
• Type R = relatively harmless
Griffith’s Rats
1. First he injected living Type S bacteria into rats:
• Second he injected dead Type S into the rats.
• Next he injected living type R bacteria
• Finally he injected a mixture of living Type R and dead Type S :
Results of experiments:
• Because the dead rat tissue showed living Type S bacteria, something “brought the Type S back to life”
• COPY: • Actually one bacterial type incorporated the
DNA, or instructions, from the dead bacteria into its own DNA
• Known as transformation. Confirmed by Avery, MacLeod, and McCarty in 1944
COPY: Oswald Avery
• COPY: • Canadian
biologist (1877-1955)
• Discovered DNA in 1944 with a team of scientists.
Copy: Hershey and Chase
• COPY:
• 1952
• Attempted to solve the debate on whether DNA or proteins are responsible for providing the genetic material.
• COPY:• They used a
bacteriophage (a virus which attacks bacteria) to prove that DNA was definitely the genetic material.
COPY: Phoebus A. COPY: Phoebus A. LeveneLevene
• Russian born; immigrated to America, moves to Europe.
• COPY: 1920’s discovered nucleotides (building blocks of DNA)
1. Sugar2. Phosphate group3. Nitrogenous base
Composition of DNA
COPY: Components and structure of DNA
• COPY: A very long molecule. 4 nitrogenous bases:
COPY: Chargaff’s rules
• COPY: The relative amounts of adenine and thymine are the same in DNA
• COPY: The relative amounts of cytosine and guanine are the same.
• Named after Erwin Chargaff
COPY: Rosalind Franklin
• COPY: Used X-Ray diffraction to get information about the structure of DNA:
COPY: Structure of DNA
• COPY:• Discovered in 1953
by two scientists:• James Watson (USA)• Francis Crick (GBR)• Known as the double-
helix model.
The double-helix
• A twisted ladder with two long chains of alternating phosphates and sugars. The nitrogenous bases act as the “rungs” joining the two strands.
How long is the DNA molecule?
Chromosomes & DNA replication
• The nucleus of one human cell contains approximately 1 meter of DNA.
• Histones = DNA tightly wrapped around a protein
• Nucleosome:
Chromosome structure:
DNA replication
• Must occur before a cell divides.
• Each new cell needs a copy of the information in order to grow.
COPY: DNA replication. Why needed?
• COPY:
• Before DNA strand can be replicated or copied it must be “unzipped”
• DNA polymerase (enzyme that unzips)
• Starts at many different points. Why?
COPY:Completing the replication
• COPY• After the DNA
molecule comes apart, bases of free nucleotides in the nucleus join their complimentary bases.
Bellringer – Part 2
• What are the 4 nitrogenous bases of DNA?
• What are the 3 parts of a nucleotide?
• What sugar does DNA have?
• What sugar does RNA have?
• How many strands does DNA have?
• How many strands does RNA have?
• What happens during DNA Replication?
COPY: RNA
• COPY:
• Very similar to DNA.
• Exceptions:
1) Ribose is the 5-carbon sugar
2) Uracil replaces thymine
3) Single-stranded
BELLRINGER- Part 3
• DEFINE RIBOSOMAL RNA
• DEFINE TRANSFER RNA
• DEFINE TRANSCRIPTION
• DEFINE RNA POLYMERASE
• DEFINE INTRON
• DEFIN EXON
• DEFINE TRANSLATION
• DEFINE CODON
COPY: mRNA (messenger)
• COPY:• Copies genetic
code of DNA by matching bases.
• Occurs in the nucleus.
• DNA changing to RNA
COPY: TRANSCRIPTION
• COPY:
• DNA is copied into mRNA with the aid of RNA polymerase.
• The RNA polymerase will bind to promoters that act as signals in the DNA sequence to make RNA.
Transcription continued:
COPY: Exons and Introns• COPY
• EXONS
• A segment of DNA in eukaryotic organisms that codes for a specific amino acid
• COPY
• INTRONS
• A segment of DNA that does NOT code for an amino acid.
Confusing genetic terms:
• COPY WORDS (DEFINE FOR HW)
• Polypeptide = a chain of amino acids.
• Protein = a complex structure composed of polypeptides
• Amino acids = smallest structural unit of a polypeptide.
• Gene = a distinct unit of material found on a chromosome
Reading the genetic code
• COPY:
• The genetic code is responsible for building all the proteins in the body using 20 different amino acids.
• How many 3 letter words can you make from the letters A,T,G and C?
• Answer: 64
Codons
• A three letter “word” that specifies an amino acid.
Genetic code:
tRNA (transfer)
• COPY
• approx. 80 nucleotides in length.
• Cross-like shape
• At one end an amino acid is attached
• At the other end there is an anticodon
• Acts like a truck
Polypeptide assembly
• COPY
• Translation = reading or “translating” the RNA code to form a chain of amino acids.
• Known as protein synthesis
• Occurs in the cytoplasm. (p.304)
COPYMutations
• COPY
• The source of variation in a genetic sequence.
• Can be either gene or chromosomal mutations.
• Point mutations = a change in a single nucleotide in a sequence of DNA.
COPY: Frameshift Mutation
• COPY: Inserting an extra nucleotide which, in turn, shifts the entire sequence one way or the other.
COPY: Chromosomal mutations
• COPY• Involves a change in the number or structure
of the chromosomes.• Deletion : when a piece of a chromosome
breaks off and is lost.• Duplication : when a segment of a
chromosome is repeated• Inversion : when a segment of a chromosome
is reversed.
More chromosomal mutations
• COPY
• Translocation : when part of a chromosome breaks off and is attached to a non-homologous chromosome.
COPY: Control of gene expression
• COPY
• Genes are often like light switches that can be turned off and on.
• Operon = occur in prokaryotes. (bacteria) different genes that work together to activate gene functions
Eukaryotic gene expression
• Controlled by complex sequences of DNA.
• Example: “TATA box”
Factors:
• Overall gene control is more difficult for eukaryotes because functional genes may be on different chromosomes.
• Environmental such as chemicals and temperature.
COPY: Hox and Oncogenes
• COPY
• Hox genes
• Genes that actively control embryonic development.
• COPY• Oncogenes• Genes known to
cause cancer.• Usually these are
switched “off”, but can be switched “on” by a number of factors.