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.