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 Birds Male = 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 ( ) 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. Levene Russian born; immigrated to America, moves to Europe. COPY: 1920’s discovered nucleotides (building blocks of DNA) 1. Sugar 2. Phosphate group 3. 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)

COPY Mutations 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.