CHAPTER 26: MODERN GENETICS

26-1: CHROMOSOMAL INHERITANCE

T.H. Morgan & Drosophila

·       Early 1900’s, he provided evidence that __________________ _________________________________

·       Used Drosophila (fruit fly) because:

à they are ______; large numbers can be kept in small spaces

à they ______________________; you can study many generations in short time span

à only _____________________________

Sex Determination and Chromosomes

Sex Chromosomes _______________________ (XX = female; XY = male) pair #23.

à Male determines sex:

Autosomes – __________________________; do not determine sex. Contain _______________________.

Sex-Linked Traits –

Ex: Eye color in drosophila is carried on the X chromosome. White eyes (r) are recessive to red eyes (R).

P Generation: white-eye male X normal eyed female (homozygous):

F1 Genotypes:                 F1 Phenotypes:

F1 Generation: red-eyed male X red-eyed female (heterozygous)

F2 Genotypes:                 F2 Phenotypes:

Morgan did ____________________ to provide evidence for his theory.

Sex-Linked Traits in Humans

·       __________________ (inability to clot blood)

·       ________________________ (gradual destruction of muscle cells)

·       __________________________________________

·       _____________________ more often/ ____________ can be “_____________” & are rarely affected

Ex: Cross a colorblind male and a normal female:

 Genotypes:                     Phenotypes:

Ex: Cross a normal male and a female who carries the colorblind allele:

Genotypes:                      Phenotypes:

Gene Linkage

Linked Genes:

Linkage Group:

(# linkage groups = # pairs)

Ex: humans have 23 pairs of chromosomes à 23 linkage groups

·       Linked genes are not distributed evenly during meiosis, _________ __________________________________________________

·       ________________________ did experiments to show that _____ ____________________________________________________, investigating flower color and pollen grains:

à Purple flowers are dominant to red flowers; Long pollen grains are dominant to round pollen grains.

à In a ___________________, you would expect _________ ratio – but it was _____, showing ____________ of genes

Crossing Over –

·       Morgan found that ______________________________________ ______________________ à sometimes genes separated

·       SOME flowers were ___________________ grains, or _________ _____________________ grains (Dom + Rec)

·       _________________________________________________ (ends/ tips) are __________________________ by crossing over

·       A _________________________________________ locating genes using these principles

Multiple-Gene (Polygenic) Inheritance –

Ex: Height, eye color, hair color

26-2: THE GENETIC MATERIAL

The Chemistry of the Gene

·       1869 –  

·       Other scientists said it was made of __________________

·       Named it “________________”

·       2 kinds:    ______ (deoxyribonucleic acid)

______ (ribonucleic acid)

·       chromosomes contain _______ & _____________

·       _____________ were thought to be _______________________

Protein vs. Nucleic Acids – Which is the genetic material?

Griffith’s Experiments on Transformation –

·       Smooth à mouse ________

·       Rough à mouse ________

·       Smooth, heat-killed à mouse __________

·       Smooth, heat killed + Rough à mouse ___________

Transformation:

Avery demonstrated that ____________________________________. (Still thought protein was hereditary info.)

Hershey & Chase determined ________________________________.

Bacteriophages à viruses that infect bacteria

·        

·        

·        

Watson & Crick – Developed a ___________ to prove _____________ __________ is a _______________________ (twisted ladder).

Levene – Determined the ___________________________:

·       Building Block of DNA = ___________________

·       Nucleotide Components:

à ___________________ (deoxyribose)

à ___________________

à ___________________

                Purines: ________________________ (Adenine, Guanine)

                Pyrimidines: _____________________ (Thymine, Cytosine)

·       4 Kinds of nucleotides (N-bases): ____________

·       A pairs with T; C pairs with G (_________________) ____; ____

DNA Molecule:

·        

DNA Replication

During S Phase à ___________________

Semi-conservative Replication à

·       _____________________ portion of _______

·       Other _____________________________ between N-bases

·       New, complementary _______________________________ _____________________________________ (A-T; C-G)

·       DNA _________________________; can carry out building ONLY in ____________ direction

·       DNA Polymerase (enzyme) involved à___________________ ________________________

Replication begins at the ___________________________ along the molecule. ________________________________________________ _______________________________________.

_________________________________________this way.

Example- Replicate the following strand of DNA:

T A G T T A C G (original strand)

_____________  (new, complementary strand)

DNA vs. RNA:

26-3: GENE EXPRESSION

Genes & Enzymes

Beadle & Tatum did experiments to confirm this – “________________ ______________________________”

This was later changed to the “_______________________________ _______________________” because genes direct synthesis of individual polypeptides (_____________________________________)

Protein Synthesis

·       DNA = ____________________________

·       ________ of DNA determined by _____________________ (ATCG)

·       DNA ___________________________

·       _______ is made in ____________ à travels to _______________

2-Step Process in Making Proteins:

1.   Transcription –

2.   Translation –

Three types of RNA involved in Protein Synthesis:

1.   mRNA (Messenger RNA) à

2.   tRNA (Transfer RNA) à

3.   rRNA (Ribosomal RNA) à

Transcription (DNA à mRNA) Nucleus

·       RNA Polymerase (enzyme) _______________________________, “Promotor region” à ____________________________________ ________________________________. (20-30 TATATATAs…)

·       _________________________ àmoves down strand, ___________ __________________________ from ____________________

·       RNA Polymerase reaches _________________________ “Terminator Region” à ______________________________; it is called “RNA Transcript”

·       _____________________________________ through nuclear pores

Translation (RNA à Protein) On ribosome (In cytoplasm)

·        

    (aa) – “Codon”

·       ______________________________________________________ to the growing polypeptide

·       There are ___amino acids; ___ possible __________ in the Genetic Code

Process:

·        

·        

·        

·        

·        

·       On the ______ molecule is a _______________________, an “anti-codon” which is _____________________________ codon. This _________________________________________________ __________________________________________ on the mRNA

·       _____________________________________ molecules, linked together by ___________________ until a STOP codon is reached.

·        

·       ______________________________ into cell

The Genetic Code:

Translate the following strand of DNA into a protein:

DNA strand:             TAC  GAC  CGC  TTA  ATC

mRNA codons:         ________________________

Amino acids:            _________________________ (polypeptide chain)

tRNA anti-codons:  _________________________

26-4 CONTROL OF GENE EXPRESSION

Gene Expression in Bacteria (Prokaryotes)

·       Jacob, Monod & Lwoff à nobel prize

·       Bacteria produce __________________________ only when _______________________ & other sources of energy aren’t available

·        

Structural Gene –

Operator Gene –

Repressor Gene –

Regulator Gene –

_________________________________________ à no transcription of structural genes

______________________________ à (Operator gene released) à transcription of structural genes

Lactose-metabolizing enzymes produced

Promotor –

Promotor & operator ________________________________________

Operon –

Gene Expression in Higher Organisms (Eukaryotes)

·        

Exons:

Introns:

·       Both ________ & ________ are ________________ into RNA

·       _________________________ and splice (____) _______

·       “_____________” & “______________” are added to ends of RNA

·       Because _____________________________________________, _________________________________________ can be made

·       Changes in the amount of coiling or in the shape of DNA affect gene expression

à

à

Enhancer –

Gene Expression and the Environment

·        

Ex: Himalayan Rabbit; Siamese Cat.

·       Light fur with ________________________________________.

·       Dark color ___________________________________________ ____________________________ (lower than body temp, 37°C).

Gene Expression in Development

Homeotic Genes –

_________________________ bind certain parts of the DNA and thus _____________________________________________.

Humans have “__________________” (similar to homeotic genes)

Oncogenes and Cancer

Oncogenes –

·        

·