define the following terms: genetics gene gene expression cell differentiation artificial selection

Define the following terms:

Genetics

Gene

Gene expression

Cell Differentiation

Artificial Selection

Genetics Introduction& Gene Regulation

Artificial Selection

• Selective breeding - allow the individuals with desired traits to produce the next generation.

• This takes advantage of naturally occurring genetic variation.

• Ex. Breeds of dogs

cockapoo puggle Yorkie Pin

Artificial Selection

• Name a situation that humans have selected for various characteristics.

• What are the advantages and disadvantages of this type of selection?

Artificial Selection

• Agriculture

• Livestock

• Domesticated animals

• Plants

Selective breeding

• Luther Burbank developed disease-resistant potato that was exported to Ireland to fight the potato blight.

• Hybridization - crossing dissimilar individuals to bring together the best of both organisms.– Ex. Burbank crossed a disease-resistant strain

with a strain that was high in food production.

Selective breeding• Inbreeding - continued

breeding of individuals with similar characteristics.

• This ensures that the characteristics of each unique breed are preserved.

• Disadvantaged and weaker species is created.

• All the individuals carry similar genetic material and have a higher chance of contracting a disorder.

Amur Leopards only have ~40 individuals in the wild.

Human Genetics

• List all the features you share in common with your parents.

• Turn to a neighbor to discuss which parent you most resemble and share the traits that you have in common with your parents.

• Why do some students not resemble either of their parents?

Heritable traits• Completely (or nearly completely) heritable:

– gender– eye color– skin color– cystic fibrosis– muscular dystrophy– deafness (many forms)

• Partially heritable:– height– cognition– body mass– personality traits (at least many traits)– diabetes– asthma– schizophrenia

• Not (or only very weakly) heritable:– scurvy (vitamin C deficiency)– distance a student lives from school

• The environment also affects how our genesare expressed.

Gene Expression

•Humans have 25,000 genes within 46 chromosomes. •How does a cell know which genes need to be regulated (turned off and on)?

• Cells would waste a lot of energy if they did not regulate the genes contained in them.

• The organism would produce a lot of waste product as well.

• Regulation allows the cell to control which genes will be expressed and when.

Gene Regulation

Gene Expression

• Gene expression – the activation of a gene that results in the formation of a protein

• Genome – the complete genetic material of an organism

• Karyotype – picture of chromosomes

Prokaryotic gene regulation

• Francois Jacob and Jacques Monod studied the regulatory elements in the DNA of the bacterium Escherichia coli

• Studied how genes control the metabolism of lactose.

•Lactose is a sugar found in milk

•Can be broken down into galactose and glucose

Gene Regulation• Operon - A series of genes that code for specific

products and the regulatory elements that control these genes.– Structural genes –code for particular polypeptides– Promoter – site at which polymerases attach to start

transcription– Operator –binding site for an inhibitory protein that

blocks transcription from proceeding

lac Operon

Gene Repression

• Jacob and Monod found that the expression of the genes were turned on only when lactose was present.

• Repression – blockage of transcription by the action of a repressor protein

• Repressor proteins – protein that stops a gene from being expressed– Regulator gene – codes for the repressor proteins – DNA binding protein – protein that binds to DNA– These proteins usually bind to the operator region of

the operon

Gene Repression

• Regulator protein is bound to operator region preventing transcription of mRNA.

A repressor protein is coded for by a(n):

a. Structural gene

b. Regulator gene

c. Promoter

d. Enhancer

Gene Activation

• Activation – start of transcription• Inducer – molecule that initiates

gene expression

– Binds to repressor and changes conformation removing it from operator

– Ex. Lactose in the lac operon

Define the following terms:Character

Trait

Hybrid

Law of Independent Assortment

Gene Activation

1. Lactose, the inducer, turns on expression by binding with the repressor protein.

2. This changes the repressors conformation and it is removed from the DNA molecule.

3. Transcription of the necessary proteins proceeds

What is the purpose of the operator?

a. Sequence of DNA that codes for the repressor protein.

b. Talks to lactose to see when the operon should be turned on.

c. Sequence that inducer binds to in order to start translation.

d. Sequence of DNA that the repressor protein binds to in order to stop transcription.

Which of these are DNA-binding proteins?

a. Repressor

b. Inducer

c. Operator

d. a & b

Eukaryotic Gene Regulation

• Most eukaryotic genes are controlled individually.

• Regulatory sequences are much more complex than the lac operon.

• Even though each cell in a multicellular organism has the entire genome, only a select few genes are expressed in a particular cell.

Eukaryotic Gene Regulation

• Enhancer - a non-coding control sequence in a eukaryotic gene – Must be activated for transcription to take place– Transcription factors - bind to enhancers and RNA

polymerase to facilitate transcription

• TATA box – region of “TATATA” or “TATAAA” that is directly upstream of a coding sequence of DNA.– Helps to align the RNA polymerase on DNA molecule

Enhancer and TATA box

Eukaryotic Gene Regulation

• Histone – protein molecule around which DNA is tightly coiled.– For transcription to occur the histones loosen and the

coil relaxes, allowing the desired gene to be transcribed into mRNA.

The control of gene expression enables organisms to:

a. Reproduce more quickly

b. Remove mutations from their DNA

c. Produce proteins only when needed

d. Form new combinations of genes

Why is gene regulation in eukaryotes more complex than in prokaryotes?

A. Prokaryotes have less chromosomes than eukaryotes.

B. All the cells in a multicellular organism cell can have a different function.

C. Prokaryotes are not multicellular organisms.

D. All of the above.

Cell Differentiation• Liver enzymes are not

expressed in nerve cells.

• Keratin in skin cells is not produced in blood cells.

• Cell specialization, in multicellular organisms, requires specific gene regulation.

Cell Differentiation• Homeotic gene – controls the

development of specific adult structures.

• Mutations in these genes have drastic effects on the development of organisms

– Ex. Fly can grow appendage on head in place of antennae.

How is the sex of an organism determined?

• A human receives 23 chromosomes from each parent.

• Autosomes – 22 non-sex chromosomes

• Sex chromosomes – determine an individuals sex

• Females have two of the same sex chromosomes (XX) and males have two different sex chromosomes (XY).

Sex Chromosomes

• Thomas Hunt Morgan was a geneticist from Columbia Univ. that began breeding fruit flies, Drosophila.

• He noticed that one set of the females chromosomes were different in shape and size than the males.

Sex Chromosomes

• X-linked genes – genes found on the X chromosome

• Y-linked genes – genes found on the Y chromosome

• Sex linkage – the presence of a gene on a sex chromosome

•Ex. Colorblindness and hemophilia

Keeping in mind that the gene for colorblindness resides on the X

chromosome, why do males exhibit this

quality more than females?

a. Colorblindness is attached to the gene for testosterone production.

b. Males only have one X chromosome and therefore all the alleles are expressed.

c. Females do not inherit an X chromosome.

d. Males determine sex so they can chose which offspring get the allele for colorblindness