Bio 110 Exam 3

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Gene

Back 1

Segment of DNA that codes for a specific trait

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Allele

Back 2

The specific version of the gene on a chromosome

-diploid organisms have 2 alleles for each gene; one for each member of a homologous pair

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Locus

Back 3

Physical location of a gene on a chromosome

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Dominant

Back 4

If present, the allele shows itself

(CAPITAL)

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Recessive

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Can be masked by a dominant allele

(lowercase)

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Homozygous

Back 6

Having 2 identical alleles for trait

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Heterozygous

Back 7

Having 2 different alleles for trait

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Genotype

Back 8

Specific alleles for an organism

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Phenotype

Back 9

The observable traits of an organism

(Not only appearance)

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Gregor Mendol

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-Studied plants in 1800's

-Used phenotypes or parents & offspring to determine genotypes

-Hypothesized that each plant had 2 units of info for each trait

-Tested this with pea plants

-Punnett Squares

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How to do Genetic Problems

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1. Parent Genotypes

2. Gametes produced by each parent

3. Offspring genotypes from crossing parents

4. Offspring phenotypes

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Genetic Disorders

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1. Chromosomal Abnormalities (errors in meiosis)

2. Spontaneous Mutation in genes to make new dangerous allele

3. Specific Inherited alleles passed through generations

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Autosomal Recessive Alleles

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-Must have 2 affected alleles to get disorder

-Heterozygotes are carriers --> have one allele but not disorder

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Autosomal Dominant Alleles

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-Only need one allele to get disorder

-affected individuals can be homozygous or heterozygous

ex: achondroplasia - type of dwarfism

Huntingtons Disorder - fatal degenerative disorder of the nervous system

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Incomplete Dominance

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-No allele is completely dominant

-Heterozygotes show blending

ex: Snapdragon flowers ---> red and white alleles can create a pink flower

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Co-Dominance

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-When different alleles are present, phenotypes of both are expressed in their pure form (NO blending)

-Blood typing in humans

-Different alleles code for different types of surface molecules on blood cells

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Pleiotrophy

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One gene affects more than one phenotypic characteristic

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Epistasis

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-Expression of trait can be masked by alleles from second gene

ex: coat color in Labrador Retrievers; one gene for color, one gene to deposit pigments

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Polygenic Inheritance

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-Phenotype determined by additive effects of 2 or more genes

-can lead to continuous variation

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Genotype/Environmental Interactions

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-Can influence expressed phenotype

-ex; coat color in Siamese cats and himalayan rabbits, flower color in hydrangeas

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DNA Structure

Back 21

-Structure discovered by Watson and Crick based on x-ray pictures and data from American Chemist Chargaff

-Two nucleic acid strands join together when bases form hydrogen bonds

-Result is double helix

-Base pairs ---> A to T, C to G

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DNA Replication

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-Two strands are separated

-Using base pair rules, DNA polymerase uses free nucleotides to make new companion strand for each parent strand

-DNA ligase connects new fragments together

-Parent strand and new strand re-form double helix

-Special enzymes check and repair

-Two new double helices, both identical to original

-two sister chromatids

-each double helix is one old and one new strand

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What is DNA used for

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-Some DNA contains instructions for protein synthesis

-Different genes code for different proteins

-Letters of DNA code determine the order of amino acids in the protein

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From DNA to RNA

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Transcription - DNA code is transcribed to messenger RNA and sent to cytoplasm

Translation - Code from mRNA is used to make protein

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Transcription

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-Happens in nucleus

-mRNA made by RNA polymerase

-uses DNA as template

-uses base pairing code

-RNA splicing ---> mRNA strand is 'edited' and sent to cytoplasm

-Used as instructions for making protein

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Translation

Back 26

Synthesis of protein using mRNA as instructions

-Takes place in cytoplasm (on ribosomes made of protein and ribosomal RNA)

-Each set of 3 nucleotides codes for 1 amino acid

-One codon signals start, 3 codon signal stop

-Some amino acids are coded for by more than one triplet

-Requires carriers (transfer RNA)

-Amino acids added one at a time, according to codons

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Silent Mutation

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Changing 3rd nucleotide may not change amino acid due to redundancy in triplet code

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Missense Mutation

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Changes one amino acid (usually from change in single nucleotide)

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Nonsense Mutation

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Gets 'stop' codon instead of amino acid, and translation stops too soon

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Frameshift Mutation

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A deletion or insertion of nucleotides can change every amino acid that follows

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Mutations and Protein Synthesis

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-Changes in DNA sequence may lead to changes in amino acid sequence

-Changes in amino acids will change protein structure

-Can make proteins non-functional or just different

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What Causes Mutations?

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Spontaneous - errors in replication or recombination

Mutagens - environmental agents

-U.V. radiation

-Ionizing radiation

-carcinogens

PROGERIA - error in DNA replication prior to meiosis

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How are Genes Controlled?

Back 33

-All cells have the same instructions, but most are specialized in structure and function

-During development, cells become differentiated (uses only genes for that role)

-Before differentiation, cells can become any type (stem cells)

(embryonic stem cells are from embryos)

(Somatic stem cells are from bone marrow, umbilical cord, etc.)

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Gene Expression

Back 34

How genetic information is revealed in an organisms phenotype

-In female mammals, on X chromosome is inactivated early in development

-Transcription is prevented by

-chromosome packing

-methylation

-Transcription also controlled by proteins that bind to DNA and either promote of inhibit transcription

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Control of Gene Expression

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Post transcription regulation - mRNA can be degraded or translation can be locked

-After translation ---> some proteins require activation before functioning, others can be broken down when no longer needed

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Biotechnology

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Use of biological agents for advancements in agriculture, medicine, industry

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Genetic Engineering

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Manipulation of DNA for practical purposes

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Recombinant DNA

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When DNA from two or more species is combined

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Restriction Enzymes

Back 39

-Occur naturally in bacteria, and cut up foreign DNA that gets into cells

-Cuts DNA into fragments at specific locations

-Allows 'pasting' together of fragments

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Polymerase Chain Reaction

Back 40

To increase amount of DNA in small sample

-Heating and cooling cycle creates copies

-Uses heat-resistance taq DNA polymerase

Front 41

Cloning

Back 41

Generally refers to a genetic copy

-Making copies of DNA fragments (gene cloning)

-Making genetic copy of an organism for reproductive purposes (reproductive cloning)

-Making genetic copy of an organism (embryonic cloning) for research purposes, including biomedical (therapeutic cloning)

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Animal Cloning

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-Nuclear transplantation

-donor egg with nucleus

-adult somatic cell with own DNA

-cells shocked to fuse and stimulate division

-Embryo can be transplanted to surrogate

-reproductive cloning

-Blastocyst is source of embryonic stem cells

-therapeutic cloning

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Cloning Genes

Back 43

-Making copies of genes using bacteria

-Plasmid ---> extra circular piece of DNA found in bacteria

-Source DNA and bacteria plasmid cut with restriction enzymes

-Recombinant plasmid taken up by bacteria

-bacteria will copy DNA when it divides

-Copies of genes can be used for research

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Reproductive Cloning

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-Has been accomplished in sheep, horses, cattle, mice, cats, dogs, goats, pigs, deer, and more

-Applications

-food animals, companion animals

-endangered species

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Therapeutic Cloning

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Goal is to obtain embryonic stem cells that are a genetic match to patient

-combine donor egg with cell from patient

-Can use healthy cells to replace patients damaged cells

(could potentially create a clone of someone else by using another persons embryo)

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Genetically Modified Organisms

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An organism that contains DNA from another species (a recombinant organism)

-Can be single celled or multicellular

-Can be used to manufacture useful gene products or for food

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Engineered Plants

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-Use engineered bacteria to "infect" plant and insert plasmid with desired gene into plant DNA

-Resistance to pesticides, insect damage, disease

-Tolerance of drought, freezing, salinity

-Increased nutritonial value

Very difficult to contain living organisms

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Engineered Animals

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Food animals

-disease resistance, higher production or better quality

-Research animals to study human genes

-Using animals to produce human proteins in milk

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Gene Therapy

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-Many disorders caused by mutated alleles

-Gene therapy

-insert "good" allele to do the work of a bad allele

-genes delivered to body in viruses or lipids

-can't guarantee where genes will insert in genome

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DNA profiling

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-DNA from blood, saliva, urine, hair, teeth, bone, tissue

-Criminal investigations ---> easier to eliminate suspects than prove guilty

-Genetic Relationships - offspring share half DNA with parents and 1/4 with siblings

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What are the ways that people test for genetic disorders in their children?

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-Prenatal Diagnosis

-obtain cells through amniocentesis

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DNA Ligase

Back 52

Type of enzyme that is used when replicating DNA

-joins the parents strand and new strand together

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DNA polymerase

Back 53

Enzymes that create DNA molecules by assembling nucleotides

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What are proteins made from?

Back 54

They're made from amino acids, joined together in chains

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Exon

Back 55

Portion of DNA sequence that is not removed from pre-mRNA and is expressed in the protien