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361 Exam 1 Study Cards 2

Terms

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locus
location of gene on a chromosome
allele
different versions of the same gene
polymorphic site
restriction sequence with more than one varient
What are the 2 classes of genetic markers?
microsatellites and SNPs
What is an SNP? # of alleles? How many are found in genome?
single base change in DNA sequence.

2

millions
How do you locate microsatellites?
PCR
Where are microsatellites NOT usually found?
exons
What are microsatellites? How many alleles do they have? How many are in genome?
repetitive DNA sequences

multiple alleles

>100000 dinucleotide repeat loci
Where are SNPs found? How are the located?
exons; introns; and intergenic regions

PCR
Which marker is better for high throughput systems?
SNPs
What was primarily used for the bovine genome sequencing project?
L1 Hereford cow
Where is mtDNA inherited from?
maternal side
introgression
incorporation of desirable alleles from unimproved lines into improved lines.
gene expression
the process with which a gene gives rise to a protein
central dogma
Sequence of nucleotides in gene specifies sequence in RNA; sequence in RNA specifies sequence of amino acids in polypeptide chain
2 ways RNA and DNA differ?
1. OH in ribose of RNA

2. RNA has uracil
4 stages of transcription?
1. recognition
2. initiation
3. enlongation
4. termination
initiation
RNA polymerase denatures DNA double helix; 1st DNA is placed at start site
enlongation
New RNA nucleotides are added to growing chain
termination
RNA polymerase terminates transcription when a loop forms in the transcript
RNA processing (3 steps)
1. splicing
2. capping
3. tail
RNA splicing
excision of the introns and joining of the exons
5' capping
5' end is altered by the addition of guanosine
Why is the 5' cap necessary?
Necessary for ribosome binding to begin protein synthesis
What is the final step of RNA processing?
Addition of poly-A tail at 3' end for mRNA stability
How long is the poly-A tail?
~200 nucleotides
What does the Booroola gene do? (2)
1. Increases ovulation rate by 1.6 ova/copy

2. Increases litter size by 1 lamb/copy
mis-sense mutation
single base substitution in a codon that results in an amino acid substitution
What is the result of a mis-sense mutation?
improper protein function
Non-sense mutation
single base substitution that changes a functional codon into a stop codon
What's the result of a non-sense mutation?
shortened protein
genetic heterogenity
recessive alleles cause one phenotype; dominant alleles cause a different phenotype
Examples of genetic heterogenity
Ehlers-Danlos Syndrome

recessive = enzymatic defect
dominant = defect in collagen gene
What is a single gene disorder?
Disorder caused by mutation w/in one gene
Examples of single gene disorders?
DUMPS; BLADS
What is a polygenic disease?
Disorder caused by collective action of alleles in many genes
Examples of polygenic diseases?
Resistance to mastitis; metritis; Johne's; milk fever
What should you do if you think you have genetic disease in your herd? (4)
1. Report to appropriate agency
2. Necropsy afflicted animal
3. Do herd history
4. Test matings to see if heritable
When do offspring express Callipyge phenotype?
Only heterozygotes inheriting CLPG from sire
imprinting
expression depends on whether allele is inherited from sire or dam
QTL
Quantitative Trait Loci
Polymerases
Proteins that synthesize DNA from individual nucleotides using one of the DNA strands as a template
reference family
group of related but genetically varied animals (usually 3 generations)
Which DNA analysis is best for parentage testing and why?
Microsatellites b/c you don't need as many as you would if you used SNPs; also more cost-effective
Which DNA analysis is best for identity testing and why?
SNPs b/c they are more precise and have fewer mutations
Which DNA analysis is best for species testing and why?
mtDNA because there is more variation between species
Promoter
site of RNA polymerase binding to DNA template
What is enzymatic synthesis of RNA molecule complementary to DNA strand?
mRNA transcription
splicing
excision of introns and joining of the exons
What are represented by looping strands of nucleic acid?
introns
Are microsatellites well conserved between species?
no
What does genetic heterogenity result from?
mutations causing the same phenotype
genetic anticipation
genetic mutations increasing from generation to generation
3 steps in PCR cycle
1. Denaturation
2. Annealing
3. Extension
How can SNPs be detected?
gene sequencing
What makes the PCR reaction specific to certain sequences?
Primers recognize a very specific order of bases as to where to cut the DNA for replication
What is the mechanism for silencing genes?
methylation
Is it possible to alter gene expression w/out changing DNA sequence?
Yes; the environment can change genes (phenocopy)
Possible consequence loss of imprinting?
Bad genes may be expressed (cancer-causing; etc.)
What is the effect of heating DNA?
Double stranded seperates to single strands
Which direction does DNA polymerization occur?
5' to 3'
What is PCR used for?
Duplicating specific DNA segment
Why would trinucleotide repeats be more likely found in coding sequences than dinucleotide repeats?
Trinucleotide repeats create codons and codons code for amino acids. You are more likely to have amino acids repeated in a protein.
What is the advantage in using microsatellites over SNPs for parentage testing?
higher polymorphism
Why is mtDNA used preferentially in forensic analysis?
higher concentration of mtDNA in the cell vs. nuclear DNA
Which parent does Maple Leaf Foods focus on genotyping?
dam
What is not a motivation for Maple Leaf Foods genotyping?
tool for genetic improvement
Name 2 reagents in PCR and explain their function
1. Taq polymerase: Can survive at high temperatures to build complementary DNA strand

2. dNTPs: Building blocks for the polymerase (ATCG)

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