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BIOL*1090 Lectures 18-21
Mendelian Inheritance, Predicting, Pedigrees, Mutations, Variation
47
Biology
Undergraduate 1
04/11/2013

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Term
True or False
Mendel used plants with a lot of genetic variation
Definition
False
He used highly inbred plants to obtain homozygous indiviuals, allowing him to study one trait at a time
e.g. Tall x Tall = only tall offspring
Term
Define homozygous
Definition
Both alleles are identical
Term
Define heterozygous
Definition
The two alleles are different
Term
What is the P generation
Definition
Parent Generation
Term
What is the first filial generation?
Definition
F1
First offspring
Term
What is Mendel's Heritable Factor commonly known as?
Definition
A gene
Term
What are the two forms of a gene?
Definition
Dominant allele & recessive allele
Term
What is the Mendel's Principle of Dominance?
Definition
In a heterozygote, one allele may conceal the presence of another
Term
What is Mendel's Principle of Segregation?
Definition
In a heterozygote, neither allele is changed by coexisting with the other
Term
What is Mendel's Principle of Independent Assortment?
Definition
The alleles of different genes will segregate independently of one another
Term
True or false
The closer genes are to one another on a chromosome, the more likely they are to cross over/recombine
Definition
False
The farther apart genes are from one another, the more susceptible they are to crossing over / recombination
Term
What are the 3 methods of predicting the outcome of a cross?
Definition
Punnett Square
Forked Line
Probability Method
Term
What is the 'p' arm on a chromosome?
Definition
The short arm
Term
What is the 'q' arm on a chromosome?
Definition
The long arm
Term
Where is the centromere found, relative to the p & q arms of a chromosome?
Definition
Between the p (short) and q (long) arms
Term
What is the general rule of thumb for the number of possible haploid genotypes produced?
Definition
For 'n' different genes assorting independtly, 2^n haploid genotypes are possible
Term
How many DIPLOID genotypes are possible by combining 4 different gametes from each of two parents?
Definition
4x4 = 16 possible DIPLOID genotypes
Term
How many HAPLOID genotypes are possible by combining 3 different genes assorting independently?
Definition
2^3 = 8 possible HAPLOID genotypes
Term
What is the multiplicative rule of probability?
Definition
If events A & B are independently & overlap, the probability that they occur together is the product of their individual probabilities of occurance

e.g. Probability of A x Probability of B
Term
What is the additive rule of probability?
Definition
If events A & B occur independently and do not overlap, the probability that at least one of them will occur is the sum of their individual probabilities of occurance

e.g. Probability of A + Probability of B
Term
Crossing two parents with an Aa genotype, what is the frequency that a recessive phenotype will occur?
Definition
25% of the time
1 AA offspring (dominant phenotype)
2 Aa offspring (dominant phenotype)
1 aa offspring (recessive phenotype)

1+2+1 = 4. 1 out of 4 is 25%
Term
Define a test cross
Definition
Crossing an individual of an unknown genotype to an individual with a homozygous recessive genotype
Term
If two Bb parents are crossed, and 4 offspring are produced, what is the likelihood that 1 offspring is bb?
Definition
n! / (X! x Y!) x [p^x][q^y]

4!/3!x1! x [3/4]^3 [1/4]^1 = 0.42
Term
What are tautomers?
Definition
The 2 forms of a nitrogenous base, the isoform is rare
Term
What will happen if an isoform is incorporated into a strand of DNA?
Definition
The DNA sequence will be altered
Term
What are the common forms of nitrogenous bases?
Definition
Keto & Amino
Term
What are the rare forms of nitrogenous bases?
Definition
Enol & Imino
Term
True or false
If a mutation occurs during mitotic division of a spermatogonia/oognia, the mutation will NOT be inherited
Definition
False
The mutation can be passed on to the offspring
Term
Where are mutations likely to occur?
Definition
Repeating sequences, symmetrical sequences, palindromes
Term
What kind of repetition is this:
AGAGAGAGAGAG
Definition
Simple dinucleotide repetition
Term
True or false
Some chemical agents (e.g. acryline dyes) are mutagenic only to replicating DNA
Definition
True
Term
True or false
Alkylating agents are mutageni only to replicating DNA
Definition
False
Alkylating agents are mutagenic to both replicating AND non-replicating DNA
Term
If a pyrimidine (e.g. cytosine) absorbs UV radiation, what is likely to occur?
Definition
Mutation in the form if dimerization
Term
Define missense mutation
Definition
changes the sequence so the codon codes for a different amino acid
Term
Define nonsense mutation
Definition
changes the sequence resulting in a stop codon (TAG, TGA, TAA) = stops translation
Term
Define a silent mutation
Definition
Mutation that doesn't actually affect the end product
Term
Why is it possible for a mutation to be silent?
Definition
Because some amino acids are coded for by a variety of codons
Term
What effect to acridines have on the double helix?
Definition
distort the double helix, resulting in deletion/addition of base pairs during replication
Term
What is transposition?
Definition
Portion of DNA is moved to another position on the chromosome
Term
What is translocation?
Definition
A portion of DNA is moved to another chromosome
Term
What is expansion?
Definition
A codon sequence is repeated, the frequency of the mutation increases with each generation
Term
What is a frameshift mutation
Definition
Addition/deletion of a base in a DNA sequence changes the way the strand is read by the reading frame

e.g. 'do not go near the door'
becomes
'don otg nea rth edo or'
Term
If a mutation occurs in the coding region, how is the protein affected?
Definition
Changed to a non-functional form
Folding is prevented, will be targeted for degradation
Term
What is the effect of a mutation in a non-coding region?
Definition
prevent/reduce transcription & translation
mRNA is unstable, ribosomes cannot bind to it
start codon may be mutated
Term
What is the result of nucleotide expansion in non-coding regions?
Definition
The mRNA may be too big for export to the cytoplasm
Term
What disease describes the expansion in the untranslated region of an mRNA?
Definition
Myotonic dystrophy type 1
Term
What is myotonic dystrophy type 2?
Definition
Expansion in an intron
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