Principles of Biology 2 Midterm 1
QUIZLETS:
https://quizlet.com/Nikol244/folders/pob-2-midterm-1?x=1xqt&i=aj20u
Practice Exam (sorry I dont have the answer key):
Copy of POB II Exam 1: Practice Exam (2020)
Week 1
Quizlet: https://quizlet.com/_b65dbz?x=1qqt&i=aj20u
Principles of Mendelian Genetics
● Probability- the likelihood that an event will occur
○ Probability(event) = Pr(event) = p(event)
○ Range from 0 to 1
○ sum of probabilities over all possible outcomes is 1
● An experiment is something that has multiple possible outcomes
● Interpretations of probabilities
○ Frequency interpretation- the probability of event A is the frequency of event A in
the limit as the number of experiments goes to infinity
○ Subjective interpretation- “my degree of belief that an experiment will yield event
A”
● Probability rules
○ Independent events: Pr(A and B) = Pr(A) x Pr(B)
■ Ex: probability both tosses are heads
○ Complementary events: Pr(not A) = 1 - Pr(A)
■ Ex: probability there is at least one tail after two tosses
○ Mutually exclusive events: Pr(A or B) = Pr(A) + Pr(B)
■ Ex: probability there is one head after two tosses
○ Conditional probability: Pr(A given B) = Pr(A and B) / Pr(B)
■ Ex: probability of two heads given there is at least one head
● Lamarck’s model of inheritance: acquired characteristics:If an organism changes during
its lifetime, these changes are passed down to its offspring (giraffes developed long
necks because of stretching), proven wrong
● Weismann’s Germ-Soma distinction: only traits that were present at conception can be
passed down to offspring
○ Weismann’s friend tried to convince Weismann of inheritance of acquired traits:
he had a scar from a dueling sword and his daughter was born with a scar in the
same place
■ Weismann’s cat experiment: cut tail off of mother cat → kitten born with
no tail
● Weismann’s explanation: father cat had mutation that caused it to
be tailless and mutation was passed down to offspring
■ Weismann’s mice experiment: cut tails off of mice, breed mice, cut tails
off, etc.
, ● Each offspring was born with a tail, no difference in tail length
● Gregor Mendel
○ Used quantitative data and mathematical model to infer the existence of genes
○ Established the field of genetics
○ Performed experimental crosses with pea plants
■
■ Removed stamens from one flower, transferred pollen from stamen to
carpel of another flower, waited for carpel to mature into pod, plant seeds
from pod
● True-breeding- organisms that produce offspring of the same variety over many
generations of self-pollination (homozygous)
● Mendel cross-pollinated two contrasting, true-breeding pea varieties (purple and white
flower; round and wrinkled pea)
● Used inbred lines- homozygous at every locus for P generation; individuals of inbred
lines breed true because they always produce progeny that look like their parents
●
○ P generation- true-breeding homozygous parental generation
○ F1 generation- first filial, hybrid (heterozygous) offspring of parental generation
○ F2 generation- second filial offspring of F1 generation
● Results of F2 generation showed 3:1 ratio
● Proved there was a dominant trait and a recessive trait
, ● Homozygous- having two identical alleles for a gene (RR or rr)
○ Homozygote- organism that is homozygous for a specific trait
● Heterozygous- having two different alleles for a given gene (Rr)
○ Heterozygote- organism that is heterozygous for a specific trait
● Mendel’s Law of Segregation- the two alleles in a pair segregate into different gametes
during gamete formation
● Gamete- haploid reproductive cell (ex: egg and sperm) that is formed in meiosis
● fertilization/syngamy- fusion of two gametes
● Gene- unit of hereditary information consisting of a specific nucleotide sequence
● Locus- specific position on a chromosome; place in genome where there are at least two
alternative versions of a gene (plural:loci)
● Allele- different version of a gene
○ Dominant allele- allele that is fully expressed in the phenotype of a heterozygote
○ Recessive allele- allele that does not affect the phenotype of a heterozygote
● Genotype- organism’s genetic makeup, genetic description of a locus
● Phenotype- organism’s appearance or observable traits
● Mendelian genetics
○ Each individual carries two copies of each gene
○ Each sperm or egg gets one of those via coin toss
○ Union of sperm and egg makes a new individual with two copies of each gene
○ The traits shown by each individual depend on the pair of gene copies they
inherit
● Punnett square- diagram that represents the probabilities of each kind of genotype that
can occur from a cross
○
Mechanisms of Mendelian Genetics
● The relationship between genotype and phenotype depends on biochemistry,
development, and physiology
○ Ex: wrinkly pea is caused by mutation in gene encoding starch-branching
enzyme, enzyme is responsible for water retention, loss of water causes pea to
be wrinkly
● Dominance is most typical when one allele is a dead version of the gene (non-linear
relationship between genotype and phenotype)
, ●
●
● Ordinary genetic variation is usually additive
● Mendel’s model, represented by the Punnett Square, accurately describes how alleles
are transmitted
● Complete dominance of the sort he observed is an unusual, special case mostly relevant
to experimental genetics and rare diseases
● Additivity- heterozygote has a phenotype that exactly intermediate between the
phenotype of the two homozygotes
○ the usual situation of ordinary genetic variation in populations
○ Linear relationship between genotype and phenotype
●
● Partial dominance- heterozygote represents one homozygote more than the other
QUIZLETS:
https://quizlet.com/Nikol244/folders/pob-2-midterm-1?x=1xqt&i=aj20u
Practice Exam (sorry I dont have the answer key):
Copy of POB II Exam 1: Practice Exam (2020)
Week 1
Quizlet: https://quizlet.com/_b65dbz?x=1qqt&i=aj20u
Principles of Mendelian Genetics
● Probability- the likelihood that an event will occur
○ Probability(event) = Pr(event) = p(event)
○ Range from 0 to 1
○ sum of probabilities over all possible outcomes is 1
● An experiment is something that has multiple possible outcomes
● Interpretations of probabilities
○ Frequency interpretation- the probability of event A is the frequency of event A in
the limit as the number of experiments goes to infinity
○ Subjective interpretation- “my degree of belief that an experiment will yield event
A”
● Probability rules
○ Independent events: Pr(A and B) = Pr(A) x Pr(B)
■ Ex: probability both tosses are heads
○ Complementary events: Pr(not A) = 1 - Pr(A)
■ Ex: probability there is at least one tail after two tosses
○ Mutually exclusive events: Pr(A or B) = Pr(A) + Pr(B)
■ Ex: probability there is one head after two tosses
○ Conditional probability: Pr(A given B) = Pr(A and B) / Pr(B)
■ Ex: probability of two heads given there is at least one head
● Lamarck’s model of inheritance: acquired characteristics:If an organism changes during
its lifetime, these changes are passed down to its offspring (giraffes developed long
necks because of stretching), proven wrong
● Weismann’s Germ-Soma distinction: only traits that were present at conception can be
passed down to offspring
○ Weismann’s friend tried to convince Weismann of inheritance of acquired traits:
he had a scar from a dueling sword and his daughter was born with a scar in the
same place
■ Weismann’s cat experiment: cut tail off of mother cat → kitten born with
no tail
● Weismann’s explanation: father cat had mutation that caused it to
be tailless and mutation was passed down to offspring
■ Weismann’s mice experiment: cut tails off of mice, breed mice, cut tails
off, etc.
, ● Each offspring was born with a tail, no difference in tail length
● Gregor Mendel
○ Used quantitative data and mathematical model to infer the existence of genes
○ Established the field of genetics
○ Performed experimental crosses with pea plants
■
■ Removed stamens from one flower, transferred pollen from stamen to
carpel of another flower, waited for carpel to mature into pod, plant seeds
from pod
● True-breeding- organisms that produce offspring of the same variety over many
generations of self-pollination (homozygous)
● Mendel cross-pollinated two contrasting, true-breeding pea varieties (purple and white
flower; round and wrinkled pea)
● Used inbred lines- homozygous at every locus for P generation; individuals of inbred
lines breed true because they always produce progeny that look like their parents
●
○ P generation- true-breeding homozygous parental generation
○ F1 generation- first filial, hybrid (heterozygous) offspring of parental generation
○ F2 generation- second filial offspring of F1 generation
● Results of F2 generation showed 3:1 ratio
● Proved there was a dominant trait and a recessive trait
, ● Homozygous- having two identical alleles for a gene (RR or rr)
○ Homozygote- organism that is homozygous for a specific trait
● Heterozygous- having two different alleles for a given gene (Rr)
○ Heterozygote- organism that is heterozygous for a specific trait
● Mendel’s Law of Segregation- the two alleles in a pair segregate into different gametes
during gamete formation
● Gamete- haploid reproductive cell (ex: egg and sperm) that is formed in meiosis
● fertilization/syngamy- fusion of two gametes
● Gene- unit of hereditary information consisting of a specific nucleotide sequence
● Locus- specific position on a chromosome; place in genome where there are at least two
alternative versions of a gene (plural:loci)
● Allele- different version of a gene
○ Dominant allele- allele that is fully expressed in the phenotype of a heterozygote
○ Recessive allele- allele that does not affect the phenotype of a heterozygote
● Genotype- organism’s genetic makeup, genetic description of a locus
● Phenotype- organism’s appearance or observable traits
● Mendelian genetics
○ Each individual carries two copies of each gene
○ Each sperm or egg gets one of those via coin toss
○ Union of sperm and egg makes a new individual with two copies of each gene
○ The traits shown by each individual depend on the pair of gene copies they
inherit
● Punnett square- diagram that represents the probabilities of each kind of genotype that
can occur from a cross
○
Mechanisms of Mendelian Genetics
● The relationship between genotype and phenotype depends on biochemistry,
development, and physiology
○ Ex: wrinkly pea is caused by mutation in gene encoding starch-branching
enzyme, enzyme is responsible for water retention, loss of water causes pea to
be wrinkly
● Dominance is most typical when one allele is a dead version of the gene (non-linear
relationship between genotype and phenotype)
, ●
●
● Ordinary genetic variation is usually additive
● Mendel’s model, represented by the Punnett Square, accurately describes how alleles
are transmitted
● Complete dominance of the sort he observed is an unusual, special case mostly relevant
to experimental genetics and rare diseases
● Additivity- heterozygote has a phenotype that exactly intermediate between the
phenotype of the two homozygotes
○ the usual situation of ordinary genetic variation in populations
○ Linear relationship between genotype and phenotype
●
● Partial dominance- heterozygote represents one homozygote more than the other
