Ch 12- Genetics and Evolution Flashcards
1
Q
DNA sequences that code for heritable traits that can be passed from one generation to the next”
A
Genes
2
Q
“Each gene may have alternative forms called”
A
Alleles
3
Q
“Each human being possesses two copies of each chromosome, called”
A
homologues
4
Q
“A ________ genotype describes a situation in which only one allele is present for a given gene, as is the case for parts of the X chromosome in males”
A
Hemizygous
5
Q
“When only one dominant and one recessive allele exist for a given gene, there is said to be
A
complete dominance”
6
Q
“When more than one dominant allele exists for a given gene, there is”
A
codominance
7
Q
__________ occurs when a heterozygote expresses a phenotype that is intermediate between the two homozygous genotypes”
A
“incomplete dominance
8
Q
2 purebreds crossed with each other in monohybrid cross F1 genotypic ration is
A
100% Rr
9
Q
“is a population measure defined as the proportion of individuals in the population carrying the allele who actually express the phenotype”
A
Penetrance
“In other words, it is the probability that, given a particular genotype, a person will express the phenotype.”
10
Q
“varying phenotypes despite identical genotypes”
A
Expressivity
11
Q
“If expressivity is _______, then all individuals with a given genotype express the same phenotype”
A
Constant
12
Q
“if expressivity is ______, then individuals with the same genotype may have different phenotypes”
A
Variable
13
Q
2 types of Expressivity
A
Constant and Variable
“If expressivity is constant, then all individuals with a given genotype express the same phenotype. However, if expressivity is variable, then individuals with the same genotype may have different phenotypes”
14
Q
________ is the proportion of the population with a given genotype who actually express the phenotype
and _______ is the different manifestations of the same genotype across the population”
A
Penetrance, Expressivity
15
Q
“There are four basic tenets of the modern interpretation of Mendel’s first law (of segregation)”
A
- Genes exist in alternative forms (alleles).
- An organism has two alleles for each gene, one inherited from each parent.
- The two alleles segregate during meiosis, resulting in gametes that carry only one allele for any inherited trait.
- If two alleles of an organism are different, only one will be fully expressed and the other will be silent. The expressed allele is said to be dominant, the silent allele recessive. ”
16
Q
Mendel first law of segregation can be correlated cellularly with what event
A
Separation of homologous chromosomes during anaphase I of meiosis
“By separating—segregating—these chromosomes into different cells, each gamete carries only one allele for any given trait.”
17
Q
“Mendel’s second law (of independent assortment) states that
A
the inheritance of one gene does not affect the inheritance of another gene. ”
18
Q
“During _______ of meiosis, homologous chromosomes pair up to form tetrads”
A
Prophase I
19
Q
“allows the inheritance of one gene to be independent of the inheritance of all others.”
A
Recombination in prophase I
20
Q
The cellular correlate of mendles second law of independent assortment is
A
Recombination in prophase 1
linked genes is the exception
21
Q
“Segregation and independent assortment allow for greater ________ in the offspring.”
A
Genetic Diversity
22
Q
“In the early to mid-1900s, it was largely believed that _______ was the heritable material.”
A
Protein
23
Q
Frederick Griffith theorized that the live, nonvirulent bacteria must have acquired the ability to form smooth capsules from the dead virulent bacteria. This was known as the
Excerpt From: Kaplan. “Kaplan MCAT Biology Review: Created for MCAT 2015 (Kaplan Test Prep).” iBooks.
A
Transforming Principle
Bacterial Tranformation
24
Q
“Three American scientists—Oswald Avery, Colin MacLeod, and Maclyn McCarty—were attempting to determine the exact material underlying the transformation principle. Concluded substance must be
A
DNA
25
This experiment once again confirmed that DNA was the heritable genetic material.”
Hershey Chase Experiment
26
Which 2 amino acids contain sulfur in their R group and allowed Hershey & chase to radioactively label with sulfur
Cysteine and Methionine
27
“All of the alleles that exist within a species are known as the
gene pool”
“When mutations or genetic leakage occur, new genes are introduced into the gene pool”
28
“a change in DNA sequence”
Mutation
29
“substances that can cause mutations are called mutagens”
Mutagen
30
“Elements known as _______ can insert and remove themselves from the genome”
Transposons
31
2 types of mutations
Nucleotide Level and Chromosomal level mutation
32
“occur when one nucleotide in DNA (A, C, T, or G) is swapped for another. ”
Point mutations
categorized as silent, missense, or nonsense mutations”
Dont change the reading frame!
33
“occur when the change in nucleotide has no effect on the final protein synthesized from the gene. This most commonly occurs when the changed nucleotide is transcribed to be the third nucleotide in a codon because there is degeneracy (wobble) in the genetic code.”
Silent mutation
Is a POINT mutation (one nucleotide is swapped for another)
34
“occur when the change in nucleotide results in substituting one amino acid for another in the final protein.”
Missense Mutation
Is a POINT mutation (one nucleotide is swapped for another)
35
“occur when the change in nucleotide results in substituting a stop codon for an amino acid in the final protein.”
Nonsense mutation
Is a POINT mutation (one nucleotide is swapped for another)
36
Difference between point mutation and frameshift mutation
Point mutation nucleotides are swapped. Frameshift mutations nucleotides are inserted or deleted
37
2 types of frameshift mutation
Insertion or deletion
38
2 things that can happen with a frameshift mutation
“changes in the amino acid sequence or premature truncation of the protein (due to the generation of a nonsense mutation)”
39
“larger-scale mutations in which large segments of DNA are affected”
Chromosomal Mutations
40
5 common chromosomal mutations
Deletion, Duplication, Inversion, Insertion, and translocation
41
“occur when a large segment of DNA is lost from a chromosome. Small deletion mutations are considered frameshift mutations”
Deletion Mutation
42
“occur when a segment of DNA is copied multiple times in the genome.”
Duplication mutations
43
“Inversion mutations occur when a segment of DNA is reversed within the chromosome.”
Inversion Mutation
44
“occur when a segment of DNA is moved from one chromosome to another. Small ______ mutations (including those where the inserted DNA is not from another chromosome) are considered frameshift mutations, as described previously.”
Insertion Mutations
45
“occur when a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome.”
Translocation Mutation
46
“One important class of deleterious mutations is known as _____. “These are defects in genes required for metabolism. ”
inborn errors of metabolism”
47
________ is a flow of genes between species”
Genetic Leakage
“In some cases, individuals from different (but closely related) species can mate to produce hybrid offspring”
48
________ refers to changes in the composition of the gene pool due to chance.”
Genetic Drift
Tends to be more profound in SMALL populations
49
“a more extreme case of genetic drift in which a small population of a species finds itself in reproductive isolation from other populations
Founder Effect
50
“drastically and suddenly reduce the size of the population available for breeding”
Bottlenecks
“Because the breeding group is small, inbreeding, or mating between two genetically related individuals, may occur in later generations”
51
“ Inbreeding encourages _______, which increases the prevalence of both homozygous dominant and recessive genotypes. ”
Homozygosity
52
“Ultimately _____ and ________ and _______, cause a reduction in genetic diversity, which is often the reason why a small population may have increased prevalence of certain traits and diseases.”
genetic drift, the founder effect, and inbreeding
53
“This loss of genetic variation may cause reduced fitness of the population, a condition known as
inbreeding depression”
“On the opposite end of the spectrum, outbreeding or outcrossing, is the introduction of unrelated individuals into a breeding group.”
54
is the introduction of unrelated individuals into a breeding group.”
outbreeding or outcrossing
55
“A cross in which only one trait is being studied is said to be”
Monozygous
56
In the genetics the offspring are the
Filial or F Generation
57
“crossing two heterozygotes in a case of complete dominance will result in a _______ distribution of genotypes (homozygous dominant:heterozygous dominant:homozygous recessive) and a ______ distribution of phenotypes (dominant:recessive)”
1:2:1, 3:1
58
In a test cross the unknown is crossed with an organism known to be _____ ______. If all of the offspring (100 percent) are of the dominant phenotype, then the unknown genotype is likely to be _______ ________
homozygous recessive
| Homozygous Dominant
59
“Because a test cross is used to determine the genotype of the parent based on the phenotypes of its offspring, test crosses are sometimes called
Back Crosses
60
“We can extend a Punnett square to account for the inheritance of two different genes using a
Dihybrid Cross
61
“If we cross two plants that are heterozygous for both traits, then the offspring have a phenotypic ratio of
9:3:3:1
“Note that the 3:1 phenotypic ratio still holds for each trait (12 tall:4 dwarf and 12 purple:4 white), reflecting Mendel’s second law.”
62
“Males, on the other hand, have only one X chromosome (and one Y chromosome) and are _______ for many genes carried on the X chromosome.”
Hemizygous
63
“On the MCAT, sex-linked is _____
X-Linked
64
“It follows that men with a sex-linked trait will have daughters who are all either _______ or who _____ (if his partner also has an affected allele), and that a man can _____ pass down a sex-linked trait to his son.”
Carriers, are affected
NEVER
65
“crossing over during ______ of meiosis causes alleles to be swapped between homologous chromosomes, supporting Mendel’s ______ ”
Prophase 1, Second Law
66
“genes that are located very close together on a chromosome are ____ ____ to be separated from each other during crossing over”
Less Likely
67
“The likelihood that two alleles are separated from each other during crossing over, called the
recombination frequency”
“is roughly proportional to the distance between the genes on the chromosome”
68
“tightly linked genes have recombination frequencies close to ____ percent; weakly linked genes have recombination frequencies approaching ____ percent, as expected from independent assortment”
0, 50
69
“By analyzing recombination frequencies, a ______ that represents the relative distance between genes on a chromosome can be constructed.”
Genetic Map
70
if two genes were 25 map units apart, we would expect ______ of the total gametes examined to show recombination somewhere between these two genes”
25%
71
“How often an allele appears in a population is known as
its allele frequency”
72
When evolution is ostensibly not occurring, Five criteria must be met for this to be possible:”
1. The population is very large (no genetic drift).
2. There are no mutations that affect the gene pool.
3. Mating between individuals in the population is random (no sexual selection).
4. There is no migration of individuals into or out of the population.
5. The genes in the population are all equally successful at reproducing (No natural Selection)
“Provided that all of these conditions are met, the population is said to be in Hardy–Weinberg equilibrium”
73
“Hardy–Weinberg equations allow you to find two pieces of information: _____ and _____
1. relative frequency of alleles in a population
| 2. the frequency of a given genotype or phenotype in the population.”
74
“Assuming that the HW conditions listed earlier are met, the allele frequencies will remain ____
constant from generation to generation.”
75
“ sometimes phrased as survival of the fittest, is the theory that certain characteristics or traits possessed by individuals within a species may help those individuals to have greater reproductive success, thus passing on those traits to offspring”
Natural Selection
76
“Individuals with a greater preponderance of these favorable variations are more likely to survive to reproductive age and produce offspring; the overall result will be in an increase in these traits in future generations. This level of reproductive success is termed ”
Fitness
“an organism’s fitness is directly related to the relative genetic contribution of this individual to the next generation.”
“Evolution is not equivalent to natural selection. The MCAT likes to test your ability to understand that natural selection is simply a mechanism for evolution. Natural selection is, however, equivalent to survival of the fittest.”
77
“The ________, sometimes called neo-Darwinism, adds knowledge of genetic inheritance and changes in the gene pool to Darwin’s original theory.”
modern synthesis model
78
_______ is a measure of an organism’s success in the population. This is based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others”
“Inclusive fitness
“promotes the idea that altruistic behavior can improve the fitness and success of a species as a whole.”
79
“In contrast to Darwin’s theory, _________ suggests that changes in some species occur in rapid bursts rather than evenly over time.”
punctuated equilibrium
80
What are the 3 modes of natural selection
Stabilizing Direction, Directional Selection, or Disruptive Selection
81
Mode of natural selection that keeps phenotypes within a specific range by selecting against extremes.”
Stabilizing Selection
82
“Adaptive pressure can lead to the emergence and dominance of an initially extreme phenotype through
directional selection”
83
“In ________, two extreme phenotypes are selected over the norm”
disruptive selection
84
________ is a related concept that describes the rapid rise of a number of different species from a common ancestor. ”
“Adaptive radiation
“The benefit of adaptive radiation is that it allows the various species to occupy different niches ”
85
“A species is defined as
the largest group of organisms capable of breeding to form fertile offspring”
86
“the formation of a new species through evolution is called
Speciation
87
“If we took two populations from the same species and separated them geographically for a long period of time, different evolutionary pressures would lead to different adaptive selections. If enough time passed, the changes would be sufficient to lead to _____, in which the progeny of these populations could no longer freely interbreed”
Isolation
88
“Reproductive isolation may occur either prezygotically or postzygotically. ________ prevent formation of the zygote completely; ________ allow for gamete fusion but yield either nonviable or sterile offspring”
Pre-zygotic Mechanisms, Post-zygotic Mechanisms
89
“Examples of prezygotic mechanisms include
temporal isolation (breeding at different times), ecological isolation (living in different niches within the same territory), behavioral isolation (a lack of attraction between members of the two species due to differences in pheromones, courtship displays, and so on), reproductive isolation (incompatibility of reproductive anatomy), or gametic isolation (intercourse can occur, but fertilization cannot).”
90
“Postzygotic mechanisms include
include hybrid inviability (formation of a zygote that cannot develop to term), hybrid sterility
91
“three patterns of evolution emerge:
divergent evolution, parallel evolution, and convergent evolution”
92
______ ______refers to the independent development of dissimilar characteristics in two or more lineages sharing a common ancestor.
“Divergent evolution
For example, seals and cats are both mammals in the order Carnivora, yet they differ markedly in general appearance. These two species live in very different environments and adapted to different selection pressures while evolving.”
93
“refers to the process whereby related species evolve in similar ways for a long period of time in response to analogous environmental selection pressures.”
Parallel Evolution
94
_______ refers to the independent development of similar characteristics in two or more lineages not sharing a recent common ancestor.
Convergent Evolution
For example, fish and dolphins have come to resemble one another physically, although they belong to different classes of vertebrates. They evolved certain similar features in adapting to the conditions of aquatic life.”
95
“ states that the inheritance of one allele does not influence the probability of inheriting a given allele for a different trait.
Mendels second law of independent assortment
96
“states that an organism has two alleles for each gene, which segregate during meiosis, resulting in gametes carrying only one allele for a trait.”
Mendels firs law of segregation
97
“The _____ experiment demonstrated the transforming principle, converting non-virulent bacteria into virulent bacteria by exposure to heat-killed virulent bacteria.”
Griffith
98
“The experiment demonstrated that DNA is the genetic material because degradation of DNA led to a cessation of bacterial transformation.”
Avery–MacLeod–McCarty
99
“The ______ experiment confirmed that DNA is the genetic material because only radiolabeled DNA could be found in bacteriophage-infected bacteria.”
Hershey–Chase
100
____ _____ is a flow of genes between species through hybrid offspring.”
Genetic Leakage
101
“The _______ accounts for mutation and recombination as mechanisms of variation and considers differential reproduction to be the mechanism of reproductive success.”
modern synthesis model (neo-Darwinism)
102
“the degree of difference in the genome between two species is related to the amount of time since the two species broke off from a common ancestor.”
molecular clock model
