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MCAT biology > chapter 4 > Flashcards

chapter 4 Flashcards

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1
Q

What is Mendelian genetics?

A
  • Gregor Mendel is now honoured as the founder of genetics
  • famous for his pea plant experiment
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2
Q

what are phenotypes?

A
  • the physical manifestation of a genetic trait
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3
Q

what are genotypes?

A
  • describes the combination of genes responsible for that phenotype
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4
Q

the ratio between a genotype and phenotype is?

A
  • not one to one.
    • certain phenotype can correspond to multiple genotypes
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5
Q

what is a gene?

A
  • defined as a sequence of DNA that codes for a given trait
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6
Q

what is an allele?

A
  • refers to variations of that gene
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7
Q

copies of the same chromosome are reffered to as?

A
  • homologues, because they contain the same set of genes, even if they have different alleles
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8
Q

what is a locus?

A
  • each gene occurs at a specific place on a chromosome known as the locus
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9
Q

What is a dominant allele?

A
  • only one copy is necessary for its associated phenotype to be expressed (Capital letters)
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10
Q

what are gain of function mutations?

A
  • the mutated protein can do something the original protein couldn’t
  • tends to be dominant
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11
Q

what are recessive alleles?

A
  • both alleles must be recessive for the phenotype in question to be expressed
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12
Q

what are loss of function mutations?

A
  • the mutated protein can no longer perform the function of the original protein
  • associated with recessive, because the presence of an unmutated allele on the other chromosome allows the cell to compensate
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13
Q

What is a Punnett square?

A
  • a common technique for illustrating genetic crosses where the parental genotypes are aligned along the top row and left-hand side of the square, and the genotypic outcomes are obtained by combining one allele from each parent
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14
Q

what is homozygosity?

A
  • homozygous organisms have 2 copies of the same allele
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15
Q

what is heterozygosity?

A

heterozygous organisms have one copy each of 2 different alleles

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16
Q

what is hemizygous?

A
  • a situation in which only one copy of a given allele is present
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17
Q

when is a test cross performed?

A
  • when we have a phenotypically dominant individual, but want to know its genotype (homozygous dominant or heterozygous)
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18
Q

what is wild type and mutated?

A
  • wild type refers to the default phenotype or genotype that is present in most members of a species, in contrast to a mutation
    • sign means has no mutation (wildtype)
  • no + sign means has the mutation (mutated)
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19
Q

what is complete dominance?

A
  • one copy of the dominant gene is enough to influence the dominant phenotype, and there is no phenotypic difference bewteen homozygous dominant individuals and heterozygotes
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20
Q

what is codominance?

A
  • takes place when 2 dominant alleles can be expressed at the same time
    • ex. ABO blood typing system
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21
Q

what is incomplete dominance?

A
  • occurs when a heterozygote displats a blended phenotype
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22
Q

what is penetrance?

A
  • refers to the likelihood that the carrier of a given genotype (most often associated with a dominant allele) will manifest the corresponding phenotype
    • (do you show it or not)
23
Q

what is expressivity?

A
  • refers to the intensity or extent of variation in the phenotype
    • (how much of an effect does a mutation have on the phenotype)
      • in humans, this can be thought of as the severity of the condition
24
Q

What is a dihybrid cross?

A
  • distribution of 9:3:3:1
25
Q

what is the law of independent assortment?

A
  • The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop. … During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random.
26
Q

what is a linkage?

A
  • Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.
27
Q

what is the recombination frequency?

A
  • describes how often a single crossover will occur between 2 genes during meiosis.
  • if the recombination frequency equals 50%, then the genes in question obey the law of independent assortment
28
Q

what is a centrimorgan?

A
  • the distance associated with a 1% increment in the recombination frequency
29
Q

what are single vs double crossovers?

A
30
Q

what is a pedigree analysis?

A
  • individuals are arranged in rows that correspond to generations, older at top, younger at bottom
  • vertical connections indicate descent by birth, while horizontal indicate mating
  • circles correspond to females and squares correspond to males
  • individuals who manifest a certain phenotype have their respective shape coloured in
31
Q

what are autosomal patterns of inheritance?

A
  • defined by the absence of a gender bias among offspring
  • dominant mutations cannot skip generations while recessive mutations can
32
Q

what is sex-linked inheritance?

A
  • takes place for genes located on the X chromosome
33
Q

x-linked mutations are much more likely to affect?

A
  • male offspring
34
Q

pedigree analysis flow chart?

A
  • ask yourself if males are disproportionally likely to be affected?
    • yes = x-linked inheritance (most likely recessive)
    • no = autosomal inheritance
      • does the phenotype skip generations?
        • yes= autosomal recessive
        • no = autosomal dominant
35
Q

what must an evolutionary system have?

A
  • variations in the population
  • a mechanism for those variations to be reproduced over time
  • environmental constraints that allow favourable variations to be reproduced more than others (differential reproduction)
36
Q

what is natural selection?

A
  • the tendency for certain phenotypes to be favoured in terms of reproduction
    • closely linked to fitness which refers to the chance of reproduction associated witha. certain phenotype compared to baselin and must be defined in terms of specific environmental constraints
37
Q

what is group selection?

A
  • natural selection could act on the level of the group, not the individual
38
Q

what is inclusive fitness?

A
  • accounts not just for the individuals but their relatives, who can share many of the same alleles
39
Q

what is altruistic behaviour?

A
  • group/kin selection
  • from the POV of a gene, it can be advantageous for an individual to engage in altruistic behaviour or even-self sacrifice to ensure the survival of more copies of the gene
40
Q

what is a gene pool?

A
  • the combined set of all genes/alleles in a population
41
Q

what is the concept of Hardy-Weinberg equilibrium?

A
  • used to model stable gene pools
    • organisms must be diploid and reproduce sexually
    • mating is random
    • the population size is very large
    • alleles are randomly distributed by sex
    • no mutations occur
    • there is no migration into or out of the population
42
Q

Hardy weinberg equation?

A
  • p + q = 1
  • p2 + 2pq + q2 = 1
43
Q

what does polygenic mean?

A
  • A polygenic trait is one whose phenotype is influenced by more than one gene. Traits that display a continuous distribution, such as height or skin color, are polygenic.
44
Q

what is stabilizing selection?

A
  • Stabilizing selection is a descriptive term for what happens to an individual trait when the extremes of the trait are selected against. This increases the frequency of the trait in the population, and the alleles and genes which help form it
45
Q

what is directional selection?

A
  • In population genetics, directional selection, or positive selection is a mode of natural selection in which an extreme phenotype is favored over other phenotypes,
46
Q

what is disruptive selection?

A
  • a mode of natural selection in which extreme values for a trait are favored over intermediate values
47
Q

what is genetic drift?

A
  • Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error).
48
Q

what is evolutionary bottleneck?

A
  • A population bottleneck is an event that drastically reduces the size of a population. The bottleneck may be caused by various events, such as an environmental disaster, the hunting of a species to the point of extinction, or habitat destruction that results in the deaths of organisms. The population bottleneck produces a decrease in the gene pool of the population because many alleles, or gene variants, that were present in the original population are lost. Due to the event, the remaining population has a very low level of genetic diversity, which means that the population as a whole has few genetic characteristics.
49
Q

what is speciation?

A
  • descirbes how a new species evolves through evolution
    • a group of organisms that can successfully breed to form fertile offspring
50
Q

what is polymorphism?

A
  • considerable phenotypic variations can exist within a single species
    • ex. ABO blood type in humans
51
Q

what are prezygotic barriers?

A
  • refer to anything that stops reproduction before the formation of a zygote
    • occupyinh different ecological niches, having different patterns of breeding, not engaging in reproductive behaviour with members of other species, incompatible reproductive anatomy, or the inability for fertilization to occur after intercourse
52
Q

what are postzygotic barriers?

A
  • various forms of reproductive isolation that can occur after a zygote is formed
    • zygote cannot develop to term, hybrids that cannot produce offspring, hybrid breakdown (fertility to break down in the second generation), leakage (genes can sometimes travel between species)
53
Q

what is meant by “molecular clock”?

A
  • the average rate at which a species’ genome accumulates mutations, used to measure their evolutionary divergence and in other calculations.
54
Q
A

MCAT biology (12 decks)

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