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Genetics & Evolution Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Evolution

A

Eventual changes in the gene pool that bring about phenotypic changes

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2
Q

Genes

A

DNA molecules in a locus of a chromosome carrying inheritable physical and biochemical traits of living organisms and passing them down generations

Have alternative forms that are expressed in variable alleles

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3
Q

Alleles

A

Alternative forms of a gene that are either

  1. dominant
  2. recessive
  3. homozygous
  4. heterozygous
  5. hemizygous
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4
Q

Genotype

A

Genetic combination possessed by a person

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5
Q

Phenotype

A

The physical expression of genotypes

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6
Q

Hemizygous

A

Gene property when only one allele is present

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7
Q

Gene Dominance Patterns

A
  1. Complete Dominance (Full phenotypic expression of one dominant allele entirely masking the expression of the recessive allele for a give gene)
  2. CoDominance (Equal phenotypic expression of two dominant alleles of a given gene)
  3. Incomplete Dominance (Intermediate phenotypic expression of two homozygous genes)
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8
Q

Gene Expression Variables

A
  1. Penetrance

2. Expressivity

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9
Q

Penetrance

A

A population parameter stating the percentage of individuals in a population that express the phenotype for the genotype that they carry

Categorized into:

  1. Full penetrance
  2. High penetrance
  3. Reduced/ low penetrance
  4. Nonpenetrant
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10
Q

Expressivity

A

Gene expression variable explored at individual level to discover the phenotype variability of a given genotype.

May be:

  1. Constant
  2. Variable
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11
Q

Mendelian Laws

A
  1. Law of Segregation - [alleles of a gene separate during meiosis and allow each gamete to carry only one allele]
  2. Law of Independent Assortment [despite recombination of genes, the inheritance of one gene is independent of that of other genes]

*Both of these laws increase the diversity of an offspring and its survival ability by making it capable of adopting to environmental changes

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12
Q

Recombination

A

Swapping of genes b/w chromatids of homologous chromosomes

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13
Q

Tennets of Mendelian Law of Segregation

A
  1. Genes exist in alternative allele forms
  2. Each gene has two alleles, one inherited from each parent
  3. The two alleles of a given gene are segregated during meiosis, allowing each gamete to carry to incorporate only one allele during fertilization
  4. The allele with the greater dominance is expressed
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14
Q

3 Strategies for Increasing Bacterial Genetic Variability

A
  1. Transformation
  2. Transduction
  3. Conjugation
  • REVIEW Chap.1 BIO
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15
Q

Experiments Performed to Confirm DNA as Inheritable Material of Genes as Opposed to Protein

A
  1. 1920s-Groups of mice were injected with virulent and nonvirulent bacteria-transformation of the nonvirulent bacteria led to mice’s death- however when nonvirulent bacteria were treated with DNA-degrading enzymes, transformation failed to occur and mice remained alive
  2. 1952-Protein and DNA radio-labeled bacteriophages were created and permitted to infect a sample of non-labeled bacteria. Upon analysis, DNA (and not protein) was confirmed to have entered the bacteria to cause disease. [Virus’s need for entry inside a cell to cause disease was known]
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16
Q

The Difference B/W Meiosis & Mitosis

A

Meiosis produces haploid gametes through two division cycles whereas mitosis divides diploid somatic cells into diploid daughter cells

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17
Q

Steps of Meiosis

A
  1. Meiosis I
    1. Interphase-[1. cell grows, 2. genetic material
      replicates/duplicates]
    2. Prophase-[1. nuclear membrane dissolves, 2.
      chromosomes condense, 3. centrosomes
      travel to opposite sides of the cell]
      [cross-over/recombination occurs
      between homologous chromosomes      ]
    3. Metaphase-[1. Chromosomes line along the
      metaphase plate, 2. microtubules push
      centrosomes to the sides of the cell
      while pulling chromosomes toward
      centrosomes]
    4. Anaphase-[homologous chromosomes completely
      separate]
      5.Telephase-[1.chromosomes unravel, 2. nuclear
      membrane redevelops, 3. cytokinesis
      occurs, 4. 2 haploid cells result]
  2. Meiosis II
    1. Prophase II: [1. chromosomes condense, 2. nuclear
      envelope dissolves, 3. centrosomes spread to
      opposite sides of the cell]
    2. Metaphase II: [chromosomes line along the plate]
    3. Anaphase II: [Microtubules pull sister chromatids
      toward centrosomes]
    4. Telephase II: [4 games result after cytokinesis,
      redevelopment of the nuclear
      envelop, and unraveling of the
      chromosomes]
18
Q

Genetic Pool

A

All of the existent alleles in a species

19
Q

Factors that Induce Genetic Variability

A
  1. Mutation (production of change in DNA sequence)
  2. Genetic leakage
  3. Genetic Drift
20
Q

Advantage of Genetic Variability

A

Promotes survival of species by allowing them to adapt to environmental changes in addition to conferring selective advantages such as delivery of viable, genetically diverse offsprings

21
Q

Means for Mutation Inducement

A
  1. Chemical Exposure
  2. Radiation
  3. Errors made by DNA polymerase in replication of DNA
  4. Presence of mutagens
  5. Presence of transposons
22
Q

Mutagens

A

Mutation inducing substances

23
Q

Transposons

A

Nucleic Acids that insert or remove themselves from gene-coding sequences

24
Q

Types of Mutations

A

A. Nucleotide-Level Mutations
I. Point Mutations [one nucleotide replaces another]
1. Silent - [No change in final protein]
2. Missense- [Replacement of 1 Amino Acid in the
protein synthesized]
3. Nonsense [Premature stop codon is introduced
into the protein synthesized]
II. Frame-Shift Mutations [one nucleotide is inserted or
removed/impacting the
reading frame/codon of DNA
sequence]
1. Insertion
2. Deletion
B. Chromosomal-Level Mutations -[Involves large DNA
segments]
1. Insertion - [involves insertion of segment from
another DNA molecule]
2. Deletion
3. Inversion- [Involves reversing DNA sequence in a
segment]
4. Translocation - [involves swapping DNA b/w 2
molecules]
5. Duplication

25
Q

Range of Effects of Mutations

A

Changes in DNA genetic sequence that may bring about either of the following:

  1. Positive Selection Advantages - [sickle cell trait
    prevents malaria due
    to short life span of
    sickle cells]
  2. Deleterious - [phenylketonuria gives rise to inborn
    error metabolites that can cause
    cognitive impairments and learning
    disabilities]
26
Q

Phenylketonuria (PKU)

A

A metabolism problem where phenylalanine hydrolase is not present to digest phenylalanine, resulting in toxic metabolite build-up that can cause neurological impairments if not recognized at birth to set limitations on diet.

27
Q

Genetic Leakage

A

Flow of genes from one species to another through mating between members of the hybrids to produce hybrids

  • Most hybrids cannot reproduce due to odd number of chromosomes (Ex: mule) but some can (like beefalo) and promote genetic flow
28
Q

Genetic Drift

A

Gene pool changes in small populations due to

  1. chance
  2. bottleneck effect - factors that drastically reduce the
    size of a population (decrease
    genetic diversity/promote disease)
  3. founder effect - isolation of a small population due to
    physical barriers and natural
    catastrophies (decrease
    genetic diversity/promote disease)
  4. inbreeding - mating of genetically related individuals
    due to bottlenecks and founder effects
    (lead to inbreeding depression due to
    loss of genetic variability and fitness)
    & 5. out-breeding or out-crossing (increases genetic
    diversity by introducing unrelated
    individuals into a breeding group)
29
Q

Biometric Techniques

A

Statistical analysis strategies in biology such as

  1. punnett square [predict phenotypic and genotypic traits of an offspring resulting from breeding of two individuals]
  2. Genetic Mapping
  3. Hardy-Weinberg Equilibrium
30
Q

Punnet-Square Notations

A
  1. Parental or P-generation
  2. Filial or F-generation (F1 & F2)

genetic diversity increases in F2 generation*

31
Q

Types of Punnet-Square Crosses

A
  1. Monohybrid cross [studies one type of trait]
  2. Test cross/back cross [uses offspring phenotype to
    predict parent genotype; crosses one known with
    one unknown genotype]
  3. Dihybrid cross [studies two traits in a 4x4 Punnet-Sq]
  4. Sex-linked cross- [uses X & Y symbols to indicate X &
    Y chromosomes-***males hemizygous for a
    disease-promoting gene are often carriers even if the
    genetic allele they carry is recessive]
32
Q

Genetic Mapping

A

Determining the linear order of genes on a chromosome using recombination frequencies

33
Q

Recombination Frequency

A

The probability of two genes separating during prophase I of meiosis given their distance from each other

Takes 2nd Mendelian Law of Independent Assortment into consideration

34
Q

Allele Frequency

A

The likelihood of finding a given allele in a gene pool

***Changes in the allele/gene frequency as a result of inbreeding, outbreeding, migration, bottleneck effect, founder effect, etc. give rise to evolution and better organism fitness.

35
Q

Hardy-Weinberg Equilibrium

A

An equilibrium in which evolution does not occur because the change in gene frequency is 0 due to

  1. lack of migration
  2. large size of population (no genetic drift)
  3. random mating
  4. absence of mutations
  5. reproductive success of all gene types

MMMRS
(Mutation-Migration-Mating-Reproductive Success-Size of Population)

36
Q

Hardy-Weinberg Equilibrium Equations

A

p+q=1 [provides allele frequency]
p^2+2pq+q^2=1 [provides phenotype/genotype
frequency]

  • p: defined as allele frequency of the dominant alle
  • *q: defined as alle frequency of the recessive alle
37
Q

Theories Explaining Evolution

A
  1. Natural Selection [proposed by Charles Darwin 1859
    states that possession of certain traits makes some
    individuals more fit to survive and to reproduce
    offsprings]
  2. Neo-Darwinism [proposed by post-Darwinists, states
    that changes in gene frequency induced by
    mutations, depending on their deleterious or
    favorable nature and depending on their ability to
    increase the fitness and reproductive ability of a
    population, give rise to evolution, either increasing or
    decreasing the frequency of the mutated gene in the
    gene pool. [This is known as differential
    reproduction    *]
  3. Inclusive Fitness [states that success of an individual
    in a population depends on traits that contribute to
    its success/long standing]
  4. Punctuated Equilibrium [proposes that in some
    populations, change occurs in rapid bursts rather than
    evenly over time]********REVIEW
38
Q

Modes of Natural Selection

A
  1. Stabilizing-maintains phenotypes in a given range
    and selects against extremes
  2. Directing-gives rise to emergence & dominance of
    an extreme phenotype
  3. Disruptive-selection of extreme phenotypes over
    the norm.
39
Q

Speciation

A

The rise of a new species as a result of evolution.

40
Q

Types of Isolations b/w 2 Populations Preventing Interbreeding

A

A. Prezygotic
1. Temporal [breeding occurs at different times]
2. Ecological [geographical niches varry]
3. Behavioral [courtship behaviors varry]
4. Reproductive [reproductive anatomies are
incompatible]
5. Gametic [gametes fail to fertilize each other]
B. Postzygotic
1. Hybrid inviability [zygote cannot be developed to
term]
2.Hybrid sterility [hybrid cannot reproduce]
3. Hybrid breakdown [hybrid’s offspring is
infertile/sterile]

41
Q

Patterns of Evolution Based on Similarities Shared by Species

Similarities could be due to genes or environment

A
  1. Divergent - [development of dissimilar traits in lineages of a common ancestor]
  2. Parallel - [development of similar traits in genetically related species due to similar environmental factors]
  3. Convergent - [development of similar characteristics in lineages with an unrelated ancestor due to similar environmental pressures]
42
Q

Molecular Clock Model

A

A model that determines the approximate time of evolution between two species based on their genomic similarities.

Biology (5 decks)

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