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Biology > ch 12 - Genetics and Evolution > Flashcards

ch 12 - Genetics and Evolution Flashcards

(72 cards)

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1
Q

chromosomes

A

organization of all genes and a large supply of noncoding DNA

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2
Q

alleles

A

alternative forms of genes

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3
Q

genotype

A

genetic combination possessed by an individual

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4
Q

phenotype

A

manifestation of a given genotype as an observable trait

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5
Q

homologues

A

two copies of a chromosome possessed by each human and applicable to every chromosome except the male sex chromosomes XY.

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6
Q

locus

A

location of a gene on a chromosome; used to describe a gene

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7
Q

hemizygous

A

genotype description in which only one allele is present for a given gene

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8
Q

complete dominance

A

only one dominant and one recessive allele exist for a given gene; presence of one dominant allele will mask the recessive allele

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9
Q

codominance

A

when more than one dominant allele exists for a given gene. Both genes are expressed (AB blood type)

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10
Q

incomplete dominance

A

when a heterozygote expresses a phenotype that is intermediate between the two homozygous genotypes. Red flower, white flower = pink flower

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11
Q

penetrance

A

population measure defined as the proportion of individuals in the population carrying the allele who actually express the phenotype

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12
Q

full penetrance

A

100% of inds with the allele show phenotype

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13
Q

expressivity

A

varying phenotypes despite identical genotypes

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14
Q

constant expressivity

A

all inds with a given genotype express the same phenotype

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15
Q

variable expressivity

A

inds with same genotype may have different phenotypes

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16
Q

Mendel’s First law (of segregation)

A

-genes exist in alternative forms (alleles); -organism has 2 alleles for each gene, one inherited from each parent; -2 alleles segregate during meiosis, resulting in gametes that carry only one allele for any inherited trait; -if two alleles for an organism are different, only one will be fully expressed and the other will be silent

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17
Q

Mendel’s Second Law: Law of Independent Assortment

A

states that inheritance of one gene does not affect the inheritance of another gene

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18
Q

mutation

A

change in DNA sequence which results in mutant allele

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19
Q

wild-type

A

alleles that are considered normal to natural and are ubiquitous in the study population

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20
Q

mutagens

A

substances that can cause mutations

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21
Q

transposons

A

elements that can insert and remove themselves from the genome and can cause mutations

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22
Q

Point mutations review

A

occur when one nucleotide in DNA (A, C, T, or G) is swapped for another. Categories are silent, missense or nonsense

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23
Q

silent mutations

A

occur when the change in nucleotide has no effect on final protein synthesized from the gene; most commonly when the change is at the third nucleotide in the codon because of the degeneracy (wobble) in genetic code

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24
Q

missense mutations

A

occur when the change in nucleotide results in substituting one amino acid for another in the final protein

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25
nonsense mutations
occur when change in nucleotide results in substituting a stop codon for an amino acid in the final protein
26
Frameshift mutations
occur when nucleotides are inserted into or deleted from the genome shifting the reading frame; categorized as insertion or deletion mutations
27
chromosomal mutations
larger-scale mutations than codon mutations in which large segments of DNA are affected
28
deletion mutations of chromosomes
occur when a large segment of DNA is lost from a chromosome
29
duplication mutations of chromosomes
occur when a segment of DNA is copied multiple times in the genome
30
Inversion mutations of chromosomes
occur when a segment of DNA is reversed within the chromosome
31
Insertion mutations of chromosomes
occur when a segment of DNA is moved from one chromosome to another
32
Translocation mutations of chromosomes
occur when a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome
33
advantageous mutations
confer positive selective advantage that may allow organism to produce more offspring
34
deleterious mutations
detrimental mutations
35
inborn errors of metabolism
a class of deleterious mutations; defects in genes required for metabolism
36
genetic leakage
flow of genes between species
37
genetic drift
refers to changes in the composition of the gene pool due to chance; more pronounced in small populations
38
founder effect
extreme case of genetic drift in which a small population of a species finds itself in reproductive isolation from other populations as a result of natural barriers, catastrophic events, or other bottlenecks that drastically and suddenly reduce the size of the population available for breeding
39
inbreeding depression
loss of genetic variation which causes reduced fitness of the population
40
outcrossing
outbreeding; introduction of unrelated individuals into a breeding group
41
monohybrid
a Punnett square cross in which only one trait is being studied
42
parent or P generation
refers to inds being crossed on Punnett square
43
filial or F generation
offspring on Punnett square
44
test cross
sometimes called back crosses; used to determine an unknown genotype; organism with an unknown genotype is crossed with an organism known to be homozygous recessive to determine unknown organism's genotype
45
dihybrid cross
extension of Punnett square to account for inheritance of two different genes
46
phenotypic ratio for heterozygous dominant and recessive combinations
3:1 and adding more just increases multiples
47
Are sex-linked traits more often dominant or recessive?
recessive (unless otherwise specified)
48
sex-linked (X-linked) traits
females have two X chromosomes and may be homozygous or heterozygous for a condition carried on the X chromosome whereas males are hemizygous and sex-linked traits are much more common in males because the one recessive gene on X chromosome is enough for expression
49
recombination frequency (represented by italicized theta)
likelihood that two alleles are separated from each other during crossing over (chiasma); roughly proportional to the distance bt the genes on the chromosome; tightly linked genes have recombination frequency close to 0%
50
genetic map
analysis of recombination frequencies allow this to be constructed; it represents the relative distance between genes on a chromosome; one map unit (centimorgan) corresponds to 1% chance of recombination occurring between two genes
51
allele frequency
how often an allele appears in a population
52
Hardy-Weinberg equilibrium
five criteria that must be met in order for evolution to not occur: -population is very large (no genetic drift); -there are no mutations that affect the gene pool; -mating between individuals in population is random (no sexual selection); -no migration of individuals into or out of the population; -genes in the population are all equally successful at reproducing
53
Two Hardy-Weinberg equations
p + q = 1 which is also to say that (p + q)(squared)= 1(squared) ; and p(squared) + 2pq + q(squared) = 1. p is frequency of dominant allele and q is frequency of recessive allele; p(squared) is occurrence of homozygous dominant genotype, 2pq is frequency of heterozygous dominant and q(squared) is frequency of homozygous recessive genotype. Note: p(squared) + 2pq represents frequency of dominant phenotype
54
natural selection
also called survival of the fittest; theory that certain characteristics or traits possessed by individuals within a species may help those individuals to have greater reproductive success passing on those traits to offspring.
55
modern synthesis model
also called Neo-Darwinism; adds knowledge of genetic inheritance and changes in the gene pool to Darwin's theory.
56
differential reproduction
when mutation or recombination results in a change that is favorable to the organism's reproductive success, that change is more likely to pass on to the next generation
57
Inclusive fitness
measure of an organism's success in the population based on number of offspring, success in supporting the offspring, and ability of the offspring to then support others
58
punctuated equilibrium
theory espoused by Niles Eldridge and Stephen Jay Gould to explain the phenomenon that little evolution would occur within a lineage of related lifeforms for very long periods of time followed by a massive explosion of evolutionary change
59
stabilizing selection
form of natural selection that keeps phenotypes within a specific range by selecting against extremes. ex is human birth weight
60
directional selection
form of natural selection in which adaptive pressure can lead to emergence and dominance of an initially extreme phenotype; ex is bacterial resistance to antibiotics over time
61
disruptive selection
form of natural selection in which two extreme phenotypes are selected over the norm; ex is type of bird which has either very large or very small beak but no in between to adapt to environment
62
polymorphisms
naturally occurring differences in form between members of the same population; facilitates disruptive selection
63
Adaptive radiation
similar concept to polymorphisms; describes rapid rise of a number of different species from a common ancestor; allows various species to occupy different niches
64
species
largest group of organisms capable of breeding to form fertile offspring
65
speciation
formation of new species through evolution
66
isolation
the progeny of single species geographically separated could no longer freely interbreed after enough time has passed. The groups would then be considered two different species
67
prezygotic mechanisms of isolation
prevent formation of zygote completely; examples are temporal isolation (different times for breeding); ecological isolation (living in different niches in same territory); behavioral isolation (lack of attraction or lack of same mating rituals, etc); reproductive isolation (incompatibility of reproductive anatomy), or gametic isolation (intercourse can occur but fertilization cannot)
68
postzygotic mechanisms of isolation
allow for gamete fusion but yield either nonviable or sterile offspring; examples include hybrid inviability, hybrid sterility, or hybrid breakdown (first generation is fertile and viable and second generation is either not viable or not fertile)
69
divergent evolution
pattern of evolution that is independent development of dissimilar characteristics in two or more lineages sharing a common ancestor
70
parallel evolution
pattern of evolution that is the process whereby related species evolve in similar ways for a long period of time in response to analogous environmental selection pressures
71
convergent evolution
pattern of evolution referring to the independent development of similar characteristics in two or more lineages not sharing a recent common ancestor; ex is fish and dolphins which are different but have developed similar phenotypic characteristics in response to aquatic life
72
molecular clock model
the more similar the genomes of two species the more recently the two species separated from each other

Biology (9 decks)

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